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1 Encoders

Encoders are configured elements in FFmpeg which allow the encoding of multimedia streams.

When you configure your FFmpeg build, all the supported native encoders are enabled by default. Encoders requiring an external library must be enabled manually via the corresponding --enable-lib option. You can list all available encoders using the configure option --list-encoders.

You can disable all the encoders with the configure option --disable-encoders and selectively enable / disable single encoders with the options --enable-encoder=ENCODER / --disable-encoder=ENCODER.

The option -encoders of the ff* tools will display the list of enabled encoders.


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2 Audio Encoders

A description of some of the currently available audio encoders follows.


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2.1 aac

Advanced Audio Coding (AAC) encoder.

This encoder is the default AAC encoder, natively implemented into FFmpeg. Its quality is on par or better than libfdk_aac at the default bitrate of 128kbps. This encoder also implements more options, profiles and samplerates than other encoders (with only the AAC-HE profile pending to be implemented) so this encoder has become the default and is the recommended choice.


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2.1.1 Options

b

Set bit rate in bits/s. Setting this automatically activates constant bit rate (CBR) mode. If this option is unspecified it is set to 128kbps.

q

Set quality for variable bit rate (VBR) mode. This option is valid only using the ffmpeg command-line tool. For library interface users, use ‘global_quality’.

cutoff

Set cutoff frequency. If unspecified will allow the encoder to dynamically adjust the cutoff to improve clarity on low bitrates.

aac_coder

Set AAC encoder coding method. Possible values:

twoloop

Two loop searching (TLS) method.

This method first sets quantizers depending on band thresholds and then tries to find an optimal combination by adding or subtracting a specific value from all quantizers and adjusting some individual quantizer a little. Will tune itself based on whether ‘aac_is’, ‘aac_ms’ and ‘aac_pns’ are enabled. This is the default choice for a coder.

anmr

Average noise to mask ratio (ANMR) trellis-based solution.

This is an experimental coder which currently produces a lower quality, is more unstable and is slower than the default twoloop coder but has potential. Currently has no support for the ‘aac_is’ or ‘aac_pns’ options. Not currently recommended.

fast

Constant quantizer method.

This method sets a constant quantizer for all bands. This is the fastest of all the methods and has no rate control or support for ‘aac_is’ or ‘aac_pns’. Not recommended.

aac_ms

Sets mid/side coding mode. The default value of "auto" will automatically use M/S with bands which will benefit from such coding. Can be forced for all bands using the value "enable", which is mainly useful for debugging or disabled using "disable".

aac_is

Sets intensity stereo coding tool usage. By default, it’s enabled and will automatically toggle IS for similar pairs of stereo bands if it’s beneficial. Can be disabled for debugging by setting the value to "disable".

aac_pns

Uses perceptual noise substitution to replace low entropy high frequency bands with imperceptible white noise during the decoding process. By default, it’s enabled, but can be disabled for debugging purposes by using "disable".

aac_tns

Enables the use of a multitap FIR filter which spans through the high frequency bands to hide quantization noise during the encoding process and is reverted by the decoder. As well as decreasing unpleasant artifacts in the high range this also reduces the entropy in the high bands and allows for more bits to be used by the mid-low bands. By default it’s enabled but can be disabled for debugging by setting the option to "disable".

aac_ltp

Enables the use of the long term prediction extension which increases coding efficiency in very low bandwidth situations such as encoding of voice or solo piano music by extending constant harmonic peaks in bands throughout frames. This option is implied by profile:a aac_low and is incompatible with aac_pred. Use in conjunction with ‘-ar’ to decrease the samplerate.

aac_pred

Enables the use of a more traditional style of prediction where the spectral coefficients transmitted are replaced by the difference of the current coefficients minus the previous "predicted" coefficients. In theory and sometimes in practice this can improve quality for low to mid bitrate audio. This option implies the aac_main profile and is incompatible with aac_ltp.

profile

Sets the encoding profile, possible values:

aac_low

The default, AAC "Low-complexity" profile. Is the most compatible and produces decent quality.

mpeg2_aac_low

Equivalent to -profile:a aac_low -aac_pns 0. PNS was introduced with the MPEG4 specifications.

aac_ltp

Long term prediction profile, is enabled by and will enable the ‘aac_ltp’ option. Introduced in MPEG4.

aac_main

Main-type prediction profile, is enabled by and will enable the ‘aac_pred’ option. Introduced in MPEG2.

If this option is unspecified it is set to ‘aac_low’.


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2.2 ac3 and ac3_fixed

AC-3 audio encoders.

These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as the undocumented RealAudio 3 (a.k.a. dnet).

The ac3 encoder uses floating-point math, while the ac3_fixed encoder only uses fixed-point integer math. This does not mean that one is always faster, just that one or the other may be better suited to a particular system. The floating-point encoder will generally produce better quality audio for a given bitrate. The ac3_fixed encoder is not the default codec for any of the output formats, so it must be specified explicitly using the option -acodec ac3_fixed in order to use it.


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2.2.1 AC-3 Metadata

The AC-3 metadata options are used to set parameters that describe the audio, but in most cases do not affect the audio encoding itself. Some of the options do directly affect or influence the decoding and playback of the resulting bitstream, while others are just for informational purposes. A few of the options will add bits to the output stream that could otherwise be used for audio data, and will thus affect the quality of the output. Those will be indicated accordingly with a note in the option list below.

These parameters are described in detail in several publicly-available documents.


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2.2.1.1 Metadata Control Options

-per_frame_metadata boolean

Allow Per-Frame Metadata. Specifies if the encoder should check for changing metadata for each frame.

0

The metadata values set at initialization will be used for every frame in the stream. (default)

1

Metadata values can be changed before encoding each frame.


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2.2.1.2 Downmix Levels

-center_mixlev level

Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo. This field will only be written to the bitstream if a center channel is present. The value is specified as a scale factor. There are 3 valid values:

0.707

Apply -3dB gain

0.595

Apply -4.5dB gain (default)

0.500

Apply -6dB gain

-surround_mixlev level

Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo. This field will only be written to the bitstream if one or more surround channels are present. The value is specified as a scale factor. There are 3 valid values:

0.707

Apply -3dB gain

0.500

Apply -6dB gain (default)

0.000

Silence Surround Channel(s)


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2.2.1.3 Audio Production Information

Audio Production Information is optional information describing the mixing environment. Either none or both of the fields are written to the bitstream.

-mixing_level number

Mixing Level. Specifies peak sound pressure level (SPL) in the production environment when the mix was mastered. Valid values are 80 to 111, or -1 for unknown or not indicated. The default value is -1, but that value cannot be used if the Audio Production Information is written to the bitstream. Therefore, if the room_type option is not the default value, the mixing_level option must not be -1.

-room_type type

Room Type. Describes the equalization used during the final mixing session at the studio or on the dubbing stage. A large room is a dubbing stage with the industry standard X-curve equalization; a small room has flat equalization. This field will not be written to the bitstream if both the mixing_level option and the room_type option have the default values.

0
notindicated

Not Indicated (default)

1
large

Large Room

2
small

Small Room


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2.2.1.4 Other Metadata Options

-copyright boolean

Copyright Indicator. Specifies whether a copyright exists for this audio.

0
off

No Copyright Exists (default)

1
on

Copyright Exists

-dialnorm value

Dialogue Normalization. Indicates how far the average dialogue level of the program is below digital 100% full scale (0 dBFS). This parameter determines a level shift during audio reproduction that sets the average volume of the dialogue to a preset level. The goal is to match volume level between program sources. A value of -31dB will result in no volume level change, relative to the source volume, during audio reproduction. Valid values are whole numbers in the range -31 to -1, with -31 being the default.

-dsur_mode mode

Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround (Pro Logic). This field will only be written to the bitstream if the audio stream is stereo. Using this option does NOT mean the encoder will actually apply Dolby Surround processing.

0
notindicated

Not Indicated (default)

1
off

Not Dolby Surround Encoded

2
on

Dolby Surround Encoded

-original boolean

Original Bit Stream Indicator. Specifies whether this audio is from the original source and not a copy.

0
off

Not Original Source

1
on

Original Source (default)


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2.2.2 Extended Bitstream Information

The extended bitstream options are part of the Alternate Bit Stream Syntax as specified in Annex D of the A/52:2010 standard. It is grouped into 2 parts. If any one parameter in a group is specified, all values in that group will be written to the bitstream. Default values are used for those that are written but have not been specified. If the mixing levels are written, the decoder will use these values instead of the ones specified in the center_mixlev and surround_mixlev options if it supports the Alternate Bit Stream Syntax.


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2.2.2.1 Extended Bitstream Information - Part 1

-dmix_mode mode

Preferred Stereo Downmix Mode. Allows the user to select either Lt/Rt (Dolby Surround) or Lo/Ro (normal stereo) as the preferred stereo downmix mode.

0
notindicated

Not Indicated (default)

1
ltrt

Lt/Rt Downmix Preferred

2
loro

Lo/Ro Downmix Preferred

-ltrt_cmixlev level

Lt/Rt Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo in Lt/Rt mode.

1.414

Apply +3dB gain

1.189

Apply +1.5dB gain

1.000

Apply 0dB gain

0.841

Apply -1.5dB gain

0.707

Apply -3.0dB gain

0.595

Apply -4.5dB gain (default)

0.500

Apply -6.0dB gain

0.000

Silence Center Channel

-ltrt_surmixlev level

Lt/Rt Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo in Lt/Rt mode.

0.841

Apply -1.5dB gain

0.707

Apply -3.0dB gain

0.595

Apply -4.5dB gain

0.500

Apply -6.0dB gain (default)

0.000

Silence Surround Channel(s)

-loro_cmixlev level

Lo/Ro Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo in Lo/Ro mode.

1.414

Apply +3dB gain

1.189

Apply +1.5dB gain

1.000

Apply 0dB gain

0.841

Apply -1.5dB gain

0.707

Apply -3.0dB gain

0.595

Apply -4.5dB gain (default)

0.500

Apply -6.0dB gain

0.000

Silence Center Channel

-loro_surmixlev level

Lo/Ro Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo in Lo/Ro mode.

0.841

Apply -1.5dB gain

0.707

Apply -3.0dB gain

0.595

Apply -4.5dB gain

0.500

Apply -6.0dB gain (default)

0.000

Silence Surround Channel(s)


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2.2.2.2 Extended Bitstream Information - Part 2

-dsurex_mode mode

Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX (7.1 matrixed to 5.1). Using this option does NOT mean the encoder will actually apply Dolby Surround EX processing.

0
notindicated

Not Indicated (default)

1
on

Dolby Surround EX Off

2
off

Dolby Surround EX On

-dheadphone_mode mode

Dolby Headphone Mode. Indicates whether the stream uses Dolby Headphone encoding (multi-channel matrixed to 2.0 for use with headphones). Using this option does NOT mean the encoder will actually apply Dolby Headphone processing.

0
notindicated

Not Indicated (default)

1
on

Dolby Headphone Off

2
off

Dolby Headphone On

-ad_conv_type type

A/D Converter Type. Indicates whether the audio has passed through HDCD A/D conversion.

0
standard

Standard A/D Converter (default)

1
hdcd

HDCD A/D Converter


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2.2.3 Other AC-3 Encoding Options

-stereo_rematrixing boolean

Stereo Rematrixing. Enables/Disables use of rematrixing for stereo input. This is an optional AC-3 feature that increases quality by selectively encoding the left/right channels as mid/side. This option is enabled by default, and it is highly recommended that it be left as enabled except for testing purposes.

cutoff frequency

Set lowpass cutoff frequency. If unspecified, the encoder selects a default determined by various other encoding parameters.


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2.2.4 Floating-Point-Only AC-3 Encoding Options

These options are only valid for the floating-point encoder and do not exist for the fixed-point encoder due to the corresponding features not being implemented in fixed-point.

-channel_coupling boolean

Enables/Disables use of channel coupling, which is an optional AC-3 feature that increases quality by combining high frequency information from multiple channels into a single channel. The per-channel high frequency information is sent with less accuracy in both the frequency and time domains. This allows more bits to be used for lower frequencies while preserving enough information to reconstruct the high frequencies. This option is enabled by default for the floating-point encoder and should generally be left as enabled except for testing purposes or to increase encoding speed.

-1
auto

Selected by Encoder (default)

0
off

Disable Channel Coupling

1
on

Enable Channel Coupling

-cpl_start_band number

Coupling Start Band. Sets the channel coupling start band, from 1 to 15. If a value higher than the bandwidth is used, it will be reduced to 1 less than the coupling end band. If auto is used, the start band will be determined by the encoder based on the bit rate, sample rate, and channel layout. This option has no effect if channel coupling is disabled.

-1
auto

Selected by Encoder (default)


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2.3 flac

FLAC (Free Lossless Audio Codec) Encoder


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2.3.1 Options

The following options are supported by FFmpeg’s flac encoder.

compression_level

Sets the compression level, which chooses defaults for many other options if they are not set explicitly. Valid values are from 0 to 12, 5 is the default.

frame_size

Sets the size of the frames in samples per channel.

lpc_coeff_precision

Sets the LPC coefficient precision, valid values are from 1 to 15, 15 is the default.

lpc_type

Sets the first stage LPC algorithm

none

LPC is not used

fixed

fixed LPC coefficients

levinson
cholesky
lpc_passes

Number of passes to use for Cholesky factorization during LPC analysis

min_partition_order

The minimum partition order

max_partition_order

The maximum partition order

prediction_order_method
estimation
2level
4level
8level
search

Bruteforce search

log
ch_mode

Channel mode

auto

The mode is chosen automatically for each frame

indep

Channels are independently coded

left_side
right_side
mid_side
exact_rice_parameters

Chooses if rice parameters are calculated exactly or approximately. if set to 1 then they are chosen exactly, which slows the code down slightly and improves compression slightly.

multi_dim_quant

Multi Dimensional Quantization. If set to 1 then a 2nd stage LPC algorithm is applied after the first stage to finetune the coefficients. This is quite slow and slightly improves compression.


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2.4 opus

Opus encoder.

This is a native FFmpeg encoder for the Opus format. Currently its in development and only implements the CELT part of the codec. Its quality is usually worse and at best is equal to the libopus encoder.


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2.4.1 Options

b

Set bit rate in bits/s. If unspecified it uses the number of channels and the layout to make a good guess.

opus_delay

Sets the maximum delay in milliseconds. Lower delays than 20ms will very quickly decrease quality.


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2.5 libfdk_aac

libfdk-aac AAC (Advanced Audio Coding) encoder wrapper.

The libfdk-aac library is based on the Fraunhofer FDK AAC code from the Android project.

Requires the presence of the libfdk-aac headers and library during configuration. You need to explicitly configure the build with --enable-libfdk-aac. The library is also incompatible with GPL, so if you allow the use of GPL, you should configure with --enable-gpl --enable-nonfree --enable-libfdk-aac.

This encoder is considered to produce output on par or worse at 128kbps to the the native FFmpeg AAC encoder but can often produce better sounding audio at identical or lower bitrates and has support for the AAC-HE profiles.

VBR encoding, enabled through the ‘vbr’ or ‘flags +qscale’ options, is experimental and only works with some combinations of parameters.

Support for encoding 7.1 audio is only available with libfdk-aac 0.1.3 or higher.

For more information see the fdk-aac project at http://sourceforge.net/p/opencore-amr/fdk-aac/.


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2.5.1 Options

The following options are mapped on the shared FFmpeg codec options.

b

Set bit rate in bits/s. If the bitrate is not explicitly specified, it is automatically set to a suitable value depending on the selected profile.

In case VBR mode is enabled the option is ignored.

ar

Set audio sampling rate (in Hz).

channels

Set the number of audio channels.

flags +qscale

Enable fixed quality, VBR (Variable Bit Rate) mode. Note that VBR is implicitly enabled when the ‘vbr’ value is positive.

cutoff

Set cutoff frequency. If not specified (or explicitly set to 0) it will use a value automatically computed by the library. Default value is 0.

profile

Set audio profile.

The following profiles are recognized:

aac_low

Low Complexity AAC (LC)

aac_he

High Efficiency AAC (HE-AAC)

aac_he_v2

High Efficiency AAC version 2 (HE-AACv2)

aac_ld

Low Delay AAC (LD)

aac_eld

Enhanced Low Delay AAC (ELD)

If not specified it is set to ‘aac_low’.

The following are private options of the libfdk_aac encoder.

afterburner

Enable afterburner feature if set to 1, disabled if set to 0. This improves the quality but also the required processing power.

Default value is 1.

eld_sbr

Enable SBR (Spectral Band Replication) for ELD if set to 1, disabled if set to 0.

Default value is 0.

signaling

Set SBR/PS signaling style.

It can assume one of the following values:

default

choose signaling implicitly (explicit hierarchical by default, implicit if global header is disabled)

implicit

implicit backwards compatible signaling

explicit_sbr

explicit SBR, implicit PS signaling

explicit_hierarchical

explicit hierarchical signaling

Default value is ‘default’.

latm

Output LATM/LOAS encapsulated data if set to 1, disabled if set to 0.

Default value is 0.

header_period

Set StreamMuxConfig and PCE repetition period (in frames) for sending in-band configuration buffers within LATM/LOAS transport layer.

Must be a 16-bits non-negative integer.

Default value is 0.

vbr

Set VBR mode, from 1 to 5. 1 is lowest quality (though still pretty good) and 5 is highest quality. A value of 0 will disable VBR, and CBR (Constant Bit Rate) is enabled.

Currently only the ‘aac_low’ profile supports VBR encoding.

VBR modes 1-5 correspond to roughly the following average bit rates:

1

32 kbps/channel

2

40 kbps/channel

3

48-56 kbps/channel

4

64 kbps/channel

5

about 80-96 kbps/channel

Default value is 0.


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2.5.2 Examples


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2.6 libmp3lame

LAME (Lame Ain’t an MP3 Encoder) MP3 encoder wrapper.

Requires the presence of the libmp3lame headers and library during configuration. You need to explicitly configure the build with --enable-libmp3lame.

See libshine for a fixed-point MP3 encoder, although with a lower quality.


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2.6.1 Options

The following options are supported by the libmp3lame wrapper. The lame-equivalent of the options are listed in parentheses.

b (-b)

Set bitrate expressed in bits/s for CBR or ABR. LAME bitrate is expressed in kilobits/s.

q (-V)

Set constant quality setting for VBR. This option is valid only using the ffmpeg command-line tool. For library interface users, use ‘global_quality’.

compression_level (-q)

Set algorithm quality. Valid arguments are integers in the 0-9 range, with 0 meaning highest quality but slowest, and 9 meaning fastest while producing the worst quality.

cutoff (--lowpass)

Set lowpass cutoff frequency. If unspecified, the encoder dynamically adjusts the cutoff.

reservoir

Enable use of bit reservoir when set to 1. Default value is 1. LAME has this enabled by default, but can be overridden by use ‘--nores’ option.

joint_stereo (-m j)

Enable the encoder to use (on a frame by frame basis) either L/R stereo or mid/side stereo. Default value is 1.

abr (--abr)

Enable the encoder to use ABR when set to 1. The lame--abr’ sets the target bitrate, while this options only tells FFmpeg to use ABR still relies on ‘b’ to set bitrate.


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2.7 libopencore-amrnb

OpenCORE Adaptive Multi-Rate Narrowband encoder.

Requires the presence of the libopencore-amrnb headers and library during configuration. You need to explicitly configure the build with --enable-libopencore-amrnb --enable-version3.

This is a mono-only encoder. Officially it only supports 8000Hz sample rate, but you can override it by setting ‘strict’ to ‘unofficial’ or lower.


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2.7.1 Options

b

Set bitrate in bits per second. Only the following bitrates are supported, otherwise libavcodec will round to the nearest valid bitrate.

4750
5150
5900
6700
7400
7950
10200
12200
dtx

Allow discontinuous transmission (generate comfort noise) when set to 1. The default value is 0 (disabled).


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2.8 libopus

libopus Opus Interactive Audio Codec encoder wrapper.

Requires the presence of the libopus headers and library during configuration. You need to explicitly configure the build with --enable-libopus.


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2.8.1 Option Mapping

Most libopus options are modelled after the opusenc utility from opus-tools. The following is an option mapping chart describing options supported by the libopus wrapper, and their opusenc-equivalent in parentheses.

b (bitrate)

Set the bit rate in bits/s. FFmpeg’s ‘b’ option is expressed in bits/s, while opusenc’s ‘bitrate’ in kilobits/s.

vbr (vbr, hard-cbr, and cvbr)

Set VBR mode. The FFmpeg ‘vbr’ option has the following valid arguments, with the opusenc equivalent options in parentheses:

off (hard-cbr)

Use constant bit rate encoding.

on (vbr)

Use variable bit rate encoding (the default).

constrained (cvbr)

Use constrained variable bit rate encoding.

compression_level (comp)

Set encoding algorithm complexity. Valid options are integers in the 0-10 range. 0 gives the fastest encodes but lower quality, while 10 gives the highest quality but slowest encoding. The default is 10.

frame_duration (framesize)

Set maximum frame size, or duration of a frame in milliseconds. The argument must be exactly the following: 2.5, 5, 10, 20, 40, 60. Smaller frame sizes achieve lower latency but less quality at a given bitrate. Sizes greater than 20ms are only interesting at fairly low bitrates. The default is 20ms.

packet_loss (expect-loss)

Set expected packet loss percentage. The default is 0.

application (N.A.)

Set intended application type. Valid options are listed below:

voip

Favor improved speech intelligibility.

audio

Favor faithfulness to the input (the default).

lowdelay

Restrict to only the lowest delay modes.

cutoff (N.A.)

Set cutoff bandwidth in Hz. The argument must be exactly one of the following: 4000, 6000, 8000, 12000, or 20000, corresponding to narrowband, mediumband, wideband, super wideband, and fullband respectively. The default is 0 (cutoff disabled).

mapping_family (mapping_family)

Set channel mapping family to be used by the encoder. The default value of -1 uses mapping family 0 for mono and stereo inputs, and mapping family 1 otherwise. The default also disables the surround masking and LFE bandwidth optimzations in libopus, and requires that the input contains 8 channels or fewer.

Other values include 0 for mono and stereo, 1 for surround sound with masking and LFE bandwidth optimizations, and 255 for independent streams with an unspecified channel layout.


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2.9 libshine

Shine Fixed-Point MP3 encoder wrapper.

Shine is a fixed-point MP3 encoder. It has a far better performance on platforms without an FPU, e.g. armel CPUs, and some phones and tablets. However, as it is more targeted on performance than quality, it is not on par with LAME and other production-grade encoders quality-wise. Also, according to the project’s homepage, this encoder may not be free of bugs as the code was written a long time ago and the project was dead for at least 5 years.

This encoder only supports stereo and mono input. This is also CBR-only.

The original project (last updated in early 2007) is at http://sourceforge.net/projects/libshine-fxp/. We only support the updated fork by the Savonet/Liquidsoap project at https://github.com/savonet/shine.

Requires the presence of the libshine headers and library during configuration. You need to explicitly configure the build with --enable-libshine.

See also libmp3lame.


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2.9.1 Options

The following options are supported by the libshine wrapper. The shineenc-equivalent of the options are listed in parentheses.

b (-b)

Set bitrate expressed in bits/s for CBR. shineenc-b’ option is expressed in kilobits/s.


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2.10 libtwolame

TwoLAME MP2 encoder wrapper.

Requires the presence of the libtwolame headers and library during configuration. You need to explicitly configure the build with --enable-libtwolame.


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2.10.1 Options

The following options are supported by the libtwolame wrapper. The twolame-equivalent options follow the FFmpeg ones and are in parentheses.

b (-b)

Set bitrate expressed in bits/s for CBR. twolameb’ option is expressed in kilobits/s. Default value is 128k.

q (-V)

Set quality for experimental VBR support. Maximum value range is from -50 to 50, useful range is from -10 to 10. The higher the value, the better the quality. This option is valid only using the ffmpeg command-line tool. For library interface users, use ‘global_quality’.

mode (--mode)

Set the mode of the resulting audio. Possible values:

auto

Choose mode automatically based on the input. This is the default.

stereo

Stereo

joint_stereo

Joint stereo

dual_channel

Dual channel

mono

Mono

psymodel (--psyc-mode)

Set psychoacoustic model to use in encoding. The argument must be an integer between -1 and 4, inclusive. The higher the value, the better the quality. The default value is 3.

energy_levels (--energy)

Enable energy levels extensions when set to 1. The default value is 0 (disabled).

error_protection (--protect)

Enable CRC error protection when set to 1. The default value is 0 (disabled).

copyright (--copyright)

Set MPEG audio copyright flag when set to 1. The default value is 0 (disabled).

original (--original)

Set MPEG audio original flag when set to 1. The default value is 0 (disabled).


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2.11 libvo-amrwbenc

VisualOn Adaptive Multi-Rate Wideband encoder.

Requires the presence of the libvo-amrwbenc headers and library during configuration. You need to explicitly configure the build with --enable-libvo-amrwbenc --enable-version3.

This is a mono-only encoder. Officially it only supports 16000Hz sample rate, but you can override it by setting ‘strict’ to ‘unofficial’ or lower.


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2.11.1 Options

b

Set bitrate in bits/s. Only the following bitrates are supported, otherwise libavcodec will round to the nearest valid bitrate.

6600
8850
12650
14250
15850
18250
19850
23050
23850
dtx

Allow discontinuous transmission (generate comfort noise) when set to 1. The default value is 0 (disabled).


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2.12 libvorbis

libvorbis encoder wrapper.

Requires the presence of the libvorbisenc headers and library during configuration. You need to explicitly configure the build with --enable-libvorbis.


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2.12.1 Options

The following options are supported by the libvorbis wrapper. The oggenc-equivalent of the options are listed in parentheses.

To get a more accurate and extensive documentation of the libvorbis options, consult the libvorbisenc’s and oggenc’s documentations. See http://xiph.org/vorbis/, http://wiki.xiph.org/Vorbis-tools, and oggenc(1).

b (-b)

Set bitrate expressed in bits/s for ABR. oggenc-b’ is expressed in kilobits/s.

q (-q)

Set constant quality setting for VBR. The value should be a float number in the range of -1.0 to 10.0. The higher the value, the better the quality. The default value is ‘3.0’.

This option is valid only using the ffmpeg command-line tool. For library interface users, use ‘global_quality’.

cutoff (--advanced-encode-option lowpass_frequency=N)

Set cutoff bandwidth in Hz, a value of 0 disables cutoff. oggenc’s related option is expressed in kHz. The default value is ‘0’ (cutoff disabled).

minrate (-m)

Set minimum bitrate expressed in bits/s. oggenc-m’ is expressed in kilobits/s.

maxrate (-M)

Set maximum bitrate expressed in bits/s. oggenc-M’ is expressed in kilobits/s. This only has effect on ABR mode.

iblock (--advanced-encode-option impulse_noisetune=N)

Set noise floor bias for impulse blocks. The value is a float number from -15.0 to 0.0. A negative bias instructs the encoder to pay special attention to the crispness of transients in the encoded audio. The tradeoff for better transient response is a higher bitrate.


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2.13 libwavpack

A wrapper providing WavPack encoding through libwavpack.

Only lossless mode using 32-bit integer samples is supported currently.

Requires the presence of the libwavpack headers and library during configuration. You need to explicitly configure the build with --enable-libwavpack.

Note that a libavcodec-native encoder for the WavPack codec exists so users can encode audios with this codec without using this encoder. See wavpackenc.


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2.13.1 Options

wavpack command line utility’s corresponding options are listed in parentheses, if any.

frame_size (--blocksize)

Default is 32768.

compression_level

Set speed vs. compression tradeoff. Acceptable arguments are listed below:

0 (-f)

Fast mode.

1

Normal (default) settings.

2 (-h)

High quality.

3 (-hh)

Very high quality.

4-8 (-hh -xEXTRAPROC)

Same as ‘3’, but with extra processing enabled.

4’ is the same as ‘-x2’ and ‘8’ is the same as ‘-x6’.


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2.14 mjpeg

Motion JPEG encoder.


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2.14.1 Options

huffman

Set the huffman encoding strategy. Possible values:

default

Use the default huffman tables. This is the default strategy.

optimal

Compute and use optimal huffman tables.


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2.15 wavpack

WavPack lossless audio encoder.

This is a libavcodec-native WavPack encoder. There is also an encoder based on libwavpack, but there is virtually no reason to use that encoder.

See also libwavpack.


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2.15.1 Options

The equivalent options for wavpack command line utility are listed in parentheses.


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2.15.1.1 Shared options

The following shared options are effective for this encoder. Only special notes about this particular encoder will be documented here. For the general meaning of the options, see @ref{codec-options,,the Codec Options chapter}.

frame_size (--blocksize)

For this encoder, the range for this option is between 128 and 131072. Default is automatically decided based on sample rate and number of channel.

For the complete formula of calculating default, see ‘libavcodec/wavpackenc.c’.

compression_level (-f, -h, -hh, and -x)

This option’s syntax is consistent with libwavpack’s.


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2.15.1.2 Private options

joint_stereo (-j)

Set whether to enable joint stereo. Valid values are:

on (1)

Force mid/side audio encoding.

off (0)

Force left/right audio encoding.

auto

Let the encoder decide automatically.

optimize_mono

Set whether to enable optimization for mono. This option is only effective for non-mono streams. Available values:

on

enabled

off

disabled


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3 Video Encoders

A description of some of the currently available video encoders follows.


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3.1 Hap

Vidvox Hap video encoder.


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3.1.1 Options

format integer

Specifies the Hap format to encode.

hap
hap_alpha
hap_q

Default value is ‘hap’.

chunks integer

Specifies the number of chunks to split frames into, between 1 and 64. This permits multithreaded decoding of large frames, potentially at the cost of data-rate. The encoder may modify this value to divide frames evenly.

Default value is 1.

compressor integer

Specifies the second-stage compressor to use. If set to ‘none’, ‘chunks’ will be limited to 1, as chunked uncompressed frames offer no benefit.

none
snappy

Default value is ‘snappy’.


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3.2 jpeg2000

The native jpeg 2000 encoder is lossy by default, the -q:v option can be used to set the encoding quality. Lossless encoding can be selected with -pred 1.


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3.2.1 Options

format

Can be set to either j2k or jp2 (the default) that makes it possible to store non-rgb pix_fmts.


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3.3 libkvazaar

Kvazaar H.265/HEVC encoder.

Requires the presence of the libkvazaar headers and library during configuration. You need to explicitly configure the build with ‘--enable-libkvazaar’.


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3.3.1 Options

b

Set target video bitrate in bit/s and enable rate control.

kvazaar-params

Set kvazaar parameters as a list of name=value pairs separated by commas (,). See kvazaar documentation for a list of options.


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3.4 libopenh264

Cisco libopenh264 H.264/MPEG-4 AVC encoder wrapper.

This encoder requires the presence of the libopenh264 headers and library during configuration. You need to explicitly configure the build with --enable-libopenh264. The library is detected using pkg-config.

For more information about the library see http://www.openh264.org.


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3.4.1 Options

The following FFmpeg global options affect the configurations of the libopenh264 encoder.

b

Set the bitrate (as a number of bits per second).

g

Set the GOP size.

maxrate

Set the max bitrate (as a number of bits per second).

flags +global_header

Set global header in the bitstream.

slices

Set the number of slices, used in parallelized encoding. Default value is 0. This is only used when ‘slice_mode’ is set to ‘fixed’.

slice_mode

Set slice mode. Can assume one of the following possible values:

fixed

a fixed number of slices

rowmb

one slice per row of macroblocks

auto

automatic number of slices according to number of threads

dyn

dynamic slicing

Default value is ‘auto’.

loopfilter

Enable loop filter, if set to 1 (automatically enabled). To disable set a value of 0.

profile

Set profile restrictions. If set to the value of ‘main’ enable CABAC (set the SEncParamExt.iEntropyCodingModeFlag flag to 1).

max_nal_size

Set maximum NAL size in bytes.

allow_skip_frames

Allow skipping frames to hit the target bitrate if set to 1.


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3.5 libtheora

libtheora Theora encoder wrapper.

Requires the presence of the libtheora headers and library during configuration. You need to explicitly configure the build with --enable-libtheora.

For more information about the libtheora project see http://www.theora.org/.


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3.5.1 Options

The following global options are mapped to internal libtheora options which affect the quality and the bitrate of the encoded stream.

b

Set the video bitrate in bit/s for CBR (Constant Bit Rate) mode. In case VBR (Variable Bit Rate) mode is enabled this option is ignored.

flags

Used to enable constant quality mode (VBR) encoding through the ‘qscale’ flag, and to enable the pass1 and pass2 modes.

g

Set the GOP size.

global_quality

Set the global quality as an integer in lambda units.

Only relevant when VBR mode is enabled with flags +qscale. The value is converted to QP units by dividing it by FF_QP2LAMBDA, clipped in the [0 - 10] range, and then multiplied by 6.3 to get a value in the native libtheora range [0-63]. A higher value corresponds to a higher quality.

q

Enable VBR mode when set to a non-negative value, and set constant quality value as a double floating point value in QP units.

The value is clipped in the [0-10] range, and then multiplied by 6.3 to get a value in the native libtheora range [0-63].

This option is valid only using the ffmpeg command-line tool. For library interface users, use ‘global_quality’.


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3.5.2 Examples


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3.6 libvpx

VP8/VP9 format supported through libvpx.

Requires the presence of the libvpx headers and library during configuration. You need to explicitly configure the build with --enable-libvpx.


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3.6.1 Options

The following options are supported by the libvpx wrapper. The vpxenc-equivalent options or values are listed in parentheses for easy migration.

To reduce the duplication of documentation, only the private options and some others requiring special attention are documented here. For the documentation of the undocumented generic options, see @ref{codec-options,,the Codec Options chapter}.

To get more documentation of the libvpx options, invoke the command ffmpeg -h encoder=libvpx, ffmpeg -h encoder=libvpx-vp9 or vpxenc --help. Further information is available in the libvpx API documentation.

b (target-bitrate)

Set bitrate in bits/s. Note that FFmpeg’s ‘b’ option is expressed in bits/s, while vpxenc’s ‘target-bitrate’ is in kilobits/s.

g (kf-max-dist)
keyint_min (kf-min-dist)
qmin (min-q)
qmax (max-q)
bufsize (buf-sz, buf-optimal-sz)

Set ratecontrol buffer size (in bits). Note vpxenc’s options are specified in milliseconds, the libvpx wrapper converts this value as follows: buf-sz = bufsize * 1000 / bitrate, buf-optimal-sz = bufsize * 1000 / bitrate * 5 / 6.

rc_init_occupancy (buf-initial-sz)

Set number of bits which should be loaded into the rc buffer before decoding starts. Note vpxenc’s option is specified in milliseconds, the libvpx wrapper converts this value as follows: rc_init_occupancy * 1000 / bitrate.

undershoot-pct

Set datarate undershoot (min) percentage of the target bitrate.

overshoot-pct

Set datarate overshoot (max) percentage of the target bitrate.

skip_threshold (drop-frame)
qcomp (bias-pct)
maxrate (maxsection-pct)

Set GOP max bitrate in bits/s. Note vpxenc’s option is specified as a percentage of the target bitrate, the libvpx wrapper converts this value as follows: (maxrate * 100 / bitrate).

minrate (minsection-pct)

Set GOP min bitrate in bits/s. Note vpxenc’s option is specified as a percentage of the target bitrate, the libvpx wrapper converts this value as follows: (minrate * 100 / bitrate).

minrate, maxrate, b end-usage=cbr

(minrate == maxrate == bitrate).

crf (end-usage=cq, cq-level)
tune (tune)
psnr (psnr)
ssim (ssim)
quality, deadline (deadline)
best

Use best quality deadline. Poorly named and quite slow, this option should be avoided as it may give worse quality output than good.

good

Use good quality deadline. This is a good trade-off between speed and quality when used with the ‘cpu-used’ option.

realtime

Use realtime quality deadline.

speed, cpu-used (cpu-used)

Set quality/speed ratio modifier. Higher values speed up the encode at the cost of quality.

nr (noise-sensitivity)
static-thresh

Set a change threshold on blocks below which they will be skipped by the encoder.

slices (token-parts)

Note that FFmpeg’s ‘slices’ option gives the total number of partitions, while vpxenc’s ‘token-parts’ is given as log2(partitions).

max-intra-rate

Set maximum I-frame bitrate as a percentage of the target bitrate. A value of 0 means unlimited.

force_key_frames

VPX_EFLAG_FORCE_KF

Alternate reference frame related
auto-alt-ref

Enable use of alternate reference frames (2-pass only).

arnr-max-frames

Set altref noise reduction max frame count.

arnr-type

Set altref noise reduction filter type: backward, forward, centered.

arnr-strength

Set altref noise reduction filter strength.

rc-lookahead, lag-in-frames (lag-in-frames)

Set number of frames to look ahead for frametype and ratecontrol.

error-resilient

Enable error resiliency features.

VP9-specific options
lossless

Enable lossless mode.

tile-columns

Set number of tile columns to use. Note this is given as log2(tile_columns). For example, 8 tile columns would be requested by setting the ‘tile-columns’ option to 3.

tile-rows

Set number of tile rows to use. Note this is given as log2(tile_rows). For example, 4 tile rows would be requested by setting the ‘tile-rows’ option to 2.

frame-parallel

Enable frame parallel decodability features.

aq-mode

Set adaptive quantization mode (0: off (default), 1: variance 2: complexity, 3: cyclic refresh, 4: equator360).

colorspace color-space

Set input color space. The VP9 bitstream supports signaling the following colorspaces:

rgbsRGB
bt709bt709
unspecifiedunknown
bt470bgbt601
smpte170msmpte170
smpte240msmpte240
bt2020_nclbt2020
row-mt boolean

Enable row based multi-threading.

For more information about libvpx see: http://www.webmproject.org/


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3.7 libwebp

libwebp WebP Image encoder wrapper

libwebp is Google’s official encoder for WebP images. It can encode in either lossy or lossless mode. Lossy images are essentially a wrapper around a VP8 frame. Lossless images are a separate codec developed by Google.


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3.7.1 Pixel Format

Currently, libwebp only supports YUV420 for lossy and RGB for lossless due to limitations of the format and libwebp. Alpha is supported for either mode. Because of API limitations, if RGB is passed in when encoding lossy or YUV is passed in for encoding lossless, the pixel format will automatically be converted using functions from libwebp. This is not ideal and is done only for convenience.


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3.7.2 Options

-lossless boolean

Enables/Disables use of lossless mode. Default is 0.

-compression_level integer

For lossy, this is a quality/speed tradeoff. Higher values give better quality for a given size at the cost of increased encoding time. For lossless, this is a size/speed tradeoff. Higher values give smaller size at the cost of increased encoding time. More specifically, it controls the number of extra algorithms and compression tools used, and varies the combination of these tools. This maps to the method option in libwebp. The valid range is 0 to 6. Default is 4.

-qscale float

For lossy encoding, this controls image quality, 0 to 100. For lossless encoding, this controls the effort and time spent at compressing more. The default value is 75. Note that for usage via libavcodec, this option is called global_quality and must be multiplied by FF_QP2LAMBDA.

-preset type

Configuration preset. This does some automatic settings based on the general type of the image.

none

Do not use a preset.

default

Use the encoder default.

picture

Digital picture, like portrait, inner shot

photo

Outdoor photograph, with natural lighting

drawing

Hand or line drawing, with high-contrast details

icon

Small-sized colorful images

text

Text-like


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3.8 libx264, libx264rgb

x264 H.264/MPEG-4 AVC encoder wrapper.

This encoder requires the presence of the libx264 headers and library during configuration. You need to explicitly configure the build with --enable-libx264.

libx264 supports an impressive number of features, including 8x8 and 4x4 adaptive spatial transform, adaptive B-frame placement, CAVLC/CABAC entropy coding, interlacing (MBAFF), lossless mode, psy optimizations for detail retention (adaptive quantization, psy-RD, psy-trellis).

Many libx264 encoder options are mapped to FFmpeg global codec options, while unique encoder options are provided through private options. Additionally the ‘x264opts’ and ‘x264-params’ private options allows one to pass a list of key=value tuples as accepted by the libx264 x264_param_parse function.

The x264 project website is at http://www.videolan.org/developers/x264.html.

The libx264rgb encoder is the same as libx264, except it accepts packed RGB pixel formats as input instead of YUV.


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3.8.1 Supported Pixel Formats

x264 supports 8- to 10-bit color spaces. The exact bit depth is controlled at x264’s configure time. FFmpeg only supports one bit depth in one particular build. In other words, it is not possible to build one FFmpeg with multiple versions of x264 with different bit depths.


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3.8.2 Options

The following options are supported by the libx264 wrapper. The x264-equivalent options or values are listed in parentheses for easy migration.

To reduce the duplication of documentation, only the private options and some others requiring special attention are documented here. For the documentation of the undocumented generic options, see @ref{codec-options,,the Codec Options chapter}.

To get a more accurate and extensive documentation of the libx264 options, invoke the command x264 --fullhelp or consult the libx264 documentation.

b (bitrate)

Set bitrate in bits/s. Note that FFmpeg’s ‘b’ option is expressed in bits/s, while x264’s ‘bitrate’ is in kilobits/s.

bf (bframes)
g (keyint)
qmin (qpmin)

Minimum quantizer scale.

qmax (qpmax)

Maximum quantizer scale.

qdiff (qpstep)

Maximum difference between quantizer scales.

qblur (qblur)

Quantizer curve blur

qcomp (qcomp)

Quantizer curve compression factor

refs (ref)

Number of reference frames each P-frame can use. The range is from 0-16.

sc_threshold (scenecut)

Sets the threshold for the scene change detection.

trellis (trellis)

Performs Trellis quantization to increase efficiency. Enabled by default.

nr (nr)
me_range (merange)

Maximum range of the motion search in pixels.

me_method (me)

Set motion estimation method. Possible values in the decreasing order of speed:

dia (dia)
epzs (dia)

Diamond search with radius 1 (fastest). ‘epzs’ is an alias for ‘dia’.

hex (hex)

Hexagonal search with radius 2.

umh (umh)

Uneven multi-hexagon search.

esa (esa)

Exhaustive search.

tesa (tesa)

Hadamard exhaustive search (slowest).

forced-idr

Normally, when forcing a I-frame type, the encoder can select any type of I-frame. This option forces it to choose an IDR-frame.

subq (subme)

Sub-pixel motion estimation method.

b_strategy (b-adapt)

Adaptive B-frame placement decision algorithm. Use only on first-pass.

keyint_min (min-keyint)

Minimum GOP size.

coder

Set entropy encoder. Possible values:

ac

Enable CABAC.

vlc

Enable CAVLC and disable CABAC. It generates the same effect as x264’s ‘--no-cabac’ option.

cmp

Set full pixel motion estimation comparison algorithm. Possible values:

chroma

Enable chroma in motion estimation.

sad

Ignore chroma in motion estimation. It generates the same effect as x264’s ‘--no-chroma-me’ option.

threads (threads)

Number of encoding threads.

thread_type

Set multithreading technique. Possible values:

slice

Slice-based multithreading. It generates the same effect as x264’s ‘--sliced-threads’ option.

frame

Frame-based multithreading.

flags

Set encoding flags. It can be used to disable closed GOP and enable open GOP by setting it to -cgop. The result is similar to the behavior of x264’s ‘--open-gop’ option.

rc_init_occupancy (vbv-init)
preset (preset)

Set the encoding preset.

tune (tune)

Set tuning of the encoding params.

profile (profile)

Set profile restrictions.

fastfirstpass

Enable fast settings when encoding first pass, when set to 1. When set to 0, it has the same effect of x264’s ‘--slow-firstpass’ option.

crf (crf)

Set the quality for constant quality mode.

crf_max (crf-max)

In CRF mode, prevents VBV from lowering quality beyond this point.

qp (qp)

Set constant quantization rate control method parameter.

aq-mode (aq-mode)

Set AQ method. Possible values:

none (0)

Disabled.

variance (1)

Variance AQ (complexity mask).

autovariance (2)

Auto-variance AQ (experimental).

aq-strength (aq-strength)

Set AQ strength, reduce blocking and blurring in flat and textured areas.

psy

Use psychovisual optimizations when set to 1. When set to 0, it has the same effect as x264’s ‘--no-psy’ option.

psy-rd (psy-rd)

Set strength of psychovisual optimization, in psy-rd:psy-trellis format.

rc-lookahead (rc-lookahead)

Set number of frames to look ahead for frametype and ratecontrol.

weightb

Enable weighted prediction for B-frames when set to 1. When set to 0, it has the same effect as x264’s ‘--no-weightb’ option.

weightp (weightp)

Set weighted prediction method for P-frames. Possible values:

none (0)

Disabled

simple (1)

Enable only weighted refs

smart (2)

Enable both weighted refs and duplicates

ssim (ssim)

Enable calculation and printing SSIM stats after the encoding.

intra-refresh (intra-refresh)

Enable the use of Periodic Intra Refresh instead of IDR frames when set to 1.

avcintra-class (class)

Configure the encoder to generate AVC-Intra. Valid values are 50,100 and 200

bluray-compat (bluray-compat)

Configure the encoder to be compatible with the bluray standard. It is a shorthand for setting "bluray-compat=1 force-cfr=1".

b-bias (b-bias)

Set the influence on how often B-frames are used.

b-pyramid (b-pyramid)

Set method for keeping of some B-frames as references. Possible values:

none (none)

Disabled.

strict (strict)

Strictly hierarchical pyramid.

normal (normal)

Non-strict (not Blu-ray compatible).

mixed-refs

Enable the use of one reference per partition, as opposed to one reference per macroblock when set to 1. When set to 0, it has the same effect as x264’s ‘--no-mixed-refs’ option.

8x8dct

Enable adaptive spatial transform (high profile 8x8 transform) when set to 1. When set to 0, it has the same effect as x264’s ‘--no-8x8dct’ option.

fast-pskip

Enable early SKIP detection on P-frames when set to 1. When set to 0, it has the same effect as x264’s ‘--no-fast-pskip’ option.

aud (aud)

Enable use of access unit delimiters when set to 1.

mbtree

Enable use macroblock tree ratecontrol when set to 1. When set to 0, it has the same effect as x264’s ‘--no-mbtree’ option.

deblock (deblock)

Set loop filter parameters, in alpha:beta form.

cplxblur (cplxblur)

Set fluctuations reduction in QP (before curve compression).

partitions (partitions)

Set partitions to consider as a comma-separated list of. Possible values in the list:

p8x8

8x8 P-frame partition.

p4x4

4x4 P-frame partition.

b8x8

4x4 B-frame partition.

i8x8

8x8 I-frame partition.

i4x4

4x4 I-frame partition. (Enabling ‘p4x4’ requires ‘p8x8’ to be enabled. Enabling ‘i8x8’ requires adaptive spatial transform (‘8x8dct’ option) to be enabled.)

none (none)

Do not consider any partitions.

all (all)

Consider every partition.

direct-pred (direct)

Set direct MV prediction mode. Possible values:

none (none)

Disable MV prediction.

spatial (spatial)

Enable spatial predicting.

temporal (temporal)

Enable temporal predicting.

auto (auto)

Automatically decided.

slice-max-size (slice-max-size)

Set the limit of the size of each slice in bytes. If not specified but RTP payload size (‘ps’) is specified, that is used.

stats (stats)

Set the file name for multi-pass stats.

nal-hrd (nal-hrd)

Set signal HRD information (requires ‘vbv-bufsize’ to be set). Possible values:

none (none)

Disable HRD information signaling.

vbr (vbr)

Variable bit rate.

cbr (cbr)

Constant bit rate (not allowed in MP4 container).

x264opts (N.A.)

Set any x264 option, see x264 --fullhelp for a list.

Argument is a list of key=value couples separated by ":". In filter and psy-rd options that use ":" as a separator themselves, use "," instead. They accept it as well since long ago but this is kept undocumented for some reason.

For example to specify libx264 encoding options with ffmpeg:

ffmpeg -i foo.mpg -c:v libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv
a53cc boolean

Import closed captions (which must be ATSC compatible format) into output. Only the mpeg2 and h264 decoders provide these. Default is 1 (on).

x264-params (N.A.)

Override the x264 configuration using a :-separated list of key=value parameters.

This option is functionally the same as the ‘x264opts’, but is duplicated for compatibility with the Libav fork.

For example to specify libx264 encoding options with ffmpeg:

ffmpeg -i INPUT -c:v libx264 -x264-params level=30:bframes=0:weightp=0:\
cabac=0:ref=1:vbv-maxrate=768:vbv-bufsize=2000:analyse=all:me=umh:\
no-fast-pskip=1:subq=6:8x8dct=0:trellis=0 OUTPUT

Encoding ffpresets for common usages are provided so they can be used with the general presets system (e.g. passing the ‘pre’ option).


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3.9 libx265

x265 H.265/HEVC encoder wrapper.

This encoder requires the presence of the libx265 headers and library during configuration. You need to explicitly configure the build with ‘--enable-libx265’.


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3.9.1 Options

preset

Set the x265 preset.

tune

Set the x265 tune parameter.

forced-idr

Normally, when forcing a I-frame type, the encoder can select any type of I-frame. This option forces it to choose an IDR-frame.

x265-params

Set x265 options using a list of key=value couples separated by ":". See x265 --help for a list of options.

For example to specify libx265 encoding options with ‘-x265-params’:

ffmpeg -i input -c:v libx265 -x265-params crf=26:psy-rd=1 output.mp4

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3.10 libxvid

Xvid MPEG-4 Part 2 encoder wrapper.

This encoder requires the presence of the libxvidcore headers and library during configuration. You need to explicitly configure the build with --enable-libxvid --enable-gpl.

The native mpeg4 encoder supports the MPEG-4 Part 2 format, so users can encode to this format without this library.


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3.10.1 Options

The following options are supported by the libxvid wrapper. Some of the following options are listed but are not documented, and correspond to shared codec options. See @ref{codec-options,,the Codec Options chapter} for their documentation. The other shared options which are not listed have no effect for the libxvid encoder.

b
g
qmin
qmax
mpeg_quant
threads
bf
b_qfactor
b_qoffset
flags

Set specific encoding flags. Possible values:

mv4

Use four motion vector by macroblock.

aic

Enable high quality AC prediction.

gray

Only encode grayscale.

gmc

Enable the use of global motion compensation (GMC).

qpel

Enable quarter-pixel motion compensation.

cgop

Enable closed GOP.

global_header

Place global headers in extradata instead of every keyframe.

trellis
me_method

Set motion estimation method. Possible values in decreasing order of speed and increasing order of quality:

zero

Use no motion estimation (default).

phods
x1
log

Enable advanced diamond zonal search for 16x16 blocks and half-pixel refinement for 16x16 blocks. ‘x1’ and ‘log’ are aliases for ‘phods’.

epzs

Enable all of the things described above, plus advanced diamond zonal search for 8x8 blocks, half-pixel refinement for 8x8 blocks, and motion estimation on chroma planes.

full

Enable all of the things described above, plus extended 16x16 and 8x8 blocks search.

mbd

Set macroblock decision algorithm. Possible values in the increasing order of quality:

simple

Use macroblock comparing function algorithm (default).

bits

Enable rate distortion-based half pixel and quarter pixel refinement for 16x16 blocks.

rd

Enable all of the things described above, plus rate distortion-based half pixel and quarter pixel refinement for 8x8 blocks, and rate distortion-based search using square pattern.

lumi_aq

Enable lumi masking adaptive quantization when set to 1. Default is 0 (disabled).

variance_aq

Enable variance adaptive quantization when set to 1. Default is 0 (disabled).

When combined with ‘lumi_aq’, the resulting quality will not be better than any of the two specified individually. In other words, the resulting quality will be the worse one of the two effects.

ssim

Set structural similarity (SSIM) displaying method. Possible values:

off

Disable displaying of SSIM information.

avg

Output average SSIM at the end of encoding to stdout. The format of showing the average SSIM is:

Average SSIM: %f

For users who are not familiar with C, %f means a float number, or a decimal (e.g. 0.939232).

frame

Output both per-frame SSIM data during encoding and average SSIM at the end of encoding to stdout. The format of per-frame information is:

       SSIM: avg: %1.3f min: %1.3f max: %1.3f

For users who are not familiar with C, %1.3f means a float number rounded to 3 digits after the dot (e.g. 0.932).

ssim_acc

Set SSIM accuracy. Valid options are integers within the range of 0-4, while 0 gives the most accurate result and 4 computes the fastest.


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3.11 mpeg2

MPEG-2 video encoder.


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3.11.1 Options

seq_disp_ext integer

Specifies if the encoder should write a sequence_display_extension to the output.

-1
auto

Decide automatically to write it or not (this is the default) by checking if the data to be written is different from the default or unspecified values.

0
never

Never write it.

1
always

Always write it.


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3.12 png

PNG image encoder.


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3.12.1 Private options

dpi integer

Set physical density of pixels, in dots per inch, unset by default

dpm integer

Set physical density of pixels, in dots per meter, unset by default


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3.13 ProRes

Apple ProRes encoder.

FFmpeg contains 2 ProRes encoders, the prores-aw and prores-ks encoder. The used encoder can be chosen with the -vcodec option.


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3.13.1 Private Options for prores-ks

profile integer

Select the ProRes profile to encode

proxy
lt
standard
hq
4444
4444xq
quant_mat integer

Select quantization matrix.

auto
default
proxy
lt
standard
hq

If set to auto, the matrix matching the profile will be picked. If not set, the matrix providing the highest quality, default, will be picked.

bits_per_mb integer

How many bits to allot for coding one macroblock. Different profiles use between 200 and 2400 bits per macroblock, the maximum is 8000.

mbs_per_slice integer

Number of macroblocks in each slice (1-8); the default value (8) should be good in almost all situations.

vendor string

Override the 4-byte vendor ID. A custom vendor ID like apl0 would claim the stream was produced by the Apple encoder.

alpha_bits integer

Specify number of bits for alpha component. Possible values are 0, 8 and 16. Use 0 to disable alpha plane coding.


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3.13.2 Speed considerations

In the default mode of operation the encoder has to honor frame constraints (i.e. not produce frames with size bigger than requested) while still making output picture as good as possible. A frame containing a lot of small details is harder to compress and the encoder would spend more time searching for appropriate quantizers for each slice.

Setting a higher ‘bits_per_mb’ limit will improve the speed.

For the fastest encoding speed set the ‘qscale’ parameter (4 is the recommended value) and do not set a size constraint.


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3.14 QSV encoders

The family of Intel QuickSync Video encoders (MPEG-2, H.264 and HEVC)

The ratecontrol method is selected as follows:

Note that depending on your system, a different mode than the one you specified may be selected by the encoder. Set the verbosity level to verbose or higher to see the actual settings used by the QSV runtime.

Additional libavcodec global options are mapped to MSDK options as follows:


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3.15 snow


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3.15.1 Options

iterative_dia_size

dia size for the iterative motion estimation


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3.16 VAAPI encoders

Wrappers for hardware encoders accessible via VAAPI.

These encoders only accept input in VAAPI hardware surfaces. If you have input in software frames, use the ‘hwupload’ filter to upload them to the GPU.

The following standard libavcodec options are used:

h264_vaapi

profile’ sets the value of profile_idc and the constraint_set*_flags. ‘level’ sets the value of level_idc.

low_power

Use low-power encoding mode.

coder

Set entropy encoder (default is cabac). Possible values:

ac
cabac

Use CABAC.

vlc
cavlc

Use CAVLC.

hevc_vaapi

profile’ and ‘level’ set the values of general_profile_idc and general_level_idc respectively.

mjpeg_vaapi

Always encodes using the standard quantisation and huffman tables - ‘global_quality’ scales the standard quantisation table (range 1-100).

mpeg2_vaapi

profile’ and ‘level’ set the value of profile_and_level_indication.

No rate control is supported.

vp8_vaapi

B-frames are not supported.

global_quality’ sets the q_idx used for non-key frames (range 0-127).

loop_filter_level
loop_filter_sharpness

Manually set the loop filter parameters.

vp9_vaapi

global_quality’ sets the q_idx used for P-frames (range 0-255).

loop_filter_level
loop_filter_sharpness

Manually set the loop filter parameters.

B-frames are supported, but the output stream is always in encode order rather than display order. If B-frames are enabled, it may be necessary to use the ‘vp9_raw_reorder’ bitstream filter to modify the output stream to display frames in the correct order.

Only normal frames are produced - the ‘vp9_superframe’ bitstream filter may be required to produce a stream usable with all decoders.


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3.17 vc2

SMPTE VC-2 (previously BBC Dirac Pro). This codec was primarily aimed at professional broadcasting but since it supports yuv420, yuv422 and yuv444 at 8 (limited range or full range), 10 or 12 bits, this makes it suitable for other tasks which require low overhead and low compression (like screen recording).


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3.17.1 Options

b

Sets target video bitrate. Usually that’s around 1:6 of the uncompressed video bitrate (e.g. for 1920x1080 50fps yuv422p10 that’s around 400Mbps). Higher values (close to the uncompressed bitrate) turn on lossless compression mode.

field_order

Enables field coding when set (e.g. to tt - top field first) for interlaced inputs. Should increase compression with interlaced content as it splits the fields and encodes each separately.

wavelet_depth

Sets the total amount of wavelet transforms to apply, between 1 and 5 (default). Lower values reduce compression and quality. Less capable decoders may not be able to handle values of ‘wavelet_depth’ over 3.

wavelet_type

Sets the transform type. Currently only 5_3 (LeGall) and 9_7 (Deslauriers-Dubuc) are implemented, with 9_7 being the one with better compression and thus is the default.

slice_width
slice_height

Sets the slice size for each slice. Larger values result in better compression. For compatibility with other more limited decoders use ‘slice_width’ of 32 and ‘slice_height’ of 8.

tolerance

Sets the undershoot tolerance of the rate control system in percent. This is to prevent an expensive search from being run.

qm

Sets the quantization matrix preset to use by default or when ‘wavelet_depth’ is set to 5


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4 Subtitles Encoders


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4.1 dvdsub

This codec encodes the bitmap subtitle format that is used in DVDs. Typically they are stored in VOBSUB file pairs (*.idx + *.sub), and they can also be used in Matroska files.


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4.1.1 Options

even_rows_fix

When set to 1, enable a work-around that makes the number of pixel rows even in all subtitles. This fixes a problem with some players that cut off the bottom row if the number is odd. The work-around just adds a fully transparent row if needed. The overhead is low, typically one byte per subtitle on average.

By default, this work-around is disabled.


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