Cabac codec

Features Overview Provides best-in-class performance, compression, and features. Achieves dramatic performance, encoding 4 or more p streams in realtime on a single consumer-level computer. Gives the best quality, having the most advanced psychovisual optimizations. The shineenc -equivalent of the options are listed in parentheses. Requires the presence of the libtwolame headers and library during configuration. You need to explicitly configure the build with --enable-libtwolame.

The following options are supported by the libtwolame wrapper. The twolame -equivalent options follow the FFmpeg ones and are in parentheses. Default value is k. Set quality for experimental VBR support.

Maximum value range is from to 50, useful range is from to The higher the value, the better the quality. Set psychoacoustic model to use in encoding.

The argument must be an integer between -1 and 4, inclusive. The default value is 3. 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. Requires the presence of the libvorbisenc headers and library during configuration.

You need to explicitly configure the build with --enable-libvorbis. The following options are supported by the libvorbis wrapper. The oggenc -equivalent of the options are listed in parentheses.

The value should be a float number in the range of Set cutoff bandwidth in Hz, a value of 0 disables cutoff. This only has effect on ABR mode. Set noise floor bias for impulse blocks. The value is a float number from 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. 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 the Codec Options chapter. For this encoder, the range for this option is between and Default is automatically decided based on sample rate and number of channel. Set whether to enable optimization for mono. This option is only effective for non-mono streams. Available values:. If disabled, every frame will always have a palette written, even if there is a global palette supplied.

Specifies the number of chunks to split frames into, between 1 and This permits multithreaded decoding of large frames, potentially at the cost of data-rate. The encoder may modify this value to divide frames evenly. Specifies the second-stage compressor to use. If set to none , chunks will be limited to 1, as chunked uncompressed frames offer no benefit.

The native jpeg 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. By default, when this option is not used, compression is done using the quality metric. This option allows for compression using compression ratio. The compression ratio for each level could be specified. The compression ratio of a layer l species the what ratio of total file size is contained in the first l layers.

This would compress the image to contain 3 layers, where the data contained in the first layer would be compressed by times, compressed by in the first two layers, and shall contain all data while using all 3 layers. Requires the presence of the rav1e headers and library during configuration. You need to explicitly configure the build with --enable-librav1e.

See rav1e --help for a list of options. Requires the presence of the libaom headers and library during configuration. You need to explicitly configure the build with --enable-libaom. By default this will use variable-bitrate mode. If maxrate and minrate are also set to the same value then it will use constant-bitrate mode, otherwise if crf is set as well then it will use constrained-quality mode.

Set key frame placement. The GOP size sets the maximum distance between key frames; if zero the output stream will be intra-only. The minimum distance is ignored unless it is the same as the GOP size, in which case key frames will always appear at a fixed interval.

Not set by default, so without this option the library has completely free choice about where to place key frames. Valid range is from 0 to 63 warning: this does not match the quantiser values actually used by AV1 - divide by four to map real quantiser values to this range. Set rate control buffering parameters. Not used if not set - defaults to unconstrained variable bitrate. Set the number of threads to use while encoding. This may require the tiles or row-mt options to also be set to actually use the specified number of threads fully.

Defaults to the number of hardware threads supported by the host machine. Set the encoding profile. Defaults to using the profile which matches the bit depth and chroma subsampling of the input. Valid range is from 0 to 8, higher numbers indicating greater speed and lower quality. The default value is 1, which will be slow and high quality. Set the maximum number of frames which the encoder may keep in flight at any one time for lookahead purposes.

Valid range is 0 to 63, higher numbers indicating lower quality and smaller output size. Only used if set; by default only the bitrate target is used. Set a change threshold on blocks below which they will be skipped by the encoder. Defined in arbitrary units as a nonnegative integer, defaulting to zero no blocks are skipped. Set a threshold for dropping frames when close to rate control bounds.

Defined as a percentage of the target buffer - when the rate control buffer falls below this percentage, frames will be dropped until it has refilled above the threshold. Defaults to zero no frames are dropped. Amount of noise to be removed for grain synthesis.

Grain synthesis is disabled if this option is not set or set to 0. Block size used for denoising for grain synthesis. If not set, AV1 codec uses the default value of Set datarate undershoot min percentage of the target bitrate. Range is -1 to Default is Set datarate overshoot max percentage of the target bitrate. Minimum percentage variation of the GOP bitrate from the target bitrate.

Default is -1 unset. Maximum percentage variation of the GOP bitrate from the target bitrate. Set the number of tiles to encode the input video with, as columns x rows. Larger numbers allow greater parallelism in both encoding and decoding, but may decrease coding efficiency. Defaults to the minimum number of tiles required by the size of the input video this is 1x1 that is, a single tile for sizes up to and including 4K. Set the number of tiles as log2 of the number of tile rows and columns.

Enable Constrained Directional Enhancement Filter. The libaom-av1 encoder enables CDEF by default. Enable block copy mode for intra block prediction.

This mode is useful for screen content. Default is true. For a list of supported options, see aomenc --help under the section "AV1 Specific Options". You need to explicitly configure the build with --enable-libsvtav1. Constant quantizer: use fixed values of qindex dependent on the frame type throughout the stream. This mode is the default. Set the quality-speed tradeoff, in the range 0 to 8. Higher values are faster but lower quality. Defaults to 8 highest speed. Requires the presence of the libkvazaar headers and library during configuration.

You need to explicitly configure the build with --enable-libkvazaar. See kvazaar documentation for a list of options.

This encoder requires the presence of the libopenh headers and library during configuration. You need to explicitly configure the build with --enable-libopenh The library is detected using pkg-config. Set the number of slices, used in parallelized encoding. Set profile restrictions. Requires the presence of the libtheora headers and library during configuration. You need to explicitly configure the build with --enable-libtheora.

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

Used to enable constant quality mode VBR encoding through the qscale flag, and to enable the pass1 and pass2 modes. A higher value corresponds to a higher quality. 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 [] range, and then multiplied by 6. Requires the presence of the libvpx headers and library during configuration. You need to explicitly configure the build with --enable-libvpx.

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 the Codec Options chapter. Further information is available in the libvpx API documentation.

Set ratecontrol buffer size in bits. Set number of bits which should be loaded into the rc buffer before decoding starts. Use best quality deadline. Poorly named and quite slow, this option should be avoided as it may give worse quality output than good.

Use good quality deadline. This is a good trade-off between speed and quality when used with the cpu-used option. Enable use of alternate reference frames 2-pass only. Values greater than 1 enable multi-layer alternate reference frames VP9 only. For example, to specify temporal scalability parameters with ffmpeg :. Professor Richardson leads an internationally renowned image and video coding research team, contributes to the MPEG industry standards group and is sought after as an expert witness and litigation consultant.

Toggle navigation. Coding a data symbol involves the following stages. A non-binary-valued symbol e. This process is similar to the process of converting a data symbol into a variable length code but the binary code is further encoded by the arithmetic coder prior to transmission. This model may be chosen from a selection of available models depending on the statistics of recently-coded data symbols.

Arithmetic encoding: An arithmetic coder encodes each bin according to the selected probability model. The private data is void??? Corresponding ACM wFormatTag : 0x ; channel number have to be read from the corresponding audio element. Description: The ac3 frame header has, similar to the mpeg-audio header a version field. Normal ac3 is defined as bitstream id 8 5 Bits, numbers are Everything below 8 is still compatible with all decoders that handle 8 correctly.

Everything higher are additions that break decoder compatibility. The private data is void. Description: DTS Express a. LBR audio streams. Description: DTS Lossless audio that does not have a core substream. Initialization: The Private Data contains the first three Vorbis packet in order.

These include the first header packet containing only the word fLaC as well as all metadata packets. Description: Channel number and sample rate have to be read from the corresponding audio element. The header and seektable are dropped. Description: The Wavpack packets consist of a stripped header followed by the frame data. For more details, check the WavPack muxing description. Each event is stored in its own Block.

The timestamp in the block header of Matroska indicates the start display time, the duration is set with the Duration element. Description: This is the graphical subtitle format used in the Digital Video Broadcasting standard.