A Codec Mapping is a set of attributes to identify, name, and contextualise the format and characteristics of encoded data that can be contained within Matroska Clusters.
Each TrackEntry used within Matroska MUST reference a defined Codec Mapping using the Codec ID to identify and describe the format of the encoded data in its associated Clusters. This Codec ID is a unique registered identifier that represents the encoding stored within the Track. Certain encodings MAY also require some form of codec initialisation in order to provide its decoder with context and technical metadata.
The intention behind this list is not to list all existing audio and video codecs, but rather to list those codecs that are currently supported in Matroska and therefore need a well defined Codec ID so that all developers supporting Matroska will use the same Codec ID. If you feel we missed support for a very important codec, please tell us on our development mailing list (cellar at ietf.org).
Support for a codec is defined in Matroska with the following values.
Each codec supported for storage in Matroska MUST have a unique Codec ID. Each Codec ID MUST be prefixed with the string from the following table according to the associated type of the codec. All characters of a Codec ID Prefix MUST be capital letters (A-Z) except for the last character of a Codec ID Prefix which MUST be an underscore ("_").
| Codec Type | Codec ID Prefix |
|---|---|
| Video | "V_" |
| Audio | "A_" |
| Subtitle | "S_" |
| Button | "B_" |
Each Codec ID MUST include a Major Codec ID immediately following the Codec ID Prefix. A Major Codec ID MAY be followed by an OPTIONAL Codec ID Suffix to communicate a refinement of the Major Codec ID. If a Codec ID Suffix is used, then the Codec ID MUST include a forward slash ("/") as a separator between the Major Codec ID and the Codec ID Suffix. The Major Codec ID MUST be composed of only capital letters (A-Z) and numbers (0-9). The Codec ID Suffix MUST be composed of only capital letters (A-Z), numbers (0-9), underscore ("_"), and forward slash ("/").
The following table provides examples of valid Codec IDs and their components:
| Codec ID Prefix | Major Codec ID | Separator | Codec ID Suffix | Codec ID |
|---|---|---|---|---|
| A_ | AAC | / | MPEG2/LC/SBR | A_AAC/MPEG2/LC/SBR |
| V_ | MPEG4 | / | ISO/ASP | V_MPEG4/ISO/ASP |
| V_ | MPEG1 | V_MPEG1 |
Each encoding supported for storage in Matroska MUST have a Codec Name. The Codec Name provides a readable label for the encoding.
An optional description for the encoding. This value is only intended for human consumption.
Each encoding supported for storage in Matroska MUST have a defined Initialisation. The Initialisation MUST describe the storage of data necessary to initialise the decoder, which MUST be stored within the CodecPrivate Element. When the Initialisation is updated within a track then that updated Initialisation data MUST be written into the CodecState Element of the first Cluster to require it. If the encoding does not require any form of Initialisation then none MUST be used to define the Initialisation and the CodecPrivate Element SHOULD NOT be written and MUST be ignored. Data that is defined Initialisation to be stored in the CodecPrivate Element is known as Private Data.
Documentation of the associated normative and informative references for the codec is RECOMMENDED.
A timestamp, expressed in [@!RFC3339] that notes when support for the Codec Mapping within Matroska was deprecated. If a Codec Mapping is defined with a Deprecation Date, then it is RECOMMENDED that Matroska writers SHOULD NOT use the Codec Mapping after the Deprecation Date.
A Codec Mapping MAY only be defined with a Superseded By value, if it has an expressed Deprecation Date. If used, the Superseded By value MUST store the Codec ID of another Codec Mapping that has superseded the Codec Mapping.
Codec ID: V_MS/VFW/FOURCC
Codec Name: Microsoft (TM) Video Codec Manager (VCM)
Description: The private data contains the VCM structure BITMAPINFOHEADER including the extra private bytes, as defined by Microsoft. The data are stored in little endian format (like on IA32 machines). Where is the Huffman table stored in HuffYUV, not AVISTREAMINFO ??? And the FourCC, not in AVISTREAMINFO.fccHandler ???
Initialisation: Private Data contains the VCM structure BITMAPINFOHEADER including the extra private bytes, as defined by Microsoft in https://msdn.microsoft.com/en-us/library/windows/desktop/dd183376(v=vs.85).aspx.
Citation: https://msdn.microsoft.com/en-us/library/windows/desktop/dd183376(v=vs.85).aspx
Codec ID: V_UNCOMPRESSED
Codec Name: Video, raw uncompressed video frames
Description: All details about the used colour specs and bit depth are to be put/read from the KaxCodecColourSpace elements.
Initialisation: none
Codec ID: V_MPEG4/ISO/SP
Codec Name: MPEG4 ISO simple profile (DivX4)
Description: Stream was created via improved codec API (UCI) or even transmuxed from AVI (no b-frames in Simple Profile), frame order is coding order.
Initialisation: none
Codec ID: V_MPEG4/ISO/ASP
Codec Name: MPEG4 ISO advanced simple profile (DivX5, XviD, FFMPEG)
Description: Stream was created via improved codec API (UCI) or transmuxed from MP4, not simply transmuxed from AVI. Note there are differences how b-frames are handled in these native streams, when being compared to a VfW created stream, as here there are no dummy frames inserted, the frame order is exactly the same as the coding order, same as in MP4 streams.
Initialisation: none
Codec ID: V_MPEG4/ISO/AP
Codec Name: MPEG4 ISO advanced profile
Description: Stream was created via improved codec API (UCI) or transmuxed from MP4, not simply transmuxed from AVI. Note there are differences how b-frames are handled in these native streams, when being compared to a VfW created stream, as here there are no dummy frames inserted, the frame order is exactly the same as the coding order, same as in MP4 streams.
Initialisation: none
Codec ID: V_MPEG4/MS/V3
Codec Name: Microsoft (TM) MPEG4 V3
Description: Microsoft (TM) MPEG4 V3 and derivates, means DivX3, Angelpotion, SMR, etc.; stream was created using VfW codec or transmuxed from AVI; note that V1/V2 are covered in VfW compatibility mode.
Initialisation: none
Codec ID: V_MPEG1
Codec Name: MPEG 1
Description: The Matroska video stream will contain a demuxed Elementary Stream (ES), where block boundaries are still to be defined. Its RECOMMENDED to use MPEG2MKV.exe for creating those files, and to compare the results with self-made implementations
Initialisation: none
Codec ID: V_MPEG2
Codec Name: MPEG 2
Description: The Matroska video stream will contain a demuxed Elementary Stream (ES), where block boundaries are still to be defined. Its RECOMMENDED to use MPEG2MKV.exe for creating those files, and to compare the results with self-made implementations
Initialisation: none
Codec ID: V_REAL/RV10
Codec Name: RealVideo 1.0 aka RealVideo 5
Description: Individual slices from the Real container are combined into a single frame.
Initialisation: The Private Data contains a real_video_props_t structure in Big Endian byte order as found in librmff.
Codec ID: V_REAL/RV20
Codec Name: RealVideo G2 and RealVideo G2+SVT
Description: Individual slices from the Real container are combined into a single frame.
Initialisation: The Private Data contains a real_video_props_t structure in Big Endian byte order as found in librmff.
Codec ID: V_REAL/RV30
Codec Name: RealVideo 8
Description: Individual slices from the Real container are combined into a single frame.
Initialisation: The Private Data contains a real_video_props_t structure in Big Endian byte order as found in librmff.
Codec ID: V_REAL/RV40
Codec Name: rv40 : RealVideo 9
Description: Individual slices from the Real container are combined into a single frame.
Initialisation: The Private Data contains a real_video_props_t structure in Big Endian byte order as found in librmff.
Codec ID: V_QUICKTIME
Codec Name: Video taken from QuickTime(TM) files
Description: Several codecs as stored in QuickTime, e.g. Sorenson or Cinepak.
Initialisation: The Private Data contains all additional data that is stored in the 'stsd' (sample description) atom in the QuickTime file after the mandatory video descriptor structure (starting with the size and FourCC fields). For an explanation of the QuickTime file format read QuickTime File Format Specification.
Codec ID: V_THEORA
Codec Name: Theora
Initialisation: The Private Data contains the first three Theora packets in order. The lengths of the packets precedes them. The actual layout is:
- Byte 1: number of distinct packets '
#p' minus one inside the CodecPrivate block. This MUST be '2' for current (as of 2016-07-08) Theora headers. - Bytes 2..n: lengths of the first '
#p' packets, coded in Xiph-style lacing. The length of the last packet is the length of the CodecPrivate block minus the lengths coded in these bytes minus one. - Bytes n+1..: The Theora identification header, followed by the commend header followed by the codec setup header. Those are described in the Theora specs.
Codec ID: V_PRORES
Codec Name: Apple ProRes
Initialisation: The Private Data contains the fourcc as found in MP4 movies:
- ap4x: ProRes 4444 XQ
- ap4h: ProRes 4444
- apch: ProRes 422 High Quality
- apcn: ProRes 422 Standard Definition
- apcs: ProRes 422 LT
- apco: ProRes 422 Proxy
this page for more technical details on ProRes
Codec ID: V_VP8
Codec Name: VP8 Codec format
Description: VP8 is an open and royalty free video compression format developed by Google and created by On2 Technologies as a successor to VP7. [@!RFC6386]
Initialisation: none
Codec ID: V_VP9
Codec Name: VP9 Codec format
Description: VP9 is an open and royalty free video compression format developed by Google as a successor to VP8. Draft VP9 Bitstream and Decoding Process Specification
Initialisation: none
Codec ID: V_FFV1
Codec Name: FF Video Codec 1
Description: FFV1 is a lossless intra-frame video encoding format designed to efficiently compress video data in a variety of pixel formats. Compared to uncompressed video, FFV1 offers storage compression, frame fixity, and self-description, which makes FFV1 useful as a preservation or intermediate video format. Draft FFV1 Specification
Initialisation: For FFV1 versions 0 or 1, Private Data SHOULD NOT be written. For FFV1 version 3 or greater, the Private Data MUST contain the FFV1 Configuration Record structure, as defined in https://tools.ietf.org/html/draft-niedermayer-cellar-ffv1-01#section-4.1, and no other data.
Codec ID: A_MPEG/L3
Codec Name: MPEG Audio 1, 2, 2.5 Layer III
Description: The data contain everything needed for playback in the MPEG Audio header of each frame. Corresponding ACM wFormatTag : 0x0055
Initialisation: none
Codec ID: A_MPEG/L2
Codec Name: MPEG Audio 1, 2 Layer II
Description: The data contain everything needed for playback in the MPEG Audio header of each frame. Corresponding ACM wFormatTag : 0x0050
Initialisation: none
Codec ID: A_MPEG/L1
Codec Name: MPEG Audio 1, 2 Layer I
Description: The data contain everything needed for playback in the MPEG Audio header of each frame. Corresponding ACM wFormatTag : 0x0050
Initialisation: none
Codec ID: A_PCM/INT/BIG
Codec Name: PCM Integer Big Endian
Description: The bitdepth has to be read and set from KaxAudioBitDepth element. Corresponding ACM wFormatTag : ???
Initialisation: none
Codec ID: A_PCM/INT/LIT
Codec Name: PCM Integer Little Endian
Description: The bitdepth has to be read and set from KaxAudioBitDepth element. Corresponding ACM wFormatTag : 0x0001
Initialisation: none
Codec ID: A_PCM/FLOAT/IEEE
Codec Name: Floating Point, IEEE compatible
Description: The bitdepth has to be read and set from KaxAudioBitDepth element (32 bit in most cases). The float are stored in little endian order (most common float format). Corresponding ACM wFormatTag : 0x0003
Initialisation: none
Codec ID: A_MPC
Codec Name: MPC (musepack) SV8
Description: The main developer for musepack has requested that we wait until the SV8 framing has been fully defined for musepack before defining how to store it in Matroska.
Codec ID: A_AC3
Codec Name: (Dolby™) AC3
Description: BSID <= 8 !! The private data is void ??? Corresponding ACM wFormatTag : 0x2000 ; channel number have to be read from the corresponding audio element
Codec ID: A_AC3/BSID9
Codec Name: (Dolby™) AC3
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 0-15). Everything below 8 is still compatible with all decoders that handle 8 correctly. Everything higher are additions that break decoder compatibility. For the samplerates 24kHz (00); 22,05kHz (01) and 16kHz (10) the BSID is 9 For the samplerates 12kHz (00); 11,025kHz (01) and 8kHz (10) the BSID is 10
Initialisation: none
Codec ID: A_AC3/BSID10
Codec Name: (Dolby™) AC3
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 0-15). Everything below 8 is still compatible with all decoders that handle 8 correctly. Everything higher are additions that break decoder compatibility. For the samplerates 24kHz (00); 22,05kHz (01) and 16kHz (10) the BSID is 9 For the samplerates 12kHz (00); 11,025kHz (01) and 8kHz (10) the BSID is 10
Initialisation: none
Codec ID: A_ALAC
Codec Name: ALAC (Apple Lossless Audio Codec)
Initialisation: The Private Data contains ALAC's magic cookie (both the codec specific configuration as well as the optional channel layout information). Its format is described in ALAC's official source code.
Codec ID: A_DTS
Codec Name: Digital Theatre System
Description: Supports DTS, DTS-ES, DTS-96/26, DTS-HD High Resolution Audio and DTS-HD Master Audio. The private data is void. Corresponding ACM wFormatTag : 0x2001
Initialisation: none
Codec ID: A_DTS/EXPRESS
Codec Name: Digital Theatre System Express
Description: DTS Express (a.k.a. LBR) audio streams. The private data is void. Corresponding ACM wFormatTag : 0x2001
Initialisation: none
Codec ID: A_DTS/LOSSLESS
Codec Name: Digital Theatre System Lossless
Description: DTS Lossless audio that does not have a core substream. The private data is void. Corresponding ACM wFormatTag : 0x2001
Initialisation: none
Codec ID: A_VORBIS
Codec Name: Vorbis
Initialisation: The Private Data contains the first three Vorbis packet in order. The lengths of the packets precedes them. The actual layout is:
- Byte 1: number of distinct packets '
#p' minus one inside the CodecPrivate block. This MUST be '2' for current (as of 2016-07-08) Vorbis headers. - Bytes 2..n: lengths of the first '
#p' packets, coded in Xiph-style lacing. The length of the last packet is the length of the CodecPrivate block minus the lengths coded in these bytes minus one. - Bytes n+1..: The Vorbis identification header, followed by the Vorbis comment header followed by the codec setup header.
Codec ID: A_FLAC
Codec Name: FLAC (Free Lossless Audio Codec)
Initialisation: The Private Data contains all the header/metadata packets before the first data packet. These include the first header packet containing only the word fLaC as well as all metadata packets.
Codec ID: A_REAL/14_4
Codec Name: Real Audio 1
Initialisation: The Private Data contains either the "real_audio_v4_props_t" or the "real_audio_v5_props_t" structure (differentiated by their "version" field; Big Endian byte order) as found in librmff.
Codec ID: A_REAL/28_8
Codec Name: Real Audio 2
Initialisation: The Private Data contains either the "real_audio_v4_props_t" or the "real_audio_v5_props_t" structure (differentiated by their "version" field; Big Endian byte order) as found in librmff.
Codec ID: A_REAL/COOK
Codec Name: Real Audio Cook Codec (codename: Gecko)
Initialisation: The Private Data contains either the "real_audio_v4_props_t" or the "real_audio_v5_props_t" structure (differentiated by their "version" field; Big Endian byte order) as found in librmff.
Codec ID: A_REAL/SIPR
Codec Name: Sipro Voice Codec
Initialisation: The Private Data contains either the "real_audio_v4_props_t" or the "real_audio_v5_props_t" structure (differentiated by their "version" field; Big Endian byte order) as found in librmff.
Codec ID: A_REAL/RALF
Codec Name: Real Audio Lossless Format
Initialisation: The Private Data contains either the "real_audio_v4_props_t" or the "real_audio_v5_props_t" structure (differentiated by their "version" field; Big Endian byte order) as found in librmff.
Codec ID: A_REAL/ATRC
Codec Name: Sony Atrac3 Codec
Initialisation: The Private Data contains either the "real_audio_v4_props_t" or the "real_audio_v5_props_t" structure (differentiated by their "version" field; Big Endian byte order) as found in librmff.
Codec ID: A_MS/ACM
Codec Name: Microsoft(TM) Audio Codec Manager (ACM)
Description: The data are stored in little endian format (like on IA32 machines).
Initialisation: The Private Data contains the ACM structure WAVEFORMATEX including the extra private bytes, as defined by Microsoft.
Codec ID: A_AAC/MPEG2/MAIN
Codec Name: MPEG2 Main Profile
Description: Channel number and sample rate have to be read from the corresponding audio element. Audio stream is stripped from ADTS headers and normal Matroska frame based muxing scheme is applied. AAC audio always uses wFormatTag 0xFF.
Initialisation: none
Codec ID: A_AAC/MPEG2/LC
Codec Name: Low Complexity
Description: Channel number and sample rate have to be read from the corresponding audio element. Audio stream is stripped from ADTS headers and normal Matroska frame based muxing scheme is applied. AAC audio always uses wFormatTag 0xFF.
Initialisation: none
Codec ID: A_AAC/MPEG2/LC/SBR
Codec Name: Low Complexity with Spectral Band Replication
Description: Channel number and sample rate have to be read from the corresponding audio element. Audio stream is stripped from ADTS headers and normal Matroska frame based muxing scheme is applied. AAC audio always uses wFormatTag 0xFF.
Initialisation: none
Codec ID: A_AAC/MPEG2/SSR
Codec Name: Scalable Sampling Rate
Description: Channel number and sample rate have to be read from the corresponding audio element. Audio stream is stripped from ADTS headers and normal Matroska frame based muxing scheme is applied. AAC audio always uses wFormatTag 0xFF.
Initialisation: none
Codec ID: A_AAC/MPEG4/MAIN
Codec Name: MPEG4 Main Profile
Description: Channel number and sample rate have to be read from the corresponding audio element. Audio stream is stripped from ADTS headers and normal Matroska frame based muxing scheme is applied. AAC audio always uses wFormatTag 0xFF.
Initialisation: none
Codec ID: A_AAC/MPEG4/LC
Codec Name: Low Complexity
Description: Channel number and sample rate have to be read from the corresponding audio element. Audio stream is stripped from ADTS headers and normal Matroska frame based muxing scheme is applied. AAC audio always uses wFormatTag 0xFF.
Initialisation: none
Codec ID: A_AAC/MPEG4/LC/SBR
Codec Name: Low Complexity with Spectral Band Replication
Description: Channel number and sample rate have to be read from the corresponding audio element. Audio stream is stripped from ADTS headers and normal Matroska frame based muxing scheme is applied. AAC audio always uses wFormatTag 0xFF.
Initialisation: none
Codec ID: A_AAC/MPEG4/SSR
Codec Name: Scalable Sampling Rate
Description: Channel number and sample rate have to be read from the corresponding audio element. Audio stream is stripped from ADTS headers and normal Matroska frame based muxing scheme is applied. AAC audio always uses wFormatTag 0xFF.
Initialisation: none
Codec ID: A_AAC/MPEG4/LTP
Codec Name: Long Term Prediction
Description: Channel number and sample rate have to be read from the corresponding audio element. Audio stream is stripped from ADTS headers and normal Matroska frame based muxing scheme is applied. AAC audio always uses wFormatTag 0xFF.
Initialisation: none
Codec ID: A_QUICKTIME
Codec Name: Audio taken from QuickTime(TM) files
Description: Several codecs as stored in QuickTime, e.g. QDesign Music v1 or v2.
Initialisation: The Private Data contains all additional data that is stored in the 'stsd' (sample description) atom in the QuickTime file after the mandatory sound descriptor structure (starting with the size and FourCC fields). For an explanation of the QuickTime file format read QuickTime File Format Specification.
Codec ID: A_QUICKTIME/QDMC
Codec Name: QDesign Music
Description:
Initialisation: The Private Data contains all additional data that is stored in the 'stsd' (sample description) atom in the QuickTime file after the mandatory sound descriptor structure (starting with the size and FourCC fields). For an explanation of the QuickTime file format read QuickTime File Format Specification.
Superseded By: A_QUICKTIME
Codec ID: A_QUICKTIME/QDM2
Codec Name: QDesign Music v2
Description:
Initialisation: The Private Data contains all additional data that is stored in the 'stsd' (sample description) atom in the QuickTime file after the mandatory sound descriptor structure (starting with the size and FourCC fields). For an explanation of the QuickTime file format read QuickTime File Format Specification.
Superseded By: A_QUICKTIME
Codec ID: A_TTA1
Codec Name: The True Audio lossless audio compressor
Description: TTA format description Each frame is kept intact, including the CRC32. The header and seektable are dropped. SamplingFrequency, Channels and BitDepth are used in the TrackEntry. wFormatTag = 0x77A1
Initialisation: none
Codec ID: A_WAVPACK4
Codec Name: WavPack lossless audio compressor
Description: The Wavpack packets consist of a stripped header followed by the frame data. For multi-track (> 2 tracks) a frame consists of many packets. For hybrid files (lossy part + correction part), the correction part is stored in an additional block (level 1). For more details, check the WavPack muxing description.
Initialisation: none
Codec ID: S_TEXT/UTF8
Codec Name: UTF-8 Plain Text
Description: Basic text subtitles. For more information, please look at the Subtitle specifications.
Codec ID: S_TEXT/SSA
Codec Name: Subtitles Format
Description: The [Script Info] and [V4 Styles] sections are stored in the codecprivate. Each event is stored in its own Block. For more information, please read the specs for SSA/ASS.
Codec ID: S_TEXT/ASS
Codec Name: Advanced Subtitles Format
Description: The [Script Info] and [V4 Styles] sections are stored in the codecprivate. Each event is stored in its own Block. For more information, please read the specs for SSA/ASS.
Codec ID: S_TEXT/USF
Codec Name: Universal Subtitle Format
Description: This is mostly defined, but not typed out yet. It will first be available on the USF specs page.
Codec ID: S_TEXT/WEBVTT
Codec Name: Web Video Text Tracks Format (WebVTT)
Description: Advanced text subtitles. For more information about the storage please look at the WebVTT in Matroska specifications.
Codec ID: S_IMAGE/BMP
Codec Name: Bitmap
Description: Basic image based subtitle format; The subtitles are stored as images, like in the DVD. The timestamp in the block header of Matroska indicates the start display time, the duration is set with the Duration element. The full data for the subtitle bitmap is stored in the Block's data section.
Codec ID: S_DVBSUB
Codec Name: Digital Video Broadcasting (DVB) subtitles
Description: This is the graphical subtitle format used in the Digital Video Broadcasting standard. For more information about the storage please look at the Digital Video Broadcasting (DVB) subtitles in Matroska specifications.
Codec ID: S_VOBSUB
Codec Name: VobSub subtitles
Description: The same subtitle format used on DVDs. Supported is only format version 7 and newer. VobSubs consist of two files, the .idx containing information, and the .sub, containing the actual data. The .idx file is stripped of all empty lines, of all comments and of lines beginning with alt: or langidx:. The line beginning with id: SHOULD be transformed into the appropriate Matroska track language element and is discarded. All remaining lines but the ones containing timestamps and file positions are put into the CodecPrivate element.
For each line containing the timestamp and file position data is read from the appropriate position in the .sub file. This data consists of a MPEG program stream which in turn contains SPU packets. The MPEG program stream data is discarded, and each SPU packet is put into one Matroska frame.
Codec ID: S_HDMV/PGS
Codec Name: HDMV presentation graphics subtitles (PGS)
Description: This is the graphical subtitle format used on Blu-rays. For more information about the storage please look at the HDMV presentation graphics subtitles in Matroska specifications.
Codec ID: S_HDMV/TEXTST
Codec Name: HDMV text subtitles
Description: This is the textual subtitle format used on Blu-rays. For more information about the storage please look at the HDMV text subtitles in Matroska specifications.
Codec ID: S_KATE
Codec Name: Karaoke And Text Encapsulation
Description: A subtitle format developed for ogg. The mapping for Matroska is described on the Xiph wiki. As for Theora and Vorbis, Kate headers are stored in the private data as xiph-laced packets.
Codec ID: B_VOBBTN
Codec Name: VobBtn Buttons
Description: Based on MPEG/VOB PCI packets. The file contains a header consisting of the string "butonDVD" followed by the width and height in pixels (16 bits integer each) and 4 reserved bytes. The rest is full PCI packets.