[Matroska-devel] Channel Positions for Multichannel LPCM Track Inside Matroska
Nithin Mathew Kurien via Matroska-devel
matroska-devel at lists.matroska.org
Sun Apr 24 17:39:55 CEST 2016
Currently the specification for storing a multichannel LPCM track (CodecID
A_PCM/INT/LIT) inside a Matroska file [1, 2], does not specify a way to
indicate the channel positions of the track. Due to this, players find it
difficult to map the channels to the correct speaker positions when playing
such a track. MakeMKV employs a workaround for this problem. It stores the
track under the CodecID A_MS/ACM, along with a WAVEFORMATEXTENSIBLE
structure in CodecPrivate. This structure contains a field called
dwChannelMask which specifies the channel positions . This is identical
to the way LPCM is stored inside AVI files. The problem with this approach
is that most players do not recognise the CodecID A_MS/ACM, except for a
few open-source players like Kodi .
In the case of a FLAC track (inside either a raw .FLAC file or a .MKA
file), we can specify an optional WAVEFORMATEXTENSIBLE_CHANNEL_MASK tag
. Could a similar solution be implemented for LPCM inside Matroska too?
On a related note, the ffmpeg documentation  specifies additional
channel positions which are not found in the Microsoft documentation ,
like Wide Left and Wide Right speakers. Are these speaker positions
recognised by players when reading WAV files?
Thanks and regards,
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