1151374 - Incorrect channel positioning with surround audio

Status: RESOLVED DUPLICATE of bug 1248861

(Core :: Audio/Video: Playback, defect)

Description

[Jean-Yves Avenard [:jya]]

Playing this video:
https://bug1073805.bugzilla.mozilla.org/attachment.cgi?id=8496419

exhibits invalid channel placement.

Supposed to be : where it "sounds"

Mac:
Left: center
Center: left
Right: right
Left surround: center with left bias
Right surround: center with right bia

FFmpeg:
Left: Left
Center: Right
Right: Center
Left surround: center (can't hear any bias toward the left)
Right surround: center (can't hear any bias toward the right)

FFmpeg uses SMPTE layout.
CoreAudio uses its own (similar to SMPTE but with rear surround swap with surround) L+R

Comment 1

[Jean-Yves Avenard [:jya]]

What channel layout is supposed to come out from the audio MediaDataDecoder?

Comment 2

[Chris Pearce [:cpearce (Not reading bugmail)]]

I'm not sure what channel layout libcubeb expects or can handle. I'm not sure what we should do here, so I'll defer this question (comment 1) to Matthew or Paul.

Comment 3

[Matthew Gregan [:kinetik]]

We have virtually zero support for multichannel audio beyond stereo.  It's on the list for this quarter.

Comment 4

[Paul Adenot (:padenot)]

What Matthew said. If it works, it's either luck or a bug, basically.

Comment 5

[Jean-Yves Avenard [:jya]]

The core issue here is that none of the MediaDataDecoders will return exactly the decoded data in the same channel ordering.

Recent version of ffmpeg always output SMTPE ordering:
which is:
 DUAL-MONO      L   R
 DUAL-MONO-LFE  L   R   LFE
 MONO           M
 MONO-LFE       M   LFE
 STEREO         L   R
 STEREO-LFE     L   R   LFE
 3F             L   R   C
 3F-LFE         L   R   C    LFE
 2F1            L   R   S
 2F1-LFE        L   R   LFE  S
 3F1            L   R   C    S
 3F1-LFE        L   R   C    LFE S
 2F2            L   R   LS   RS
 2F2-LFE        L   R   LFE  LS   RS
 3F2            L   R   C    LS   RS
 3F2-LFE        L   R   C    LFE  LS   RS
 3F3R-LFE       L   R   C    LFE  BC   LS   RS
 3F4-LFE        L   R   C    LFE  Rls  Rrs  LS   RS

Apple's CoreAudio appears to be problematic as the only reference I can find is that the channel ordering used is dependent on the input format.

For WMF I see that the API let you configure the output, but I don't see a default

Comment 6

[u514836]

We currently have a multichannel audio program available streaming on demand, available until 30th January: http://www.bbc.co.uk/programmes/p03cchwf.

Unfortunately we are having to advise users to use an alternative user agent since Firefox does not route channels correctly.