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Bug 448861 - Problems with multichannel AAC -> Vorbis transcoding
Problems with multichannel AAC -> Vorbis transcoding
Status: RESOLVED FIXED
Product: GStreamer
Classification: Platform
Component: gst-plugins-base
git master
Other Linux
: Normal normal
: 0.10.20
Assigned To: GStreamer Maintainers
GStreamer Maintainers
Depends on:
Blocks:
 
 
Reported: 2007-06-18 18:16 UTC by Tristan Brindle
Modified: 2008-06-20 11:07 UTC
See Also:
GNOME target: ---
GNOME version: ---



Description Tristan Brindle 2007-06-18 18:16:19 UTC
The file 

http://images.apple.com/movies/fox/fantastic_4-silver_surfer/fantastic4silversurfer-tlr1_h720p.mov

contains, according to Totem, a 7.1-channel AAC track (although VLC says it's 6-channel). Attempting to transcode the audio to Vorbis with the standard pipeline:

gst-launch-0.10 filesrc location=1.mov ! decodebin ! queue ! audioconvert ! vorbisenc ! oggmux ! filesink location=2.ogg

generates a mono Vorbis stream rather than the multichannel one would expect.

Forcing the caps to "audio/x-raw-float, channels=5" (for example) in between audioconvert and vorbisenc will generate a multichannel vorbis file, but the channel mapping seems to be incorrect (centre audio seems to come through the right speaker, for example).

I'm not sure whether this is a bug in faad, audioconvert or vorbisenc, so I'm leaving it as "don't know".

If you need any more info, please let me know
Comment 1 Christian Fredrik Kalager Schaller 2008-06-20 11:03:57 UTC
With the latest fixes to audioconvert in gst-plugins-base this transcoding now produce a 5.1 file correctly. Haven't been able to verify 100% if the channel mapping is correct though, but so far things look ok.
Comment 2 Sebastian Dröge (slomo) 2008-06-20 11:07:36 UTC
This is fixed in 0.10.20 now by

2008-05-29  Sebastian Dröge  <slomo@circular-chaos.org>

        * ext/vorbis/vorbisdec.c: (vorbis_handle_identification_packet):
        * ext/vorbis/vorbisenc.c: (gst_vorbis_enc_generate_sink_caps):
        Add sane defaults for the 7 and 8 channel layouts as those are
        undefined in the Vorbis spec. Use NONE channel layouts when decoding
        more than 8 channels instead of erroring out. Fixes bug #535356.

The case with the capsfilter should be fixed by one of the audioconvert changes between 0.10.19 and 0.10.20.