as i rememer audio resampling routine is able to that.
see av_audio_resample
01.07.2009, в 20:02, tbartdev написал(а):
Hi!
I am working on extending fobs4jmf (fobs.sf.net), a java wrapper
around
ffmpeg.
The current problem is this:
Whenever I have audio tracks with more than two channels (for
example, a 4
channel wav file), I am unable to give only 2 channels to java (as
it needs
to get only 2).
request_channels is only advisory, as I read
(http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-December/039192.html
)
and indeed, it does not work.
The way ffplay does it, is to set channels to 4 in the wanted_spec
struct,
but SDL returns only 2 channels in its resulting spec struct, so
effectively, SDL does the downmixing (or throwing away of excess
channels).
I don't really care whether excess channels are just thrown away or
I get a
real downmix, I just want to be able to play *some* sound.
What's the programmatical way of doing this? Can I somehow manually
only
request the first two channels?
Mplayer has the -af channels=2 function for this, which works as
expected.
libav's av_audio_resample_init tells me downmixing of more than 2
channels
is unsupported (reproducible with using ffmpeg -ac 2 on a multichannel
file).
I am a newb in all of this, so please be patient and try to explain
suggested code if you can!
The current code can be found at
http://www.orpheus.co.at/fobs/Decoder.cpp
http://www.orpheus.co.at/fobs/Decoder.h
Lines 333-420 are the interesting part.
Any help is really appreciated, I've invested so much time for the
accompanying processes that I really need to get this working.
Please help!
Thanks a lot in advance!
th
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