[MPlayer-cygwin] multichannel sound

[Szecsi Gabor]

SS> Hi,
SS> I just commited a patch for initial mutlichannel support on windows.
SS> It is completely untested by me. I don't have a sundcard that supports more 
SS> than 2 channels.
SS> Someone tested it with SB Audigy2 and it did not work, however he also
SS> told me that other Apps using waveout can't get more than 2 channels
SS> with this card either (ac3filter). The  code is almost the same as in
SS> videolan or ac3filter. The cannel mapping is probably completely broken, 
SS> though. Please test.


SS> Sascha

SS> P.S. There were at least 2 people who wanted to write a directsound output 
SS> plugin. How far have you come with this?

I have tested the output on two different cards: SBLive! Value
4-channel and a C-Media 8738 5.1 channel card. Both of them works in
multichannel modes both DirectSound and waveOut under ac3filter and
videolan player.
with ac3filter everything seemed to be good (can someone send me an
ac3 sample which tells ie. left channel, right channel etc. in the
correct speakers?) but videolan made some interesting things with the
sblive card. Videolan player played the sound correctly when I set it
to play 5.1 however the sblive has only 4 channels. If I set it to 4
channels mode (2 front + 2 back) it mixed some channels.
Interestingly the c-media did work well...
Now about ao_win32.c. I have changed the channel masks so that 4
channels means 2 front + 2 rear. The sblive did not work again, it
seemd to me (but not sure) that it played the front channels on the
rear speakers. The c-media card worked again. With one thing: if
autosync was turned on the sound became VERY choppy. Without it the
video played too fast. Maybe some bandwith calculation problems.
Conclusion: I will try to tamper with bandwith calc routines and
channel masking/routing.
Anyway I don't know what causes that strange difference in the
behaviour of the two cards, c-media works fine while sblive seems to
swap channels - although they both work with ac3filter. With waveOut
of course. I think this has to do with the maximum channel number of
the card.

I wanted to write a directsound output but not started due to lack of
time. Maybe someday I will begin writing it.