[MPlayer-dev-eng] [PATCH] liba52 problems with 2-ch vob, 6-ch output

[Arpi]

Hi,

> I was trying out the new liba52 with some vobs (with -channels 6).
> It works great with vobs that have 5+1 channels.
> 
> The problem:
> Some of the vobs have ac3 sound with only 2 channels (A52_DOLBY format).
> Liba52 does not "upmix" the output to 5+1 channels, so this causes a lot of
> garbage in the sound output (this is described in liba52.txt).

i think this should be fixed in liba52's downsample.c, or at worst case, at
resample.c. (there are upsampling code too at downsample.c)

> Patch below adjusts the number of output channels if the ac3 input has less
> channels than the user-specified number of channels. It's against the latest
> CVS. With this my vobs play perfectly.
what about 3 and 5 channel cases? are there any card supporting these?

i think, if user wants 6 channels, he should get it.
especially for dolby, we should upmix dolby encoded channels to 6
independent channels (dolby decoder).

afaik there was such code in libac3, and shoudl be in liba52 too.

> By the way, my soundcard is a Cmedia 8738-6ch-LX (only $12 :-)), which works
> great with 2, 4 or 6 channels (using the oss driver of Linux 2.4.x). Maybe
> you could add this to the soundcard list.

> Index: dec_audio.c
about the patch. it's messy, the channel setup code shoudl go into new
function, or directly at liba52 init part, instead of placing it in decoder
loop with option to enable it only at init part.


A'rpi / Astral & ESP-team

--
mailto:arpi at thot.banki.hu
http://esp-team.scene.hu