Re: writing an alsa driver for an MPEG decoder chip

[James Courtier-Dutton <James@superbug.co.uk>]

Nicolas Boullis wrote:
> Hi,
> 
> I am a member of the dxr3 project, that tries to write a linux driver 
> for the MPEG decoder em8300 chip that is mainly used in Sigma Design's 
> Hollywood+ and Creative Labs DXR3 boards.
> This chip handles hardware decoding of MPEG video, but is also able do 
> perform some limited audio playback.
> We corrently have a working OSS interface for the audio playbak, that 
> I'd like to replace with an ALSA one.
> I tried to write one, using Takashi Iwai's excellent "Writing an ALSA 
> Driver" guide. Unfortunately, the driver that I managed to write seems 
> to work fine when playing sound with xmms, but all other apps that I 
> tried failed to get any sound.
> 
> Anyone can help me figure out whet I missed?
> You can grab the relevant file at
> http://dxr3.sourceforge.net/download/em8300_alsa.c
> 
> Thanks in advance,
> 
> Nicolas Boullis
> 
> 
> PS: I am not subscribed to this list, please CC replies to me.
> 

I looked at the code. The period and buffer size selection looks a bit 
wrong. Can you explain to me what the actual buffer contraints are for 
the em8300 card? It looks to me that the only current contraint is 
number of periods. This seems to me to be rather a strange contrain to have.

James



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