[alsa-devel] MCP7A HDMI passthrough audio Linux/ALSA

Stéphane BERTHELOT sberthelot at emisfr.com
Fri Jul 3 20:07:09 CEST 2009

Takashi Iwai a écrit :
> At Wed, 01 Jul 2009 11:18:15 +0200,
> Stéphane BERTHELOT wrote:
>> Takashi Iwai a écrit :
>>     At Tue, 30 Jun 2009 22:51:03 +0200,
>>     Stephane BERTHELOT wrote:
>>     Hm, so apparently your TV doesn't accept non-audio format?
>>     But TV accepted the ac3dec output with -R option, right?
>>     (Make sure this -- otherwise ac3dec might have decoded by itself.)
>>     Basically, -R means to send the encoded an AC3 stream (packed in the
>>     SPDIF format) without setting non-audio bit.  Whether non-audio bit is
>>     1 or 0 is the only difference between -C and -R.  So, if -R really
>>     works but not -C, it means that the non-audio bit must be off no
>>     matter what you send.  Weird.
>> I'm sure the TV only accepted -R and not -C (or -P) with the same ac3 file.
>> But I'm confused since I was quite sure -R would *decode* ac3 to PCM and then
>> send it in LPCM format.
> Ah, yes, of course.  That's logical, then, that -R works.
> Hm, then it's an issue of receiver side?
> Can Windows send the raw AC3 and TV decodes it properly?
> Takashi
Thanks you Takashi,

After investigating on the Windows side (damn!) I finally found that 
with the latest Nvidia official HDMI audio out drivers I was also 
receiving only stereo PCM.
I'm very angry against Sharp since their TV set outputs AC3 when 
switched on DVB tuner mode, it even offer "digital audio out settings" 
on analog inputs (scart / component /...) but strangely this menu is no 
more available when on an HDMI channel.
I'm very upset about this, since this TV set is about 6 months old seems 
already deprecated.
I'm trying to get someone at Sharp service to make an upgrade to get 
digital audio through HDMI to the optical output but I have little hope 
about this. I still can't figure why they do that, is it a digital 
entertainment system or not ? My old frist-gen dvd player does better ...

Thanks anyway for your help and if you can give me some hints about how 
to convince Sharp to make an upgrade for this I will be welcome. I'm 
pretty sure some other users have had the same kind of problems...

I now need either to buy an USB audio card with SPDIF out (or in/out) or 
an HDMI switch (some have spdif out) or even a real new HD Audio Amp, 
but this is getting more and more expensive ...

Thanks a lot Takashi, and I hope I'll find a 'not so expensive' solution 
for this. (If anyone can give me pointer on cheap USB  or HMDI hardware 
... :) )


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