[alsa-devel] PCM rules for FireWave in speaker.c

Takashi Sakamoto o-takashi at sakamocchi.jp
Fri Feb 28 12:28:33 CET 2014


> The current rules in speakers.c disallow rates less than 48 kHz if there
> are less than six channels, and disallow two channels if the rate is
> less than 48 kHz.  This means that the allowed parameter combinations
> are 2ch at 48/96 kHz, and 6ch at 32/44.1/48/96 kHz.

Oh, I misunderstood it...

>> Recently, with Jay Fenlason's help, I got some information about its
>> stream format. I'll show them in the end of this message.
>> As a result, I realized FireWave has stream formats below:
>>   - 6ch PCM at 32.0/44.1/48.0/96.0kHz
>>   - 2ch IEC 60958-3 at 32.0/44.1/48.0kHz
>> Although there are no stream formats for 2ch PCM at 48.0/96.0kHz, the
>> driver has it. Do you know the reason? Are there any model quirks?
> I don't have any of the AV/C audio specifications; these rules were
> determined experimentally.  In other words, when the sample rate is set
> to 48 or 96 kHz, sending a stream with two PCM channels appears to work.

OK. You confirmed it.

> If you wanted to support these undocumented formats in your driver, you
> would have to add some kind of quirk.

Exactly. For PCM, I need to add hard-coded rule. On the other hand, I 
want to omit IEC 60958-3 mode because I don't know whether ALSA has 
proper interfaces for it. It will not be PCM.

# I wonder why this mailman sometimes don't deliver my mail...


Takashi Sakamoto
o-takashi at sakamocchi.jp

More information about the Alsa-devel mailing list