Re: ac3 in/out

[Johannes Berg <johannes@sipsolutions.net>]

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On Tue, 2006-03-21 at 19:37 +0100, Takashi Iwai wrote:

> The SPDIF status bits are generic and rather depending on the data
> than the device you output.  That is, more or less, the SPDIF I/O is
> abstracted.

Are you talking about alsa or spdif itself?

> Regarding AC3, I'm not against to create a new easy-to-use API
> function.  One reason is that AC3 over SPDIF needs conversions of
> packets and also requires the sync work, in addition to the SPDIF
> status bits mentioned in the above.  Such a job can be certainly
> hidden in the system instead of application itself.

Yes, but apparently some hardware is capable of doing the conversion
(the chip apple uses for example: pcm3052, download data sheet for
pcm3052a if you're interested, it's the same chip)

On the other hand, some other chips seem to rely on software to
multiplex the channel status bits into the bitstream which is currently
done by userspace as far as I can tell.

> If we create a new one, we should better think of other compressed
> formats, too...

They're essentially the same to the spdif output though -- just a
non-pcm bitstream.

johannes

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