[alsa-devel] HW decoding abstracted in ALSA

Takashi Iwai tiwai at suse.de
Mon Feb 25 13:03:03 CET 2008

At Mon, 25 Feb 2008 12:27:00 +0530,
Harsha priya gupta wrote:
> Hi,
> I am new to ALSA and audio stack in Linux. I have a sound card that can do
> HW decoding as well. I am looking at writing an ALSA driver such that
> whatever may be the player or MMF above, it should use the HW decoder and
> not the inherit SW decoder that is available with the player.
> Can someone help me with some pointers or existing like-drivers?

Which format is in mind?  In theoery, you can implement the h/w
decoder on the ALSA framework, but there are some restrictions:

- ALSA PCM assumes the constant bitrate
- The format bit must be defined
- The specific app recognizes and supports that format

In the case of AC3 or DTS, it's embedded in SPDIF frames so the PCM
core stuff doesn't take care of the above.  But, in the case of native
(non-PCM) formats, the support can be difficult as is.


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