On Fri, Mar 14, 2008 at 6:57 PM, Eliot Blennerhassett <linux@xxxxxxxxxxxxxxxx> wrote: > On Saturday 15 March 2008 11:35:20 Lee Revell wrote: > > On Fri, Mar 14, 2008 at 12:35 AM, Harsha priya gupta > > > > <harshapriya@xxxxxxxxx> wrote: > > > Hi, > > > > > > I am ramping up on ALSA architecture and framework. I have a couple of > > > basic questions. I apologize if these questions are very basic to be > > > raised in this mailing list. If anyone can help me find answers, it would > > > be great. Thanks in advance. > > > > > > 1. My assumption is that ALSA handles only PCM streams today. Does it > > > handle encoded streams from application to sound card (Which can do > > > hardware decoding)? > > > > Someone else could probably give a better answer, but I believe that > > currently ALSA has no API for cards that do HW decoding. > > Not AFAIK, and certainly the architecture assumes a constant data rate. I.e X > bytes consumed implies elapsed time of (X * constant) = the _period_ > > Alsa headers do define some format constants for compressed audio. > > We would like to support compressed audio for our cards, which can do hardware > decoding. I did try to implement it early on, but got lost in the quagmire of > driver midlevel code and alsa-lib. > > A first step would be to allow CBR compressed formats to pass through to the > driver unaltered. For these there is a defined bits per sample, though it can > be non-integer which might be a problem. I would look at how ALSA implements AC3 passthrough. Lee _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
