On Wed, 2011-03-16 at 16:08 +0530, Mark Brown wrote: > On Tue, Mar 15, 2011 at 11:31:18AM -0700, Patrick Lai wrote: > > > Is there a precedent for playback/capture compressed audio stream > > through ALSA playback/capture interface if underlying hardware supports > > decoder + sink & encoder + source capabilities? > > I'm not sure if ALSA is the best API to use for this - the ALSA APIs are > strongly oriented around data where the size is consistent in time while > most compressed audio formats don't do that. There's also existing APIs > in userspace like gstreamer and the various OpenMAXish things to slot in > with, everything below those is usually black boxed per implementation. I would agree with Mark, our best approach would be to do a clean design of a new API set which takes care of both CBR, VBR and be generic enough for any format. > > Within ASoC the current tunneled audio stuff I've seen does something > like representing the decompressor output as a DAPM input and showing > that as active when there's a stream being decoded. Portions of the > implementation for Moorestown are in mainline in sound/soc/mid-x86, > though I'm not sure if it's all fully hooked up yet or not. The current implementation in soc/mid-x86 is for PCM only. The compressed path offload bits are in staging/intel_sst. I will be working to make these bits move to soc/mid-x86 and also to make them more suited for generic frameworks. > > Nobody's really tried to do more yet but this may end up being the best > choice overall as there's substantial variation in how the DSPs are > structured both physically and OS wise which make the abstractions below > the userspace API level less clear. I was thinking more on having a generic framework which coexists with alsa, asoc (dapm), and provided a way to write driver for your dsp to do decoder, sink + decoder and other variations. The implementation of these can be specific to DSP in question, but framework should be able to push and pull data, timing information around with a standard way which coexists with current frameworks Thoughts....? -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
