[pulseaudio-discuss] How to use ALSA compress API in Pulseaudio with passthrough mode

[Arun Raghavan]

On 17 September 2014 20:29, Pierre-Louis Bossart
<pierre-louis.bossart at linux.intel.com> wrote:
>
>>>> and last you strip the header and pass the
>>>> payload to your hardware decoder using the compressed API.
>>>
>>>
>>> Do you mean by stripping the IEC header frame with MP3 header will be
>>> there and pass the same to hardware decoder?
>>
>>
>> I'm not sure what Pierre meant. PulseAudio expects the alsa device to
>> consume the IEC-wrapped data. I guess you could make an alsa plugin that
>> shows up as a PCM device to PulseAudio, and the plugin then receives the
>> wrapped data from PulseAudio, unwraps the MP3 data and finally feeds it
>> to the compressed API.
>
>
> Depends on what your hardware supports. The compressed API can handle either
> IEC-based payload or elementary streams (i.e. raw MP3). The pulseaudio sink
> needs to make the adjustments if needed.

A compressed sink would be nice indeed. Someone on IRC was writing up,
I think, but I don't know what state that got to. Probably needs some
messing around in internals since we do have a bunch of code that
depends on being able to do bytes<->time conversion for latency
calculations.

-- Arun