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

[Pierre-Louis Bossart]

On 9/21/14, 8:15 AM, Kiran Krishnappa wrote:
>  >>Someone on IRC was writing up,
>  >>I think, but I don't know what state that got to.
>
>
> Arun, below is the status of compressed sink:
>
> I was facing some issues in reporting timing to PA client. The compress
> library that I am using does provides an API to query playback time from
> DSP.  Initially, I thought of adding a new API (for passthrough streams
> only)to protocol-native to obtain correct timing from driver. Dropped
> that idea,  decided to stuff the timing info in response to
> "pa_stream_update_timing_info" info. It seems the timing reporting issue
> is resolved now.

?? There should be support to query the time from the compress API, 
without it the implementation is clearly broken.

> Now , I need to look into timing issue in case of seek operation.

This can't be handled in PulseAudio, you have to do it somewhere else 
(gstreamer)

>
> Apart from this,
> * there were couple of changes at gstreamer side (pulsesink) to avoid
> packeting data into IEC frames

What? This is needed to force PulseAudio to keep working with its 
default byte->time conversion. If you removed the padding and 
packetization the timing will be completely in the weeds

> * Introduced new API's to tinycompress to get  device file descriptor
> which inturn added to pa_rtpoll_run

can you share this code please?

> * Not sure how to calculate sink latency in case variable bitrate

You can keep track of the IEC frames you provided to the sink and work 
from there: it's constant bitrate. Of course if you removed the IEC 
framing you are on your own...

>
> Regards,
> Kiran
>
>
>
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