How to determine / find "period_size" of ALSASRC (LATENCY of alsasrc)

[Nicolas Dufresne]

Le lundi 18 janvier 2016 à 01:33 -0800, Ashish Kumar Mishra a écrit :
> Could any one please let me know how could we know the "PERIOD-SIZE"
> for an
> alsasrc plugin. 
> "PERIOD-SIZE" would affect the "LATENCY"  ( along with affect
> "BUFFER-TIME"
> & "BUFFER-SIZE " )
> 
> This factor seems to be important when in case when we have problem
> of audio
> - video sync issue.. 
> I have faced audio - video sync problem using VIDEOTESTSRC + ALSA
> +AVIMUX. 
> This problem i was able to improve , by some random trail and error
> methord
> along with some sample configuration. 
> 
> My question is how to determine "PERIOD-SIZE"  so that we get proper
> latency
> value for alsa-src.

I believe you are looking for "latency-time" property. It controls the
size of a buffer (in duration) and define the capture latency as you
need to capture for that amount of time before you have a complete
buffer you can push forward. "buffer-time" property controls the size
of the ringbuffer, hence should be larger then the "latency-time". It
controls how much time alsasrc can accumulate data while pushing
downstream. It's also that time the element can spend pushing data
before data start being lost. It's defined as the maximum latency in
GStreamer. Careful, since those same two properties don't mean exactly
the same thing in alsasink.

Nicolas
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