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

[Ashish Kumar Mishra]

Let me explain  

My pipeline is as mentioned below
filesrc ->  qtdemux -> avdec_h264  -> videoconvert -> timeoverlay ->  q1       
                                                                                                                    
-> avimux -> filesink 
                                                             audiotestsrc ->
capsfilter -> q2 

1) I am building an audio + video splitter . Currently using Filesrc as
video source & Alsasrc for audio. 
    When i play the recorded file in VLC. ( in seconds ) , below was the
problem i faced
    1)  t=0  to t= 2 
         The video is played back properly and VLC seek (BLUE seek )  bar is
also progressing. 
   
   2)  t=2 to t= 4/5 
         No video is played rather its like FREEZED / PAUSE . 
         The seek bar  ( Orange seek ) progress till t=4/5 . Please note
that during this time VLC seek bar 
         is ORANGE and is progressing. But the video is not played. 
  
  3)  t=4/5 
      The VLC orange seek bar re-positions itself to t=2. Seek bar turns
BLUE and video & seek bar is played 
      properly. 
  This behavior continues for complete file.


2) Now to address this problem , some pointers i got was to look at the
buffer time-stamp ( discussed as problem )
http://gstreamer-devel.966125.n4.nabble.com/quot-do-timestamp-quot-leds-to-no-moov-atom-within-the-first-10-MB-problem-in-pipeline-td4675118.html

3) It then when i started looking for the problem zone .Started looking for
with buffer size & latency of alsasrc. 
    With random trail and error i am able to improve the sync issue ,hence
wanted to understand 
    How to calculate the required value of "latency-time" parameter for
alsasrc ?
    or
    How to calculate "period-size"of latency parameter for alsasrc ( as
period-size will directly affect the latency-time ) ?


*Please note that my aim is how to find value latency-time for alsasrc . *


Thanks ,
Ashish Kumar Mishra       
 



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