[gst-devel] A/V sync issues

Pavan Kumar Patale pavanpatale at hotmail.com
Fri Dec 15 19:09:49 CET 2006

Hi Zaheer,

I tried to localise the problem and observed that if set the 
max-size-time=700 for demux_audio_queue the A/V sync is perfectly achieved.

gst-launch-0.10 filesrc location=test.avi ! queue ! avidemux name=demux 
demux.video_00 ! queue ! video_decoder ! ffmpegcolorspace ! timeoverlay ! 
xvimagesink sync=false demux.audio_00 ! queue max-size-time=700 ! 
audio_decoder ! audio_sink

But, I am just wondering will this be a permanent solution ?
If this kind of queue manipulation has to be done at recording itself so 
that other players will playback with A/V sync, what would be the better 
approach ?
Third query is before sending to avimux should we explicitly handle A/V sync 


>On 12/12/06, Pavan Kumar Patale <pavanpatale at hotmail.com> wrote:
>> >Firstly, you have a live source at the end going to a synchronised sink. 
>>  This will produce exactly  >> >what you mentioned, ie. not  smooth 
>>playback and frames being dropped.
>> >Also remember framerate is a fraction, so better to specify framerate as
>> >15/1.
>> >
>> >You are better off recording to a file, and then trying to playback the
>> >file.  The file is not a live >source and you'll be able to tell better 
>> >a/v sync and the quality of the recording and resulting
>> >playback than by capturing, encoding, muxing, demuxing, decoding and
>> >playing back in the same >pipeline.
>>Yes, actually i recorded to a file using the below pipeline :-
>>gst-launch-0.10 avimux name=mux ! filesink location=test.avi v4l2src !
>>ffmpegcolorspace ! tee name=t t.src0 ! queue ! timeoverlay ! xvimagesink
>>t.src1 ! queue ! video/x-raw-yuv, width=176, height=144, framerate=15/1 !
>>videorate ! video_encoder ! mux. audio_source ! queue ! audio_encoder ! 
>>using the below pipeline playback is very smoth, but there is 2 seconds of
>>audio lag :-
>>gst-launch-0.10 filesrc location=test.avi ! queue ! avidemux name=demux
>>! queue ! video_decoder ! ffmpegcolorspace ! timeoverlay ! xvimagesink
>>sync=false demux.audio_00 ! queue ! audio_decoder ! audio_sink
>>Then to analyze the problem tried to directly demux instead of  writing to
>>the file as mentioned in my previous mail.
>>Is there a way to reduce this audio lag?
>>Get up-to-date with movies, music and TV. Its happening on MSN 
>Please could you file a bug in bugzilla actually stating the pipeline
>with the encoders and decoders you use so we can try to reproduce.

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