[gst-devel] Video frame timings (revisited)

[Darren Staples]

Hi, I'm hoping someone can help with this please, as I'm struggling...

When doing audio and video decoding of a H.264 MP4 file I find that
the timing of the video frames seems to be affected by the processing
of the audio frames.
My pipeline looks like this:

                    / ffmpegcolorspace - queue - appsink
uridecodebin
                    \ audioconvert - queue - appsink

I have setup callbacks on both the audio and video appsinks.
In the video callback I get the buffer from the appsink and then call
gst_element_query_position() to get the frame time.
In the audio callback I'm just getting the buffer and discarding it (for now).

The frame times I see in the video callback seem to be affected by the
audio decoding i.e. I don't see the regular frame times that I
expected. They're quite variable and there seem to be extended periods
(1-3s) between some frames.
If I remove the audio branch of the pipeline I see perfectly regular
(exactly 40ms or 25fps) video frame times.

Am I missing some vital component from my piepline ?
Can anyone suggest, please, where I might be going wrong ?

Thanks in advance,
Darren