Tracking PTS of decoded H264 frames with leaky queue

[Jan Alexander Steffens]

On Tue, Feb 5, 2019, 15:12 barapa <ben.rapaport at gmail.com wrote:

> I have an annex-b H264 stream that I am decoding via a gstreamer
> command-line
> pipeline that looks something like:
>
> gst-launch-1.0 fdsrc ! queue ! h264parse ! avdec_h264 ! videoconvert !
> 'video/x-raw, format=RGB'  ! fdsink sync=false
>
> I run this as a subprocess from another program, communicating over
> stdin/stdout. I cannot easily build gstreamer into this program, so for
> now,
> I am stuck running it as a subprocess like this.
>
> Before writing each frame to stdin, I know the PTS of the frame, and I need
> to know this PTS on the RGB image I read out of stdout. At the moment, I
> simply match the incoming to outgoing frames one-to-one. However, I want
> gstreamer to be able to drop frames to keep up by introducing a leaky
> queue.
> However, in doing so, I lose track of which PTS belongs to which output RGB
> image.
>
> Is there any way to write the PTS values into the stream somehow and
> recover
> them after decoding (while continuing to use a command-line pipeline)? Or,
> can I get gstreamer to somehow notify me of a dropped frame, preferably by
> outputting something to stdout that I could parse?
>

Ending your pipeline with "! identity silent=0 ! fdsink sync=0" and
starting gst-launch with -v (or was it -m?) should print buffer info to
stderr right before writing each frame.

Needless to say this isn't considered a stable interface. Or a good one,
for that matter.

>
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