Get back to realtime without loosing data

[Peter Biro]

Hi all,

In my application I need to record streaming video (and audio audio) while I also have to record some time before the recording is initiated by the user. Currently Im doing this by have a small c++ application which executes the follwoing pipeline:

udpsrc multicast-group=<VIDEO_SRC_IP> auto-multicast=true port=<VIDEO_SRC_PORT>
        ! application/x-rtp,media=video,encoding-name=VP8,payload=96 ! rtpjitterbuffer ! rtpvp8depay ! tee name=video_stream_spilt
        udpsrc port=<AUDIO_SRC_PORT>
        ! application/x-rtp,media=audio,clock-rate=44100,encoding-name=L24,encoding-params=1,channels=1,payload=96,ssrc=687131883,timestamp-offset=3784732336,seqnum-offset=8272
        ! rtpL24depay ! audioconvert ! audioresample ! queue name=file_sink_audio_queue ! voaacenc ! queue name=q2 max-size-bytes=0 max-size-buffers=0 max-size-time=0 ! aacparse ! faad ! audioresample ! audioconvert ! voaacenc ! video_mux.
        video_stream_spilt. ! queue name=file_sink_video_queue ! omxvp8dec ! videoconvert ! omxh264enc bitrate=8000000 control-rate=2 insert-sps-pps=true ! matroskamux name=video_mux
        ! filesink name=file_sink location=<OUTPUT_FILENAME>
        video_stream_spilt. ! fakesink

In the c++ application logic I configure the "max-size-time" on the "file_sink_video_queue" and "file_sink_audio_queue" queues to video and audio data from the past and blocking the src pads on the queues. When the record start event arrives it will wait for the first keyframe in the video and the unblock the the pads to start to record the audio and video data into the file.

I would like to simplify this application by splitting it into two simpler application. First by adding a new pipeline running in the middle which would be responsible for delaying and returning the stream to realtime. Then a simple recorder component which receives the audio and video streams at the end.

So basically what I would like to achieve is that instead of blocking/unblocking the the queues I would have a "delayed stream" and I'm searching for an event that I can send to the pipeline (or some other way) to reduce the delay to realtime again (or minimize it to close to zero) in a way that it would flush / send out the data from the queue instead of dismissing it.

I found this example:
https://stackoverflow.com/questions/32908047/gstreamer-increase-and-decrease-delay-on-the-fly

But this covers a slightly different use case, with this when I reset the que params it jumps to the present and drops all the data in the buffer.

Do you have any idea how could I solve this? 

Thank you for your help!

Bests,
Peter
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