Video and audio not synchronous when using appsrc

[J. Krieg]

Hello,



I’m currently developing an application to display live TV using GStreamer
on a Raspberry Pi 2B.



Therefore I use two appsrc elements (one for video and one for audio) to
connect them to the V4L DVB demux device ‘/dev/dvb/adapter0/demux0’.

My pipelines are:



Video

  V4L DVB demux (DMX_OUT_TAP) -> appsrc ! h264parse ! v4l2h264dec ! queue !
kmssink

Audio

  V4L DVB demux (DMX_OUT_TAP) -> appsrc ! mpegaudioparse ! mpg123audiodec !
queue ! alsasink



I’ve created a thread which feeds the output of the 2 video and audio demux
devices into my appsrc elements and they feed them to both pipelines:



uint8_t vbuf[65536];

uint8_t abuf[4096];



// Read data from demux

vrc = read(vdfd, vbuf, sizeof(vbuf));

arc = read(adfd, abuf, sizeof(abuf));



// Create a new empty buffer and fill data into it

gvbuffer = gst_buffer_new_allocate(NULL, vrc, NULL);

gst_buffer_fill(gvbuffer, 0, vbuf, vrc);

gabuffer = gst_buffer_new_allocate(NULL, arc, NULL);

gst_buffer_fill(gabuffer, 0, abuf, arc);



// Push the buffer into the appsrc

g_signal_emit_by_name (((CustomData *)data)->vappsrc, "push-buffer",
gvbuffer, &vrb);

g_signal_emit_by_name (((CustomData *)data)->aappsrc, "push-buffer",
gabuffer, &arb);



// Free the buffers now that we are done with it

gst_buffer_unref (gvbuffer);

gst_buffer_unref (gabuffer);



This works quite well and I’ve got video and audio.



The only thing which doesn’t work as expected is that video and audio isn’t
synchronous.



What am I missing here and how to get video and audio synchronous?



Thanks for any advice.



Best Regards,

Joerg
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