[Bug 750794] New: Lipsync problem using mp4mux with late v4l2src
GStreamer (GNOME Bugzilla)
bugzilla at gnome.org
Thu Jun 11 07:41:37 PDT 2015
https://bugzilla.gnome.org/show_bug.cgi?id=750794
Bug ID: 750794
Summary: Lipsync problem using mp4mux with late v4l2src
Classification: Platform
Product: GStreamer
Version: git master
OS: Linux
Status: NEW
Severity: normal
Priority: Normal
Component: gst-plugins-good
Assignee: gstreamer-bugs at lists.freedesktop.org
Reporter: frederic.sureau at veo-labs.com
QA Contact: gstreamer-bugs at lists.freedesktop.org
GNOME version: ---
From:
http://lists.freedesktop.org/archives/gstreamer-devel/2015-June/053159.html
I am facing lipsync problems while muxing live sources into an mp4 file.
Here is the pipeline:
gst-launch-1.0 -ev mp4mux name=mux ! filesink location=test.mp4
v4l2src device=/dev/v4l/by-path/ipu1-capture io-mode=dmabuf !
"video/x-raw,format=NV12,width=1280,height=720,framerate=50/1" !
v4l2h264enc device=/dev/v4l/by-path/vpu-encoder
output-io-mode=dmabuf-import !
h264parse ! queue ! mux.
alsasrc device=hw:sndcard0,0 ! "audio/x-raw, rate=48000" ! faac !
aacparse ! queue ! mux.
The v4l2src element takes some time to initialize, so the first buffer
arrives after 300ms or 400ms.
Timestamps start accordingly around 0:00:00.300
Timestamps are conserved after the encoder element (checked using identity)
Sound start immediately at 0
Audio/video sync is OK when using matroskamux, flvmux or tsmux but
desynchronized when using mp4mux. This is weird because *video* is late,
as if the real lateness was compensated 2 times.
I fixed the problem by removing calls to update_edit_list function
in the qtmux element:
https://gitlab.com/veo-labs/gst-plugins-good/commit/1febe4fc6fe2fe1322d5ae5c062da2903990680a
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