Tee causing invalid h264 file

[Tim-Philipp Müller]

Hi Peter,

> When I run with this pipeline:
> gst-launch-1.0 -ve sunxisrc keyint=12 bitrate=5000 !  video/x-
> h264,width=1280,height=720,framerate=60/1 ! h264parse ! tee name=t \
>      t. ! queue !  filesink location=TeeTestNoOtherTee.h264
> I get a valid file.
> 
> When I run with 
> gst-launch-1.0 -ve sunxisrc keyint=12 bitrate=5000 !  video/x-
> h264,width=1280,height=720,framerate=60/1 ! h264parse ! tee name=t \
>      t. ! queue !  filesink location=TeeTestWithOtherTee.h264 \
>      t. ! queue ! rtph264pay mtu=1024 !  rtph264depay ! h264parse
> config-interval=1 ! fakesink
> 
> I get an h264 file that fails to play with ffplay: (snip details)
> Any thoughts about what is going on?

H.264 can be packetised in different stream formats. In one case you
end up writing video/x-h264,stream-format=byte-stream into the file
(aka "Annex B" format), in the other case video/x-h264,stream-
format=avc3. Annex B is self-synchronising and can be detected and read
from a file, whereas AVC/AVC3 format isn't really meant for writing
into a stream or file without external packetisation and should go into
a container such as Matroska or mp4. (In general, it's best to always
use a container in any case)

You can force the output format by putting a capsfilter with filtercaps
behind h264parse, e.g.

   h264parse ! video/x-h264,stream-format=byte-stream ! ....

Automatic negotiation with a tee and multiple tee branches in the mix
is a bit tricky, and doesn't always work right unfortunately. (It may
or may not be fixed in newer versions of GStreamer, I haven't checked.
1.18 is quite old now.)

Cheers
 Tim

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