h264parse behavior with stream-format=byte-stream, alignment=nal input caps

Michał Wróbel michal.wrobel at flytronic.pl
Mon Dec 15 04:35:02 PST 2014


I am investigating behavior of h264parse (1.2.4) being fed with
video/x-h264, stream-format=byte-stream, alignment=nal. It seems that
h264parse doesn't use the "alignment=nal" information for speeding up
the parsing - instead of pushing the NALs as soon as they arrive at the
sink, it waits for the next NAL or rather the byte stream delimiter each
NAL in stream-format=byte-stream starts with.

You can easily notice this behavior using the following pipeline:

gst-launch-1.0 -v videotestsrc pattern=ball num-buffers=100 \
! "video/x-raw, framerate=(fraction)25" \
! x264enc aud=false \
! h264parse \
! "video/x-h264, stream-format=byte-stream, alignment=nal" \
! identity silent=false \
! h264parse \
! identity silent=false \
! avdec_h264 \
! fakesink sync=false

Is there any reason for such a behavior or is it a bug?

Best regards,
Michał Wróbel

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