[FFmpeg-devel] [PATCH v3] avformat/rtpdec_rfc4175: Fix incorrect copy_offset calculation

[Michael Niedermayer]

On Thu, Jun 27, 2019 at 06:06:22AM +0000, Jacob Siddall wrote:
> The previous calculation code did not account for the fact that the
> copy_offset for the start of the frame array is at index 0, yet the
> scan line number from the rfc4175 RTP header starts at 1.
> This caused 2 issues to appear:
> - The first scan line was being copied into the array where the second
>   scan line should be. This caused the resulting video to have a green
>   line at the top of it.
> - Since the packet containing the last scan line would fail the
>   calculation, the packet with the RTP marker would not be processed
>   which caused a log message saying "Missed previous RTP marker" to be
>   outputted for each frame.
> 
> Signed-off-by: Jacob Siddall <kobe at live.com.au>
> ---
> Changes in v2:
>   - Don't handle packet if the line number is less than 1
> 
> Section 12 in the VSF technical recommendation TR-03 specifies that the
> video scan line numbers should start at 1.
> http://www.videoservicesforum.org/download/technical_recommendations/VSF_TR-03_2015-11-12.pdf
> 
> Changes in v3:
>   - Changed the commit hash abbreviation in the patch file diff to be 10
>     characters in length rather than 7. This was causing the patch file
>     to fail when it was applied. 
> 
>  libavformat/rtpdec_rfc4175.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

The patch looks reasonable to me but i dont really know rfc4175
Ideally someone who knows rfc4175 should make the final decission to apply it
maybe whoever applies it can also bump the micro version so user apps have
a way to detect this line shifting change

Thanks

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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