[FFmpeg-devel] [PATCH] libx265: support ATSC A/53 captions

[Eran Kornblau]

> 
> On 08.11.2022 15:25, Eran Kornblau wrote:
> >>
> >> -----Original Message-----
> >> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of 
> >> Timo Rothenpieler
> >> Sent: Tuesday, 8 November 2022 13:33
> >> To: ffmpeg-devel at ffmpeg.org
> >> Subject: Re: [FFmpeg-devel] [PATCH] libx265: support ATSC A/53 
> >> captions
> >>
> >>>
> >>> The attached patch adds rendering of ATSC A/53 captions as HEVC SEI messages.
> >>> The option name/implementation is aligned with the corresponding libx264 feature.
> >>
> >> What frees the sei data on success?
> >>
> > Thanks Timo, good point!
> >
> > I missed the fact that libx264 gets a callback for freeing the SEI payloads (sei_free).
> > It seems libx265 does not have this option, so I added some 'for' loop to free the payloads after the call to encoder_encode.
> >
> > In addition:
> > 1. I added av_memdup on the 'user-data-unregistered' side data so that it won't be freed twice.
> > 2. I added a 'free_picture' function for freeing the x265_picture in case of error.
> > (both changes are aligned with the implementation in libx264.c)
> >
> > Updated patch attached.
> 
> One nit: splitting the first line of free_picture() in two isn't really neccesary and makes the function a bit uglier.
> 
Fixed

> One small problem: libx265 now needs to select atsc_a53 in configure, analog to how libx264 and all the others do.
> Otherwise the file containing the a53 code might not get compiled.
> 
Fixed

> LGTM otherwise
> 
Thanks!

Eran

> > While checking the point you raised, I ran some libx265 transcode with valgrind, and it reported errors unrelated to this patch.
> > Attaching the full output, in case anyone wants to have a look.
> 
> x265 has a bunch of issues related to SEI data.
> See for example https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftrac.ffmpeg.org%2Fticket%2F9666%23comment%3A1&data=05%7C01%7C%7C5cd31da5382f4946e0c508dac198454d%7C0c503748de3f4e2597e26819d53a42b6%7C1%7C0%7C638035156992542567%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=9AdmTE%2B4dzHED8KLN0ps2GvvynacXfrWjhVJk4SBWJo%3D&reserved=0
> 
> i.e. if the number of per-frame sei data ever increases past its initial count, it'll just straight up explode.
> _______________________________________________

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