[FFmpeg-devel] [RFC PATCH 0/5] Properly handle CEA-708 caption data when transcoding

[BUCCIANTINI Francesco - ADECCO]

This is indeed very welcome.
Being able to re-encode from 25i to 50p while preserving subtitles has been something I've been trying to do for a while, so seeing this patch for CEA-708 is definitely a nice thing.

I have a question, though: will something similar be done for OP-47 subtitles too?
Currently they suffer the same issue when a re-encode changes the frame rate... :(

On Mar 17, 2023 21:10, Devin Heitmueller <devin.heitmueller at ltnglobal.com> wrote:
ATTENZIONE: mail esterna. Se il messaggio è sospetto, invialo come allegato a bedatasmart at skytv.it<mailto:bedatasmart at skytv.it>


This patch series is intended to address long-standing known issues where
CEA-708 caption data is either duplicated or corrupted (i.e. 50% of the data
is lost).  We employ an intermediate queue, which is available to filters that
change the frame rate of the video, which stashes the 608/708 data and
reconstructs properly formed 708 tuples on the output side (injecting
appropriate padding as needed).

The common functions are implemented in libavutil, but I am open to
suggestions.  While all the users in this patch series are within
libavfilter, there are use cases where this functionality would
be useful within libavformat (which is why libavutil was chosen).

Comments/feedback are welcomed.

Thanks,

Devin

Devin Heitmueller (5):
  ccfifo: Properly handle CEA-708 captions through framerate conversion
  vf_fps: properly preserve CEA-708 captions
  yadif: Properly preserve CEA-708 closed captions
  tinterlace: Properly preserve CEA-708 closed captions
  vf_ccrepack: Add new filter to repack CEA-708 side data

 doc/filters.texi            |  10 ++
 libavfilter/Makefile        |   1 +
 libavfilter/allfilters.c    |   1 +
 libavfilter/tinterlace.h    |   2 +
 libavfilter/vf_bwdif.c      |   7 ++
 libavfilter/vf_ccrepack.c   |  95 ++++++++++++++++++
 libavfilter/vf_fps.c        |   9 +-
 libavfilter/vf_tinterlace.c |  10 ++
 libavfilter/vf_yadif.c      |   6 ++
 libavfilter/vf_yadif_cuda.c |   8 ++
 libavfilter/yadif.h         |   2 +
 libavfilter/yadif_common.c  |   5 +
 libavutil/Makefile          |   2 +
 libavutil/ccfifo.c          | 192 ++++++++++++++++++++++++++++++++++++
 libavutil/ccfifo.h          |  85 ++++++++++++++++
 15 files changed, 434 insertions(+), 1 deletion(-)
 create mode 100644 libavfilter/vf_ccrepack.c
 create mode 100644 libavutil/ccfifo.c
 create mode 100644 libavutil/ccfifo.h

--
2.35.1.655.ga68dfadae5

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