| Message ID | 20230317200941.3936-1-dheitmueller@ltnglobal.com |
|---|---|
| Headers | show |
| Series | Properly handle CEA-708 caption data when transcoding | expand |
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@ltnglobal.com> wrote: ATTENZIONE: mail esterna. Se il messaggio è sospetto, invialo come allegato a bedatasmart@skytv.it<mailto:bedatasmart@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
On Fri, Mar 17, 2023 at 7:23 PM BUCCIANTINI Francesco - ADECCO <francesco.bucciantini.adecco@skytv.it> wrote: > > 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... :( I don't have any plans to work on OP-47, and I'm not sure if anyone else does. While I've done a bit of work with it in the SDI domain, I'm not super familiar with how it's treated by ffmpeg, or whether a similar approach is appropriate for dealing with it. I can say that the FIFO here is highly specific to the CEA-708 standard, as we have to disassemble and reassemble the payloads to meet the specification (i.e. not applicable to OP-47). Devin