[FFmpeg-devel] [PATCH v4] avformat/rcwtdec: add RCWT Closed Captions demuxer

[Stefano Sabatini]

On date Saturday 2024-03-16 23:29:41 -0500, Marth64 wrote:
> Raw Captions With Time (RCWT) is a format native to ccextractor, a commonly
> used open source tool for processing 608/708 Closed Captions (CC) sources.
> RCWT can be used to archive the original CC bitstream. The muxer was added
> in January 2024. In this commit, add the demuxer.
> 
> One can now demux RCWT files for rendering in ccaption_dec or interoperate
> with ccextractor (which produces RCWT). Using the muxer/demuxer combination,
> the CC bits can be kept for further processing or rendering with either tool.
> This can be an effective approach to backup original CC presentations.
> 
> Prior to this, the next best solution was FFmpeg's SCC muxer, but SCC itself
> is not compatible with ccextractor (which is a de facto OSS CC processing tool)
> and it is a proprietary format.
> 
> Tests will follow.
> 
> Signed-off-by: Marth64 <marth64 at proxyid.net>
> ---
>  libavformat/Makefile     |   1 +
>  libavformat/allformats.c |   1 +
>  libavformat/rcwtdec.c    | 153 +++++++++++++++++++++++++++++++++++++++

missing Changelog entry

>  3 files changed, 155 insertions(+)
>  create mode 100644 libavformat/rcwtdec.c
> 
> diff --git a/libavformat/Makefile b/libavformat/Makefile
> index 94a949f555..a6de720d8c 100644
> --- a/libavformat/Makefile
> +++ b/libavformat/Makefile
> @@ -493,6 +493,7 @@ OBJS-$(CONFIG_QOA_DEMUXER)               += qoadec.o
>  OBJS-$(CONFIG_R3D_DEMUXER)               += r3d.o
>  OBJS-$(CONFIG_RAWVIDEO_DEMUXER)          += rawvideodec.o
>  OBJS-$(CONFIG_RAWVIDEO_MUXER)            += rawenc.o
> +OBJS-$(CONFIG_RCWT_DEMUXER)              += rcwtdec.o subtitles.o
>  OBJS-$(CONFIG_RCWT_MUXER)                += rcwtenc.o subtitles.o
>  OBJS-$(CONFIG_REALTEXT_DEMUXER)          += realtextdec.o subtitles.o
>  OBJS-$(CONFIG_REDSPARK_DEMUXER)          += redspark.o
> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> index e15d0fa6d7..3140018f8d 100644
> --- a/libavformat/allformats.c
> +++ b/libavformat/allformats.c
> @@ -391,6 +391,7 @@ extern const FFInputFormat  ff_qoa_demuxer;
>  extern const FFInputFormat  ff_r3d_demuxer;
>  extern const FFInputFormat  ff_rawvideo_demuxer;
>  extern const FFOutputFormat ff_rawvideo_muxer;
> +extern const FFInputFormat  ff_rcwt_demuxer;
>  extern const FFOutputFormat ff_rcwt_muxer;
>  extern const FFInputFormat  ff_realtext_demuxer;
>  extern const FFInputFormat  ff_redspark_demuxer;
> diff --git a/libavformat/rcwtdec.c b/libavformat/rcwtdec.c
> new file mode 100644
> index 0000000000..1fd35be41b
> --- /dev/null
> +++ b/libavformat/rcwtdec.c
> @@ -0,0 +1,153 @@
> +/*
> + * RCWT (Raw Captions With Time) demuxer
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/*
> + * RCWT (Raw Captions With Time) is a format native to ccextractor, a commonly
> + * used open source tool for processing 608/708 Closed Captions (CC) sources.
> + * It can be used to archive the original, raw CC bitstream and to produce
> + * a source file for later CC processing or conversion. As a result,
> + * it also allows for interopability with ccextractor for processing CC data
> + * extracted via ffmpeg. The format is simple to parse and can be used
> + * to retain all lines and variants of CC.
> + *
> + * This demuxer implements the specification as of March 2024, which has
> + * been stable and unchanged since April 2014.
> + *
> + * A free specification of RCWT can be found here:
> + * @url{https://github.com/CCExtractor/ccextractor/blob/master/docs/BINARY_FILE_FORMAT.TXT}
> + */

move part of this content to doc/demuxers.texi

Also having some practical example might be useful.

[...]

LGTM otherwise, thanks.