[FFmpeg-devel] [PATCH v6 1/4] avformat/rcwtdec: add RCWT Closed Captions demuxer
Stefano Sabatini
stefasab at gmail.com
Wed Mar 20 16:37:38 EET 2024
On date Tuesday 2024-03-19 17:44:26 -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>
> ---
> Changelog | 2 +-
> libavformat/Makefile | 1 +
> libavformat/allformats.c | 1 +
> libavformat/rcwtdec.c | 150 +++++++++++++++++++++++++++++++++++++++
missing docs in the update?
> 4 files changed, 153 insertions(+), 1 deletion(-)
> create mode 100644 libavformat/rcwtdec.c
>
> diff --git a/Changelog b/Changelog
> index e3ca52430c..abe5f79b85 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -19,7 +19,7 @@ version <next>:
> - lavu/eval: introduce randomi() function in expressions
> - VVC decoder
> - fsync filter
> -- Raw Captions with Time (RCWT) closed caption muxer
> +- RCWT (Raw Captions with Time) Closed Captions muxer and demuxer
> - ffmpeg CLI -bsf option may now be used for input as well as output
> - ffmpeg CLI options may now be used as -/opt <path>, which is equivalent
> to -opt <contents of file <path>>
> 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..0d9eba025a
> --- /dev/null
> +++ b/libavformat/rcwtdec.c
> @@ -0,0 +1,150 @@
> +/*
> + * 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.
> + *
> + * 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}
> + */
> +
> +#include "avformat.h"
> +#include "demux.h"
> +#include "internal.h"
> +#include "subtitles.h"
> +#include "libavutil/intreadwrite.h"
> +
> +#define RCWT_CLUSTER_MAX_BLOCKS 65535
> +#define RCWT_BLOCK_SIZE 3
> +#define RCWT_HEADER_SIZE 11
> +
> +typedef struct RCWTContext {
> + FFDemuxSubtitlesQueue q;
> +} RCWTContext;
> +
> +static int rcwt_read_header(AVFormatContext *avf)
> +{
> + RCWTContext *rcwt = avf->priv_data;
> +
> + AVPacket *sub = NULL;
> + AVStream *st;
> + uint8_t header[RCWT_HEADER_SIZE] = {0};
> + int nb_bytes = 0;
> +
> + /* validate the header */
> + nb_bytes = avio_read(avf->pb, header, RCWT_HEADER_SIZE);
> + if (nb_bytes != RCWT_HEADER_SIZE) {
> + av_log(avf, AV_LOG_ERROR, "Header does not have the expected size "
> + "(expected=%d actual=%d)\n",
> + RCWT_HEADER_SIZE, nb_bytes);
> + return AVERROR_INVALIDDATA;
> + }
> +
> + if (AV_RB16(header + 6) != 0x0001) {
> + av_log(avf, AV_LOG_ERROR, "RCWT format version is not compatible "
> + "(only version 0.001 is known)\n");
> + return AVERROR_INVALIDDATA;
> + }
> +
> + av_log(avf, AV_LOG_DEBUG, "RCWT writer application: %02X version: %02x\n",
> + header[3], header[5]);
> +
> + /* setup AVStream */
> + st = avformat_new_stream(avf, NULL);
> + if (!st)
> + return AVERROR(ENOMEM);
> +
> + st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
> + st->codecpar->codec_id = AV_CODEC_ID_EIA_608;
> +
> + avpriv_set_pts_info(st, 64, 1, 1000);
> +
> + /* demux */
> + while (!avio_feof(avf->pb)) {
> + int64_t cluster_pts = AV_NOPTS_VALUE;
> + int cluster_nb_blocks = 0;
> + int cluster_size = 0;
do you need to init these ones?
[...]
Looks good to me otherwise.
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