On date Friday 2024-01-05 20:14:58 -0600, Marth64 wrote: > Signed-off-by: Marth64 <mart...@proxyid.net> > > Raw Captions With Time (RCWT) is a format native to ccextractor, a commonly > used open source tool for processing 608/708 closed caption (CC) sources. > It can be used to archive the original, raw CC bitstream and to produce > a source file file for later CC processing or conversion. As a result,
file file > 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. > > A free specification of RCWT can be found here: > https://github.com/CCExtractor/ccextractor/blob/master/docs/BINARY_FILE_FORMAT.TXT > This muxer implements the specification as of 01/05/2024, which has nit: use 2023-01-05 or EU format (2024/01/05) to avoid ambiguity > been stable and unchanged for 10 years as of this writing. > > This muxer will have some nuances from the way that ccextractor muxes RCWT. > No compatibility issues when processing the output with ccextractor > have been observed as a result of this so far, but mileage may vary > and outputs will not be a bit-exact match. > > Specifically, the differences are: > (1) This muxer will identify as "FF" as the writing program identifier, so > as to be honest about the output's origin. > > (2) ffmpeg's MPEG-1/2, H264, HEVC, etc. decoders extract closed captioning > data differently than ccextractor from embedded SEI/user data. > For example, DVD captioning bytes will be translated to ATSC A53 format. > This allows ffmpeg to handle 608/708 in a consistant way downstream. > This is a lossless conversion and the meaningful data is retained. > > (3) This muxer will not alter the extracted data except to remove invalid > packets in between valid CC blocks. On the other hand, ccextractor > will by default remove mid-stream padding, and add padding at the end > of the stream (in order to convey the end time of the source video). This is a nice highlight and should be probably partially moved to muxers.texi to expose this information to users (although many/most are not documented, we should start to do so). > --- > libavformat/Makefile | 1 + > libavformat/allformats.c | 1 + > libavformat/rcwtenc.c | 203 +++++++++++++++++++++++++++++++++++++++ > tests/fate/subtitles.mak | 3 + > tests/ref/fate/sub-rcwt | 1 + missing Changelog entry, and I don't remember if new elements addition entails a minor library bump (probably it should) > 5 files changed, 209 insertions(+) > create mode 100644 libavformat/rcwtenc.c > create mode 100644 tests/ref/fate/sub-rcwt > > diff --git a/libavformat/Makefile b/libavformat/Makefile > index 45dba53044..03c2c70e67 100644 > --- a/libavformat/Makefile > +++ b/libavformat/Makefile > @@ -489,6 +489,7 @@ 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-$(CONFIG_RCWT_MUXER) += rcwtenc.o subtitles.o > OBJS-$(CONFIG_REALTEXT_DEMUXER) += realtextdec.o subtitles.o > OBJS-$(CONFIG_REDSPARK_DEMUXER) += redspark.o > OBJS-$(CONFIG_RKA_DEMUXER) += rka.o apetag.o img2.o > diff --git a/libavformat/allformats.c b/libavformat/allformats.c > index dc2acf575c..fb14f15739 100644 > --- a/libavformat/allformats.c > +++ b/libavformat/allformats.c > @@ -388,6 +388,7 @@ extern const AVInputFormat ff_qoa_demuxer; > extern const AVInputFormat ff_r3d_demuxer; > extern const AVInputFormat ff_rawvideo_demuxer; > extern const FFOutputFormat ff_rawvideo_muxer; > +extern const FFOutputFormat ff_rcwt_muxer; > extern const AVInputFormat ff_realtext_demuxer; > extern const AVInputFormat ff_redspark_demuxer; > extern const AVInputFormat ff_rka_demuxer; > diff --git a/libavformat/rcwtenc.c b/libavformat/rcwtenc.c > new file mode 100644 > index 0000000000..f70a80b175 > --- /dev/null > +++ b/libavformat/rcwtenc.c > @@ -0,0 +1,203 @@ > +/* > + * Raw Captions With Time (RCWT) muxer > + * Author: Marth64 <mart...@proxyid.net> > + * > + * 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 > + */ > + > +/* > + * Raw Captions With Time (RCWT) is a format native to ccextractor, a > commonly > + * used open source tool for processing 608/708 closed caption (CC) sources. > + * It can be used to archive the original, raw CC bitstream and to produce > + * a source file 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. > + * > + * A free specification of RCWT can be found here: > + * > https://github.com/CCExtractor/ccextractor/blob/master/docs/BINARY_FILE_FORMAT.TXT > + * This muxer implements the specification as of 01/05/2024, which has > + * been stable and unchanged for 10 years as of this writing. > + * > + * This muxer will have some nuances from the way that ccextractor muxes > RCWT. > + * No compatibility issues when processing the output with ccextractor > + * have been observed as a result of this so far, but mileage may vary > + * and outputs will not be a bit-exact match. > + * > + * Specifically, the differences are: > + * (1) This muxer will identify as "FF" as the writing program identifier, > so > + * as to be honest about the output's origin. > + * (2) ffmpeg's MPEG-1/2, H264, HEVC, etc. decoders extract closed > captioning > + * data differently than ccextractor from embedded SEI/user data. > + * For example, DVD captioning bytes will be translated to ATSC A53 > format. > + * This allows ffmpeg to handle 608/708 in a consistant way downstream. > + * This is a lossless conversion and the meaningful data is retained. > + * (3) This muxer will not alter the extracted data except to remove invalid > + * packets in between valid CC blocks. On the other hand, ccextractor > + * will by default remove mid-stream padding, and add padding at the end > + * of the stream (in order to convey the end time of the source video). > + */ ditto > + > +#include "avformat.h" > +#include "internal.h" > +#include "mux.h" > +#include "libavutil/log.h" > +#include "libavutil/intreadwrite.h" > + > +#define RCWT_CLUSTER_MAX_BLOCKS 65535 > +#define RCWT_BLOCK_SIZE 3 * sizeof(uint8_t) or just use 3 > + > +typedef struct RCWTContext { > + int cluster_nb_blocks; > + int cluster_pos; > + int64_t cluster_pts; > + uint8_t cluster_buf[RCWT_CLUSTER_MAX_BLOCKS * RCWT_BLOCK_SIZE]; > +} RCWTContext; > + > +static void rcwt_init_cluster(AVFormatContext *avf) > +{ > + RCWTContext *rcwt = avf->priv_data; > + > + rcwt->cluster_nb_blocks = 0; > + rcwt->cluster_pos = 0; > + rcwt->cluster_pts = AV_NOPTS_VALUE; > + memset(rcwt->cluster_buf, 0, sizeof(rcwt->cluster_buf)); > +} > + > +static void rcwt_flush_cluster(AVFormatContext *avf) > +{ > + RCWTContext *rcwt = avf->priv_data; > + > + if (rcwt->cluster_nb_blocks > 0) { > + avio_wl64(avf->pb, rcwt->cluster_pts); > + avio_wl16(avf->pb, rcwt->cluster_nb_blocks); > + avio_write(avf->pb, rcwt->cluster_buf, > + (rcwt->cluster_nb_blocks * RCWT_BLOCK_SIZE)); nit: weird indent > + } > + > + rcwt_init_cluster(avf); > +} > + > +static int rcwt_write_header(AVFormatContext *avf) > +{ > + if (avf->nb_streams != 1 > + || avf->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE > + || avf->streams[0]->codecpar->codec_id != AV_CODEC_ID_EIA_608) { nit+: weird indent > + av_log(avf, AV_LOG_ERROR, > + "RCWT supports only one CC (608/708) stream\n"); this could be more explicit: "RCWT supports only one CC (608/708) stream, more than one stream was provided or its codec type was not CC (608/708)\n"); > + return AVERROR(EINVAL); > + } > + > + avpriv_set_pts_info(avf->streams[0], 64, 1, 1000); > + > + /* magic number */ > + avio_wb16(avf->pb, 0xCCCC); > + avio_w8(avf->pb, 0xED); > + > + /* program version (identify as ffmpeg) */ > + avio_wb16(avf->pb, 0xFF00); > + avio_w8(avf->pb, 0x60); > + > + /* format version, only version 0.001 supported for now */ > + avio_wb16(avf->pb, 0x0001); > + > + /* reserved */ > + avio_wb16(avf->pb, 0x000); > + avio_w8(avf->pb, 0x00); > + > + rcwt_init_cluster(avf); > + > + return 0; > +} > + > +static int rcwt_write_packet(AVFormatContext *avf, AVPacket *pkt) > +{ > + RCWTContext *rcwt = avf->priv_data; > + > + int in_block = 0; > + int nb_block_bytes = 0; > + > + if (pkt->size == 0) > + return 0; > + > + /* new PTS, new cluster */ > + if (pkt->pts != rcwt->cluster_pts) { > + rcwt_flush_cluster(avf); > + rcwt->cluster_pts = pkt->pts; > + } > + > + if (pkt->pts == AV_NOPTS_VALUE) { > + av_log(avf, AV_LOG_WARNING, "Ignoring CC packet with no PTS\n"); > + return 0; > + } > + > + for (int i = 0; i < pkt->size; i++) { > + uint8_t cc_valid; > + uint8_t cc_type; > + > + if (rcwt->cluster_nb_blocks == RCWT_CLUSTER_MAX_BLOCKS) { > + av_log(avf, AV_LOG_WARNING, > + "Starting new cluster due to size\n"); > + rcwt_flush_cluster(avf); > + } > + > + cc_valid = (pkt->data[i] & 0x04) >> 2; nit: no need to shift > + cc_type = pkt->data[i] & 0x03; > + > + if (!in_block && !(cc_valid || cc_type == 3)) > + continue; > + > + memcpy(&rcwt->cluster_buf[rcwt->cluster_pos], > + &pkt->data[i], sizeof(uint8_t)); indent > + rcwt->cluster_pos++; > + > + if (!in_block) { > + in_block = 1; > + nb_block_bytes = 1; > + continue; > + } > + > + nb_block_bytes++; > + > + if (nb_block_bytes == RCWT_BLOCK_SIZE) { > + in_block = 0; > + nb_block_bytes = 0; > + rcwt->cluster_nb_blocks++; > + } > + } > + > + return 0; > +} > + > +static int rcwt_write_trailer(AVFormatContext *avf) > +{ > + rcwt_flush_cluster(avf); > + > + return 0; > +} > + > +const FFOutputFormat ff_rcwt_muxer = { > + .p.name = "rcwt", > + .p.long_name = NULL_IF_CONFIG_SMALL("Raw Captions With Time"), > + .p.extensions = "bin", > + .p.flags = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS | > AVFMT_TS_NONSTRICT, > + .p.subtitle_codec = AV_CODEC_ID_EIA_608, > + .priv_data_size = sizeof(RCWTContext), > + .write_header = rcwt_write_header, > + .write_packet = rcwt_write_packet, > + .write_trailer = rcwt_write_trailer > +}; No more comments from me, thanks. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
