@@ -18,6 +18,7 @@ version <next>:
- lavu/eval: introduce randomi() function in expressions
- VVC decoder
- fsync filter
+- Raw Captions with Time (RCWT) closed caption demuxer
version 6.1:
- libaribcaption decoder
@@ -2232,6 +2232,46 @@ Extensions: thd
SMPTE 421M / VC-1 video.
+@anchor{rcwt}
+@section rcwt
+
+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 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 muxer implements the specification as of 2024-01-05, 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:
+@enumerate
+@item
+This muxer will identify as "FF" as the writing program identifier, so
+as to be honest about the output's origin.
+@item
+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.
+@item
+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).
+@end enumerate
+
+A free specification of RCWT can be found here:
+@url{https://github.com/CCExtractor/ccextractor/blob/master/docs/BINARY_FILE_FORMAT.TXT}
+
@anchor{segment}
@section segment, stream_segment, ssegment
@@ -490,6 +490,7 @@ 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
@@ -389,6 +389,7 @@ 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;
new file mode 100644
@@ -0,0 +1,166 @@
+/*
+ * Raw Captions With Time (RCWT) muxer
+ * Author: Marth64 <marth64@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
+ */
+
+#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
+
+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));
+ }
+
+ rcwt_init_cluster(avf);
+}
+
+static int rcwt_write_header(AVFormatContext *avf)
+{
+ if (avf->nb_streams != 1 || avf->streams[0]->codecpar->codec_id != AV_CODEC_ID_EIA_608) {
+ av_log(avf, AV_LOG_ERROR,
+ "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;
+ 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], 1);
+ 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
+};
@@ -118,6 +118,9 @@ fate-sub-scc: CMD = fmtstdout ass -ss 57 -i $(TARGET_SAMPLES)/sub/witch.scc
FATE_SUBTITLES-$(call DEMMUX, SCC, SCC) += fate-sub-scc-remux
fate-sub-scc-remux: CMD = fmtstdout scc -i $(TARGET_SAMPLES)/sub/witch.scc -ss 4:00 -map 0 -c copy
+FATE_SUBTITLES-$(call DEMMUX, SCC, RCWT) += fate-sub-rcwt
+fate-sub-rcwt: CMD = md5 -i $(TARGET_SAMPLES)/sub/witch.scc -map 0 -c copy -f rcwt
+
FATE_SUBTITLES-$(call ALLYES, MPEGTS_DEMUXER DVBSUB_DECODER DVBSUB_ENCODER) += fate-sub-dvb
fate-sub-dvb: CMD = framecrc -i $(TARGET_SAMPLES)/sub/dvbsubtest_filter.ts -map s:0 -c dvbsub
new file mode 100644
@@ -0,0 +1 @@
+d86f179094a5752d68aa97d82cf887b0