This commit adds preliminary support for decoding the SRV3 subtitle format.
SRV3 is the internal format YouTube uses for their captions. Supporting it
in ffmpeg allows video players to play a significant subset of SRV3
mostly correctly by converting it to ASS.
Currently the following features are unsupported:
- Vertical text
- Scrolling text
- Ruby text
- Background box support is janky
These issues are mostly due to limitations of the ASSv3 format.
---
This is my first time interacting with the ffmpeg-devel mailing list so
please bear with me, I've been sitting on these changes for almost a
year and only now managed to kind of overcome the intimidating nature of
ffmpeg-devel.
At first it seemed to me like the demuxer should take care of parsing
the subtitle file so I did it this way and added opaque side data that
contains pointers to an internal representation of SRV3 metadata. I don't
know whether this is the right approach though, please correct me if it
isn't.
I haven't added tests since I haven't looked into how that would be
done, but I've been using it in my mpv build for almost a year now and
it seems to work fine.
Although as if specifically to inconvenience me libass appears to have
introduced what seems to be a bug into their background rendering that I
just discovered as I'm writing this. I don't think this patch is at
fault though.
configure | 2 +
libavcodec/Makefile | 1 +
libavcodec/allcodecs.c | 1 +
libavcodec/codec_desc.c | 7 +
libavcodec/codec_id.h | 1 +
libavcodec/packet.c | 2 +
libavcodec/packet.h | 12 +
libavcodec/srv3dec.c | 260 +++++++++++++++++++
libavformat/Makefile | 1 +
libavformat/allformats.c | 1 +
libavformat/srv3.h | 95 +++++++
libavformat/srv3dec.c | 542 +++++++++++++++++++++++++++++++++++++++
12 files changed, 925 insertions(+)
create mode 100644 libavcodec/srv3dec.c
create mode 100644 libavformat/srv3.h
create mode 100644 libavformat/srv3dec.c
diff --git a/configure b/configure
index bf55ba67fa..a61333a93d 100755
--- a/configure
+++ b/configure
@@ -3724,6 +3724,8 @@ wtv_demuxer_select="mpegts_demuxer riffdec"
wtv_muxer_select="mpegts_muxer riffenc"
xmv_demuxer_select="riffdec"
xwma_demuxer_select="riffdec"
+srv3_demuxer_deps="libxml2"
+srv3_demuxer_select="srv3dec"
# indevs / outdevs
android_camera_indev_deps="android camera2ndk mediandk pthreads"
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index c946444175..a89b5c27f2 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -707,6 +707,7 @@ OBJS-$(CONFIG_SP5X_DECODER) += sp5xdec.o
OBJS-$(CONFIG_SRGC_DECODER) += mscc.o
OBJS-$(CONFIG_SRT_DECODER) += srtdec.o ass.o htmlsubtitles.o
OBJS-$(CONFIG_SRT_ENCODER) += srtenc.o ass_split.o
+OBJS-$(CONFIG_SRV3_DECODER) += srv3dec.o ass.o
OBJS-$(CONFIG_STL_DECODER) += textdec.o ass.o
OBJS-$(CONFIG_SUBRIP_DECODER) += srtdec.o ass.o htmlsubtitles.o
OBJS-$(CONFIG_SUBRIP_ENCODER) += srtenc.o ass_split.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index 0b559dfc58..7bb2a4170d 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -738,6 +738,7 @@ extern const FFCodec ff_webvtt_encoder;
extern const FFCodec ff_webvtt_decoder;
extern const FFCodec ff_xsub_encoder;
extern const FFCodec ff_xsub_decoder;
+extern const FFCodec ff_srv3_decoder;
/* external libraries */
extern const FFCodec ff_aac_at_encoder;
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index bc9163bf98..2832e817b5 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -3634,6 +3634,13 @@ static const AVCodecDescriptor codec_descriptors[] = {
.long_name = NULL_IF_CONFIG_SMALL("ARIB STD-B24 caption"),
.profiles = NULL_IF_CONFIG_SMALL(ff_arib_caption_profiles),
},
+ {
+ .id = AV_CODEC_ID_SRV3,
+ .type = AVMEDIA_TYPE_SUBTITLE,
+ .name = "srv3",
+ .long_name = NULL_IF_CONFIG_SMALL("SRV3 subtitle"),
+ .props = AV_CODEC_PROP_TEXT_SUB,
+ },
/* other kind of codecs and pseudo-codecs */
{
diff --git a/libavcodec/codec_id.h b/libavcodec/codec_id.h
index 6bfaa02601..774de43f4d 100644
--- a/libavcodec/codec_id.h
+++ b/libavcodec/codec_id.h
@@ -579,6 +579,7 @@ enum AVCodecID {
AV_CODEC_ID_HDMV_TEXT_SUBTITLE,
AV_CODEC_ID_TTML,
AV_CODEC_ID_ARIB_CAPTION,
+ AV_CODEC_ID_SRV3,
/* other specific kind of codecs (generally used for attachments) */
AV_CODEC_ID_FIRST_UNKNOWN = 0x18000, ///< A dummy ID pointing at
the start of various fake codecs.
diff --git a/libavcodec/packet.c b/libavcodec/packet.c
index 5104eb98b1..c6425c8c1d 100644
--- a/libavcodec/packet.c
+++ b/libavcodec/packet.c
@@ -288,6 +288,8 @@ const char *av_packet_side_data_name(enum
AVPacketSideDataType type)
case AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL: return "Matroska
BlockAdditional";
case AV_PKT_DATA_WEBVTT_IDENTIFIER: return "WebVTT ID";
case AV_PKT_DATA_WEBVTT_SETTINGS: return "WebVTT Settings";
+ case AV_PKT_DATA_SRV3_HEAD: return "SRV3 Head";
+ case AV_PKT_DATA_SRV3_EVENT: return "SRV3 Event metatada";
case AV_PKT_DATA_METADATA_UPDATE: return "Metadata Update";
case AV_PKT_DATA_MPEGTS_STREAM_ID: return "MPEGTS Stream ID";
case AV_PKT_DATA_MASTERING_DISPLAY_METADATA: return "Mastering display
metadata";
diff --git a/libavcodec/packet.h b/libavcodec/packet.h
index c1f1ad7b43..d3ccb97809 100644
--- a/libavcodec/packet.h
+++ b/libavcodec/packet.h
@@ -345,6 +345,18 @@ enum AVPacketSideDataType {
*/
AV_PKT_DATA_LCEVC,
+ /**
+ * SRV3 subtitle header.
+ * Not part of public API, do not rely on its existance or layout.
+ */
+ AV_PKT_DATA_SRV3_HEAD,
+
+ /**
+ * SRV3 metadata associated with a single subtitle event.
+ * Not part of public API, do not rely on its existance or layout.
+ */
+ AV_PKT_DATA_SRV3_EVENT,
+
/**
* The number of side data types.
* This is not part of the public API/ABI in the sense that it may
diff --git a/libavcodec/srv3dec.c b/libavcodec/srv3dec.c
new file mode 100644
index 0000000000..a924c1e50f
--- /dev/null
+++ b/libavcodec/srv3dec.c
@@ -0,0 +1,260 @@
+/*
+ * Copyright (c) 2024 Hubert Głuchowski
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * SRV3/YTT subtitle decoder
+ * @see https://github.com/arcusmaximus/YTSubConverter
+ */
+
+#include "avcodec.h"
+#include "ass.h"
+#include "codec_internal.h"
+#include "libavformat/srv3.h"
+#include "libavutil/bprint.h"
+#include "version.h"
+
+const int PLAY_RES_X = 1280;
+const int PLAY_RES_Y = 720;
+const int BASE_FONT_SIZE = 38;
+
+// From
https://github.com/arcusmaximus/YTSubConverter/blob/38fb2ab469f37e8f3a5a6a27adf91d9d0e81ea4f/YTSubConverter.Shared/Formats/YttDocument.cs#L1123
+static const char *srv3_font_style_to_font_name(int font_style) {
+ switch(font_style) {
+ case 1:
+ return "Courier New";
+ case 2:
+ return "Times New Roman";
+ case 3:
+ return "Lucida Console";
+ case 4:
+ return "Comic Sans Ms";
+ case 6:
+ return "Monotype Corsiva";
+ case 7:
+ return "Carrois Gothic Sc";
+ default:
+ return "Roboto";
+ };
+}
+
+static int srv3_point_to_ass_alignment(int point) {
+ if (point >= 6)
+ return point - 5;
+ else if (point < 3)
+ return point + 7;
+ return point + 1;
+}
+
+static int srv3_coord_to_ass(int coord, int max) {
+ return (2.0 + coord * 0.96) / 100.0 * max;
+}
+
+static float srv3_font_size_to_ass(int size) {
+ return BASE_FONT_SIZE * (1.0 + ((size / 100.0) - 1.0) / 4.0);
+}
+
+#define RGB2BGR(color) (((color) & 0x0000FF) << 16 | ((color) & 0x00FF00) |
((color) & 0xFF0000) >> 16)
+#define RGB2ASS(color, alpha) RGB2BGR(color) | ((0xFF - (alpha)) << 24)
+#define ASSBOOL(value) ((value) > 0) * -1
+
+static void srv3_style_segment(AVCodecContext *ctx, AVBPrint *buf, SRV3Segment
*segment) {
+ av_bprintf(buf, "{\\rP%i}", segment->pen->id + 1);
+
+ if (segment->pen->background_alpha == 0) {
+ switch(segment->pen->edge_type) {
+ case SRV3_EDGE_HARD_SHADOW:
+ av_bprintf(buf, "{\\shad2}");
+ break;
+ /*
+ * I think falling back to a glow effect on soft shadow is better than
just using a normal shadow.
+ * YTSubConverter doesn't agree with me on this and I'm not completely
sure whether it's the right choice.
+ */
+ case SRV3_EDGE_SOFT_SHADOW:
+ case SRV3_EDGE_GLOW:
+ av_bprintf(buf, "{\\bord2\\blur3}");
+ break;
+ case SRV3_EDGE_BEVEL:
+ av_bprintf(buf, "{\\shad2}");
+ break;
+ case SRV3_EDGE_NONE:
+ break;
+ default:
+ av_log(ctx, AV_LOG_WARNING, "bug: Unhandled edge type %i in
decoder\n", segment->pen->edge_type);
+ break;
+ }
+ } else if (segment->pen->edge_type) {
+ /*
+ * ASS doesn't support text shadows or outlines with BorderStyle 3.
+ * TODO: Add an option to enable BorderStyle 4 usage
+ */
+ }
+}
+
+static void srv3_process_text(AVBPrint *buf, const char *text, int count) {
+ for (int i = 0; i < count; ++i) {
+ if (text[i] == '\r')
+ continue;
+ else if (text[i] == '\n')
+ av_bprintf(buf, "\\N");
+ else
+ av_bprintf(buf, "%c", text[i]);
+ }
+}
+
+static void srv3_position_event(SRV3EventMeta *event, int *x, int *y, int
*align) {
+ if (event->wp) {
+ *x = srv3_coord_to_ass(event->wp->x , PLAY_RES_X);
+ *y = srv3_coord_to_ass(event->wp->y, PLAY_RES_Y);
+ *align = srv3_point_to_ass_alignment(event->wp->point);
+ } else {
+ *x = srv3_coord_to_ass(50, PLAY_RES_X);
+ *y = srv3_coord_to_ass(100, PLAY_RES_Y);
+ *align = 2;
+ }
+}
+
+static void srv3_event_text_ass(AVCodecContext *ctx, AVBPrint *buf, const char
*text, SRV3EventMeta *event)
+{
+ SRV3Segment *segment;
+ int x, y, alignment;
+
+ srv3_position_event(event, &x, &y, &alignment);
+ av_bprintf(buf, "{\\an%i\\pos(%i,%i)}", alignment, x, y);
+
+ for (segment = event->segments; segment; segment = segment->next) {
+ srv3_style_segment(ctx, buf, segment);
+ srv3_process_text(buf, text, segment->size);
+ text += segment->size;
+ }
+}
+
+static int srv3_decode_frame(AVCodecContext *avctx, AVSubtitle *sub,
+ int *got_sub_ptr, const AVPacket *avpkt)
+{
+ int ret = 0;
+ FFASSDecoderContext *ctx = avctx->priv_data;
+ const char *text = avpkt->data;
+ SRV3EventMeta *event = (SRV3EventMeta*)av_packet_get_side_data(avpkt,
AV_PKT_DATA_SRV3_EVENT, NULL);
+ AVBPrint buf;
+
+ if (!text || avpkt->size == 0)
+ return 0;
+
+ av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
+
+ srv3_event_text_ass(avctx, &buf, text, event);
+ if (av_bprint_is_complete(&buf))
+ ret = ff_ass_add_rect(sub, buf.str, ctx->readorder++, 0, NULL, NULL);
+ else
+ ret = AVERROR(ENOMEM);
+
+ av_bprint_finalize(&buf, NULL);
+
+ if (ret < 0)
+ return ret;
+ *got_sub_ptr = sub->num_rects > 0;
+ return avpkt->size;
+}
+
+static av_cold int srv3_decoder_init(AVCodecContext *avctx) {
+ int ret = 0;
+ AVBPrint header;
+ const AVPacketSideData *head_sd;
+ SRV3Pen *pen;
+
+ av_bprint_init(&header, 0, AV_BPRINT_SIZE_UNLIMITED);
+
+ av_bprintf(&header,
+ "[Script Info]\r\n"
+ "; Script generated by FFmpeg/Lavc%s\r\n"
+ "ScriptType: v4.00+\r\n"
+ "PlayResX: %i\r\n"
+ "PlayResY: %i\r\n"
+ "WrapStyle: 0\r\n"
+ "ScaledBorderAndShadow: yes\r\n"
+ "YCbCr Matrix: None\r\n"
+ "\r\n"
+ "[V4+ Styles]\r\n"
+ "Format: Name, "
+ "Fontname, Fontsize, "
+ "PrimaryColour, SecondaryColour, OutlineColour, BackColour, "
+ "Bold, Italic, Underline, StrikeOut, "
+ "ScaleX, ScaleY, "
+ "Spacing, Angle, "
+ "BorderStyle, Outline, Shadow, "
+ "Alignment, MarginL, MarginR, MarginV, "
+ "Encoding\r\n",
+ !(avctx->flags & AV_CODEC_FLAG_BITEXACT) ?
AV_STRINGIFY(LIBAVCODEC_VERSION) : "",
+ PLAY_RES_X, PLAY_RES_Y);
+
+ head_sd = av_packet_side_data_get(avctx->coded_side_data,
avctx->nb_coded_side_data, AV_PKT_DATA_SRV3_HEAD);
+ if (head_sd) {
+ for (pen = ((SRV3Head*)head_sd->data)->pens; pen; pen = pen->next)
+ av_bprintf(&header,
+ "Style: "
+ "P%i," /* Name */
+ "%s,%f," /* Font{name,size} */
+ "&H%x,&H0,&H%x,&H%x," /*
{Primary,Secondary,Outline,Back}Colour */
+ "%i,%i,0,0," /* Bold, Italic, Underline,
StrikeOut */
+ "100,100," /* Scale{X,Y} */
+ "0,0," /* Spacing, Angle */
+ "%i,%i,0," /* BorderStyle, Outline, Shadow
*/
+ "2,0,0,0," /* Alignment, Margin[LRV] */
+ "1\r\n", /* Encoding */
+ pen->id + 1,
+ srv3_font_style_to_font_name(pen->font_style),
srv3_font_size_to_ass(pen->font_size),
+ RGB2ASS(pen->foreground_color, pen->foreground_alpha),
+ pen->background_alpha > 0
+ ? RGB2ASS(pen->background_color,
pen->background_alpha)
+ : RGB2ASS(pen->edge_color, pen->foreground_alpha),
+ pen->background_alpha > 0
+ ? RGB2ASS(pen->background_color,
pen->background_alpha)
+ : RGB2ASS(pen->edge_color, pen->foreground_alpha),
+ ASSBOOL(pen->attrs & SRV3_PEN_ATTR_BOLD),
ASSBOOL(pen->attrs & SRV3_PEN_ATTR_ITALIC),
+ pen->background_alpha > 0 ? 3 : (pen->edge_type > 0),
pen->background_alpha > 0);
+ }
+
+ av_bprintf(&header,
+ "[Events]\r\n"
+ "Format: Layer, Start, End, Style, Name, MarginL, MarginR,
MarginV, Effect, Text\r\n");
+
+ av_bprint_finalize(&header, (char**)&avctx->subtitle_header);
+ if (!avctx->subtitle_header) {
+ ret = AVERROR(ENOMEM);
+ goto end;
+ }
+ avctx->subtitle_header_size = header.len;
+
+end:
+ av_bprint_finalize(&header, NULL);
+ return ret;
+}
+
+const FFCodec ff_srv3_decoder = {
+ .p.name = "srv3",
+ CODEC_LONG_NAME("SRV3 subtitle"),
+ .p.type = AVMEDIA_TYPE_SUBTITLE,
+ .p.id = AV_CODEC_ID_SRV3,
+ FF_CODEC_DECODE_SUB_CB(srv3_decode_frame),
+ .init = srv3_decoder_init,
+ .flush = ff_ass_decoder_flush,
+ .priv_data_size = sizeof(FFASSDecoderContext),
+};
diff --git a/libavformat/Makefile b/libavformat/Makefile
index dd96bf7ba8..1c44f35bbc 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -570,6 +570,7 @@ OBJS-$(CONFIG_SPEEX_MUXER) += oggenc.o \
vorbiscomment.o
OBJS-$(CONFIG_SRT_DEMUXER) += srtdec.o subtitles.o
OBJS-$(CONFIG_SRT_MUXER) += srtenc.o
+OBJS-$(CONFIG_SRV3_DEMUXER) += srv3dec.o subtitles.o
OBJS-$(CONFIG_STL_DEMUXER) += stldec.o subtitles.o
OBJS-$(CONFIG_STR_DEMUXER) += psxstr.o
OBJS-$(CONFIG_STREAMHASH_MUXER) += hashenc.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 445f13f42a..f56eb34a90 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -451,6 +451,7 @@ extern const FFInputFormat ff_spdif_demuxer;
extern const FFOutputFormat ff_spdif_muxer;
extern const FFInputFormat ff_srt_demuxer;
extern const FFOutputFormat ff_srt_muxer;
+extern const FFInputFormat ff_srv3_demuxer;
extern const FFInputFormat ff_str_demuxer;
extern const FFInputFormat ff_stl_demuxer;
extern const FFOutputFormat ff_streamhash_muxer;
diff --git a/libavformat/srv3.h b/libavformat/srv3.h
new file mode 100644
index 0000000000..45bf997654
--- /dev/null
+++ b/libavformat/srv3.h
@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2024 Hubert Głuchowski
+ *
+ * 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
+ */
+
+#ifndef AVFORMAT_SRV3_H
+#define AVFORMAT_SRV3_H
+
+#include "avformat.h"
+#include "internal.h"
+
+enum SRV3PenAttrs {
+ SRV3_PEN_ATTR_ITALIC = 1,
+ SRV3_PEN_ATTR_BOLD = 2,
+};
+
+//
https://github.com/arcusmaximus/YTSubConverter/blob/38fb2ab469f37e8f3a5a6a27adf91d9d0e81ea4f/YTSubConverter.Shared/Formats/YttDocument.cs#L1019C14-L1019C14
+enum SRV3EdgeType {
+ SRV3_EDGE_NONE = 0,
+ SRV3_EDGE_HARD_SHADOW = 1,
+ SRV3_EDGE_BEVEL = 2,
+ SRV3_EDGE_GLOW = 3,
+ SRV3_EDGE_SOFT_SHADOW = 4,
+};
+
+enum SRV3RubyPart {
+ SRV3_RUBY_NONE = 0,
+ SRV3_RUBY_BASE = 1,
+ SRV3_RUBY_PARENTHESIS = 2,
+ SRV3_RUBY_BEFORE = 4,
+ SRV3_RUBY_AFTER = 5,
+};
+
+typedef struct SRV3Pen {
+ int id;
+
+ int font_size, font_style;
+ int attrs;
+
+ int edge_type, edge_color;
+
+ int ruby_part;
+
+ int foreground_color, foreground_alpha;
+ int background_color, background_alpha;
+
+ struct SRV3Pen *next;
+} SRV3Pen;
+
+typedef struct SRV3WindowPos {
+ int id;
+
+ int point, x, y;
+
+ struct SRV3WindowPos *next;
+} SRV3WindowPos;
+
+typedef struct SRV3Head {
+ SRV3Pen *pens;
+} SRV3Head;
+
+typedef struct SRV3Segment {
+ int size;
+ SRV3Pen *pen;
+
+ /*
+ * The next segment in the same event.
+ */
+ struct SRV3Segment *next;
+} SRV3Segment;
+
+typedef struct SRV3EventMeta {
+ /*
+ * An ordered list of segments.
+ */
+ SRV3Segment *segments;
+ SRV3WindowPos *wp;
+} SRV3EventMeta;
+
+#endif // AVFORMAT_SRV3_H
diff --git a/libavformat/srv3dec.c b/libavformat/srv3dec.c
new file mode 100644
index 0000000000..c8ccd5cac2
--- /dev/null
+++ b/libavformat/srv3dec.c
@@ -0,0 +1,542 @@
+/*
+ * Copyright (c) 2024 Hubert Głuchowski
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * SRV3/YTT subtitle demuxer
+ * This is a youtube specific subtitle format that utilizes XML.
+ * Because there is currently no official documentation some information about
the format,
+ * some information was acquired by reading YTSubConverter code.
+ * @see https://github.com/arcusmaximus/YTSubConverter
+ */
+
+#include <libxml/parser.h>
+#include <libxml/tree.h>
+#include "srv3.h"
+#include "avformat.h"
+#include "demux.h"
+#include "internal.h"
+#include "subtitles.h"
+#include "libavutil/bprint.h"
+#include "libavutil/opt.h"
+#include "libavutil/mem.h"
+
+typedef struct SRV3GlobalSegments {
+ SRV3Segment *list;
+ struct SRV3GlobalSegments *next;
+} SRV3GlobalSegments;
+
+typedef struct SRV3Context {
+ const AVClass *class;
+ FFDemuxSubtitlesQueue q;
+ SRV3Pen *pens;
+ SRV3WindowPos *wps;
+ SRV3GlobalSegments *segments;
+} SRV3Context;
+
+static SRV3Pen srv3_default_pen = {
+ .id = -1,
+
+ .font_size = 100,
+ .font_style = 0,
+ .attrs = 0,
+
+ .edge_type = 0,
+ .edge_color = 0x020202,
+
+ .ruby_part = SRV3_RUBY_NONE,
+
+ .foreground_color = 0xFFFFFF,
+ .foreground_alpha = 254,
+ .background_color = 0x080808,
+ .background_alpha = 192,
+
+ .next = NULL
+};
+
+static void srv3_free_context_data(SRV3Context *ctx) {
+ void *next;
+
+#define FREE_LIST(type, list, until) \
+do { \
+ for (void *current = list; current && current != until; current = next) {
\
+ next = ((type*)current)->next; \
+ av_free(current); \
+ } \
+} while(0)
+
+ FREE_LIST(SRV3Pen, ctx->pens, &srv3_default_pen);
+ FREE_LIST(SRV3WindowPos, ctx->wps, NULL);
+
+ for (SRV3GlobalSegments *segments = ctx->segments; segments; segments =
next) {
+ FREE_LIST(SRV3Segment, segments->list, NULL);
+ next = segments->next;
+ av_free(segments);
+ }
+}
+
+static SRV3Pen *srv3_get_pen(SRV3Context *ctx, int id) {
+ for (SRV3Pen *pen = ctx->pens; pen; pen = pen->next)
+ if (pen->id == id)
+ return pen;
+ return NULL;
+}
+
+static int srv3_probe(const AVProbeData *p)
+{
+ if (strstr(p->buf, "<timedtext format=\"3\">"))
+ return AVPROBE_SCORE_MAX;
+
+ return 0;
+}
+
+static int srv3_parse_numeric_value(SRV3Context *ctx, const char *parent,
const char *name, const char *value, int base, int *out, int min, int max)
+{
+ char *endptr;
+ long parsed;
+
+ parsed = strtol(value, &endptr, base);
+
+ if (*endptr != 0) {
+ av_log(ctx, AV_LOG_WARNING, "Failed to parse value \"%s\" of %s
attribute %s as an integer\n", value, parent, name);
+ return AVERROR_INVALIDDATA;
+ } else if (parsed < min || parsed > max) {
+ av_log(ctx, AV_LOG_WARNING, "Value %li out of range for %s attribute
%s ([%i, %i])\n", parsed, parent, name, min, max);
+ return AVERROR(ERANGE);
+ } else if(out) {
+ *out = parsed;
+ return 0;
+ } else return parsed;
+}
+
+static int srv3_parse_numeric_attr(SRV3Context *ctx, const char *parent,
xmlAttrPtr attr, int *out, int min, int max)
+{
+ return srv3_parse_numeric_value(ctx, parent, attr->name,
attr->children->content, 10, out, min, max) == 0;
+}
+
+static void srv3_parse_color_attr(SRV3Context *ctx, const char *parent,
xmlAttrPtr attr, int *out)
+{
+ srv3_parse_numeric_value(ctx, parent, attr->name, attr->children->content
+ (*attr->children->content == '#'), 16, out, 0, 0xFFFFFF);
+}
+
+static int srv3_read_pen(SRV3Context *ctx, xmlNodePtr element)
+{
+ SRV3Pen *pen = av_malloc(sizeof(SRV3Pen));
+ if (!pen)
+ return AVERROR(ENOMEM);
+ memcpy(pen, &srv3_default_pen, sizeof(SRV3Pen));
+ pen->next = ctx->pens;
+ ctx->pens = pen;
+
+ for (xmlAttrPtr attr = element->properties; attr; attr = attr->next) {
+ if (!strcmp(attr->name, "id"))
+ srv3_parse_numeric_attr(ctx, "pen", attr, &pen->id, 0, INT_MAX);
+ else if (!strcmp(attr->name, "sz"))
+ srv3_parse_numeric_attr(ctx, "pen", attr, &pen->font_size, 0,
INT_MAX);
+ else if (!strcmp(attr->name, "fs"))
+ srv3_parse_numeric_attr(ctx, "pen", attr, &pen->font_style, 1, 7);
+ else if (!strcmp(attr->name, "et"))
+ srv3_parse_numeric_attr(ctx, "pen", attr, &pen->edge_type, 1, 4);
+ else if (!strcmp(attr->name, "ec"))
+ srv3_parse_color_attr(ctx, "pen", attr, &pen->edge_color);
+ else if (!strcmp(attr->name, "fc"))
+ srv3_parse_color_attr(ctx, "pen", attr, &pen->foreground_color);
+ else if (!strcmp(attr->name, "fo"))
+ srv3_parse_numeric_attr(ctx, "pen", attr, &pen->foreground_alpha,
0, 0xFF);
+ else if (!strcmp(attr->name, "bc"))
+ srv3_parse_color_attr(ctx, "pen", attr, &pen->background_color);
+ else if (!strcmp(attr->name, "bo"))
+ srv3_parse_numeric_attr(ctx, "pen", attr, &pen->background_alpha,
0, 0xFF);
+ else if (!strcmp(attr->name, "rb")) {
+ srv3_parse_numeric_attr(ctx, "pen", attr, &pen->ruby_part, 0, 5);
+ /*
+ * For whatever reason three seems to be an unused value for this
enum.
+ */
+ if (pen->ruby_part == 3) {
+ pen->ruby_part = 0;
+ av_log(ctx, AV_LOG_WARNING, "Encountered unknown ruby part
3\n");
+ }
+ } else if (!strcmp(attr->name, "i"))
+ pen->attrs |= (!strcmp(attr->children->content, "1")) *
SRV3_PEN_ATTR_ITALIC;
+ else if (!strcmp(attr->name, "b"))
+ pen->attrs |= (!strcmp(attr->children->content, "1")) *
SRV3_PEN_ATTR_BOLD;
+ else {
+ av_log(ctx, AV_LOG_WARNING, "Unhandled pen property %s\n",
attr->name);
+ continue;
+ }
+ }
+
+ return 0;
+}
+
+static int srv3_read_window_pos(SRV3Context *ctx, xmlNodePtr element)
+{
+ SRV3WindowPos *wp = av_mallocz(sizeof(SRV3Pen));
+ if (!wp)
+ return AVERROR(ENOMEM);
+ wp->next = ctx->wps;
+ ctx->wps = wp;
+
+ for (xmlAttrPtr attr = element->properties; attr; attr = attr->next) {
+ if (!strcmp(attr->name, "id"))
+ srv3_parse_numeric_attr(ctx, "window pos", attr, &wp->id, 0,
INT_MAX);
+ else if (!strcmp(attr->name, "ap"))
+ srv3_parse_numeric_attr(ctx, "window pos", attr, &wp->point, 0, 8);
+ else if (!strcmp(attr->name, "ah"))
+ srv3_parse_numeric_attr(ctx, "window pos", attr, &wp->x, 0, 100);
+ else if (!strcmp(attr->name, "av"))
+ srv3_parse_numeric_attr(ctx, "window pos", attr, &wp->y, 0, 100);
+ else {
+ av_log(ctx, AV_LOG_WARNING, "Unhandled window pos property %s\n",
attr->name);
+ continue;
+ }
+ }
+
+ return 0;
+}
+
+static int srv3_read_pens(SRV3Context *ctx, xmlNodePtr head)
+{
+ int ret;
+
+ for (xmlNodePtr element = head->children; element; element =
element->next) {
+ if (!strcmp(element->name, "pen")) {
+ if ((ret = srv3_read_pen(ctx, element)) < 0)
+ return ret;
+ } else if (!strcmp(element->name, "wp")) {
+ if ((ret = srv3_read_window_pos(ctx, element)) < 0)
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+#define ZERO_WIDTH_SPACE "\u200B"
+#define YTSUBCONV_PADDING_SPACE ZERO_WIDTH_SPACE " " ZERO_WIDTH_SPACE
+
+static int srv3_clean_segment_text(char *text) {
+ char *out = text, *start = text;
+
+ while (1) {
+ char *zw = strstr(start, ZERO_WIDTH_SPACE);
+ char *pad = strstr(start, YTSUBCONV_PADDING_SPACE);
+ char *end = pad ? pad : zw;
+ unsigned cnt = end ? (unsigned)(end - start) : (unsigned)strlen(start);
+
+ memmove(out, start, cnt);
+ out += cnt;
+ if (end) {
+ if (pad)
+ start = pad + strlen(YTSUBCONV_PADDING_SPACE);
+ else
+ start = zw + strlen(ZERO_WIDTH_SPACE);
+ } else break;
+ }
+
+ *out = '\0';
+ return out - text;
+}
+
+static int srv3_read_body(SRV3Context *ctx, xmlNodePtr body)
+{
+ int ret = 0;
+ AVBPrint textbuf;
+ char *text;
+ AVPacket *sub;
+ SRV3WindowPos *wp;
+ SRV3EventMeta *event;
+ int start, duration;
+
+ av_bprint_init(&textbuf, 0, AV_BPRINT_SIZE_UNLIMITED);
+
+ for (xmlNodePtr element = body->children; element; element =
element->next) {
+ if (!strcmp(element->name, "p")) {
+ SRV3Segment **segments_tail_next, *segments_tail = NULL;
+ SRV3GlobalSegments *global_segments;
+ int textlen, lastlen = 0;
+ SRV3Pen *event_pen = &srv3_default_pen;
+
+ if ((event = av_mallocz(sizeof(SRV3EventMeta))) == NULL) {
+ ret = AVERROR(ENOMEM);
+ goto end;
+ }
+
+ segments_tail_next = &event->segments;
+
+ for (xmlAttrPtr attr = element->properties; attr; attr =
attr->next) {
+ if (!strcmp(attr->name, "t"))
+ srv3_parse_numeric_attr(ctx, "event", attr, &start, 0,
INT_MAX);
+ else if (!strcmp(attr->name, "d"))
+ srv3_parse_numeric_attr(ctx, "event", attr, &duration, 0,
INT_MAX);
+ else if (!strcmp(attr->name, "wp")) {
+ int id;
+ srv3_parse_numeric_attr(ctx, "event", attr, &id, 0,
INT_MAX);
+ for (wp = ctx->wps; wp; wp = wp->next)
+ if (wp->id == id) {
+ event->wp = wp;
+ break;
+ }
+ if (!event->wp)
+ av_log(ctx, AV_LOG_WARNING, "Non-existent window pos
%i assigned to event\n", id);
+ } else if (!strcmp(attr->name, "p")) {
+ int id;
+ if(srv3_parse_numeric_attr(ctx, "event", attr, &id, 0,
INT_MAX)) {
+ SRV3Pen *pen = srv3_get_pen(ctx, id);
+ if(pen)
+ event_pen = pen;
+ else
+ av_log(ctx, AV_LOG_WARNING, "Non-existent pen %i
assigned to event\n", id);
+ }
+ } else if (!strcmp(attr->name, "ws")) {
+ // TODO: Handle window styles
+ } else {
+ av_log(ctx, AV_LOG_WARNING, "Unhandled event property
%s\n", attr->name);
+ continue;
+ }
+ }
+
+ for (xmlNodePtr node = element->children; node; node = node->next)
{
+ SRV3Segment *segment;
+
+ if (node->type != XML_ELEMENT_NODE && node->type !=
XML_TEXT_NODE) {
+ av_log(ctx, AV_LOG_WARNING, "Unexpected event child node
type %i\n", node->type);
+ continue;
+ } else if(node->type == XML_ELEMENT_NODE && strcmp(node->name,
"s")) {
+ av_log(ctx, AV_LOG_WARNING, "Unknown event child node name
%s\n", node->name);
+ continue;
+ } else if (node->type == XML_ELEMENT_NODE && !node->children)
+ continue;
+
+ segment = av_mallocz(sizeof(SRV3Segment));
+ if (!segment) {
+ ret = AVERROR(ENOMEM);
+ goto end;
+ }
+
+ segment->pen = event_pen;
+
+ if (node->type == XML_ELEMENT_NODE)
+ for (xmlAttrPtr attr = node->properties; attr; attr =
attr->next) {
+ if (!strcmp(attr->name, "p")) {
+ int id;
+ if(srv3_parse_numeric_attr(ctx, "segment", attr,
&id, 0, INT_MAX)) {
+ SRV3Pen *pen = srv3_get_pen(ctx, id);
+ if(pen)
+ segment->pen = pen;
+ else
+ av_log(ctx, AV_LOG_WARNING, "Non-existent
pen %i assigned to segment\n", id);
+ }
+ } else {
+ av_log(ctx, AV_LOG_WARNING, "Unhandled segment
property %s\n", attr->name);
+ continue;
+ }
+ }
+
+ text = node->type == XML_ELEMENT_NODE ?
node->children->content : node->content;
+ textlen = srv3_clean_segment_text(text);
+
+ if (textlen > 0) {
+ for (int i = 0; i < textlen; ++i)
+ if (text[i] != '\n' && text[i] != '\r')
+ goto add_segment;
+
+ av_bprint_append_data(&textbuf, text, textlen);
+
+ // If possible append this segment's text to the previous
segment
+ // Otherwise leave it here for it to be prepended to the
next segment
+ if (segments_tail && (segments_tail->pen->font_size ==
segment->pen->font_size || segment->next == NULL)) {
+ segments_tail->size += textlen;
+ lastlen = textbuf.len;
+ }
+ }
+
+ av_free(segment);
+ continue;
+
+add_segment:
+ av_bprint_append_data(&textbuf, text, textlen);
+
+ segment->size = textbuf.len - lastlen;
+ lastlen = textbuf.len;
+ *segments_tail_next = segment;
+ segments_tail_next = &segment->next;
+ segments_tail = segment;
+ }
+
+ if (!av_bprint_is_complete(&textbuf)) {
+ ret = AVERROR(ENOMEM);
+ goto end;
+ }
+
+ global_segments = av_mallocz(sizeof(SRV3GlobalSegments));
+ if (!global_segments) {
+ ret = AVERROR(ENOMEM);
+ goto end;
+ }
+ global_segments->list = event->segments;
+ global_segments->next = ctx->segments;
+ ctx->segments = global_segments;
+
+ sub = ff_subtitles_queue_insert(&ctx->q, textbuf.str, textbuf.len,
0);
+ if (!sub) {
+ ret = AVERROR(ENOMEM);
+ goto end;
+ }
+ sub->pts = start;
+ sub->duration = duration;
+
+ if ((ret = av_packet_add_side_data(sub, AV_PKT_DATA_SRV3_EVENT,
(uint8_t*)event, sizeof(SRV3EventMeta))) < 0)
+ goto end;
+
+ av_bprint_clear(&textbuf);
+ }
+ }
+
+end:
+ av_bprint_finalize(&textbuf, NULL);
+ return ret;
+}
+
+static int srv3_read_header(AVFormatContext *s)
+{
+ int ret = 0;
+ SRV3Context *ctx = s->priv_data;
+ AVPacketSideData *head_sd;
+ SRV3Head *head;
+ AVBPrint content;
+ xmlDocPtr document = NULL;
+ xmlNodePtr root_element;
+ AVStream *st;
+
+ av_bprint_init(&content, 0, INT_MAX);
+
+ st = avformat_new_stream(s, NULL);
+ if (!st) {
+ ret = AVERROR(ENOMEM);
+ goto end;
+ }
+ avpriv_set_pts_info(st, 64, 1, 1000);
+ st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
+ st->codecpar->codec_id = AV_CODEC_ID_SRV3;
+ st->disposition = AV_DISPOSITION_CAPTIONS;
+
+ if (!(head_sd = av_packet_side_data_new(&st->codecpar->coded_side_data,
&st->codecpar->nb_coded_side_data, AV_PKT_DATA_SRV3_HEAD, sizeof(SRV3Head),
0))) {
+ ret = AVERROR(ENOMEM);
+ goto end;
+ }
+ head = (SRV3Head*)head_sd->data;
+
+ if ((ret = avio_read_to_bprint(s->pb, &content, SIZE_MAX)) < 0)
+ goto end;
+ if (!avio_feof(s->pb) || !av_bprint_is_complete(&content)) {
+ ret = AVERROR_INVALIDDATA;
+ goto end;
+ }
+
+ LIBXML_TEST_VERSION;
+
+ document = xmlReadMemory(content.str, content.len, s->url, NULL, 0);
+
+ if (!document) {
+ ret = AVERROR_INVALIDDATA;
+ goto end;
+ }
+
+ root_element = xmlDocGetRootElement(document);
+
+ for (xmlAttrPtr attr = root_element->properties; attr; attr = attr->next) {
+ if (!strcmp(attr->name, "format")) {
+ if (!attr->children || strcmp(attr->children->content, "3"))
+ av_log(s, AV_LOG_WARNING, "Unrecognized timedtext format
version: %s\nParsing will still be attempted but may produce unexpected
results\n", attr->children->content);
+ }
+ }
+
+ ctx->pens = &srv3_default_pen;
+
+ for (xmlNodePtr element = root_element->children; element; element =
element->next) {
+ if (!strcmp(element->name, "head"))
+ if ((ret = srv3_read_pens(ctx, element)) < 0)
+ goto end;
+ }
+
+ for (xmlNodePtr element = root_element->children; element; element =
element->next) {
+ if (!strcmp(element->name, "body"))
+ if ((ret = srv3_read_body(ctx, element)) < 0)
+ goto end;
+ }
+
+ head->pens = ctx->pens;
+ ff_subtitles_queue_finalize(s, &ctx->q);
+
+end:
+ xmlFreeDoc(document);
+ av_bprint_finalize(&content, NULL);
+ return ret;
+}
+
+static int srv3_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+ SRV3Context *ctx = s->priv_data;
+ return ff_subtitles_queue_read_packet(&ctx->q, pkt);
+}
+
+static int srv3_read_seek(AVFormatContext *s, int stream_index,
+ int64_t min_ts, int64_t ts, int64_t max_ts, int
flags)
+{
+ SRV3Context *ctx = s->priv_data;
+ return ff_subtitles_queue_seek(&ctx->q, s, stream_index,
+ min_ts, ts, max_ts, flags);
+}
+
+static int srv3_read_close(AVFormatContext *s)
+{
+ SRV3Context *ctx = s->priv_data;
+ ff_subtitles_queue_clean(&ctx->q);
+ srv3_free_context_data(ctx);
+ return 0;
+}
+
+#define OFFSET(x) offsetof(SRV3Context, x)
+#define KIND_FLAGS AV_OPT_FLAG_SUBTITLE_PARAM|AV_OPT_FLAG_DECODING_PARAM
+
+static const AVOption options[] = {
+ { NULL }
+};
+
+static const AVClass srv3_demuxer_class = {
+ .class_name = "SRV3 demuxer",
+ .option = options,
+ .version = LIBAVUTIL_VERSION_INT,
+};
+
+const FFInputFormat ff_srv3_demuxer = {
+ .p.name = "srv3",
+ .p.long_name = NULL_IF_CONFIG_SMALL("SRV3 subtitle"),
+ .p.extensions = "srv3",
+ .p.priv_class = &srv3_demuxer_class,
+ .priv_data_size = sizeof(SRV3Context),
+ .flags_internal = FF_INFMT_FLAG_INIT_CLEANUP,
+ .read_probe = srv3_probe,
+ .read_header = srv3_read_header,
+ .read_packet = srv3_read_packet,
+ .read_seek2 = srv3_read_seek,
+ .read_close = srv3_read_close,
+};
--
2.47.0
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