WebVTT demuxer and decoder.

Changelog

@@ -63,6 +63,7 @@ version next:
 - Smooth Streaming live segmenter muxer
 - F4V muxer
 - sendcmd and asendcmd filters
+- WebVTT demuxer and decoder (simple tags supported)
 
 
 version 0.11:

doc/general.texi

@@ -898,6 +898,7 @@ performance on systems without hardware floating point support).
 @item SubRip (SRT)     @tab X @tab X @tab X @tab X
 @item SubViewer        @tab   @tab X @tab   @tab X
 @item 3GPP Timed Text  @tab   @tab   @tab X @tab X
+@item WebVTT           @tab   @tab X @tab   @tab X
 @item XSUB             @tab   @tab   @tab X @tab X
 @end multitable
 

libavcodec/Makefile

@@ -463,6 +463,7 @@ OBJS-$(CONFIG_VP6_DECODER)             += vp6.o vp56.o vp56data.o vp56dsp.o \
 OBJS-$(CONFIG_VP8_DECODER)             += vp8.o vp8dsp.o vp56rac.o
 OBJS-$(CONFIG_VQA_DECODER)             += vqavideo.o
 OBJS-$(CONFIG_WAVPACK_DECODER)         += wavpack.o
+OBJS-$(CONFIG_WEBVTT_DECODER)          += webvttdec.o
 OBJS-$(CONFIG_WMALOSSLESS_DECODER)     += wmalosslessdec.o wma_common.o
 OBJS-$(CONFIG_WMAPRO_DECODER)          += wmaprodec.o wma.o wma_common.o
 OBJS-$(CONFIG_WMAV1_DECODER)           += wmadec.o wma.o wma_common.o aactab.o

libavcodec/allcodecs.c

@@ -422,6 +422,7 @@ void avcodec_register_all(void)
     REGISTER_ENCDEC  (SRT, srt);
     REGISTER_ENCDEC  (SUBRIP, subrip);
     REGISTER_DECODER (SUBVIEWER, subviewer);
+    REGISTER_DECODER (WEBVTT, webvtt);
     REGISTER_ENCDEC  (XSUB, xsub);
 
     /* external libraries */

libavcodec/avcodec.h

@@ -448,6 +448,7 @@ enum AVCodecID {
     AV_CODEC_ID_REALTEXT   = MKBETAG('R','T','X','T'),
     AV_CODEC_ID_SUBVIEWER  = MKBETAG('S','u','b','V'),
     AV_CODEC_ID_SUBRIP     = MKBETAG('S','R','i','p'),
+    AV_CODEC_ID_WEBVTT     = MKBETAG('W','V','T','T'),
 
     /* 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.

libavcodec/codec_desc.c

@@ -2342,6 +2342,12 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .name      = "subviewer",
         .long_name = NULL_IF_CONFIG_SMALL("SubViewer subtitle"),
     },
+    {
+        .id        = AV_CODEC_ID_WEBVTT,
+        .type      = AVMEDIA_TYPE_SUBTITLE,
+        .name      = "webvtt",
+        .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
+    },
     {
         .id        = AV_CODEC_ID_BINTEXT,
         .type      = AVMEDIA_TYPE_VIDEO,

libavcodec/version.h

@@ -27,7 +27,7 @@
  */
 
 #define LIBAVCODEC_VERSION_MAJOR 54
-#define LIBAVCODEC_VERSION_MINOR 57
+#define LIBAVCODEC_VERSION_MINOR 58
 #define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \

libavcodec/webvttdec.c

@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2012 Clément Bœsch
+ *
+ * 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
+ * WebVTT subtitle decoder
+ * @see http://dev.w3.org/html5/webvtt/
+ * @todo need to support extended markups and cue settings
+ */
+
+#include "avcodec.h"
+#include "ass.h"
+#include "libavutil/bprint.h"
+
+static const struct {
+    const char *from;
+    const char *to;
+} webvtt_tag_replace[] = {
+    {"<i>", "{\\i1}"}, {"</i>", "{\\i0}"},
+    {"<b>", "{\\b1}"}, {"</b>", "{\\b0}"},
+    {"<u>", "{\\u1}"}, {"</u>", "{\\u0}"},
+    {"{", "\\{"}, {"}", "\\}"}, // escape to avoid ASS markup conflicts
+};
+
+static int webvtt_event_to_ass(AVBPrint *buf, const char *p)
+{
+    int i, skip = 0;
+
+    while (*p) {
+
+        for (i = 0; i < FF_ARRAY_ELEMS(webvtt_tag_replace); i++) {
+            const char *from = webvtt_tag_replace[i].from;
+            const size_t len = strlen(from);
+            if (!strncmp(p, from, len)) {
+                av_bprintf(buf, "%s", webvtt_tag_replace[i].to);
+                p += len;
+                break;
+            }
+        }
+        if (!*p)
+            break;
+
+        if (*p == '<')
+            skip = 1;
+        else if (*p == '>')
+            skip = 0;
+        else if (p[0] == '\n' && p[1])
+            av_bprintf(buf, "\\N");
+        else if (!skip && *p != '\r')
+            av_bprint_chars(buf, *p, 1);
+        p++;
+    }
+    av_bprintf(buf, "\r\n");
+    return 0;
+}
+
+static int webvtt_decode_frame(AVCodecContext *avctx,
+                               void *data, int *got_sub_ptr, AVPacket *avpkt)
+{
+    AVSubtitle *sub = data;
+    const char *ptr = avpkt->data;
+    AVBPrint buf;
+
+    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
+    if (ptr && avpkt->size > 0 && !webvtt_event_to_ass(&buf, ptr)) {
+        int ts_start     = av_rescale_q(avpkt->pts, avctx->time_base, (AVRational){1,100});
+        int ts_duration  = avpkt->duration != -1 ?
+                           av_rescale_q(avpkt->duration, avctx->time_base, (AVRational){1,100}) : -1;
+        ff_ass_add_rect(sub, buf.str, ts_start, ts_duration, 0);
+    }
+    *got_sub_ptr = sub->num_rects > 0;
+    av_bprint_finalize(&buf, NULL);
+    return avpkt->size;
+}
+
+AVCodec ff_webvtt_decoder = {
+    .name           = "webvtt",
+    .long_name      = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
+    .type           = AVMEDIA_TYPE_SUBTITLE,
+    .id             = AV_CODEC_ID_WEBVTT,
+    .decode         = webvtt_decode_frame,
+    .init           = ff_ass_subtitle_header_default,
+};

libavformat/Makefile

@@ -355,6 +355,7 @@ OBJS-$(CONFIG_WC3_DEMUXER)               += wc3movie.o
 OBJS-$(CONFIG_WEBM_MUXER)                += matroskaenc.o matroska.o \
                                             isom.o avc.o \
                                             flacenc_header.o avlanguage.o
+OBJS-$(CONFIG_WEBVTT_DEMUXER)            += webvttdec.o
 OBJS-$(CONFIG_WSAUD_DEMUXER)             += westwood_aud.o
 OBJS-$(CONFIG_WSVQA_DEMUXER)             += westwood_vqa.o
 OBJS-$(CONFIG_WTV_DEMUXER)               += wtvdec.o wtv.o asfdec.o asf.o asfcrypt.o \

libavformat/allformats.c

@@ -252,6 +252,7 @@ void av_register_all(void)
     REGISTER_MUXDEMUX (WAV, wav);
     REGISTER_DEMUXER  (WC3, wc3);
     REGISTER_MUXER    (WEBM, webm);
+    REGISTER_DEMUXER  (WEBVTT, webvtt);
     REGISTER_DEMUXER  (WSAUD, wsaud);
     REGISTER_DEMUXER  (WSVQA, wsvqa);
     REGISTER_MUXDEMUX (WTV, wtv);

libavformat/version.h

@@ -30,8 +30,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 54
-#define LIBAVFORMAT_VERSION_MINOR 27
-#define LIBAVFORMAT_VERSION_MICRO 101
+#define LIBAVFORMAT_VERSION_MINOR 28
+#define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \

libavformat/webvttdec.c

@@ -0,0 +1,188 @@
+/*
+ * Copyright (c) 2012 Clément Bœsch
+ *
+ * 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
+ * WebVTT subtitle demuxer
+ * @see http://dev.w3.org/html5/webvtt/
+ */
+
+#include "avformat.h"
+#include "internal.h"
+#include "subtitles.h"
+#include "libavutil/bprint.h"
+#include "libavutil/intreadwrite.h"
+
+typedef struct {
+    FFDemuxSubtitlesQueue q;
+} WebVTTContext;
+
+static int webvtt_probe(AVProbeData *p)
+{
+    const uint8_t *ptr = p->buf;
+
+    if (AV_RB24(ptr) == 0xEFBBBF)
+        ptr += 3;  /* skip UTF-8 BOM */
+    if (!strncmp(ptr, "WEBVTT", 6) &&
+        (!ptr[6] || strchr("\n\r\t ", ptr[6])))
+        return AVPROBE_SCORE_MAX;
+    return 0;
+}
+
+static int64_t read_ts(const char *s)
+{
+    int hh, mm, ss, ms;
+    if (sscanf(s, "%u:%u:%u.%u", &hh, &mm, &ss, &ms) == 4) return (hh*3600 + mm*60 + ss) * 1000 + ms;
+    if (sscanf(s,    "%u:%u.%u",      &mm, &ss, &ms) == 3) return (          mm*60 + ss) * 1000 + ms;
+    return AV_NOPTS_VALUE;
+}
+
+static int64_t extract_cue(AVBPrint *buf, AVIOContext *pb)
+{
+    int prev_chr_is_eol = 0;
+    int64_t pos = avio_tell(pb);
+
+    av_bprint_clear(buf);
+    for (;;) {
+        char c = avio_r8(pb);
+        if (!c)
+            break;
+        if (c == '\r' || c == '\n') {
+            if (prev_chr_is_eol)
+                break;
+            prev_chr_is_eol = (c == '\n');
+        } else
+            prev_chr_is_eol = 0;
+        if (c != '\r')
+            av_bprint_chars(buf, c, 1);
+    }
+    av_bprint_chars(buf, '\0', 1);
+    return pos;
+}
+
+static int webvtt_read_header(AVFormatContext *s)
+{
+    WebVTTContext *webvtt = s->priv_data;
+    AVBPrint header, cue;
+    int res = 0;
+    AVStream *st = avformat_new_stream(s, NULL);
+
+    if (!st)
+        return AVERROR(ENOMEM);
+    avpriv_set_pts_info(st, 64, 1, 1000);
+    st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
+    st->codec->codec_id   = AV_CODEC_ID_WEBVTT;
+
+    av_bprint_init(&header, 0, AV_BPRINT_SIZE_UNLIMITED);
+    av_bprint_init(&cue,    0, AV_BPRINT_SIZE_UNLIMITED);
+
+    for (;;) {
+        int i, len;
+        int64_t pos = extract_cue(&cue, s->pb);
+        AVPacket *sub;
+        const char *p = cue.str;
+        const char *identifier = p;
+        //const char *settings = NULL;
+        int64_t ts_start, ts_end;
+
+        if (!*p) // EOF
+            break;
+
+        /* ignore header chunk */
+        if (!strncmp(p, "\xEF\xBB\xBFWEBVTT", 9) ||
+            !strncmp(p, "WEBVTT", 6))
+            continue;
+
+        /* optional cue identifier (can be a number like in SRT or some kind of
+         * chaptering id), silently skip it */
+        for (i = 0; p[i] && p[i] != '\n'; i++) {
+            if (!strncmp(p + i, "-->", 3)) {
+                identifier = NULL;
+                break;
+            }
+        }
+        if (identifier)
+            p += strcspn(p, "\n");
+
+        /* cue timestamps */
+        if ((ts_start = read_ts(p)) == AV_NOPTS_VALUE)
+            break;
+        if (!(p = strstr(p, "-->")))
+            break;
+        p += 3;
+        do p++; while (*p == ' ' || *p == '\t');
+        if ((ts_end = read_ts(p)) == AV_NOPTS_VALUE)
+            break;
+
+        /* optional cue settings, TODO: store in side_data */
+        p += strcspn(p, "\n\t ");
+        while (*p == '\t' || *p == ' ')
+            p++;
+        if (*p != '\n') {
+            //settings = p;
+            p += strcspn(p, "\n");
+        }
+        if (*p == '\n')
+            p++;
+
+        /* create packet */
+        len = cue.str + cue.len - p - 1;
+        sub = ff_subtitles_queue_insert(&webvtt->q, p, len, 0);
+        if (!sub) {
+            res = AVERROR(ENOMEM);
+            goto end;
+        }
+        sub->pos = pos;
+        sub->pts = ts_start;
+        sub->duration = ts_end - ts_start;
+    }
+
+    ff_subtitles_queue_finalize(&webvtt->q);
+
+end:
+    av_bprint_finalize(&cue,    NULL);
+    av_bprint_finalize(&header, NULL);
+    return res;
+}
+
+static int webvtt_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    WebVTTContext *webvtt = s->priv_data;
+    return ff_subtitles_queue_read_packet(&webvtt->q, pkt);
+}
+
+static int webvtt_read_close(AVFormatContext *s)
+{
+    WebVTTContext *webvtt = s->priv_data;
+    ff_subtitles_queue_clean(&webvtt->q);
+    return 0;
+}
+
+AVInputFormat ff_webvtt_demuxer = {
+    .name           = "webvtt",
+    .long_name      = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
+    .priv_data_size = sizeof(WebVTTContext),
+    .read_probe     = webvtt_probe,
+    .read_header    = webvtt_read_header,
+    .read_packet    = webvtt_read_packet,
+    .read_close     = webvtt_read_close,
+    .flags          = AVFMT_GENERIC_INDEX,
+    .extensions     = "vtt",
+};

tests/fate/subtitles.mak

@@ -25,5 +25,8 @@ fate-sub-subripenc: CMD = md5 -i $(SAMPLES)/sub/MovText_capability_tester.mp4 -s
 FATE_SUBTITLES += fate-sub-subviewer
 fate-sub-subviewer: CMD = md5 -i $(SAMPLES)/sub/SubViewer_capability_tester.sub -f ass
 
+FATE_SUBTITLES += fate-sub-webvtt
+fate-sub-webvtt: CMD = md5 -i $(SAMPLES)/sub/WebVTT_capability_tester.vtt -f ass
+
 FATE_SAMPLES_FFMPEG += $(FATE_SUBTITLES)
 fate-subtitles: $(FATE_SUBTITLES)

tests/ref/fate/sub-webvtt

@@ -0,0 +1 @@
+5384a70c89ddca4b007fb7ffba95cffb