WebVTT demuxer and decoder.

1 files changed, 100 insertions, 0 deletions

diff --git a/libavcodec/webvttdec.c b/libavcodec/webvttdec.c
new file mode 100644
index 0000000000..6b86bedbe9
--- /dev/null
+++ b/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,
+};