[FFmpeg-cvslog] lavf/webvttenc: Require webvtt file to contain exactly one WebVTT stream.

[Simon Thelen]

ffmpeg | branch: release/2.7 | Simon Thelen <ffmpeg-dev at c-14.de> | Fri Sep 11 21:49:07 2015 +0200| [d1de4923305b326990ace91f3a56c2916cda1037] | committer: Michael Niedermayer

lavf/webvttenc: Require webvtt file to contain exactly one WebVTT stream.

Not requiring this can end up producing hilariously broken files
together with -c:s copy (e.g. a webvtt file containing binary subtitle data).

Signed-off-by: Simon Thelen <ffmpeg-dev at c-14.de>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit b84232694ef0c6897e82b52326c9ea4027c69ec4)

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=d1de4923305b326990ace91f3a56c2916cda1037
---

 libavformat/webvttenc.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libavformat/webvttenc.c b/libavformat/webvttenc.c
index b93993d..c386538 100644
--- a/libavformat/webvttenc.c
+++ b/libavformat/webvttenc.c
@@ -46,8 +46,14 @@ static void webvtt_write_time(AVIOContext *pb, int64_t millisec)
 static int webvtt_write_header(AVFormatContext *ctx)
 {
     AVStream     *s = ctx->streams[0];
+    AVCodecContext *avctx = ctx->streams[0]->codec;
     AVIOContext *pb = ctx->pb;
 
+    if (ctx->nb_streams != 1 || avctx->codec_id != AV_CODEC_ID_WEBVTT) {
+        av_log(ctx, AV_LOG_ERROR, "Exactly one WebVTT stream is needed.\n");
+        return AVERROR(EINVAL);
+    }
+
     avpriv_set_pts_info(s, 64, 1, 1000);
 
     avio_printf(pb, "WEBVTT\n");