[libav-stable] lavf: prevent infinite loops while flushing in avformat_find_stream_info

Janne Grunau git at libav.org
Thu Jan 26 00:45:13 CET 2012


Module: libav
Branch: master
Commit: b3461c29c1aee7d62eeb02a59d46593c60362679

Author:    Janne Grunau <janne-libav at jannau.net>
Committer: Janne Grunau <janne-libav at jannau.net>
Date:      Wed Jan 18 10:59:32 2012 +0100

lavf: prevent infinite loops while flushing in avformat_find_stream_info

If no data was seen for a stream decoder are returning 0 when fed with
empty packets for flushing. We can stop flushing when the decoder does
not return delayed delayed frames anymore. Changes try_decode_frame()
return value to got_picture or negative error.

CC: libav-stable at libav.org

---

 libavformat/utils.c |   22 ++++++++++++++--------
 1 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/libavformat/utils.c b/libavformat/utils.c
index 093389b..17eec07 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -2130,6 +2130,7 @@ static int has_decode_delay_been_guessed(AVStream *st)
         st->info->nb_decoded_frames >= 6;
 }
 
+/* returns 1 or 0 if or if not decoded data was returned, or a negative error */
 static int try_decode_frame(AVStream *st, AVPacket *avpkt, AVDictionary **options)
 {
     AVCodec *codec;
@@ -2177,6 +2178,7 @@ static int try_decode_frame(AVStream *st, AVPacket *avpkt, AVDictionary **option
                 st->info->nb_decoded_frames++;
             pkt.data += ret;
             pkt.size -= ret;
+            ret       = got_picture;
         }
     }
     return ret;
@@ -2401,16 +2403,20 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
                 st = ic->streams[i];
 
                 /* flush the decoders */
-                while ((err = try_decode_frame(st, &empty_pkt,
-                                               (options && i < orig_nb_streams) ?
-                                                &options[i] : NULL)) >= 0)
-                    if (has_codec_parameters(st->codec))
-                        break;
-
-                if (!has_codec_parameters(st->codec)){
+                do {
+                    err = try_decode_frame(st, &empty_pkt,
+                                           (options && i < orig_nb_streams) ?
+                                           &options[i] : NULL);
+                } while (err > 0 && !has_codec_parameters(st->codec));
+
+                if (err < 0) {
+                    av_log(ic, AV_LOG_WARNING,
+                           "decoding for stream %d failed\n", st->index);
+                } else if (!has_codec_parameters(st->codec)){
                     char buf[256];
                     avcodec_string(buf, sizeof(buf), st->codec, 0);
-                    av_log(ic, AV_LOG_WARNING, "Could not find codec parameters (%s)\n", buf);
+                    av_log(ic, AV_LOG_WARNING,
+                           "Could not find codec parameters (%s)\n", buf);
                 } else {
                     ret = 0;
                 }



More information about the libav-stable mailing list