[FFmpeg-cvslog] nutdec: fix infinite resync loops

[Andreas Cadhalpun]

ffmpeg | branch: release/2.4 | Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com> | Wed May 20 00:06:05 2015 +0200| [936a5dd2c5c9141bcc02c4bd6749e26f1e4454b2] | committer: Michael Niedermayer

nutdec: fix infinite resync loops

nut->last_syncpoint_pos doesn't necessarily change between resync
attempts, so find_any_startcode can return the same startcode again.

Thus remember where the last resync happened and don't try to resync
before that.

This can't be done locally in nut_read_packet, because this wouldn't
prevent infinite resync loops, where after the resync a packet is
returned and while reading a following packet the resync happens again.

Reviewed-by: Michael Niedermayer <michaelni at gmx.at>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
(cherry picked from commit 37e679881d364b6da817d829d35869d657218ab3)

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=936a5dd2c5c9141bcc02c4bd6749e26f1e4454b2
---

 libavformat/nut.h    |    1 +
 libavformat/nutdec.c |    5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/libavformat/nut.h b/libavformat/nut.h
index 943081c..0c678a5 100644
--- a/libavformat/nut.h
+++ b/libavformat/nut.h
@@ -102,6 +102,7 @@ typedef struct NUTContext {
     unsigned int max_distance;
     unsigned int time_base_count;
     int64_t last_syncpoint_pos;
+    int64_t last_resync_pos;
     int header_count;
     AVRational *time_base;
     struct AVTreeNode *syncpoints;
diff --git a/libavformat/nutdec.c b/libavformat/nutdec.c
index 488ae16..3fdbd72 100644
--- a/libavformat/nutdec.c
+++ b/libavformat/nutdec.c
@@ -1129,7 +1129,8 @@ static int nut_read_packet(AVFormatContext *s, AVPacket *pkt)
         default:
 resync:
             av_log(s, AV_LOG_DEBUG, "syncing from %"PRId64"\n", pos);
-            tmp = find_any_startcode(bc, nut->last_syncpoint_pos + 1);
+            tmp = find_any_startcode(bc, FFMAX(nut->last_syncpoint_pos, nut->last_resync_pos) + 1);
+            nut->last_resync_pos = avio_tell(bc);
             if (tmp == 0)
                 return AVERROR_INVALIDDATA;
             av_log(s, AV_LOG_DEBUG, "sync\n");
@@ -1230,6 +1231,8 @@ static int read_seek(AVFormatContext *s, int stream_index,
     for (i = 0; i < s->nb_streams; i++)
         nut->stream[i].skip_until_key_frame = 1;
 
+    nut->last_resync_pos = 0;
+
     return 0;
 }