[FFmpeg-cvslog] h264: enable low delay only if no delayed frames were seen

[Janne Grunau]

ffmpeg | branch: master | Janne Grunau <janne-libav at jannau.net> | Fri Nov 16 14:31:09 2012 +0100| [706acb558a38eba633056773280155d66c2f4b24] | committer: Janne Grunau

h264: enable low delay only if no delayed frames were seen

Dropping frames is undesirable but that is the only way by which the
decoder could return to low delay mode. Instead emit a warning and
continue with delayed frames.
Fixes a crash in fuzzed sample nasa-8s2.ts_s20033 caused by a larger
than expected has_b_frames value. Low delay keeps getting re-enabled
from a presumely broken SPS.

CC: libav-stable at libav.org

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=706acb558a38eba633056773280155d66c2f4b24
---

 libavcodec/h264.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index f45c572..658d865 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -3867,8 +3867,14 @@ again:
 
                 if (s->flags & CODEC_FLAG_LOW_DELAY ||
                     (h->sps.bitstream_restriction_flag &&
-                     !h->sps.num_reorder_frames))
-                    s->low_delay = 1;
+                     !h->sps.num_reorder_frames)) {
+                    if (s->avctx->has_b_frames > 1 || h->delayed_pic[0])
+                        av_log(avctx, AV_LOG_WARNING, "Delayed frames seen "
+                               "reenabling low delay requires a codec "
+                               "flush.\n");
+                        else
+                            s->low_delay = 1;
+                }
 
                 if (avctx->has_b_frames < 2)
                     avctx->has_b_frames = !s->low_delay;