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

[Janne Grunau]

ffmpeg | branch: release/0.7 | Janne Grunau <janne-libav at jannau.net> | Fri Nov 16 14:31:09 2012 +0100| [5fa739e685bcbd29dd83139c245935099112beed] | committer: Reinhard Tartler

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
(cherry picked from commit 706acb558a38eba633056773280155d66c2f4b24)

Conflicts:

	libavcodec/h264.c

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=5fa739e685bcbd29dd83139c245935099112beed
---

 libavcodec/h264.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index 0940335..98c68d8 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -3847,9 +3847,16 @@ static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size){
             init_get_bits(&s->gb, ptr, bit_length);
             ff_h264_decode_seq_parameter_set(h);
 
-            if (s->flags& CODEC_FLAG_LOW_DELAY ||
-                (h->sps.bitstream_restriction_flag && !h->sps.num_reorder_frames))
-                s->low_delay=1;
+            if (s->flags & CODEC_FLAG_LOW_DELAY ||
+                (h->sps.bitstream_restriction_flag &&
+                 !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;