[FFmpeg-cvslog] lavc/svq3: Fix regression decoding some files.

[Nikolas Bowe]

ffmpeg | branch: release/3.3 | Nikolas Bowe <nbowe at google.com> | Mon Jul 30 17:22:02 2018 -0700| [e2d052d5c8321487338979568c1e372727002603] | committer: Michael Niedermayer

lavc/svq3: Fix regression decoding some files.

Fixes some SVQ3 encoded files which fail to decode correctly after 6d6faa2a2d.
These files exhibit lots of artifacts and logs show "Media key encryption is not implemented".
However they decode without artifacts before 6d6faa2a2d.
The attatched patch allows these files to successfully decode, but also reject media key files.

Tested on the files in #6094 and http://samples.mplayerhq.hu/V-codecs/SVQ3/Vertical400kbit.sorenson3.mov

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 5aeb3b008080d8d4a38f245d557dbc9bd6c36dcf)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=e2d052d5c8321487338979568c1e372727002603
---

 libavcodec/svq3.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/libavcodec/svq3.c b/libavcodec/svq3.c
index 5cb5bd45b7..e5bbb393e0 100644
--- a/libavcodec/svq3.c
+++ b/libavcodec/svq3.c
@@ -1065,16 +1065,15 @@ static int svq3_decode_slice_header(AVCodecContext *avctx)
         av_log(s->avctx, AV_LOG_ERROR, "illegal slice type %u \n", slice_id);
         return -1;
     }
-    if (get_bits1(&s->gb_slice)) {
-        avpriv_report_missing_feature(s->avctx, "Media key encryption");
-        return AVERROR_PATCHWELCOME;
-    }
 
     s->slice_type = ff_h264_golomb_to_pict_type[slice_id];
 
     if ((header & 0x9F) == 2) {
-        i = (s->mb_num < 64) ? 5 : av_log2(s->mb_num - 1);
+        i = (s->mb_num < 64) ? 6 : (1 + av_log2(s->mb_num - 1));
         get_bits(&s->gb_slice, i);
+    } else if (get_bits1(&s->gb_slice)) {
+        avpriv_report_missing_feature(s->avctx, "Media key encryption");
+        return AVERROR_PATCHWELCOME;
     }
 
     s->slice_num      = get_bits(&s->gb_slice, 8);