[FFmpeg-cvslog] h264: Fix ticket #3147 H264 - Wrong field order

[Thomas Mundt]

ffmpeg | branch: master | Thomas Mundt <loudmax at yahoo.de> | Sun Sep 27 22:11:47 2015 +0100| [2b6567722a48656c526ca2d6c1dcab88be3c18f7] | committer: Michael Niedermayer

h264: Fix ticket #3147 H264 - Wrong field order

Default field order to top field first when interlaced frame is detected and pic_struct_present_flag is not set.
Since bottom field first comes from the old NTSC standard and is not used with HD anymore I think it´s straight forward to favor the majority.

Signed-off-by: Thomas Mundt <loudmax at yahoo.de>
Reviewed-by: Kieran Kunhya <kierank at obe.tv>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2b6567722a48656c526ca2d6c1dcab88be3c18f7
---

 libavcodec/h264.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index b797893..8b95003 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -803,7 +803,7 @@ static void decode_postinit(H264Context *h, int setup_finished)
         /* Derive top_field_first from field pocs. */
         cur->f->top_field_first = cur->field_poc[0] < cur->field_poc[1];
     } else {
-        if (cur->f->interlaced_frame || h->sps.pic_struct_present_flag) {
+        if (h->sps.pic_struct_present_flag) {
             /* Use picture timing SEI information. Even if it is a
              * information of a past frame, better than nothing. */
             if (h->sei_pic_struct == SEI_PIC_STRUCT_TOP_BOTTOM ||
@@ -811,6 +811,10 @@ static void decode_postinit(H264Context *h, int setup_finished)
                 cur->f->top_field_first = 1;
             else
                 cur->f->top_field_first = 0;
+        } else if (cur->f->interlaced_frame) {
+            /* Default to top field first when pic_struct_present_flag
+             * is not set but interlaced frame detected */
+            cur->f->top_field_first = 1;
         } else {
             /* Most likely progressive */
             cur->f->top_field_first = 0;