h264dec: track the last seen value of x264_build

Do not use the one in the SEI directly as that is reset at certain
points.

Inspired by patches from Michael Niedermayer <michaelni@gmx.at> and
Anton Mitrofanov <BugMaster@narod.ru>.

CC: libav-stable@libav.org

libavcodec/h264_direct.c

@@ -391,7 +391,7 @@ single_col:
              (l1ref0[0] < 0 && !l1ref1[0] &&
               FFABS(l1mv1[0][0]) <= 1 &&
               FFABS(l1mv1[0][1]) <= 1 &&
-              h->sei.unregistered.x264_build > 33U))) {
+              h->x264_build > 33U))) {
             a = b = 0;
             if (ref[0] > 0)
                 a = mv[0];
@@ -426,7 +426,7 @@ single_col:
                 (l1ref0[i8] == 0 ||
                  (l1ref0[i8] < 0 &&
                   l1ref1[i8] == 0 &&
-                  h->sei.unregistered.x264_build > 33U))) {
+                  h->x264_build > 33U))) {
                 const int16_t (*l1mv)[2] = l1ref0[i8] == 0 ? l1mv0 : l1mv1;
                 if (IS_SUB_8X8(sub_mb_type)) {
                     const int16_t *mv_col = l1mv[x8 * 3 + y8 * 3 * b4_stride];

libavcodec/h264_slice.c

@@ -403,6 +403,7 @@ int ff_h264_update_thread_context(AVCodecContext *dst,
 
     h->enable_er       = h1->enable_er;
     h->workaround_bugs = h1->workaround_bugs;
+    h->x264_build      = h1->x264_build;
     h->droppable       = h1->droppable;
 
     // extradata/NAL handling
@@ -509,6 +510,9 @@ static int h264_frame_start(H264Context *h)
 
     h->mb_aff_frame = h->ps.sps->mb_aff && (h->picture_structure == PICT_FRAME);
 
+    if (h->sei.unregistered.x264_build >= 0)
+        h->x264_build = h->sei.unregistered.x264_build;
+
     assert(h->cur_pic_ptr->long_ref == 0);
 
     return 0;
@@ -847,7 +851,7 @@ static int h264_slice_header_init(H264Context *h)
 
     if (sps->timing_info_present_flag) {
         int64_t den = sps->time_scale;
-        if (h->sei.unregistered.x264_build < 44U)
+        if (h->x264_build < 44U)
             den *= 2;
         av_reduce(&h->avctx->framerate.den, &h->avctx->framerate.num,
                   sps->num_units_in_tick, den, 1 << 30);

libavcodec/h264dec.c

@@ -293,6 +293,7 @@ static int h264_init_context(AVCodecContext *avctx, H264Context *h)
     h->flags                 = avctx->flags;
     h->poc.prev_poc_msb      = 1 << 16;
     h->recovery_frame        = -1;
+    h->x264_build            = -1;
     h->frame_recovered       = 0;
 
     h->next_outputed_poc = INT_MIN;

libavcodec/h264dec.h

@@ -361,6 +361,7 @@ typedef struct H264Context {
     int context_initialized;
     int flags;
     int workaround_bugs;
+    int x264_build;
     /* Set when slice threading is used and at least one slice uses deblocking
      * mode 1 (i.e. across slice boundaries). Then we disable the loop filter
      * during normal MB decoding and execute it serially at the end.