Temporary fix for #11159: Fix playback of HD-PVR recording

This revert FFmpeg commit bfca351
(ref https://ffmpeg.org/trac/ffmpeg/ticket/2062)

mythtv/external/FFmpeg/libavcodec/h264.c

@@ -1452,25 +1452,6 @@ static void decode_postinit(H264Context *h, int setup_finished)
         s->low_delay           = 0;
     }
 
-    for (i = 0; 1; i++) {
-        if(i == MAX_DELAYED_PIC_COUNT || cur->poc < h->last_pocs[i]){
-            if(i)
-                h->last_pocs[i-1] = cur->poc;
-            break;
-        } else if(i) {
-            h->last_pocs[i-1]= h->last_pocs[i];
-        }
-    }
-    out_of_order = MAX_DELAYED_PIC_COUNT - i;
-    if(   cur->f.pict_type == AV_PICTURE_TYPE_B
-       || (h->last_pocs[MAX_DELAYED_PIC_COUNT-2] > INT_MIN && h->last_pocs[MAX_DELAYED_PIC_COUNT-1] - h->last_pocs[MAX_DELAYED_PIC_COUNT-2] > 2))
-        out_of_order = FFMAX(out_of_order, 1);
-    if(s->avctx->has_b_frames < out_of_order && !h->sps.bitstream_restriction_flag){
-        av_log(s->avctx, AV_LOG_VERBOSE, "Increasing reorder buffer to %d\n", out_of_order);
-        s->avctx->has_b_frames = out_of_order;
-        s->low_delay = 0;
-    }
-
     pics = 0;
     while (h->delayed_pic[pics])
         pics++;
@@ -1496,6 +1477,29 @@ static void decode_postinit(H264Context *h, int setup_finished)
         h->next_outputed_poc = INT_MIN;
     out_of_order = out->poc < h->next_outputed_poc;
 
+    if (h->sps.bitstream_restriction_flag &&
+        s->avctx->has_b_frames >= h->sps.num_reorder_frames) {
+    } else if (out_of_order && pics - 1 == s->avctx->has_b_frames &&
+               s->avctx->has_b_frames < MAX_DELAYED_PIC_COUNT) {
+        int cnt = 0, invalid = 0;
+        for (i = 0; i < MAX_DELAYED_PIC_COUNT; i++) {
+            cnt += out->poc < h->last_pocs[i];
+            invalid += h->last_pocs[i] == INT_MIN;
+        }
+        if (invalid + cnt < MAX_DELAYED_PIC_COUNT) {
+            s->avctx->has_b_frames = FFMAX(s->avctx->has_b_frames, cnt);
+        } else if (cnt) {
+            for (i = 0; i < MAX_DELAYED_PIC_COUNT; i++)
+                h->last_pocs[i] = INT_MIN;
+        }
+        s->low_delay = 0;
+    } else if (s->low_delay &&
+               ((h->next_outputed_poc != INT_MIN && out->poc > h->next_outputed_poc + 2) ||
+                cur->f.pict_type == AV_PICTURE_TYPE_B)) {
+        s->low_delay = 0;
+        s->avctx->has_b_frames++;
+    }
+
     if (out_of_order || pics > s->avctx->has_b_frames) {
         out->f.reference &= ~DELAYED_PIC_REF;
         // for frame threading, the owner must be the second field's thread or
@@ -1504,6 +1508,8 @@ static void decode_postinit(H264Context *h, int setup_finished)
         for (i = out_idx; h->delayed_pic[i]; i++)
             h->delayed_pic[i] = h->delayed_pic[i + 1];
     }
+    memmove(h->last_pocs, &h->last_pocs[1], sizeof(*h->last_pocs) * (MAX_DELAYED_PIC_COUNT - 1));
+    h->last_pocs[MAX_DELAYED_PIC_COUNT - 1] = out->poc;
     if (!out_of_order && pics > s->avctx->has_b_frames) {
         h->next_output_pic = out;
         if (out_idx == 0 && h->delayed_pic[0] && (h->delayed_pic[0]->f.key_frame || h->delayed_pic[0]->mmco_reset)) {