codecparsers: h264: add support for Recovery Point SEI message.

The recovery point SEI message helps a decoder in determining if the
decoding process would produce acceptable pictures for display after
the decoder initiates random access or after the encoder indicates
a broken link in the coded video sequence.

This is not used in the h264parse element, but it could help debugging.

https://bugzilla.gnome.org/show_bug.cgi?id=723380

gst-libs/gst/codecparsers/gsth264parser.c

@@ -852,6 +852,31 @@ error:
   return GST_H264_PARSER_ERROR;
 }
 
+static GstH264ParserResult
+gst_h264_parser_parse_recovery_point (GstH264NalParser * nalparser,
+    GstH264RecoveryPoint * rp, NalReader * nr)
+{
+  GstH264SPS *const sps = nalparser->last_sps;
+
+  GST_DEBUG ("parsing \"Recovery point\"");
+  if (!sps || !sps->valid) {
+    GST_WARNING ("didn't get the associated sequence paramater set for the "
+        "current access unit");
+    goto error;
+  }
+
+  READ_UE_ALLOWED (nr, rp->recovery_frame_cnt, 0, sps->max_frame_num - 1);
+  READ_UINT8 (nr, rp->exact_match_flag, 1);
+  READ_UINT8 (nr, rp->broken_link_flag, 1);
+  READ_UINT8 (nr, rp->changing_slice_group_idc, 2);
+
+  return GST_H264_PARSER_OK;
+
+error:
+  GST_WARNING ("error parsing \"Recovery point\"");
+  return GST_H264_PARSER_ERROR;
+}
+
 static GstH264ParserResult
 gst_h264_parser_parse_sei_message (GstH264NalParser * nalparser,
     NalReader * nr, GstH264SEIMessage * sei)
@@ -893,6 +918,10 @@ gst_h264_parser_parse_sei_message (GstH264NalParser * nalparser,
       res = gst_h264_parser_parse_pic_timing (nalparser,
           &sei->payload.pic_timing, nr);
       break;
+    case GST_H264_SEI_RECOVERY_POINT:
+      res = gst_h264_parser_parse_recovery_point (nalparser,
+          &sei->payload.recovery_point, nr);
+      break;
     default:
       /* Just consume payloadSize bytes, which does not account for
          emulation prevention bytes */

gst-libs/gst/codecparsers/gsth264parser.h

@@ -156,6 +156,7 @@ typedef enum
  * GstH264SEIPayloadType:
  * @GST_H264_SEI_BUF_PERIOD: Buffering Period SEI Message
  * @GST_H264_SEI_PIC_TIMING: Picture Timing SEI Message
+ * @GST_H264_SEI_RECOVERY_POINT: Recovery Point SEI Message (D.2.7)
  * ...
  *
  * The type of SEI message.
@@ -163,7 +164,8 @@ typedef enum
 typedef enum
 {
   GST_H264_SEI_BUF_PERIOD = 0,
-  GST_H264_SEI_PIC_TIMING = 1
+  GST_H264_SEI_PIC_TIMING = 1,
+  GST_H264_SEI_RECOVERY_POINT = 6,
       /* and more...  */
 } GstH264SEIPayloadType;
 
@@ -234,6 +236,7 @@ typedef struct _GstH264SliceHdr               GstH264SliceHdr;
 typedef struct _GstH264ClockTimestamp         GstH264ClockTimestamp;
 typedef struct _GstH264PicTiming              GstH264PicTiming;
 typedef struct _GstH264BufferingPeriod        GstH264BufferingPeriod;
+typedef struct _GstH264RecoveryPoint          GstH264RecoveryPoint;
 typedef struct _GstH264SEIMessage             GstH264SEIMessage;
 
 /**
@@ -706,6 +709,14 @@ struct _GstH264BufferingPeriod
   guint8 vcl_initial_cpb_removal_delay_offset[32];
 };
 
+struct _GstH264RecoveryPoint
+{
+  guint32 recovery_frame_cnt;
+  guint8 exact_match_flag;
+  guint8 broken_link_flag;
+  guint8 changing_slice_group_idc;
+};
+
 struct _GstH264SEIMessage
 {
   GstH264SEIPayloadType payloadType;
@@ -713,6 +724,7 @@ struct _GstH264SEIMessage
   union {
     GstH264BufferingPeriod buffering_period;
     GstH264PicTiming pic_timing;
+    GstH264RecoveryPoint recovery_point;
     /* ... could implement more */
   } payload;
 };

gst/videoparsers/gsth264parse.c

@@ -501,6 +501,16 @@ gst_h264_parse_process_sei (GstH264Parse * h264parse, GstH264NalUnit * nalu)
             "new buffering period; ts_trn_nb updated: %" GST_TIME_FORMAT,
             GST_TIME_ARGS (h264parse->ts_trn_nb));
         break;
+
+        /* Additional messages that are not innerly useful to the
+         * element but for debugging purposes */
+      case GST_H264_SEI_RECOVERY_POINT:
+        GST_LOG_OBJECT (h264parse, "recovery point found: %u %u %u %u",
+            sei.payload.recovery_point.recovery_frame_cnt,
+            sei.payload.recovery_point.exact_match_flag,
+            sei.payload.recovery_point.broken_link_flag,
+            sei.payload.recovery_point.changing_slice_group_idc);
+        break;
     }
   }
   g_array_free (messages, TRUE);