v4l2codecs: h264: Set frame flags

V4L spec now requires coded buffer flags to be set in accordance to the
frame type. In particular this is required by H.264 decoder of NVIDIA Tegra
SoC to operate properly. Set the flags based on type of parsed slices.

subprojects/gst-plugins-bad/sys/v4l2codecs/gstv4l2codech264dec.c

@@ -68,6 +68,7 @@ struct _GstV4l2CodecH264Dec
   guint chroma_format_idc;
   guint num_slices;
   gboolean first_slice;
+  guint frame_flags;
 
   GstV4l2CodecAllocator *sink_allocator;
   GstV4l2CodecAllocator *src_allocator;
@@ -981,6 +982,7 @@ gst_v4l2_codec_h264_dec_start_picture (GstH264Decoder * decoder,
       dpb);
 
   self->first_slice = TRUE;
+  self->frame_flags = 0;
 
   return GST_FLOW_OK;
 }
@@ -1288,6 +1290,20 @@ gst_v4l2_codec_h264_dec_decode_slice (GstH264Decoder * decoder,
       slice->nalu.size);
   self->bitstream_map.size += nal_size;
 
+  switch (slice->header.type % 5) {
+    case GST_H264_P_SLICE:
+      self->frame_flags |= V4L2_BUF_FLAG_PFRAME;
+      break;
+
+    case GST_H264_B_SLICE:
+      self->frame_flags |= V4L2_BUF_FLAG_BFRAME;
+      break;
+
+    case GST_H264_I_SLICE:
+      self->frame_flags |= V4L2_BUF_FLAG_KEYFRAME;
+      break;
+  }
+
   return GST_FLOW_OK;
 }
 
@@ -1296,11 +1312,11 @@ gst_v4l2_codec_h264_dec_end_picture (GstH264Decoder * decoder,
     GstH264Picture * picture)
 {
   GstV4l2CodecH264Dec *self = GST_V4L2_CODEC_H264_DEC (decoder);
-  guint flags = 0;
+  guint flags = self->frame_flags;
 
   /* Hold on the output frame if this is first field of a pair */
   if (picture->field != GST_H264_PICTURE_FIELD_FRAME && !picture->second_field)
-    flags = V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF;
+    flags |= V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF;
 
   if (!gst_v4l2_codec_h264_dec_submit_bitstream (self, picture, flags))
     return GST_FLOW_ERROR;