ivfparse: detect and propagate resolution changes.

Detect resolution changes on key frames, and propagate the resulting
caps to the src pad. Only the uncompressed data chunk is decoded, so
avoid using the new VP8 bitstream parsing library for now.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>

gst/ivfparse/gstivfparse.c

@@ -116,8 +116,11 @@ static void
 gst_ivf_parse_reset (GstIvfParse * ivf)
 {
   ivf->state = GST_IVF_PARSE_START;
+  ivf->width = 0;
+  ivf->height = 0;
   ivf->fps_n = 0;
   ivf->fps_d = 0;
+  ivf->update_caps = FALSE;
 }
 
 /* initialize the new element
@@ -168,6 +171,53 @@ gst_ivf_parse_stop (GstBaseParse * parse)
   return TRUE;
 }
 
+static void
+gst_ivf_parse_set_size (GstIvfParse * ivf, guint width, guint height)
+{
+  if (ivf->width != width || ivf->height != height) {
+    GST_INFO_OBJECT (ivf, "resolution changed to %ux%u", width, height);
+    ivf->width = width;
+    ivf->height = height;
+    ivf->update_caps = TRUE;
+  }
+}
+
+static void
+gst_ivf_parse_set_framerate (GstIvfParse * ivf, guint fps_n, guint fps_d)
+{
+  if (ivf->fps_n != fps_n || ivf->fps_d != fps_d) {
+    GST_INFO_OBJECT (ivf, "framerate changed to %u/%u", fps_n, fps_d);
+    ivf->fps_n = fps_n;
+    ivf->fps_d = fps_d;
+    ivf->update_caps = TRUE;
+  }
+}
+
+static void
+gst_ivf_parse_update_src_caps (GstIvfParse * ivf)
+{
+  GstCaps *caps;
+
+  if (!ivf->update_caps &&
+      G_LIKELY (gst_pad_has_current_caps (GST_BASE_PARSE_SRC_PAD (ivf))))
+    return;
+  ivf->update_caps = FALSE;
+
+  /* Create src pad caps */
+  caps = gst_caps_new_simple ("video/x-vp8", "width", G_TYPE_INT, ivf->width,
+      "height", G_TYPE_INT, ivf->height, NULL);
+
+  if (ivf->fps_n > 0 && ivf->fps_d > 0) {
+    gst_base_parse_set_frame_rate (GST_BASE_PARSE_CAST (ivf),
+        ivf->fps_n, ivf->fps_d, 0, 0);
+    gst_caps_set_simple (caps, "framerate", GST_TYPE_FRACTION, ivf->fps_n,
+        ivf->fps_d, NULL);
+  }
+
+  gst_pad_set_caps (GST_BASE_PARSE_SRC_PAD (ivf), caps);
+  gst_caps_unref (caps);
+}
+
 static GstFlowReturn
 gst_ivf_parse_handle_frame_start (GstIvfParse * ivf, GstBaseParseFrame * frame,
     gint * skipsize)
@@ -175,7 +225,6 @@ gst_ivf_parse_handle_frame_start (GstIvfParse * ivf, GstBaseParseFrame * frame,
   GstBuffer *const buffer = frame->buffer;
   GstMapInfo map;
   GstFlowReturn ret = GST_FLOW_OK;
-  GstCaps *caps;
 
   gst_buffer_map (buffer, &map, GST_MAP_READ);
   if (map.size >= IVF_FILE_HEADER_SIZE) {
@@ -199,23 +248,11 @@ gst_ivf_parse_handle_frame_start (GstIvfParse * ivf, GstBaseParseFrame * frame,
       goto end;
     }
 
-    ivf->fps_n = fps_n;
+    gst_ivf_parse_set_size (ivf, width, height);
-    ivf->fps_d = fps_d;
+    gst_ivf_parse_set_framerate (ivf, fps_n, fps_d);
-    gst_base_parse_set_frame_rate (GST_BASE_PARSE_CAST (ivf),
-        ivf->fps_n, ivf->fps_d, 0, 0);
-
-    /* create src pad caps */
-    caps = gst_caps_new_simple ("video/x-vp8",
-        "width", G_TYPE_INT, width, "height", G_TYPE_INT, height,
-        "framerate", GST_TYPE_FRACTION, ivf->fps_n, ivf->fps_d, NULL);
-
-    GST_INFO_OBJECT (ivf, "Found stream: %" GST_PTR_FORMAT, caps);
 
     GST_LOG_OBJECT (ivf, "Stream has %d frames", num_frames);
 
-    gst_pad_set_caps (GST_BASE_PARSE_SRC_PAD (ivf), caps);
-    gst_caps_unref (caps);
-
     /* move along */
     ivf->state = GST_IVF_PARSE_DATA;
     gst_base_parse_set_min_frame_size (GST_BASE_PARSE_CAST (ivf),
@@ -273,12 +310,29 @@ gst_ivf_parse_handle_frame_data (GstIvfParse * ivf, GstBaseParseFrame * frame,
     gst_buffer_replace (&frame->out_buffer, out_buffer);
     gst_buffer_unref (out_buffer);
 
+    /* Detect resolution changes on key frames */
+    if (gst_buffer_map (frame->out_buffer, &map, GST_MAP_READ)) {
+      guint32 frame_tag, width, height;
+
+      frame_tag = GST_READ_UINT24_LE (map.data);
+      if (!(frame_tag & 0x01) && map.size >= 10) {      /* key frame */
+        GST_DEBUG_OBJECT (ivf, "key frame detected");
+
+        width = GST_READ_UINT16_LE (map.data + 6) & 0x3fff;
+        height = GST_READ_UINT16_LE (map.data + 8) & 0x3fff;
+        gst_ivf_parse_set_size (ivf, width, height);
+      }
+      gst_buffer_unmap (frame->out_buffer, &map);
+    }
+
     if (ivf->fps_n > 0) {
       GST_BUFFER_TIMESTAMP (out_buffer) =
           gst_util_uint64_scale_int (GST_SECOND * frame_pts, ivf->fps_d,
           ivf->fps_n);
     }
 
+    gst_ivf_parse_update_src_caps (ivf);
+
     ret = gst_base_parse_finish_frame (GST_BASE_PARSE_CAST (ivf), frame,
         IVF_FRAME_HEADER_SIZE + frame_size);
     *skipsize = 0;

gst/ivfparse/gstivfparse.h

@@ -52,8 +52,11 @@ struct _GstIvfParse
 
   GstIvfParseState state;
 
+  guint width;
+  guint height;
   guint fps_n;
   guint fps_d;
+  gboolean update_caps;
 };
 
 struct _GstIvfParseClass