srtsink: filter stream-config already sent

- Only sent buffer with GST_BUFFER_FLAG_HEADER if this buffer is not present in
  the streamheader

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8373>

subprojects/gst-plugins-bad/ext/srt/gstsrtsink.c

@@ -138,6 +138,7 @@ gst_srt_sink_finalize (GObject * object)
 static void
 gst_srt_sink_init (GstSRTSink * self)
 {
+  self->streamconfig_sent = FALSE;
   self->srtobject = gst_srt_object_new (GST_ELEMENT (self));
   gst_srt_object_set_uri (self->srtobject, GST_SRT_DEFAULT_URI, NULL);
 }
@@ -173,6 +174,36 @@ gst_srt_sink_stop (GstBaseSink * bsink)
   return TRUE;
 }
 
+typedef struct
+{
+  GstBuffer *buf;
+  GstMapInfo *map_info;
+} StreamheaderCheckContext;
+
+static gboolean
+is_buffer_different (GstBuffer ** buffer, guint idx, gpointer data)
+{
+  StreamheaderCheckContext *ctx = (StreamheaderCheckContext *) data;
+  gboolean retval = FALSE;
+  g_return_val_if_fail (buffer != NULL, FALSE);
+  g_return_val_if_fail (GST_IS_BUFFER (*buffer), FALSE);
+  g_return_val_if_fail (ctx != NULL, FALSE);
+  g_return_val_if_fail (GST_IS_BUFFER (ctx->buf), FALSE);
+  g_return_val_if_fail (ctx->map_info != NULL, FALSE);
+
+  if (*buffer == ctx->buf)
+    return FALSE;
+
+  if (gst_buffer_get_size (*buffer) != gst_buffer_get_size (ctx->buf))
+    return TRUE;
+
+  if (gst_buffer_memcmp (*buffer, 0, ctx->map_info->data, ctx->map_info->size)
+      != 0)
+    retval = TRUE;
+
+  return retval;
+}
+
 static GstFlowReturn
 gst_srt_sink_render (GstBaseSink * sink, GstBuffer * buffer)
 {
@@ -180,21 +211,38 @@ gst_srt_sink_render (GstBaseSink * sink, GstBuffer * buffer)
   GstFlowReturn ret = GST_FLOW_OK;
   GstMapInfo info;
   GError *error = NULL;
+  StreamheaderCheckContext ctx = { 0 };
 
   if (g_cancellable_is_cancelled (self->srtobject->cancellable)) {
     ret = GST_FLOW_FLUSHING;
   }
 
-  if (self->headers && GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_HEADER)) {
-    GST_DEBUG_OBJECT (self, "Have streamheaders,"
-        " ignoring header %" GST_PTR_FORMAT, buffer);
-    return GST_FLOW_OK;
+  if (!self->streamconfig_sent && GST_BUFFER_FLAG_IS_SET (buffer,
+          GST_BUFFER_FLAG_HEADER)) {
+
+    if (!gst_buffer_map (buffer, &info, GST_MAP_READ)) {
+      GST_ELEMENT_ERROR (self, RESOURCE, READ,
+          ("Could not map the input stream"), (NULL));
+      return GST_FLOW_ERROR;
+    }
+    ctx.map_info = &info;
+    ctx.buf = buffer;
+
+    if (!gst_buffer_list_foreach (self->headers, is_buffer_different, &ctx)) {
+      GST_DEBUG_OBJECT (self, "Have streamheaders,"
+          " ignoring header %" GST_PTR_FORMAT, buffer);
+      return GST_FLOW_OK;
+    }
   }
 
-  if (!gst_buffer_map (buffer, &info, GST_MAP_READ)) {
-    GST_ELEMENT_ERROR (self, RESOURCE, READ,
-        ("Could not map the input stream"), (NULL));
-    return GST_FLOW_ERROR;
+  self->streamconfig_sent = TRUE;
+
+  if (ctx.map_info != &info) {
+    if (!gst_buffer_map (buffer, &info, GST_MAP_READ)) {
+      GST_ELEMENT_ERROR (self, RESOURCE, READ,
+          ("Could not map the input stream"), (NULL));
+      return GST_FLOW_ERROR;
+    }
   }
 
   if (gst_srt_object_write (self->srtobject, self->headers, &info, &error) < 0) {
@@ -250,6 +298,7 @@ gst_srt_sink_set_caps (GstBaseSink * bsink, GstCaps * caps)
   GST_DEBUG_OBJECT (self, "setcaps %" GST_PTR_FORMAT, caps);
 
   g_clear_pointer (&self->headers, gst_buffer_list_unref);
+  self->streamconfig_sent = FALSE;
 
   s = gst_caps_get_structure (caps, 0);
   streamheader = gst_structure_get_value (s, "streamheader");

subprojects/gst-plugins-bad/ext/srt/gstsrtsink.h

@@ -48,6 +48,8 @@ struct _GstSRTSink {
   GstBufferList *headers;
 
   GstSRTObject *srtobject;
+
+  gboolean streamconfig_sent;
 };
 
 struct _GstSRTSinkClass {