srtsink: Fix header buffer filtering

Cleans up the code and fixes two issues:

- If there are no streamheaders in the caps but we have `HEADER`
  buffers, it would run `gst_buffer_list_foreach` with `self->headers`
  being `NULL`.
- The code forgot to unmap the buffer if it decided to ignore it.

Fixes: 0a562a92d7ee38d8919d1b802add84d3c93b59eb
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9284>

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

@@ -138,7 +138,6 @@ 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);
 }
@@ -169,6 +168,7 @@ gst_srt_sink_stop (GstBaseSink * bsink)
   GstSRTSink *self = GST_SRT_SINK (bsink);
 
   g_clear_pointer (&self->headers, gst_buffer_list_unref);
+  self->headers_sent = FALSE;
   gst_srt_object_close (self->srtobject);
 
   return TRUE;
@@ -184,7 +184,7 @@ 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);
@@ -199,9 +199,9 @@ is_buffer_different (GstBuffer ** buffer, guint idx, gpointer data)
 
   if (gst_buffer_memcmp (*buffer, 0, ctx->map_info->data, ctx->map_info->size)
       != 0)
-    retval = TRUE;
+    return TRUE;
 
-  return retval;
+  return FALSE;
 }
 
 static GstFlowReturn
@@ -211,39 +211,30 @@ 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->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;
+  }
 
-    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 (!self->headers_sent && self->headers &&
+      GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_HEADER)) {
+    StreamheaderCheckContext ctx = {.buf = buffer,.map_info = &info };
 
     if (!gst_buffer_list_foreach (self->headers, is_buffer_different, &ctx)) {
       GST_DEBUG_OBJECT (self, "Have streamheaders,"
           " ignoring header %" GST_PTR_FORMAT, buffer);
+      gst_buffer_unmap (buffer, &info);
       return GST_FLOW_OK;
     }
   }
 
-  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;
-    }
-  }
+  self->headers_sent = TRUE;
 
   if (gst_srt_object_write (self->srtobject, self->headers, &info, &error) < 0) {
     GST_ELEMENT_ERROR (self, RESOURCE, WRITE,
@@ -298,7 +289,7 @@ 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;
+  self->headers_sent = FALSE;
 
   s = gst_caps_get_structure (caps, 0);
   streamheader = gst_structure_get_value (s, "streamheader");

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

@@ -46,10 +46,9 @@ struct _GstSRTSink {
   GstBaseSink parent;
 
   GstBufferList *headers;
+  gboolean headers_sent;
 
   GstSRTObject *srtobject;
-
-  gboolean streamconfig_sent;
 };
 
 struct _GstSRTSinkClass {