rtsp-server: Make onvif sample support different codecs

Add some autoplugging to the onvif example to make it handle
different video codecs automatically, and add support for
outputting the audio stream too, if any.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8378>

subprojects/gst-rtsp-server/examples/test-onvif-client.c

@@ -22,6 +22,9 @@
 #include <gst/gst.h>
 #include <gst/rtsp/rtsp.h>
 
+/* Uncomment to enable audio output */
+// #define OUTPUT_AUDIO
+
 typedef struct
 {
   gchar *range;
@@ -34,6 +37,8 @@ typedef struct
 typedef struct
 {
   GstElement *src;
+  GstElement *vconv;            /* decodebin -> vconv */
+
   GstElement *sink;
   GstElement *pipe;
   SeekParameters *seek_params;
@@ -103,28 +108,137 @@ G_STMT_START { \
 #define DEFAULT_REVERSE FALSE
 
 static void
-pad_added_cb (GstElement * src, GstPad * srcpad, GstElement * peer)
+decode_pad_added_cb (GstElement * src, GstPad * srcpad, Context * ctx)
 {
-  GstPad *sinkpad = gst_element_get_static_pad (peer, "sink");
+  /* Try to link to video output */
+  GstCaps *caps = gst_pad_get_current_caps (srcpad);
+  if (caps == NULL)
+    goto no_caps;
 
-  gst_pad_link (srcpad, sinkpad);
+  const GstStructure *s = gst_caps_get_structure (caps, 0);
+  if (s == NULL) {
+    goto no_caps;
+  }
 
+  GstElement *peer = NULL;
+  if (gst_structure_has_name (s, "video/x-raw")) {
+    GST_INFO ("Have decoded video stream");
+    peer = ctx->vconv;
+  }
+#if defined(OUTPUT_AUDIO)
+  else if (gst_structure_has_name (s, "audio/x-raw")) {
+    GstElement *aconv, *asink;
+
+    GST_INFO ("Have decoded audio stream");
+    MAKE_AND_ADD (aconv, ctx->pipe, "audioconvert", fail, NULL);
+    MAKE_AND_ADD (asink, ctx->pipe, "autoaudiosink", fail, NULL);
+
+    gst_element_set_state (aconv, GST_STATE_PLAYING);
+    gst_element_set_state (asink, GST_STATE_PLAYING);
+
+    if (!gst_element_link (aconv, asink)) {
+      goto fail;
+    }
+    peer = aconv;
+  }
+#endif
+
+  gst_caps_replace (&caps, NULL);
+
+  if (peer != NULL) {
+    GstPad *sinkpad = gst_element_get_static_pad (peer, "sink");
+    if (gst_pad_link (srcpad, sinkpad) != GST_PAD_LINK_OK) {
+      goto not_negotiated;
+    }
+    gst_object_unref (sinkpad);
+  }
+
+  return;
+
+no_caps:
+  GST_ELEMENT_ERROR (ctx->pipe, CORE, NEGOTIATION, (NULL),
+      ("decoded pad %" GST_PTR_FORMAT " did not have caps", srcpad));
+  gst_caps_replace (&caps, NULL);
+  return;
+not_negotiated:
+  GST_ELEMENT_ERROR (ctx->pipe, CORE, NEGOTIATION, (NULL),
+      ("Failed to link decoded pad %" GST_PTR_FORMAT " to output", srcpad));
+  return;
+#if defined(OUTPUT_AUDIO)
+fail:
+  GST_ELEMENT_ERROR (ctx->pipe, CORE, NEGOTIATION, (NULL),
+      ("Failed to connect %" GST_PTR_FORMAT " to output", srcpad));
+  return;
+#endif
+}
+
+static void
+pad_added_cb (GstElement * src, GstPad * srcpad, Context * ctx)
+{
+  GstCaps *caps = gst_pad_get_current_caps (srcpad);
+  if (caps == NULL)
+    goto no_caps;
+
+  const GstStructure *s = gst_caps_get_structure (caps, 0);
+  if (s == NULL) {
+    goto no_caps;
+  }
+
+  /* If the media is not audio or video, ignore it. (Could put ONVIF metadata to an appsink here though */
+  const gchar *media = gst_structure_get_string (s, "media");
+  if (media == NULL || (!g_str_equal (media, "video") &&
+          !g_str_equal (media, "audio"))) {
+    GST_INFO ("Ignoring rtsp pad %" GST_PTR_FORMAT " with caps %"
+        GST_PTR_FORMAT, srcpad, caps);
+    return;
+  }
+
+  GstElement *queue, *onvifparse, *dec;
+
+  /* Create decode chain */
+  MAKE_AND_ADD (queue, ctx->pipe, "queue", fail, NULL);
+  MAKE_AND_ADD (onvifparse, ctx->pipe, "rtponvifparse", fail, NULL);
+  MAKE_AND_ADD (dec, ctx->pipe, "decodebin", fail, NULL);
+
+  gst_element_set_state (queue, GST_STATE_PLAYING);
+  gst_element_set_state (onvifparse, GST_STATE_PLAYING);
+  gst_element_set_state (dec, GST_STATE_PLAYING);
+
+  g_signal_connect (dec, "pad-added", G_CALLBACK (decode_pad_added_cb), ctx);
+
+  if (!gst_element_link_many (queue, onvifparse, dec, NULL)) {
+    goto fail;
+  }
+
+  /* Connect srcpad to decode chain */
+  GstPad *sinkpad = gst_element_get_static_pad (queue, "sink");
+  if (gst_pad_link (srcpad, sinkpad) != GST_PAD_LINK_OK) {
+    goto fail;
+  }
   gst_object_unref (sinkpad);
+
+  return;
+
+no_caps:
+  GST_ELEMENT_ERROR (ctx->pipe, CORE, NEGOTIATION, (NULL),
+      ("decoded pad %" GST_PTR_FORMAT " did not have caps", srcpad));
+  return;
+fail:
+  GST_ELEMENT_ERROR (ctx->pipe, CORE, NEGOTIATION, (NULL),
+      ("Could not link input stream to decoders handling pad %" GST_PTR_FORMAT,
+          srcpad));
+  return;
 }
 
 static gboolean
 setup (Context * ctx)
 {
-  GstElement *onvifparse, *queue, *vdepay, *vdec, *vconv, *toverlay, *tee,
-      *vqueue;
+  GstElement *toverlay, *tee, *vqueue;
   gboolean ret = FALSE;
 
   MAKE_AND_ADD (ctx->src, ctx->pipe, "rtspsrc", done, NULL);
-  MAKE_AND_ADD (queue, ctx->pipe, "queue", done, NULL);
-  MAKE_AND_ADD (onvifparse, ctx->pipe, "rtponvifparse", done, NULL);
-  MAKE_AND_ADD (vdepay, ctx->pipe, "rtph264depay", done, NULL);
-  MAKE_AND_ADD (vdec, ctx->pipe, "avdec_h264", done, NULL);
-  MAKE_AND_ADD (vconv, ctx->pipe, "videoconvert", done, NULL);
+
+  MAKE_AND_ADD (ctx->vconv, ctx->pipe, "videoconvert", done, NULL);
   MAKE_AND_ADD (toverlay, ctx->pipe, "timeoverlay", done, NULL);
   MAKE_AND_ADD (tee, ctx->pipe, "tee", done, NULL);
   MAKE_AND_ADD (vqueue, ctx->pipe, "queue", done, NULL);
@@ -137,10 +251,10 @@ setup (Context * ctx)
 
   g_object_set (toverlay, "datetime-format", "%a %d, %b %Y - %T", NULL);
 
-  g_signal_connect (ctx->src, "pad-added", G_CALLBACK (pad_added_cb), queue);
+  g_signal_connect (ctx->src, "pad-added", G_CALLBACK (pad_added_cb), ctx);
 
-  if (!gst_element_link_many (queue, onvifparse, vdepay, vdec, vconv, toverlay,
-          tee, vqueue, ctx->sink, NULL)) {
+  if (!gst_element_link_many (ctx->vconv, toverlay, tee, vqueue, ctx->sink,
+          NULL)) {
     goto done;
   }