camerabin2: Fix A/V sync for captures

Audio src was pushing newsegments starting from 0, even when its buffers
were not starting with 0 as their timestamps. Add a buffer probe that
checks the ts of the first buffer and uses that to push a newsegment,
just like we do for video on wrappercamerabinsrc.

gst/camerabin2/gstcamerabin2.c

@@ -430,6 +430,7 @@ gst_camera_bin_start_capture (GstCameraBin2 * camerabin)
 
   g_signal_emit_by_name (camerabin->src, "start-capture", NULL);
   if (camerabin->mode == MODE_VIDEO) {
+    camerabin->audio_send_newseg = TRUE;
     if (camerabin->audio_src)
       gst_element_set_state (camerabin->audio_src, GST_STATE_PLAYING);
 
@@ -1436,18 +1437,46 @@ gst_camera_bin_image_sink_event_probe (GstPad * pad, GstEvent * event,
 }
 
 static gboolean
-gst_camera_bin_audio_src_event_probe (GstPad * pad, GstEvent * event,
+gst_camera_bin_audio_src_data_probe (GstPad * pad, GstMiniObject * obj,
     gpointer data)
 {
   GstCameraBin2 *camera = data;
   gboolean ret = TRUE;
 
+  if (GST_IS_BUFFER (obj)) {
+    if (G_UNLIKELY (camera->audio_send_newseg)) {
+      GstBuffer *buf = GST_BUFFER_CAST (obj);
+      GstClockTime ts = GST_BUFFER_TIMESTAMP (buf);
+      GstPad *peer;
+
+      if (!GST_CLOCK_TIME_IS_VALID (ts)) {
+        ts = 0;
+      }
+
+      peer = gst_pad_get_peer (pad);
+      g_return_val_if_fail (peer != NULL, TRUE);
+
+      gst_pad_send_event (peer, gst_event_new_new_segment (FALSE, 1.0,
+              GST_FORMAT_TIME, ts, -1, 0));
+
+      gst_object_unref (peer);
+
+      camera->audio_send_newseg = FALSE;
+    }
+  } else {
+    GstEvent *event = GST_EVENT_CAST (obj);
     if (GST_EVENT_TYPE (event) == GST_EVENT_EOS) {
       /* we only let an EOS pass when the user is stopping a capture */
       if (camera->audio_drop_eos) {
         ret = FALSE;
       } else {
         camera->audio_drop_eos = TRUE;
+        /* should already be false, but reinforce in case no buffers get
+         * pushed */
+        camera->audio_send_newseg = FALSE;
+      }
+    } else if (GST_EVENT_TYPE (event) == GST_EVENT_NEWSEGMENT) {
+      ret = FALSE;
     }
   }
 
@@ -1803,10 +1832,11 @@ gst_camera_bin_create_elements (GstCameraBin2 * camera)
 
     srcpad = gst_element_get_static_pad (camera->audio_src, "src");
 
-    /* drop EOS for audiosrc elements that push them on state_changes
+    /* 1) drop EOS for audiosrc elements that push them on state_changes
-     * (basesrc does this) */
+     * (basesrc does this) 
-    gst_pad_add_event_probe (srcpad,
+     * 2) Fix newsegment events to have start time = first buffer ts */
-        (GCallback) gst_camera_bin_audio_src_event_probe, camera);
+    gst_pad_add_data_probe (srcpad,
+        (GCallback) gst_camera_bin_audio_src_data_probe, camera);
 
     gst_object_unref (srcpad);
   }
@@ -1864,6 +1894,7 @@ gst_camera_bin_change_state (GstElement * element, GstStateChange trans)
     case GST_STATE_CHANGE_READY_TO_PAUSED:
       GST_CAMERA_BIN2_RESET_PROCESSING_COUNTER (camera);
       camera->audio_drop_eos = TRUE;
+      camera->audio_send_newseg = FALSE;
       break;
     case GST_STATE_CHANGE_PAUSED_TO_READY:
       if (GST_STATE (camera->videosink) >= GST_STATE_PAUSED)

gst/camerabin2/gstcamerabin2.h

@@ -126,6 +126,7 @@ struct _GstCameraBin2
   gboolean image_profile_switch;
 
   gboolean audio_drop_eos;
+  gboolean audio_send_newseg;
 
   GMutex *video_capture_mutex;
   GCond *video_state_cond;