v4l2: videodec: Move the capture setup into the processing loop

In previous implementation that job was split between handle_frame and
the processing loop and it wasn't clear if this mechanism was race
free. The capture setup would also be tried for every buffer, which was
not necessary.

This also simplify the handling of SRC_CH event, dropping the unneeded
atomic boolean.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4525>

2 files changed, 20 insertions, 32 deletions

diff --git a/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.c b/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.c
index 2883605093..a701ef5037 100644
--- a/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.c
+++ b/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.c
@@ -185,7 +185,6 @@ gst_v4l2_video_dec_start (GstVideoDecoder * decoder)
 
   gst_v4l2_object_unlock (self->v4l2output);
   g_atomic_int_set (&self->active, TRUE);
-  g_atomic_int_set (&self->capture_configuration_change, FALSE);
   self->output_flow = GST_FLOW_OK;
 
   return TRUE;
@@ -708,28 +707,22 @@ gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
   GstFlowReturn ret;
 
   GST_VIDEO_DECODER_STREAM_LOCK (decoder);
-  if (g_atomic_int_get (&self->capture_configuration_change)) {
-    gst_v4l2_object_stop (self->v4l2capture);
+  /* FIXME at the moment we need a capture pool to poll for SRC_CH, they may
+   * cause suprious reallocation. */
+  if (G_UNLIKELY (!GST_V4L2_IS_ACTIVE (self->v4l2capture))) {
     ret = gst_v4l2_video_dec_setup_capture (decoder);
     if (ret != GST_FLOW_OK) {
+      GST_ERROR_OBJECT (decoder, "Failed setup capture queue.\n");
       GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
-
-      /* if caps negotiation failed, avoid trying it repeatly */
-      if (ret == GST_FLOW_NOT_NEGOTIATED) {
-        GST_ERROR_OBJECT (decoder,
-            "capture configuration change fail, return negotiation fail");
-        goto beach;
-      } else {
-        return;
-      }
+      goto beach;
     }
-    g_atomic_int_set (&self->capture_configuration_change, FALSE);
+
+    /* just a safety, as introducing mistakes in setup_capture seems rather
+     * easy.*/
+    g_return_if_fail (GST_V4L2_IS_ACTIVE (self->v4l2capture));
   }
   GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
 
-  if (G_UNLIKELY (!GST_V4L2_IS_ACTIVE (self->v4l2capture)))
-    return;
-
   GST_LOG_OBJECT (decoder, "Allocate output buffer");
 
   self->output_flow = GST_FLOW_OK;
@@ -752,8 +745,7 @@ gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
 
     if (ret == GST_V4L2_FLOW_RESOLUTION_CHANGE) {
       GST_INFO_OBJECT (decoder, "Received resolution change");
-      g_atomic_int_set (&self->capture_configuration_change, TRUE);
-      return;
+      goto resolution_changed;
     }
 
     if (ret != GST_FLOW_OK)
@@ -771,8 +763,7 @@ gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
 
     if (ret == GST_V4L2_FLOW_RESOLUTION_CHANGE) {
       GST_INFO_OBJECT (decoder, "Received resolution change");
-      g_atomic_int_set (&self->capture_configuration_change, TRUE);
-      return;
+      goto resolution_changed;
     }
   } while (ret == GST_V4L2_FLOW_CORRUPTED_BUFFER);
 
@@ -846,6 +837,13 @@ gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
 
   return;
 
+resolution_changed:
+  GST_VIDEO_DECODER_STREAM_LOCK (decoder);
+  /* FIXME, should be draining here */
+  gst_v4l2_object_stop (self->v4l2capture);
+  GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
+  return;
+
 beach:
   GST_DEBUG_OBJECT (decoder, "Leaving output thread: %s",
       gst_flow_get_name (ret));
@@ -862,7 +860,7 @@ gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
 {
   GstV4l2Error error = GST_V4L2_ERROR_INIT;
   GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
-  GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (self->v4l2output);
+  GstBufferPool *pool = NULL;
   GstFlowReturn ret = GST_FLOW_OK;
   gboolean processed = FALSE;
   GstBuffer *tmp;
@@ -881,14 +879,7 @@ gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
       goto not_negotiated;
   }
 
-  if (!g_atomic_int_get (&self->capture_configuration_change)) {
-    ret = gst_v4l2_video_dec_setup_capture (decoder);
-    if (ret != GST_FLOW_OK) {
-      GST_ERROR_OBJECT (decoder, "setup capture fail\n");
-      goto not_negotiated;
-    }
-  }
-
+  pool = gst_v4l2_object_get_buffer_pool (self->v4l2output);
   if (G_UNLIKELY (!gst_buffer_pool_is_active (pool))) {
     GstBuffer *codec_data;
     GstStructure *config = gst_buffer_pool_get_config (pool);
diff --git a/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.h b/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.h
index 5af08ac935..6696fcb35e 100644
--- a/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.h
+++ b/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.h
@@ -62,9 +62,6 @@ struct _GstV4l2VideoDec
   GstVideoCodecState *input_state;
   gboolean active;
   GstFlowReturn output_flow;
-
-  /* dynamic resolution change flag */
-  gboolean capture_configuration_change;
 };
 
 struct _GstV4l2VideoDecClass