[Bug 706083] v4l2src: UVC Allocated buffers wrapped in GstBuffer get orphaned by GstBuffer API

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=706083
  GStreamer | gst-plugins-good | git

--- Comment #21 from Robert Krakora <rob.krakora at messagenetsystems.com> 2013-09-19 19:47:02 UTC ---
Review of attachment 255308:
 --> (https://bugzilla.gnome.org/review?bug=706083&attachment=255308)

::: sys/v4l2/gstv4l2bufferpool.c
@@ +681,2 @@
   index = meta->vbuffer.index;
+  meta->vbuffer.bytesused = meta->vbuffer.length;

So, vbuffer.length is the size of the v4l2 buffer and vbuffer.bytesused the
actual number of bytes used in the buffer.  So, IMHO, this should be valid. 
The meta data obtained from the GstBuffer is used to obtain the length of the
vbuffer.

@@ +695,3 @@
+    gst_memory_new_wrapped (GST_MEMORY_FLAG_NO_SHARE,
+        meta->mem, meta->vbuffer.length, 0, meta->vbuffer.length, NULL,
+        NULL));

Why not?

@@ +794,3 @@
+            meta->mem, vbuffer.bytesused, 0, vbuffer.bytesused, NULL,
+            NULL));
+  /* with vbuffer.bytesused as the size and replace the    */

Huh?  gst_buffer_resize() is the problem.  It can replace the wrapped memory
object referenced by the GstBuffer with a new one that meets the new size
constraint and then the previously wrapped memory object, which wraps a v4l2
buffer, is "lost in space".

@@ +800,2 @@
   *buffer = outbuf;
+  GST_V4L2_BUFFER_POOL_UNLOCK (pool);

Trying to protect the pool structure from being accessed on different thread
times.  I am assuming that a buffer can get dequeued on another thread time.

@@ +912,3 @@

+            /* copy the buffer with memory */
+            copy = gst_buffer_copy_region (*buffer, GST_BUFFER_COPY_DEEP, 0,
-1);

O.K.

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