v4l2src: Avoid decide allocation on active pool

v4l2src will renegotiate only if the format have changed. As of now,
it's not possible to change the allocationw without resetting the
camera. To avoid unwanted side effect, simply keep the old allocation
if no renegotiation is taking place. This fixes assertion and possible
failures in USERPTR or DMABUF import mode (when using downstream pools).

https://bugzilla.gnome.org/show_bug.cgi?id=754042

diff --git a/sys/v4l2/gstv4l2src.c b/sys/v4l2/gstv4l2src.c
index 235eda4..348ab7f 100644 (file)
--- a/sys/v4l2/gstv4l2src.c
+++ b/sys/v4l2/gstv4l2src.c
@@ -489,6 +489,34 @@ gst_v4l2src_decide_allocation (GstBaseSrc * bsrc, GstQuery * query)
     ret = gst_v4l2src_set_format (src, caps);
     gst_caps_unref (caps);
     src->pending_set_fmt = FALSE;
+  } else if (gst_buffer_pool_is_active (src->v4l2object->pool)) {
+    /* Trick basesrc into not deactivating the active pool. Renegotiating here
+     * would otherwise turn off and on the camera. */
+    GstAllocator *allocator;
+    GstAllocationParams params;
+    GstBufferPool *pool;
+
+    gst_base_src_get_allocator (bsrc, &allocator, &params);
+    pool = gst_base_src_get_buffer_pool (bsrc);
+
+    if (gst_query_get_n_allocation_params (query))
+      gst_query_set_nth_allocation_param (query, 0, allocator, &params);
+    else
+      gst_query_add_allocation_param (query, allocator, &params);
+
+    if (gst_query_get_n_allocation_pools (query))
+      gst_query_set_nth_allocation_pool (query, 0, pool,
+          src->v4l2object->info.size, 1, 0);
+    else
+      gst_query_add_allocation_pool (query, pool, src->v4l2object->info.size, 1,
+          0);
+
+    if (pool)
+      gst_object_unref (pool);
+    if (allocator)
+      gst_object_unref (allocator);
+
+    return GST_BASE_SRC_CLASS (parent_class)->decide_allocation (bsrc, query);
   }
 
   if (ret) {