From 0a945e7099159950f5ff14b13f7545dc53d2a57c Mon Sep 17 00:00:00 2001
From: Thiago Santos <thiagoss@osg.samsung.com>
Date: Fri, 13 Mar 2015 18:48:03 +0000
Subject: [PATCH] v4l2src: delay renegotiation until it is likely buffers were
 reclaimed

Allow renegotiation to happen when buffers have returned after an allocation
query. As the allocation query is serialized, all buffers from the pool
should have returned and we can stop it to create a new one for the
new format

https://bugzilla.gnome.org/show_bug.cgi?id=682770
---
 sys/v4l2/gstv4l2src.c | 74 ++++++++++++++++++++++++++++++++++++---------------
 sys/v4l2/gstv4l2src.h |  2 ++
 2 files changed, 55 insertions(+), 21 deletions(-)

diff --git a/sys/v4l2/gstv4l2src.c b/sys/v4l2/gstv4l2src.c
index 8775612..28a2d0f 100644
--- a/sys/v4l2/gstv4l2src.c
+++ b/sys/v4l2/gstv4l2src.c
@@ -290,20 +290,11 @@ gst_v4l2src_fixate (GstBaseSrc * basesrc, GstCaps * caps)
 static gboolean
 gst_v4l2src_negotiate (GstBaseSrc * basesrc)
 {
-  GstV4l2Src *v4l2src;
-  GstV4l2Object *obj;
   GstCaps *thiscaps;
   GstCaps *caps = NULL;
   GstCaps *peercaps = NULL;
   gboolean result = FALSE;
 
-  v4l2src = GST_V4L2SRC (basesrc);
-  obj = v4l2src->v4l2object;
-
-  /* We don't allow renegotiation, just return TRUE in that case */
-  if (GST_V4L2_IS_ACTIVE (obj))
-    return TRUE;
-
   /* first see what is possible on our source pad */
   thiscaps = gst_pad_query_caps (GST_BASE_SRC_PAD (basesrc), NULL);
   GST_DEBUG_OBJECT (basesrc, "caps of src: %" GST_PTR_FORMAT, thiscaps);
@@ -432,6 +423,23 @@ gst_v4l2src_get_caps (GstBaseSrc * src, GstCaps * filter)
 }
 
 static gboolean
+gst_v4l2src_set_format (GstV4l2Src * v4l2src, GstCaps * caps)
+{
+  GstV4l2Object *obj;
+
+  obj = v4l2src->v4l2object;
+
+  g_signal_emit (v4l2src, gst_v4l2_signals[SIGNAL_PRE_SET_FORMAT], 0,
+      v4l2src->v4l2object->video_fd, caps);
+
+  if (!gst_v4l2_object_set_format (obj, caps))
+    /* error already posted */
+    return FALSE;
+
+  return TRUE;
+}
+
+static gboolean
 gst_v4l2src_set_caps (GstBaseSrc * src, GstCaps * caps)
 {
   GstV4l2Src *v4l2src;
@@ -444,16 +452,24 @@ gst_v4l2src_set_caps (GstBaseSrc * src, GstCaps * caps)
   if (gst_v4l2_object_caps_equal (obj, caps))
     return TRUE;
 
-  /* make sure we stop capturing and dealloc buffers */
-  if (!gst_v4l2_object_stop (obj))
-    return FALSE;
-
-  g_signal_emit (v4l2src, gst_v4l2_signals[SIGNAL_PRE_SET_FORMAT], 0,
-      v4l2src->v4l2object->video_fd, caps);
+  if (GST_V4L2_IS_ACTIVE (obj)) {
+    /* Just check if the format is acceptable, once we know
+     * no buffers should be outstanding we try S_FMT.
+     *
+     * Basesrc will do an allocation query that
+     * should indirectly reclaim buffers, after that we can
+     * set the format and then configure our pool */
+    if (gst_v4l2_object_try_format (obj, caps))
+      v4l2src->pending_set_fmt = TRUE;
+    else
+      return FALSE;
+  } else {
+    /* make sure we stop capturing and dealloc buffers */
+    if (!gst_v4l2_object_stop (obj))
+      return FALSE;
 
-  if (!gst_v4l2_object_set_format (obj, caps))
-    /* error already posted */
-    return FALSE;
+    return gst_v4l2src_set_format (v4l2src, caps);
+  }
 
   return TRUE;
 }
@@ -462,10 +478,23 @@ static gboolean
 gst_v4l2src_decide_allocation (GstBaseSrc * bsrc, GstQuery * query)
 {
   GstV4l2Src *src = GST_V4L2SRC (bsrc);
-  gboolean ret = FALSE;
+  gboolean ret = TRUE;
+
+  if (src->pending_set_fmt) {
+    GstCaps *caps = gst_pad_get_current_caps (GST_BASE_SRC_PAD (bsrc));
 
-  if (gst_v4l2_object_decide_allocation (src->v4l2object, query))
-    ret = GST_BASE_SRC_CLASS (parent_class)->decide_allocation (bsrc, query);
+    if (!gst_v4l2_object_stop (src->v4l2object))
+      return FALSE;
+    ret = gst_v4l2src_set_format (src, caps);
+    gst_caps_unref (caps);
+    src->pending_set_fmt = FALSE;
+  }
+
+  if (ret) {
+    ret = gst_v4l2_object_decide_allocation (src->v4l2object, query);
+    if (ret)
+      ret = GST_BASE_SRC_CLASS (parent_class)->decide_allocation (bsrc, query);
+  }
 
   if (ret) {
     if (!gst_buffer_pool_set_active (src->v4l2object->pool, TRUE))
@@ -597,6 +626,9 @@ gst_v4l2src_stop (GstBaseSrc * src)
     if (!gst_v4l2_object_stop (obj))
       return FALSE;
   }
+
+  v4l2src->pending_set_fmt = FALSE;
+
   return TRUE;
 }
 
diff --git a/sys/v4l2/gstv4l2src.h b/sys/v4l2/gstv4l2src.h
index 2d90553..79dec17 100644
--- a/sys/v4l2/gstv4l2src.h
+++ b/sys/v4l2/gstv4l2src.h
@@ -61,6 +61,8 @@ struct _GstV4l2Src
 
   GstClockTime ctrl_time;
 
+  gboolean pending_set_fmt;
+
   /* Timestamp sanity check */
   GstClockTime last_timestamp;
   gboolean has_bad_timestamp;
-- 
2.7.4