[vlc-devel] [PATCH] vmem: lock/unlock pictures from pool callback

[Thomas Guillem]

Pictures are now locked just before decoding, and unlocked before the picture
is displayed. This is the behavior expected by users and by the
libvlc_video_lock_cb/libvlc_video_unlock_cb documentation.

Furthermore, lock callbacks can now fail (planes[0] is checked before
continuing).
---
 modules/video_output/vmem.c | 73 +++++++++++++++++++++++++++++----------------
 1 file changed, 48 insertions(+), 25 deletions(-)

diff --git a/modules/video_output/vmem.c b/modules/video_output/vmem.c
index 64aefa1..fa05360 100644
--- a/modules/video_output/vmem.c
+++ b/modules/video_output/vmem.c
@@ -83,6 +83,9 @@ vlc_module_end()
  *****************************************************************************/
 struct picture_sys_t {
     void *id;
+    void *opaque;
+    void *(*lock)(void *sys, void **plane);
+    void (*unlock)(void *sys, void *id, void *const *plane);
 };
 
 /* NOTE: the callback prototypes must match those of LibVLC */
@@ -107,20 +110,6 @@ static picture_pool_t *Pool  (vout_display_t *, unsigned);
 static void           Display(vout_display_t *, picture_t *, subpicture_t *);
 static int            Control(vout_display_t *, int, va_list);
 
-static void Unlock(void *data, picture_t *pic)
-{
-    vout_display_sys_t *sys = data;
-    picture_sys_t *picsys = pic->p_sys;
-    void *planes[PICTURE_PLANE_MAX];
-
-    assert(!picture_IsReferenced(pic));
-
-    for (int i = 0; i < pic->i_planes; i++)
-        planes[i] = pic->p[i].p_pixels;
-
-    sys->unlock(sys->opaque, picsys->id, planes);
-}
-
 /*****************************************************************************
  * Open: allocates video thread
  *****************************************************************************
@@ -252,14 +241,39 @@ static void Close(vlc_object_t *object)
         sys->cleanup(sys->opaque);
 
     if (sys->pool)
-    {
-        if (sys->unlock != NULL)
-            picture_pool_Enum(sys->pool, Unlock, sys);
         picture_pool_Release(sys->pool);
-    }
     free(sys);
 }
 
+static int PoolLockPicture(picture_t *pic)
+{
+    picture_sys_t *picsys = pic->p_sys;
+    void *planes[PICTURE_PLANE_MAX] = {};
+
+    picsys->id = picsys->lock(picsys->opaque, planes);
+    if (planes[0] == NULL)
+        return -1;
+
+    for (int i = 0; i < pic->i_planes; i++)
+        pic->p[i].p_pixels = planes[i];
+    return 0;
+
+}
+
+static void PoolUnlockPicture(picture_t *pic)
+{
+    picture_sys_t *picsys = pic->p_sys;
+
+    if (picsys->unlock != NULL)
+    {
+        void *planes[PICTURE_PLANE_MAX] = {};
+        for (int i = 0; i < pic->i_planes; i++)
+            planes[i] = pic->p[i].p_pixels;
+
+        picsys->unlock(picsys->opaque, picsys->id, planes);
+    }
+}
+
 static picture_pool_t *Pool(vout_display_t *vd, unsigned count)
 {
     vout_display_sys_t *sys = vd->sys;
@@ -280,14 +294,14 @@ static picture_pool_t *Pool(vout_display_t *vd, unsigned count)
             break;
         }
         picsys->id = NULL;
+        picsys->opaque = sys->opaque;
+        picsys->lock = sys->lock;
+        picsys->unlock = sys->unlock;
 
         picture_resource_t rsc = { .p_sys = picsys };
-        void *planes[PICTURE_PLANE_MAX];
-
-        picsys->id = sys->lock(sys->opaque, planes);
 
         for (unsigned i = 0; i < PICTURE_PLANE_MAX; i++) {
-            rsc.p[i].p_pixels = planes[i];
+            rsc.p[i].p_pixels = NULL;
             rsc.p[i].i_lines  = sys->lines[i];
             rsc.p[i].i_pitch  = sys->pitches[i];
         }
@@ -301,7 +315,13 @@ static picture_pool_t *Pool(vout_display_t *vd, unsigned count)
     }
 
     /* */
-    sys->pool = picture_pool_New(count, pictures);
+    picture_pool_configuration_t pool_cfg = {
+        .picture_count = count,
+        .picture = pictures,
+        .lock = PoolLockPicture,
+        .unlock = PoolUnlockPicture,
+    };
+    sys->pool = picture_pool_NewExtended(&pool_cfg);
     if (!sys->pool) {
         for (unsigned i = 0; i < count; i++)
             picture_Release(pictures[i]);
@@ -314,10 +334,13 @@ static void Display(vout_display_t *vd, picture_t *pic, subpicture_t *subpic)
 {
     vout_display_sys_t *sys = vd->sys;
 
+    /* Unlock the picture buffer before the picture is displayed */
+    void *id = pic->p_sys->id;
+    picture_Release(pic);
+
     if (sys->display != NULL)
-        sys->display(sys->opaque, pic->p_sys->id);
+        sys->display(sys->opaque, id);
 
-    picture_Release(pic);
     VLC_UNUSED(subpic);
 }
 
-- 
2.8.1