gstreamer/gst-libs/gst/vaapi/gstvaapicontext.c

/*
 *  gstvaapicontext.c - VA context abstraction
 *
 *  Copyright (C) 2010-2011 Splitted-Desktop Systems
 *    Author: Gwenole Beauchesne <gwenole.beauchesne@splitted-desktop.com>
 *  Copyright (C) 2011-2014 Intel Corporation
 *    Author: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public License
 *  as published by the Free Software Foundation; either version 2.1
 *  of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free
 *  Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA 02110-1301 USA
 */

/**
 * SECTION:gstvaapicontext
 * @short_description: VA context abstraction
 */

#include "sysdeps.h"
#include "gstvaapicompat.h"
#include "gstvaapicontext.h"
#include "gstvaapidisplay_priv.h"
#include "gstvaapiobject_priv.h"
#include "gstvaapisurface.h"
#include "gstvaapisurface_priv.h"
#include "gstvaapisurfacepool.h"
#include "gstvaapisurfaceproxy.h"
#include "gstvaapivideopool_priv.h"
#include "gstvaapiimage.h"
#include "gstvaapisubpicture.h"
#include "gstvaapiutils.h"

#define DEBUG 1
#include "gstvaapidebug.h"

typedef struct _GstVaapiOverlayRectangle GstVaapiOverlayRectangle;
struct _GstVaapiOverlayRectangle
{
  GstVaapiContext *context;
  GstVaapiSubpicture *subpicture;
  GstVaapiRectangle render_rect;
  guint seq_num;
  guint layer_id;
  GstBuffer *rect_buffer;
  GstVideoOverlayRectangle *rect;
  guint is_associated:1;
};

static inline void
gst_video_overlay_rectangle_replace (GstVideoOverlayRectangle ** old_rect_ptr,
    GstVideoOverlayRectangle * new_rect)
{
  gst_mini_object_replace ((GstMiniObject **) old_rect_ptr,
      GST_MINI_OBJECT_CAST (new_rect));
}

#define overlay_rectangle_ref(overlay) \
    gst_vaapi_mini_object_ref(GST_VAAPI_MINI_OBJECT(overlay))

#define overlay_rectangle_unref(overlay) \
    gst_vaapi_mini_object_unref(GST_VAAPI_MINI_OBJECT(overlay))

#define overlay_rectangle_replace(old_overlay_ptr, new_overlay) \
    gst_vaapi_mini_object_replace((GstVaapiMiniObject **)(old_overlay_ptr), \
        (GstVaapiMiniObject *)(new_overlay))

static void overlay_rectangle_finalize (GstVaapiOverlayRectangle * overlay);

static gboolean
overlay_rectangle_associate (GstVaapiOverlayRectangle * overlay);

static gboolean
overlay_rectangle_deassociate (GstVaapiOverlayRectangle * overlay);

static inline const GstVaapiMiniObjectClass *
overlay_rectangle_class (void)
{
  static const GstVaapiMiniObjectClass GstVaapiOverlayRectangleClass = {
    sizeof (GstVaapiOverlayRectangle),
    (GDestroyNotify) overlay_rectangle_finalize
  };
  return &GstVaapiOverlayRectangleClass;
}

static GstVaapiOverlayRectangle *
overlay_rectangle_new (GstVideoOverlayRectangle * rect,
    GstVaapiContext * context, guint layer_id)
{
  GstVaapiOverlayRectangle *overlay;
  GstVaapiRectangle *render_rect;
  guint width, height, flags;
  gint x, y;

  overlay = (GstVaapiOverlayRectangle *)
      gst_vaapi_mini_object_new0 (overlay_rectangle_class ());
  if (!overlay)
    return NULL;

  overlay->context = context;
  overlay->seq_num = gst_video_overlay_rectangle_get_seqnum (rect);
  overlay->layer_id = layer_id;
  overlay->rect = gst_video_overlay_rectangle_ref (rect);

  flags = gst_video_overlay_rectangle_get_flags (rect);
  gst_buffer_replace (&overlay->rect_buffer,
      gst_video_overlay_rectangle_get_pixels_unscaled_raw (rect, flags));
  if (!overlay->rect_buffer)
    goto error;

  overlay->subpicture =
      gst_vaapi_subpicture_new_from_overlay_rectangle (GST_VAAPI_OBJECT_DISPLAY
      (context), rect);
  if (!overlay->subpicture)
    goto error;

  gst_video_overlay_rectangle_get_render_rectangle (rect,
      &x, &y, &width, &height);
  render_rect = &overlay->render_rect;
  render_rect->x = x;
  render_rect->y = y;
  render_rect->width = width;
  render_rect->height = height;
  return overlay;

error:
  overlay_rectangle_unref (overlay);
  return NULL;
}

static void
overlay_rectangle_finalize (GstVaapiOverlayRectangle * overlay)
{
  gst_buffer_replace (&overlay->rect_buffer, NULL);
  gst_video_overlay_rectangle_unref (overlay->rect);

  if (overlay->subpicture) {
    overlay_rectangle_deassociate (overlay);
    gst_vaapi_object_unref (overlay->subpicture);
    overlay->subpicture = NULL;
  }
}

static gboolean
overlay_rectangle_associate (GstVaapiOverlayRectangle * overlay)
{
  GstVaapiSubpicture *const subpicture = overlay->subpicture;
  GPtrArray *const surfaces = overlay->context->surfaces;
  guint i, n_associated;

  if (overlay->is_associated)
    return TRUE;

  n_associated = 0;
  for (i = 0; i < surfaces->len; i++) {
    GstVaapiSurface *const surface = g_ptr_array_index (surfaces, i);
    if (gst_vaapi_surface_associate_subpicture (surface, subpicture,
            NULL, &overlay->render_rect))
      n_associated++;
  }

  overlay->is_associated = TRUE;
  return n_associated == surfaces->len;
}

static gboolean
overlay_rectangle_deassociate (GstVaapiOverlayRectangle * overlay)
{
  GstVaapiSubpicture *const subpicture = overlay->subpicture;
  GPtrArray *const surfaces = overlay->context->surfaces;
  guint i, n_associated;

  if (!overlay->is_associated)
    return TRUE;

  n_associated = surfaces->len;
  for (i = 0; i < surfaces->len; i++) {
    GstVaapiSurface *const surface = g_ptr_array_index (surfaces, i);
    if (gst_vaapi_surface_deassociate_subpicture (surface, subpicture))
      n_associated--;
  }

  overlay->is_associated = FALSE;
  return n_associated == 0;
}

static gboolean
overlay_rectangle_changed_pixels (GstVaapiOverlayRectangle * overlay,
    GstVideoOverlayRectangle * rect)
{
  guint flags;
  GstBuffer *buffer;

  if (overlay->seq_num == gst_video_overlay_rectangle_get_seqnum (rect))
    return FALSE;

  flags =
      to_GstVideoOverlayFormatFlags (gst_vaapi_subpicture_get_flags
      (overlay->subpicture));

  buffer = gst_video_overlay_rectangle_get_pixels_unscaled_raw (rect, flags);
  if (!buffer)
    return FALSE;
#if GST_CHECK_VERSION(1,0,0)
  {
    const guint n_blocks = gst_buffer_n_memory (buffer);
    gsize ofs;
    guint i;

    if (buffer == overlay->rect_buffer)
      return TRUE;

    if (n_blocks != gst_buffer_n_memory (overlay->rect_buffer))
      return FALSE;

    for (i = 0; i < n_blocks; i++) {
      GstMemory *const mem1 = gst_buffer_peek_memory (buffer, i);
      GstMemory *const mem2 = gst_buffer_peek_memory (overlay->rect_buffer, i);
      if (!gst_memory_is_span (mem1, mem2, &ofs))
        return FALSE;
    }
  }
#else
  if (GST_BUFFER_DATA (overlay->rect_buffer) != GST_BUFFER_DATA (buffer))
    return FALSE;
#endif
  return TRUE;
}

static gboolean
overlay_rectangle_changed_render_rect (GstVaapiOverlayRectangle * overlay,
    GstVideoOverlayRectangle * rect)
{
  GstVaapiRectangle *const render_rect = &overlay->render_rect;
  guint width, height;
  gint x, y;

  gst_video_overlay_rectangle_get_render_rectangle (rect,
      &x, &y, &width, &height);

  if (x == render_rect->x &&
      y == render_rect->y &&
      width == render_rect->width && height == render_rect->height)
    return FALSE;

  render_rect->x = x;
  render_rect->y = y;
  render_rect->width = width;
  render_rect->height = height;
  return TRUE;
}

static inline gboolean
overlay_rectangle_update_global_alpha (GstVaapiOverlayRectangle * overlay,
    GstVideoOverlayRectangle * rect)
{
#ifdef HAVE_GST_VIDEO_OVERLAY_HWCAPS
  const guint flags = gst_video_overlay_rectangle_get_flags (rect);
  if (!(flags & GST_VIDEO_OVERLAY_FORMAT_FLAG_GLOBAL_ALPHA))
    return TRUE;
#endif
  return gst_vaapi_subpicture_set_global_alpha (overlay->subpicture,
      gst_video_overlay_rectangle_get_global_alpha (rect));
}

static gboolean
overlay_rectangle_update (GstVaapiOverlayRectangle * overlay,
    GstVideoOverlayRectangle * rect, gboolean * reassociate_ptr)
{
  if (overlay_rectangle_changed_pixels (overlay, rect))
    return FALSE;
  if (overlay_rectangle_changed_render_rect (overlay, rect))
    *reassociate_ptr = TRUE;
  if (!overlay_rectangle_update_global_alpha (overlay, rect))
    return FALSE;
  gst_video_overlay_rectangle_replace (&overlay->rect, rect);
  return TRUE;
}

static inline GPtrArray *
overlay_new (void)
{
  return g_ptr_array_new_with_free_func (
      (GDestroyNotify) gst_vaapi_mini_object_unref);
}

static void
overlay_destroy (GPtrArray ** overlay_ptr)
{
  GPtrArray *const overlay = *overlay_ptr;

  if (!overlay)
    return;
  g_ptr_array_unref (overlay);
  *overlay_ptr = NULL;
}

static void
overlay_clear (GPtrArray * overlay)
{
  if (overlay && overlay->len > 0)
    g_ptr_array_remove_range (overlay, 0, overlay->len);
}

static GstVaapiOverlayRectangle *
overlay_lookup (GPtrArray * overlays, GstVideoOverlayRectangle * rect)
{
  guint i;

  for (i = 0; i < overlays->len; i++) {
    GstVaapiOverlayRectangle *const overlay = g_ptr_array_index (overlays, i);

    if (overlay->rect == rect)
      return overlay;
  }
  return NULL;
}

static gboolean
overlay_reassociate (GPtrArray * overlays)
{
  guint i;

  for (i = 0; i < overlays->len; i++)
    overlay_rectangle_deassociate (g_ptr_array_index (overlays, i));

  for (i = 0; i < overlays->len; i++) {
    if (!overlay_rectangle_associate (g_ptr_array_index (overlays, i)))
      return FALSE;
  }
  return TRUE;
}

static void
context_clear_overlay (GstVaapiContext * context)
{
  overlay_clear (context->overlays[0]);
  overlay_clear (context->overlays[1]);
  context->overlay_id = 0;
}

static inline void
context_destroy_overlay (GstVaapiContext * context)
{
  context_clear_overlay (context);
}

static void
unref_surface_cb (GstVaapiSurface * surface)
{
  gst_vaapi_surface_set_parent_context (surface, NULL);
  gst_vaapi_object_unref (surface);
}

static void
context_destroy_surfaces (GstVaapiContext * context)
{
  context_destroy_overlay (context);

  if (context->surfaces) {
    g_ptr_array_unref (context->surfaces);
    context->surfaces = NULL;
  }
  gst_vaapi_video_pool_replace (&context->surfaces_pool, NULL);
}

static void
context_destroy (GstVaapiContext * context)
{
  GstVaapiDisplay *const display = GST_VAAPI_OBJECT_DISPLAY (context);
  VAContextID context_id;
  VAStatus status;

  context_id = GST_VAAPI_OBJECT_ID (context);
  GST_DEBUG ("context 0x%08x", context_id);

  if (context_id != VA_INVALID_ID) {
    GST_VAAPI_DISPLAY_LOCK (display);
    status = vaDestroyContext (GST_VAAPI_DISPLAY_VADISPLAY (display),
        context_id);
    GST_VAAPI_DISPLAY_UNLOCK (display);
    if (!vaapi_check_status (status, "vaDestroyContext()"))
      GST_WARNING ("failed to destroy context 0x%08x", context_id);
    GST_VAAPI_OBJECT_ID (context) = VA_INVALID_ID;
  }

  if (context->va_config != VA_INVALID_ID) {
    GST_VAAPI_DISPLAY_LOCK (display);
    status = vaDestroyConfig (GST_VAAPI_DISPLAY_VADISPLAY (display),
        context->va_config);
    GST_VAAPI_DISPLAY_UNLOCK (display);
    if (!vaapi_check_status (status, "vaDestroyConfig()"))
      GST_WARNING ("failed to destroy config 0x%08x", context->va_config);
    context->va_config = VA_INVALID_ID;
  }
}

static gboolean
context_create_overlay (GstVaapiContext * context)
{
  if (!context->overlays[0] || !context->overlays[1])
    return FALSE;

  context_clear_overlay (context);
  return TRUE;
}

static gboolean
context_create_surfaces (GstVaapiContext * context)
{
  const GstVaapiContextInfo *const cip = &context->info;
  GstVideoInfo vi;
  GstVaapiSurface *surface;
  guint i, num_surfaces;

  /* Number of scratch surfaces beyond those used as reference */
  const guint SCRATCH_SURFACES_COUNT = 4;

  if (!context_create_overlay (context))
    return FALSE;

  num_surfaces = cip->ref_frames + SCRATCH_SURFACES_COUNT;
  if (!context->surfaces) {
    context->surfaces = g_ptr_array_new_full (num_surfaces,
        (GDestroyNotify) unref_surface_cb);
    if (!context->surfaces)
      return FALSE;
  }

  if (!context->surfaces_pool) {
    gst_video_info_set_format (&vi, GST_VIDEO_FORMAT_ENCODED,
        cip->width, cip->height);
    context->surfaces_pool =
        gst_vaapi_surface_pool_new (GST_VAAPI_OBJECT_DISPLAY (context), &vi);
    if (!context->surfaces_pool)
      return FALSE;
  }
  gst_vaapi_video_pool_set_capacity (context->surfaces_pool, num_surfaces);

  for (i = context->surfaces->len; i < num_surfaces; i++) {
    surface = gst_vaapi_surface_new (GST_VAAPI_OBJECT_DISPLAY (context),
        GST_VAAPI_CHROMA_TYPE_YUV420, cip->width, cip->height);
    if (!surface)
      return FALSE;
    gst_vaapi_surface_set_parent_context (surface, context);
    g_ptr_array_add (context->surfaces, surface);
    if (!gst_vaapi_video_pool_add_object (context->surfaces_pool, surface))
      return FALSE;
  }
  return TRUE;
}

static gboolean
context_create (GstVaapiContext * context)
{
  const GstVaapiContextInfo *const cip = &context->info;
  GstVaapiDisplay *const display = GST_VAAPI_OBJECT_DISPLAY (context);
  guint va_rate_control;
  VAConfigAttrib attribs[2];
  guint num_attribs;
  VAContextID context_id;
  VASurfaceID surface_id;
  VAStatus status;
  GArray *surfaces = NULL;
  gboolean success = FALSE;
  guint i;

  if (!context->surfaces && !context_create_surfaces (context))
    goto cleanup;

  surfaces = g_array_sized_new (FALSE,
      FALSE, sizeof (VASurfaceID), context->surfaces->len);
  if (!surfaces)
    goto cleanup;

  for (i = 0; i < context->surfaces->len; i++) {
    GstVaapiSurface *const surface = g_ptr_array_index (context->surfaces, i);
    if (!surface)
      goto cleanup;
    surface_id = GST_VAAPI_OBJECT_ID (surface);
    g_array_append_val (surfaces, surface_id);
  }
  g_assert (surfaces->len == context->surfaces->len);

  if (!cip->profile || !cip->entrypoint)
    goto cleanup;
  context->va_profile = gst_vaapi_profile_get_va_profile (cip->profile);
  context->va_entrypoint =
      gst_vaapi_entrypoint_get_va_entrypoint (cip->entrypoint);

  num_attribs = 0;
  attribs[num_attribs++].type = VAConfigAttribRTFormat;
  if (cip->entrypoint == GST_VAAPI_ENTRYPOINT_SLICE_ENCODE)
    attribs[num_attribs++].type = VAConfigAttribRateControl;

  GST_VAAPI_DISPLAY_LOCK (display);
  status = vaGetConfigAttributes (GST_VAAPI_DISPLAY_VADISPLAY (display),
      context->va_profile, context->va_entrypoint, attribs, num_attribs);
  GST_VAAPI_DISPLAY_UNLOCK (display);
  if (!vaapi_check_status (status, "vaGetConfigAttributes()"))
    goto cleanup;
  if (!(attribs[0].value & VA_RT_FORMAT_YUV420))
    goto cleanup;

  if (cip->entrypoint == GST_VAAPI_ENTRYPOINT_SLICE_ENCODE) {
    va_rate_control = from_GstVaapiRateControl (cip->rc_mode);
    if (va_rate_control == VA_RC_NONE)
      attribs[1].value = VA_RC_NONE;
    if ((attribs[1].value & va_rate_control) != va_rate_control) {
      GST_ERROR ("unsupported %s rate control",
          string_of_VARateControl (va_rate_control));
      goto cleanup;
    }
    attribs[1].value = va_rate_control;
  }

  GST_VAAPI_DISPLAY_LOCK (display);
  status = vaCreateConfig (GST_VAAPI_DISPLAY_VADISPLAY (display),
      context->va_profile, context->va_entrypoint, attribs, num_attribs,
      &context->va_config);
  GST_VAAPI_DISPLAY_UNLOCK (display);
  if (!vaapi_check_status (status, "vaCreateConfig()"))
    goto cleanup;

  GST_VAAPI_DISPLAY_LOCK (display);
  status = vaCreateContext (GST_VAAPI_DISPLAY_VADISPLAY (display),
      context->va_config, cip->width, cip->height, VA_PROGRESSIVE,
      (VASurfaceID *) surfaces->data, surfaces->len, &context_id);
  GST_VAAPI_DISPLAY_UNLOCK (display);
  if (!vaapi_check_status (status, "vaCreateContext()"))
    goto cleanup;

  GST_DEBUG ("context 0x%08x", context_id);
  GST_VAAPI_OBJECT_ID (context) = context_id;
  success = TRUE;

cleanup:
  if (surfaces)
    g_array_free (surfaces, TRUE);
  return success;
}

static inline void
gst_vaapi_context_init (GstVaapiContext * context,
    const GstVaapiContextInfo * cip)
{
  context->info = *cip;
  context->va_config = VA_INVALID_ID;
  context->overlays[0] = overlay_new ();
  context->overlays[1] = overlay_new ();
}

static void
gst_vaapi_context_finalize (GstVaapiContext * context)
{
  overlay_destroy (&context->overlays[0]);
  overlay_destroy (&context->overlays[1]);
  context_destroy (context);
  context_destroy_surfaces (context);
}

GST_VAAPI_OBJECT_DEFINE_CLASS (GstVaapiContext, gst_vaapi_context);

/**
 * gst_vaapi_context_new:
 * @display: a #GstVaapiDisplay
 * @cip: a pointer to the #GstVaapiContextInfo
 *
 * Creates a new #GstVaapiContext with the configuration specified by
 * @cip, thus including profile, entry-point, encoded size and maximum
 * number of reference frames reported by the bitstream.
 *
 * Return value: the newly allocated #GstVaapiContext object
 */
GstVaapiContext *
gst_vaapi_context_new (GstVaapiDisplay * display,
    const GstVaapiContextInfo * cip)
{
  GstVaapiContext *context;

  g_return_val_if_fail (cip->profile, NULL);
  g_return_val_if_fail (cip->entrypoint, NULL);
  g_return_val_if_fail (cip->width > 0, NULL);
  g_return_val_if_fail (cip->height > 0, NULL);

  context = gst_vaapi_object_new (gst_vaapi_context_class (), display);
  if (!context)
    return NULL;

  gst_vaapi_context_init (context, cip);
  if (!context_create (context))
    goto error;
  return context;

error:
  gst_vaapi_object_unref (context);
  return NULL;
}

/**
 * gst_vaapi_context_reset:
 * @context: a #GstVaapiContext
 * @new_cip: a pointer to the new #GstVaapiContextInfo details
 *
 * Resets @context to the configuration specified by @new_cip, thus
 * including profile, entry-point, encoded size and maximum number of
 * reference frames reported by the bitstream.
 *
 * Return value: %TRUE on success
 */
gboolean
gst_vaapi_context_reset (GstVaapiContext * context,
    const GstVaapiContextInfo * new_cip)
{
  GstVaapiContextInfo *const cip = &context->info;
  gboolean size_changed, config_changed;

  size_changed = cip->width != new_cip->width || cip->height != new_cip->height;
  if (size_changed) {
    cip->width = new_cip->width;
    cip->height = new_cip->height;
  }

  config_changed = cip->profile != new_cip->profile ||
      cip->entrypoint != new_cip->entrypoint;
  if (config_changed) {
    cip->profile = new_cip->profile;
    cip->entrypoint = new_cip->entrypoint;
  }

  switch (new_cip->entrypoint) {
    case GST_VAAPI_ENTRYPOINT_SLICE_ENCODE:
      if (cip->rc_mode != new_cip->rc_mode) {
        cip->rc_mode = new_cip->rc_mode;
        config_changed = TRUE;
      }
      break;
    default:
      break;
  }

  if (size_changed)
    context_destroy_surfaces (context);
  if (config_changed)
    context_destroy (context);

  if (size_changed && !context_create_surfaces (context))
    return FALSE;
  if (config_changed && !context_create (context))
    return FALSE;
  return TRUE;
}

/**
 * gst_vaapi_context_get_id:
 * @context: a #GstVaapiContext
 *
 * Returns the underlying VAContextID of the @context.
 *
 * Return value: the underlying VA context id
 */
GstVaapiID
gst_vaapi_context_get_id (GstVaapiContext * context)
{
  g_return_val_if_fail (context != NULL, VA_INVALID_ID);

  return GST_VAAPI_OBJECT_ID (context);
}

/**
 * gst_vaapi_context_get_surface_proxy:
 * @context: a #GstVaapiContext
 *
 * Acquires a free surface, wrapped into a #GstVaapiSurfaceProxy. The
 * returned surface will be automatically released when the proxy is
 * destroyed. So, it is enough to call gst_vaapi_surface_proxy_unref()
 * after usage.
 *
 * This function returns %NULL if there is no free surface available
 * in the pool. The surfaces are pre-allocated during context creation
 * though.
 *
 * Return value: a free surface, or %NULL if none is available
 */
GstVaapiSurfaceProxy *
gst_vaapi_context_get_surface_proxy (GstVaapiContext * context)
{
  g_return_val_if_fail (context != NULL, NULL);

  return
      gst_vaapi_surface_proxy_new_from_pool (GST_VAAPI_SURFACE_POOL
      (context->surfaces_pool));
}

/**
 * gst_vaapi_context_get_surface_count:
 * @context: a #GstVaapiContext
 *
 * Retrieves the number of free surfaces left in the pool.
 *
 * Return value: the number of free surfaces available in the pool
 */
guint
gst_vaapi_context_get_surface_count (GstVaapiContext * context)
{
  g_return_val_if_fail (context != NULL, 0);

  return gst_vaapi_video_pool_get_size (context->surfaces_pool);
}

/**
 * gst_vaapi_context_apply_composition:
 * @context: a #GstVaapiContext
 * @composition: a #GstVideoOverlayComposition
 *
 * Applies video composition planes to all surfaces bound to @context.
 * This helper function resets any additional subpictures the user may
 * have associated himself. A %NULL @composition will also clear all
 * the existing subpictures.
 *
 * Return value: %TRUE if all composition planes could be applied,
 *   %FALSE otherwise
 */
gboolean
gst_vaapi_context_apply_composition (GstVaapiContext * context,
    GstVideoOverlayComposition * composition)
{
  GPtrArray *curr_overlay, *next_overlay;
  guint i, n_rectangles;
  gboolean reassociate = FALSE;

  g_return_val_if_fail (context != NULL, FALSE);

  if (!context->surfaces)
    return FALSE;

  if (!composition) {
    context_clear_overlay (context);
    return TRUE;
  }

  curr_overlay = context->overlays[context->overlay_id];
  next_overlay = context->overlays[context->overlay_id ^ 1];
  overlay_clear (next_overlay);

  n_rectangles = gst_video_overlay_composition_n_rectangles (composition);
  for (i = 0; i < n_rectangles; i++) {
    GstVideoOverlayRectangle *const rect =
        gst_video_overlay_composition_get_rectangle (composition, i);
    GstVaapiOverlayRectangle *overlay;

    overlay = overlay_lookup (curr_overlay, rect);
    if (overlay && overlay_rectangle_update (overlay, rect, &reassociate)) {
      overlay_rectangle_ref (overlay);
      if (overlay->layer_id != i)
        reassociate = TRUE;
    } else {
      overlay = overlay_rectangle_new (rect, context, i);
      if (!overlay) {
        GST_WARNING ("could not create VA overlay rectangle");
        goto error;
      }
      reassociate = TRUE;
    }
    g_ptr_array_add (next_overlay, overlay);
  }

  overlay_clear (curr_overlay);
  context->overlay_id ^= 1;

  if (reassociate && !overlay_reassociate (next_overlay))
    return FALSE;
  return TRUE;

error:
  context_clear_overlay (context);
  return FALSE;
}

/**
 * gst_vaapi_context_get_attribute:
 * @context: a #GstVaapiContext
 * @type: a VA config attribute type
 * @out_value_ptr: return location for the config attribute value
 *
 * Determines the value for the VA config attribute @type.
 *
 * Note: this function only returns success if the VA driver does
 * actually know about this config attribute type and that it returned
 * a valid value for it.
 *
 * Return value: %TRUE if the VA driver knows about the requested
 *   config attribute and returned a valid value, %FALSE otherwise
 */
gboolean
gst_vaapi_context_get_attribute (GstVaapiContext * context,
    VAConfigAttribType type, guint * out_value_ptr)
{
  VAConfigAttrib attrib;
  VAStatus status;

  g_return_val_if_fail (context != NULL, FALSE);

  GST_VAAPI_OBJECT_LOCK_DISPLAY (context);
  attrib.type = type;
  status = vaGetConfigAttributes (GST_VAAPI_OBJECT_VADISPLAY (context),
      context->va_profile, context->va_entrypoint, &attrib, 1);
  GST_VAAPI_OBJECT_UNLOCK_DISPLAY (context);
  if (!vaapi_check_status (status, "vaGetConfigAttributes()"))
    return FALSE;

  if (out_value_ptr)
    *out_value_ptr = attrib.value;
  return TRUE;
}