vpx/vpx_scale/generic/yv12config.c

/*
 *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */


#include "vpx_scale/yv12config.h"
#include "vpx_mem/vpx_mem.h"

/****************************************************************************
*  Exports
****************************************************************************/

/****************************************************************************
 *
 ****************************************************************************/
int
vp8_yv12_de_alloc_frame_buffer(YV12_BUFFER_CONFIG *ybf) {
  if (ybf) {
    vpx_free(ybf->buffer_alloc);

    /* buffer_alloc isn't accessed by most functions.  Rather y_buffer,
      u_buffer and v_buffer point to buffer_alloc and are used.  Clear out
      all of this so that a freed pointer isn't inadvertently used */
    vpx_memset(ybf, 0, sizeof(YV12_BUFFER_CONFIG));
  } else {
    return -1;
  }

  return 0;
}

/****************************************************************************
 *
 ****************************************************************************/
int
vp8_yv12_alloc_frame_buffer(YV12_BUFFER_CONFIG *ybf, int width, int height, int border) {
  /*NOTE:*/

  if (ybf) {
    int y_stride = ((width + 2 * border) + 31) & ~31;
    int yplane_size = (height + 2 * border) * y_stride;
    int uv_width = width >> 1;
    int uv_height = height >> 1;
    /** There is currently a bunch of code which assumes
      *  uv_stride == y_stride/2, so enforce this here. */
    int uv_stride = y_stride >> 1;
    int uvplane_size = (uv_height + border) * uv_stride;

    vp8_yv12_de_alloc_frame_buffer(ybf);

    /** Only support allocating buffers that have a height and width that
      *  are multiples of 16, and a border that's a multiple of 32.
      * The border restriction is required to get 16-byte alignment of the
      *  start of the chroma rows without intoducing an arbitrary gap
      *  between planes, which would break the semantics of things like
      *  vpx_img_set_rect(). */
    if ((width & 0xf) | (height & 0xf) | (border & 0x1f))
      return -3;

    ybf->y_width  = width;
    ybf->y_height = height;
    ybf->y_stride = y_stride;

    ybf->uv_width = uv_width;
    ybf->uv_height = uv_height;
    ybf->uv_stride = uv_stride;

    ybf->border = border;
    ybf->frame_size = yplane_size + 2 * uvplane_size;

    ybf->buffer_alloc = (unsigned char *) vpx_memalign(32, ybf->frame_size);

    if (ybf->buffer_alloc == NULL)
      return -1;

    ybf->y_buffer = ybf->buffer_alloc + (border * y_stride) + border;
    ybf->u_buffer = ybf->buffer_alloc + yplane_size + (border / 2  * uv_stride) + border / 2;
    ybf->v_buffer = ybf->buffer_alloc + yplane_size + uvplane_size + (border / 2  * uv_stride) + border / 2;

    ybf->corrupted = 0; /* assume not currupted by errors */
  } else {
    return -2;
  }

  return 0;
}