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107 lines
4.1 KiB
C
107 lines
4.1 KiB
C
/* GStreamer
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* Copyright (C) <2013> Wim Taymans <wim.taymans@gmail.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <gst/video/video-tile.h>
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/**
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* gst_video_tile_get_index:
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* @mode: a #GstVideoTileMode
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* @x: x coordinate
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* @y: y coordinate
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* @x_tiles: number of horizintal tiles
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* @y_tiles: number of vertical tiles
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*
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* Get the tile index of the tile at coordinates @x and @y in the tiled
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* image of @x_tiles by @y_tiles.
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*
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* Use this method when @mode is of type %GST_VIDEO_TILE_TYPE_INDEXED.
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*
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* Returns: the index of the tile at @x and @y in the tiled image of
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* @x_tiles by @y_tiles.
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*
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* Since: 1.4
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*/
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guint
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gst_video_tile_get_index (GstVideoTileMode mode, gint x, gint y,
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gint x_tiles, gint y_tiles)
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{
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gsize offset;
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g_return_val_if_fail (GST_VIDEO_TILE_MODE_IS_INDEXED (mode), 0);
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switch (mode) {
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case GST_VIDEO_TILE_MODE_ZFLIPZ_2X2:
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/* Due to the zigzag pattern we know that tiles are numbered like:
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* (see http://linuxtv.org/downloads/v4l-dvb-apis/re31.html)
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*
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* | Column (x)
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* | 0 1 2 3 4 5 6 7
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* -------|---------------------------------------
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* 0 | 0 1 6 7 8 9 14 15
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* R 1 | 2 3 4 5 10 11 12 13
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* o 2 | 16 17 22 23 24 25 30 31
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* w 3 | 18 19 20 21 26 27 28 29
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* 4 | 32 33 38 39 40 41 46 47
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* (y) 5 | 34 35 36 37 42 43 44 45
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* 6 | 48 49 50 51 52 53 54 55
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*
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* From this we can see that:
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*
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* For even rows:
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* - The first block in a row is always mapped to memory block 'y * width'.
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* - For all even rows, except for the last one when 'y' is odd, from the first
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* block number an offset is then added to obtain the block number for
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* the other blocks in the row. The offset is 'x' plus the corresponding
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* number in the series [0, 0, 4, 4, 4, 4, 8, 8, 8, 8, 12, ...], which can be
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* expressed as 'GST_ROUND_DOWN_4 (x + 2)'.
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* f(x,y,width,height) = y * width + x + GST_ROUND_DOWN_4 (x + 2)
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*
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* - For the last row when 'y' is odd the offset is simply 'x'.
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* f(x,y,width,height) = y * width + x
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* - Note that 'y' is even, so 'GST_ROUNDOWN_2 (y) == y' in this case
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*
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* For odd rows:
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* - The first block in the row is always mapped to memory block
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* 'GST_ROUND_DOWN_2(y) * width + 2'.
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* - From the first block number an offset is then added to obtain the block
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* number for the other blocks in the row. The offset is 'x' plus the
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* corresponding number in the series [0, 0, 0, 0, 4, 4, 4, 4, 8, 8, 8, 8, 12, ...],
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* which can be expressed as GST_ROUND_DOWN_4 (x).
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* f(x,y,width,height) = GST_ROUND_DOWN_2 (y) * width + bx 2 + GST_ROUND_DOWN_4 (x)
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*/
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/* Common to all cases */
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offset = GST_ROUND_DOWN_2 (y) * x_tiles + x;
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if (y & 1) {
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/* For odd row */
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offset += 2 + GST_ROUND_DOWN_4 (x);
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} else if ((y_tiles & 1) == 0 || y != (y_tiles - 1)) {
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/* For even row except for the last row when odd height */
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offset += GST_ROUND_DOWN_4 (x + 2);
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}
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break;
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default:
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offset = 0;
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break;
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}
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return offset;
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}
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