Make the step and offset fields of the component descriptor express a
[libav.git] / libavcodec / pixdesc.h
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9b61d838 1/*
e0cffbe7 2 * pixel format descriptor
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3 * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22#include <inttypes.h>
23
24#include "libavutil/intreadwrite.h"
25
26typedef struct AVComponentDescriptor{
27 uint16_t plane :2; ///< which of the 4 planes contains the component
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28
29 /**
30 * Number of elements between 2 horizontally consecutive pixels minus 1.
31 * Elements are bits for bitstream formats, bytes otherwise.
32 */
33 uint16_t step_minus1 :3;
34
35 /**
36 * Number of elements before the component of the first pixel plus 1.
37 * Elements are bits for bitstream formats, bytes otherwise.
38 */
39 uint16_t offset_plus1 :3;
78679783 40 uint16_t shift :3; ///< number of least significant bits that must be shifted away to get the value
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41 uint16_t depth_minus1 :4; ///< number of bits in the component minus 1
42}AVComponentDescriptor;
43
d3bcbf57 44/**
e0cffbe7 45 * Descriptor that unambiguously describes how the bits of a pixel are
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46 * stored in the up to 4 data planes of an image. It also stores the
47 * subsampling factors and number of components.
48 *
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49 * @note This is separate of the colorspace (RGB, YCbCr, YPbPr, JPEG-style YUV
50 * and all the YUV variants) AVPixFmtDescriptor just stores how values
51 * are stored not what these values represent.
d3bcbf57 52 */
9b61d838 53typedef struct AVPixFmtDescriptor{
1e896640 54 const char *name;
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55 uint8_t nb_channels; ///< The number of components each pixel has, (1-4)
56
57 /**
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58 * Amount to shift the luma width right to find the chroma width.
59 * For YV12 this is 1 for example.
60 * chroma_width = -((-luma_width) >> log2_chroma_w)
61 * The note above is needed to ensure rounding up.
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62 */
63 uint8_t log2_chroma_w; ///< chroma_width = -((-luma_width )>>log2_chroma_w)
64
65 /**
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66 * Amount to shift the luma height right to find the chroma height.
67 * For YV12 this is 1 for example.
68 * chroma_height= -((-luma_height) >> log2_chroma_h)
69 * The note above is needed to ensure rounding up.
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70 */
71 uint8_t log2_chroma_h;
72 uint8_t flags;
e0cffbe7 73 AVComponentDescriptor comp[4]; ///< parameters that describe how pixels are packed
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74}AVPixFmtDescriptor;
75
e0cffbe7 76#define PIX_FMT_BE 1 ///< big-endian
d3f76612 77#define PIX_FMT_PAL 2 ///< Pixel format has a palette in data[1], values are indexes in this palette.
e0cffbe7 78#define PIX_FMT_BITSTREAM 4 ///< All values of a component are bit-wise packed end to end.
9b61d838 79
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80/**
81 * The array of all the pixel format descriptors.
82 */
83extern const AVPixFmtDescriptor av_pix_fmt_descriptors[];
9b61d838 84
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85/**
86 * Reads a line from an image, and writes to \p dst the values of the
87 * pixel format component \p c.
88 *
89 * @param data the array containing the pointers to the planes of the image
90 * @param linesizes the array containing the linesizes of the image
91 * @param desc the pixel format descriptor for the image
92 * @param x the horizontal coordinate of the first pixel to read
93 * @param y the vertical coordinate of the first pixel to read
94 * @param w the width of the line to read, that is the number of
95 * values to write to \p dst
96 */
30266c92 97static inline void read_line(uint16_t *dst, const uint8_t *data[4], const int linesize[4], const AVPixFmtDescriptor *desc, int x, int y, int c, int w)
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98{
99 AVComponentDescriptor comp= desc->comp[c];
100 int plane= comp.plane;
101 int depth= comp.depth_minus1+1;
102 int mask = (1<<depth)-1;
103 int shift= comp.shift;
104 int step = comp.step_minus1+1;
105 int flags= desc->flags;
106 const uint8_t *p= data[plane]+y*linesize[plane] + x * step + comp.offset_plus1 - 1;
107
108 //FIXME initial x in case of PIX_FMT_BITSTREAM is wrong
109
110 while(w--){
111 int val;
112 if(flags & PIX_FMT_BE) val= AV_RB16(p);
113 else val= AV_RL16(p);
114 val = (val>>shift) & mask;
115 if(flags & PIX_FMT_PAL)
116 val= data[1][4*val + c];
117 if(flags & PIX_FMT_BITSTREAM){
118 shift-=depth;
119 while(shift<0){
120 shift+=8;
121 p++;
122 }
123 }else
124 p+= step;
125 *dst++= val;
126 }
127}