libavcodec/pixdesc.h

   1 /*
   2  * pixel format descriptor
   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
  26 typedef struct AVComponentDescriptor{
  27     uint16_t plane        :2;            ///< which of the 4 planes contains the component
  28     uint16_t step_minus1  :3;            ///< number of bytes between 2 horizontally consecutive pixels minus 1
  29     uint16_t offset_plus1 :3;            ///< number of bytes before the component of the first pixel plus 1
  30     uint16_t shift        :3;            ///< number of least significant bits that must be shifted away to get the value
  31     uint16_t depth_minus1 :4;            ///< number of bits in the component minus 1
  32 }AVComponentDescriptor;
  33
  34 /**
  35  * Descriptor that unambiguously describes how the bits of a pixel are
  36  * stored in the up to 4 data planes of an image. It also stores the
  37  * subsampling factors and number of components.
  38  *
  39  * @note This is separate of the colorspace (RGB, YCbCr, YPbPr, JPEG-style YUV
  40  *       and all the YUV variants) AVPixFmtDescriptor just stores how values
  41  *       are stored not what these values represent.
  42  */
  43 typedef struct AVPixFmtDescriptor{
  44     const char *name;
  45     uint8_t nb_channels;        ///< The number of components each pixel has, (1-4)
  46
  47     /**
  48      * Amount to shift the luma width right to find the chroma width.
  49      * For YV12 this is 1 for example.
  50      * chroma_width = -((-luma_width) >> log2_chroma_w)
  51      * The note above is needed to ensure rounding up.
  52      */
  53     uint8_t log2_chroma_w;      ///< chroma_width = -((-luma_width )>>log2_chroma_w)
  54
  55     /**
  56      * Amount to shift the luma height right to find the chroma height.
  57      * For YV12 this is 1 for example.
  58      * chroma_height= -((-luma_height) >> log2_chroma_h)
  59      * The note above is needed to ensure rounding up.
  60      */
  61     uint8_t log2_chroma_h;
  62     uint8_t flags;
  63     AVComponentDescriptor comp[4]; ///< parameters that describe how pixels are packed
  64 }AVPixFmtDescriptor;
  65
  66 #define PIX_FMT_BE        1 ///< big-endian
  67 #define PIX_FMT_PAL       2 ///< Pixel format has a palette in data[1], values are indexes in this palette.
  68 #define PIX_FMT_BITSTREAM 4 ///< All values of a component are bit-wise packed end to end.
  69
  70 /**
  71  * The array of all the pixel format descriptors.
  72  */
  73 extern const AVPixFmtDescriptor av_pix_fmt_descriptors[];
  74
  75 static inline void read_line(uint16_t *dst, const uint8_t *data[4], const int linesize[4], AVPixFmtDescriptor *desc, int x, int y, int c, int w)
  76 {
  77     AVComponentDescriptor comp= desc->comp[c];
  78     int plane= comp.plane;
  79     int depth= comp.depth_minus1+1;
  80     int mask = (1<<depth)-1;
  81     int shift= comp.shift;
  82     int step = comp.step_minus1+1;
  83     int flags= desc->flags;
  84     const uint8_t *p= data[plane]+y*linesize[plane] + x * step + comp.offset_plus1 - 1;
  85
  86     //FIXME initial x in case of PIX_FMT_BITSTREAM is wrong
  87
  88     while(w--){
  89         int val;
  90         if(flags & PIX_FMT_BE) val= AV_RB16(p);
  91         else                   val= AV_RL16(p);
  92         val = (val>>shift) & mask;
  93         if(flags & PIX_FMT_PAL)
  94             val= data[1][4*val + c];
  95         if(flags & PIX_FMT_BITSTREAM){
  96             shift-=depth;
  97             while(shift<0){
  98                 shift+=8;
  99                 p++;
 100             }
 101         }else
 102             p+= step;
 103         *dst++= val;
 104     }
 105 }