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/* ------------------------------------------------------------------------
* Creative YUV Video Decoder
*
* Dr. Tim Ferguson, 2001.
* For more details on the algorithm:
* http://www.csse.monash.edu.au/~timf/videocodec.html
*
* This is a very simple predictive coder. A video frame is coded in YUV411
* format. The first pixel of each scanline is coded using the upper four
* bits of its absolute value. Subsequent pixels for the scanline are coded
* using the difference between the last pixel and the current pixel (DPCM).
* The DPCM values are coded using a 16 entry table found at the start of the
* frame. Thus four bits per component are used and are as follows:
* UY VY YY UY VY YY UY VY...
* This code assumes the frame width will be a multiple of four pixels. This
* should probably be fixed.
* ------------------------------------------------------------------------ */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
/* ------------------------------------------------------------------------
* This function decodes a buffer containing a CYUV encoded frame.
*
* buf - the input buffer to be decoded
* size - the size of the input buffer
* frame - the output frame buffer (UYVY format)
* width - the width of the output frame
* height - the height of the output frame
* bit_per_pixel - ignored for now: may be used later for conversions.
*/
void decode_cyuv(unsigned char *buf, int size, unsigned char *frame, int width, int height, int bit_per_pixel)
{
int i, xpos, ypos, cur_Y = 0, cur_U = 0, cur_V = 0;
char *delta_y_tbl, *delta_c_tbl, *ptr;
delta_y_tbl = buf + 16;
delta_c_tbl = buf + 32;
ptr = buf + (16 * 3);
for(ypos = 0; ypos < height; ypos++)
for(xpos = 0; xpos < width; xpos += 4)
{
if(xpos == 0) /* first pixels in scanline */
{
cur_U = *(ptr++);
cur_Y = (cur_U & 0x0f) << 4;
cur_U = cur_U & 0xf0;
*frame++ = cur_U;
*frame++ = cur_Y;
cur_V = *(ptr++);
cur_Y = (cur_Y + delta_y_tbl[cur_V & 0x0f]) & 0xff;
cur_V = cur_V & 0xf0;
*frame++ = cur_V;
*frame++ = cur_Y;
}
else /* subsequent pixels in scanline */
{
i = *(ptr++);
cur_U = (cur_U + delta_c_tbl[i >> 4]) & 0xff;
cur_Y = (cur_Y + delta_y_tbl[i & 0x0f]) & 0xff;
*frame++ = cur_U;
*frame++ = cur_Y;
i = *(ptr++);
cur_V = (cur_V + delta_c_tbl[i >> 4]) & 0xff;
cur_Y = (cur_Y + delta_y_tbl[i & 0x0f]) & 0xff;
*frame++ = cur_V;
*frame++ = cur_Y;
}
i = *(ptr++);
cur_Y = (cur_Y + delta_y_tbl[i & 0x0f]) & 0xff;
*frame++ = cur_U;
*frame++ = cur_Y;
cur_Y = (cur_Y + delta_y_tbl[i >> 4]) & 0xff;
*frame++ = cur_V;
*frame++ = cur_Y;
}
}
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