Example 2.13. V4L2_PIX_FMT_YUYV 4 × 4 pixelimage
|
start + 0: |
Y'00 |
Cb00 |
Y'01 |
Cr00 |
Y'02 |
Cb01 |
Y'03 |
Cr01 |
|
start + 8: |
Y'10 |
Cb10 |
Y'11 |
Cr10 |
Y'12 |
Cb11 |
Y'13 |
Cr11 |
|
start + 16: |
Y'20 |
Cb20 |
Y'21 |
Cr20 |
Y'22 |
Cb21 |
Y'23 |
Cr21 |
|
start + 24: |
Y'30 |
Cb30 |
Y'31 |
Cr30 |
Y'32 |
Cb31 |
Y'33 |
Cr31 |
YUV422码流存放位置
(转自http://www.chineselinuxuniversity.net/kerneldocs/media/V4L2-PIX-FMT-YUYV.html)
Example 2.18. V4L2_PIX_FMT_YUV420 4 × 4 pixelimage
|
start + 0: |
Y'00 |
Y'01 |
Y'02 |
Y'03 |
|
start + 4: |
Y'10 |
Y'11 |
Y'12 |
Y'13 |
|
start + 8: |
Y'20 |
Y'21 |
Y'22 |
Y'23 |
|
start + 12: |
Y'30 |
Y'31 |
Y'32 |
Y'33 |
|
start + 16: |
Cb00 |
Cb01 |
||
|
start + 18: |
Cb10 |
Cb11 |
||
|
start + 20: |
Cr00 |
Cr01 |
||
|
start + 22: |
Cr10 |
Cr11 |
||
YUV420码流存放位置
(转自http://www.chineselinuxuniversity.net/kerneldocs/media/re18.html该处是YVU420)
这里要顺带提一下YUV444,既无损YUV色彩空间.一个Y带一个Cb一个Cr,即YCbCr.
YUV422采样即从YUV444基础上,从第一个Y开始只保留Cb,剔去Cr,第二个Y只保留Cr剔去Cb…...这样交替采样,长度大小为width*height*2,Y:U:V=4:2:2,一个色彩分量占一个字节.
而YUV420即从YUV422基础上进行隔行采样,例如第一行只保留Cb,第二行只保留Cr……这样交替进行,Y:U:V=4:2:0并不是没有V分量,也可以是Y:U:V=4:0:2.相信这样大家容易理解.最后在这个基础上,把Y,U,V三种分量打包排列,即如上图,长度大小为width*height*3/2.
说了这么多,是时候贴上具体代码.
- <span style="font-size:14px;">#include <stdio.h>
- #include <string.h>
- #define READ_WRITE_FILE_SIZE 176*144*2 //YUV422 图像分辨率为177x144
- unsigned char filebuf[38017] = {0};
- int YUV422To420(unsigned char yuv422[], unsigned char yuv420[], int width, int height)
- {
- int ynum=width*height;
- int i,j,k=0;
- //得到Y分量
- for(i=0;i<ynum;i++){
- yuv420[i]=yuv422[i*2];
- }
- //得到U分量
- for(i=0;i<height;i++){
- if((i%2)!=0)continue;
- for(j=0;j<(width/2);j++){
- if((4*j+1)>(2*width))break;
- yuv420[ynum+k*2*width/4+j]=yuv422[i*2*width+4*j+1];
- }
- k++;
- }
- k=0;
- //得到V分量
- for(i=0;i<height;i++){
- if((i%2)==0)continue;
- for(j=0;j<(width/2);j++){
- if((4*j+3)>(2*width))break;
- yuv420[ynum+ynum/4+k*2*width/4+j]=yuv422[i*2*width+4*j+3];
- }
- k++;
- }
- return 1;
- }
- int main(void)
- {
- int len = 0;
- FILE *fpr, *fpw;
- unsigned char buf[READ_WRITE_FILE_SIZE];
- fpr = fopen( "WEBCAM-00012.YUV", "rb" );
- fpw = fopen( "yuyv_2_yy_u_v.yuv", "wb" );
- if( fpr == NULL || fpw == NULL )
- {
- printf("can not read or write file\n");
- fcloseall();
- return 1;
- }
- fread( buf, READ_WRITE_FILE_SIZE, 1, fpr );
- if(YUV422To420(buf,filebuf,176,144))printf("ok\n");
- printf("size:%d",sizeof(filebuf));
- fwrite( &filebuf, sizeof(filebuf), 1, fpw );
- fcloseall();
- return 0;
- }
- </span>
- <span style="font-size:14px;">#include <stdio.h>
- #include <string.h>
- #define READ_WRITE_FILE_SIZE 176*144*2 //YUV422 图像分辨率为177x144
- unsigned char filebuf[38017] = {0};
- int YUV422To420(unsigned char yuv422[], unsigned char yuv420[], int width, int height)
- {
- int ynum=width*height;
- int i,j,k=0;
- //得到Y分量
- for(i=0;i<ynum;i++){
- yuv420[i]=yuv422[i*2];
- }
- //得到U分量
- for(i=0;i<height;i++){
- if((i%2)!=0)continue;
- for(j=0;j<(width/2);j++){
- if((4*j+1)>(2*width))break;
- yuv420[ynum+k*2*width/4+j]=yuv422[i*2*width+4*j+1];
- }
- k++;
- }
- k=0;
- //得到V分量
- for(i=0;i<height;i++){
- if((i%2)==0)continue;
- for(j=0;j<(width/2);j++){
- if((4*j+3)>(2*width))break;
- yuv420[ynum+ynum/4+k*2*width/4+j]=yuv422[i*2*width+4*j+3];
- }
- k++;
- }
- return 1;
- }
- int main(void)
- {
- int len = 0;
- FILE *fpr, *fpw;
- unsigned char buf[READ_WRITE_FILE_SIZE];
- fpr = fopen( "WEBCAM-00012.YUV", "rb" );
- fpw = fopen( "yuyv_2_yy_u_v.yuv", "wb" );
- if( fpr == NULL || fpw == NULL )
- {
- printf("can not read or write file\n");
- fcloseall();
- return 1;
- }
- fread( buf, READ_WRITE_FILE_SIZE, 1, fpr );
- if(YUV422To420(buf,filebuf,176,144))printf("ok\n");
- printf("size:%d",sizeof(filebuf));
- fwrite( &filebuf, sizeof(filebuf), 1, fpw );
- fcloseall();
- return 0;
- }