YUV格式学习:NV12和YUV420P格式互换
NV12和YUV420的转换是在相同采样空间的转换,只是个别分量位置的调整,只要明白了Y、U、V分量的布置,就很容易写出来。
代码如下:
/** yyyy yyyy uv uv -> yyyy yyyy uu vv */ void yuv420sp_to_yuv420p(unsigned char* yuv420sp, unsigned char* yuv420p, int width, int height) { int i, j; int y_size = width * height; unsigned char* y = yuv420sp; unsigned char* uv = yuv420sp + y_size; unsigned char* y_tmp = yuv420p; unsigned char* u_tmp = yuv420p + y_size; unsigned char* v_tmp = yuv420p + y_size * 5 / 4; // y memcpy(y_tmp, y, y_size); // u for (j = 0, i = 0; j < y_size/2; j+=2, i++) { u_tmp[i] = uv[j]; v_tmp[i] = uv[j+1]; } } /** yyyy yyyy uu vv -> yyyy yyyy uv uv */ void yuv420p_to_yuv420sp(unsigned char* yuv420p, unsigned char* yuv420sp, int width, int height) { int i, j; int y_size = width * height; unsigned char* y = yuv420p; unsigned char* u = yuv420p + y_size; unsigned char* v = yuv420p + y_size * 5 / 4; unsigned char* y_tmp = yuv420sp; unsigned char* uv_tmp = yuv420sp + y_size; // y memcpy(y_tmp, y, y_size); // u for (j = 0, i = 0; j < y_size/2; j+=2, i++) { // 此处可调整U、V的位置,变成NV12或NV21 #if 01 uv_tmp[j] = u[i]; uv_tmp[j+1] = v[i]; #else uv_tmp[j] = v[i]; uv_tmp[j+1] = u[i]; #endif } }
后记:
一口气把自己研究很久的东西写出来,好像都没写到点子上。以前也尝试过写技术性很强的文章,到处找资料,找出处,但后来发觉自己不是那块料,于是就直接贴代码,理论的东西反而不说——因为说不清,也怕说错。
关于YUV,初步听说是在6、7年前的大学,开始接触是在4、5年前,而真正了解其原理,却是近些年。学习进度不可谓不慢。写出来,也算有个交待。也为自己准备实现的YUV播放器做些准备。
迟 2015.8.5 晚上
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