编解码(1)之基本像素格式转换

编解码(1)之基本像素格式转换后面会适当更新记录

今天项目中发现以前移过来的代码有转BGR24到NV12的代码一堆for 还用了opencv 的cvtColor最后还是图像绘框还有问题琢磨不透，果断用ffmpeg的一套swscale神器来搞了,效率还不差。

主要模式两个函数的理解：

被转frame 目标frame

struct SwsContext* swsCtx = sws_getContext(pYUV420->width, pYUV420->height,pYUV420->format,
        pBGR24->width, pBGR24->height,pBGR24->format, SWS_AREA, NULL, NULL, NULL);
    sws_scale(swsCtx, pYUV420->data, pYUV420->linesize, 0,pYUV420->height,
        pBGR24->data, pBGR24->linesize);

举一反三解决AVframe 转AVframe的格式

YUV420转BGR24

void YUV420pToBGR24(AVFrame* pYUV420, AVFrame* pBGR24)
{/*通常在外面定义创建[下面仅供理解pYUV420]*///AVFrame* pYUV420 = av_frame_alloc();//pYUV420->format = AV_PIX_FMT_YUV420P;//av_frame_get_buffer(pYUV420, 1);//memcpy(pYUV420->data[0], buff, buffSize);/*通常在外面定义创建[下面仅供理解pBGR24]*///AVFrame* pBGR24 = av_frame_alloc();//pBGR24->format = AV_PIX_FMT_BGR24;//av_frame_get_buffer(pBGR24, 1);/*设置转码参数调用ffmpeg 转换*/struct SwsContext* swsCtx = sws_getContext(pYUV420->width, pYUV420->height,(AVPixelFormat)pYUV420->format, pBGR24->width, pBGR24->height, (AVPixelFormat)pBGR24->format, SWS_AREA, NULL, NULL, NULL);sws_scale(swsCtx, pYUV420->data, pYUV420->linesize, 0, pYUV420->height, pBGR24->data, pBGR24->linesize);if (swsCtx)sws_freeContext(swsCtx);/*通常在外面释放*///av_frame_unref(pYUV420);//av_frame_free(&pYUV420);//pYUV420 = NULL;//av_frame_unref(pBGR24);//av_frame_free(&pBGR24);//pBGR24 = NULL;
}

BGR24反转 YUV420

void BGR24ToYUV420p(AVFrame* pBGR24, AVFrame* pYUV420)
{/*设置转码参数调用ffmpeg 转换*/struct SwsContext* swsCtx = sws_getContext(pBGR24->width, pBGR24->height,(AVPixelFormat)pBGR24->format, pYUV420->width, pYUV420->height,(AVPixelFormat)pYUV420->format, SWS_AREA, NULL, NULL, NULL);sws_scale(swsCtx, pBGR24->data, pBGR24->linesize, 0, pBGR24->height,pYUV420->data, pYUV420->linesize);if (swsCtx)sws_freeContext(swsCtx);
}

BGR的数据流转YUV420数据流

void BGR2YUV(uint8_t* bgr24, int width, int height, uint8_t* yuv420p)
{//bgr24和yuv420p指针数据由外面创建维护AVFrame* pBGR24 = av_frame_alloc();pBGR24->format = AV_PIX_FMT_BGR24;pBGR24->width = width;pBGR24->height = height;av_frame_get_buffer(pBGR24, 1);memcpy(pBGR24->data[0], bgr24, width * height * 3);         //计算大小拷贝//待转换的格式AVFrame* pYUV = av_frame_alloc();pYUV->format = AV_PIX_FMT_YUV420P;pYUV->width = width;pYUV->height = height;av_frame_get_buffer(pYUV, 1);//设置转码参数struct SwsContext* swsCtx = sws_getContext(pBGR24->width, pBGR24->height, (AVPixelFormat)pBGR24->format, pYUV->width, pYUV->height, (AVPixelFormat)pYUV->format, SWS_AREA, NULL, NULL, NULL);sws_scale(swsCtx, pBGR24->data, pBGR24->linesize, 0, pBGR24->height, pYUV->data, pYUV->linesize);memcpy(yuv420p, pYUV->data[0], width * height * 3 / 2);    //计算大小拷贝if (swsCtx)sws_freeContext(swsCtx);av_frame_unref(pBGR24);av_frame_free(&pBGR24);av_frame_unref(pYUV);av_frame_free(&pYUV);
}

其他的格式可以参考AVPixelFormat用到的宏以及图像的大小空间的分配。

举一反三就好解决了