sws_scale解出来的RGB图像颠倒问题

最新推荐文章于 2022-02-18 14:31:05 发布

rightorwrong

最新推荐文章于 2022-02-18 14:31:05 发布

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文章标签： null codec video

本文链接：https://blog.youkuaiyun.com/rightorwrong/article/details/6432042

本文介绍如何使用FFmpeg库进行视频解码，并将解码后的YUV格式转换为RGB格式，涉及AVFrame结构体的data和linesize字段操作及SwsContext上下文设置。

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AVFrame* pFrame; // Frame AVCodecContext* pContext; // Codec Context int nUsedBytes = avcodec_decode_video(pContext, pFrame, &nFrame, pSrcBuffer, nSrcLength); if(nUsedBytes > 0) { AVFrame out_pic; SwsContext* img_convert_ctx = sws_getContext(pContext->width, pContext->height, pContext->pix_fmt, nDestW, nDestH,(PixelFormat)PIX_FMT_BGR24,SWS_BICUBIC, NULL, NULL, NULL); if(img_convert_ctx != NULL) { if(avpicture_alloc((AVPicture *)&out_pic, PIX_FMT_RGB24, nDestW, nDestH)>=0) { pFrame->data[0] = pFrame->data[0]+pFrame->linesize[0]*(pContext->height-1); pFrame->data[1] = pFrame->data[1]+pFrame->linesize[0]*pContext->height/4-1; pFrame->data[2] = pFrame->data[2]+pFrame->linesize[0]*pContext->height/4-1; pFrame->linesize[0] *= -1; pFrame->linesize[1] *= -1; pFrame->linesize[2] *= -1; sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pContext->height, out_pic.data, out_pic.linesize); avpicture_free((AVPicture *)&out_pic); } sws_freeContext(img_convert_ctx); } }

AVFrame的data和linesize：

YUV: linesize[0] = width + padding size(16+16),linesize[1]=linesize[0]/2

data[0],data[1],data[2]分别代表yuv

RGB: linesize[0] = width*pixel_size for RGB
data[0]为packet rgb

pFrame->data[0] = pFrame->data[0]+pFrame->linesize[0]*(pContext->height-1);
pFrame->data[1] = pFrame->data[1]+pFrame->linesize[1]*(pContext->height/2-1);
pFrame->data[2] = pFrame->data[2]+pFrame->linesize[2]*(pContext->height/2-1);