尝试在C ++中的ffmpeg中设置MJPEG编码器 [英] Trying to setup MJPEG encoder in ffmpeg in C++

问题描述

您好



我想让MJPG编码正常工作，我有AV_CODEC_ID_MPEG1VIDEO正常工作，但当我切换到AV_CODEC_ID_MJPEG时出现错误-22



代码在最后一部分失败，无法打开编解码器。



任何帮助都将不胜感激这是代码：

Hi There

I am trying to get MJPG encoding working, I have AV_CODEC_ID_MPEG1VIDEO working, but when I switched to AV_CODEC_ID_MJPEG I get an error -22

The code fails on the last part with "could not open codec".

Any help would be greatly appreciated!

This is the code:

AVCodecID codec_id = AV_CODEC_ID_MJPEG; //AV_CODEC_ID_MPEG1VIDEO;
    AVCodec* codec = avcodec_find_encoder(codec_id);
    if (!codec) 
    { 
        printf("Codec not found\n"); 
        return -1;
    }

    // Initialize codec. 
    AVCodecContext* codecContext = avcodec_alloc_context3(codec); 

    codecContext->codec_id = codec_id;
    codecContext->codec_type = AVMEDIA_TYPE_VIDEO;
    codecContext->pix_fmt = PIX_FMT_YUV422P; 
    codecContext->bit_rate = 400000;
    codecContext->width = 320; 
    codecContext->height = 240;
    codecContext->time_base.num = 1; 
    codecContext->time_base.den = 25; 

   int retval;
    // Open the codec. 
    if ((retval = avcodec_open2(codecContext, codec, NULL)) < 0) 
    { 
        printf("could not open codec\n"); 
        return -2;
    }

推荐答案

尝试使用PIX_FMT_YUV J 422P而不是PIX_FMT_YUV422P。

我发现在这个 [ ^ ]论坛问题。这个问题和答案是从2012年10月开始的，所以事情本来可以改变。



如果这不能解决你的问题，我注意到<$ c $中的以下评论c> pixfmt.h ：

Try using PIX_FMT_YUVJ422P instead of PIX_FMT_YUV422P.
I found that in this[^] forum question. That question and answer is from Oct. 2012, so things could have changed.

If that does not solve your problem, I noticed the following comment in pixfmt.h:

AV_PIX_FMT_YUVJ422P,  ///< planar YUV 4:2:2, 16bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV422P and setting color_range

所以你可能只需要指定颜色范围以使其工作。不幸的是，我不知道正确的方法（我只使用了MJPEG解码器，而不是编码器）。



作为一方 - 请注意，我相信您应该将您的命名约定从 PIX_FMT_xxxx 更改为较新的 AV_PIX_FMT_xxxx 。但是，它们在各自的枚举中确实具有相同的价值，因此这不是您的问题。



Soren Madsen

So you may just have to specify the color range to make it work. Unfortunately, I don't know the right way to do that off-hand (I have only used the MJPEG decoder, not the encoder).

As a side-note, I believe you should change your naming convention from PIX_FMT_xxxx to the newer AV_PIX_FMT_xxxx. However, they do have the same value in their respective enums, so that is not your problem.

Soren Madsen

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