Trying to setup MJPEG encoder in ffmpeg in C++

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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:

C++

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;
    }

Posted 14-Mar-14 16:00pm

godspeed123

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KarstenK 15-Mar-14 4:25am

it isnt a video codec .-O

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SoMad · Answer 1 · 2014-03-15T01:20:00

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:

C++

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

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