FFMPEG - format not available?

问题:

I'm converting some code from FFMPEG 0.8 to FFMPEG 1.2. I have an error during the call to the method avcodec_open2(): "Specified pixel format %s is invalid or not supported". The format I use is : AV_PIX_FMT_RGB24. It should be enabled by default, right?

Below is my code:

av_register_all();

codec = avcodec_find_encoder(AV_CODEC_ID_MPEG2VIDEO);

if(!codec)
{
    throw SystemException("codec not found");
}

codecContext = avcodec_alloc_context3(codec);

codecContext->bit_rate = 200000;
codecContext->time_base.den = 1;
codecContext->time_base.num = 90000;
codecContext->gop_size = 8;
codecContext->pix_fmt = AV_PIX_FMT_RGB24;

_codecContext->width = 320
_codecContext->height = 240

if(avcodec_open2(_codecContext, _codec, NULL) < 0)
{
    throw SystemException("Unable to open codec");
}

回答1:

In latest version of ffmpeg MPEG2/MPEG1 AV_PIX_FMT_RGB24 is not supported.

You will need to use AV_PIX_FMT_YUV420P or AV_PIX_FMT_YUV422P.

So I if your input PIX format is not AV_PIX_FMT_YUV420P/AV_PIX_FMT_YUV422P, you will need a conversion. You can make use of Sws_Context and sws_scale for the same.

回答2:

Instead of converting to YUV420P you could also use libx264rgb codec, rather than libx264. It supports the current AV_PIX_FMT_RGB24 type.