ffmpeg H264 編解碼配置

ffmpeg H264編解碼前面有文章介紹下，本文主要介紹一些參數配置。

編碼:

int InitEncoderCodec( int iWidth, int iHeight)
{
	AVCodec *  pH264Codec = avcodec_find_encoder(AV_CODEC_ID_H264);
	if(NULL == pH264Codec)
	{
		printf("%s", "avcodec_find_encoder failed");
		return  -1;
	}
	outPutEncContext = avcodec_alloc_context3(pH264Codec);
	outPutEncContext->gop_size = 30;
	outPutEncContext->has_b_frames = 0;
	outPutEncContext->max_b_frames = 0;
	outPutEncContext->codec_id = pH264Codec->id;
	outPutEncContext->time_base.num = 2;
	outPutEncContext->time_base.den = 15;
	outPutEncContext->pix_fmt            = *pH264Codec->pix_fmts;
	outPutEncContext->width              =  iWidth;
	outPutEncContext->height             = iHeight;
	outPutEncContext->qmin = 34;
	outPutEncContext->qmax = 50;
	AVDictionary *options = nullptr;
	outPutEncContext->flags |= AV_CODEC_FLAG_GLOBAL_HEADER; 
	av_opt_set(outPutEncContext->priv_data,"tune","zerolatency",0);
　　　　　av_dict_set(&options,"preset","ultrafast",0);
	int ret = avcodec_open2(outPutEncContext, pH264Codec, &options);
	if (ret < 0)
	{
		printf("%s", "open codec failed");
		return  ret;
	}
	return 1;
}

　 解碼:

codecContext->flags |=CODEC_FLAG_LOW_DELAY;

　　

編碼codec 的time_base實際上表示視頻的幀率，qmin,qmax決定了編碼的質量，qmin，qmax越大編碼的質量越差。zerolatency參數的作用是提搞編碼的實時性。

解碼codec 加上CODEC_FLAG_LOW_DELAY，可提高解碼速度（低延時）。

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