02-编码-YUV转H264

整体方案：

采集端：摄像头采集（YUV）->编码（YUV转H264）->RTMP推流

客户端：RTMP拉流->解码（H264转YUV）->YUV显示（SDL2）

YUV转H264是一个视频编码的过程，具体的代码实现过程如下：

#include <math.h>
#include <stdlib.h>
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavutil/opt.h>
#include <libavcodec/avcodec.h>
#include <libavutil/channel_layout.h>
#include <libavutil/common.h>
#include <libavutil/imgutils.h>
#include <libavutil/mathematics.h>
#include <libavutil/samplefmt.h>
#include <libavutil/frame.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#ifdef __cplusplus
}
#endif

int framenum = 0;

int main(int argc, char **argv)
{
    AVFrame *frame;
    AVCodec *codec = NULL;
    AVPacket packet;
    AVCodecContext *codecContext;
    int readSize=0;
    int ret=0,getPacket;
    FILE * fileIn,*fileOut;
    int frameCount=0;
    /* register all the codecs */
    av_register_all();

    if(argc!=2){
        fprintf(stdout,"usage:./test input.yuv\n");
        return -1;
    }

    //1.我们需要读一帧一帧的数据，所以需要AVFrame结构
    //读出的一帧数据保存在AVFrame中。
    frame  = av_frame_alloc();
    frame->width = 640;
    frame->height = 360;
    //fprintf(stdout,"transf para width=%d,height=%d\n",frame->width,frame->height);
    frame->format = AV_PIX_FMT_YUV420P;
	//根据指定的宽，高，和像素格式申请图像内存，最后一个参数表示内存对齐的值，32位对齐4字节,导致352*288时候绿屏，尝试修改成16位对齐
	//修改成16位对齐之后
    av_image_alloc(frame->data,frame->linesize,frame->width,frame->height,frame->format,16);
    fileIn =fopen(argv[1],"r+");

    //2.读出来的数据保存在AVPacket中，因此，我们还需要AVPacket结构体
    //初始化packet
    av_init_packet(&packet);

    //3.读出来的数据，我们需要编码，因此需要编码器
    //下面的函数找到h.264类型的编码器
    /* find the mpeg1 video encoder */
	fprintf(stdout, "find encoder AV_CODEC_ID_H264\n");
    codec = avcodec_find_encoder(AV_CODEC_ID_H264);
    if (!codec) {
        fprintf(stderr, "Codec not found\n");
        exit(1);
    }

    //有了编码器，我们还需要编码器的上下文环境，用来控制编码的过程
    codecContext = avcodec_alloc_context3(codec);//分配AVCodecContext实例
    if (!codecContext)
    {
        fprintf(stderr, "Could not allocate video codec context\n");
        return -1;
    }
	//设置编码器参数控制编码
	/* put sample parameters */
    codecContext->bit_rate = 400000;		//参数为400000的时候，编码出来的busH264文件为254KB
    /* resolution must be a multiple of two */
    codecContext->width = 640;	
    codecContext->height = 360;
    /* frames per second */
    codecContext->time_base = (AVRational){1,25};
    /* emit one intra frame every ten frames
     * check frame pict_type before passing frame
     * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
     * then gop_size is ignored and the output of encoder
     * will always be I frame irrespective to gop_size
     */
    codecContext->gop_size = 10;			//每10帧发送一帧I帧
    /*
	* vcodec_encode_video2函数输出的延时仅仅跟max_b_frames的设置有关，  
	* 想进行实时编码，将max_b_frames设置为0便没有编码延时了
	*/
    codecContext->max_b_frames = 0;			//每两个非B帧之间最多一个B帧
    codecContext->pix_fmt = AV_PIX_FMT_YUV420P;  
	/** 
 	* ultrafast,superfast, veryfast, faster, fast, medium 
	* slow, slower, veryslow, placebo.　这是x264编码速度的选项 
	*/  
    //av_opt_set(codecContext->priv_data, "preset", "slow", 0);
	av_opt_set(codecContext->priv_data, "preset", "ultrafast", 0);
    //准备好了编码器和编码器上下文环境，现在可以打开编码器了
    fprintf(stdout, "open encoder AV_CODEC_ID_H264\n");
    if (avcodec_open2(codecContext, codec, NULL) < 0)      //根据编码器上下文打开编码器
    {
        fprintf(stderr, "Could not open codec\n");
        return -1;
    }

    //4.准备输出文件
    fileOut= fopen("out.h264","w+");
    //下面开始编码
    while(1){
        //读一帧数据出来
        readSize = fread(frame->data[0],1,frame->linesize[0]*frame->height,fileIn);
		fprintf(stdout,"fread data[0] frame->linesize[0] %d,frame->height %d,readSize %d\n",frame->linesize[0],frame->height,readSize);
        if(readSize == 0){
            fprintf(stdout,"end of file\n");
            frameCount++;
            break;
        }
        readSize = fread(frame->data[1],1,frame->linesize[1]*frame->height/2,fileIn);
		fprintf(stdout,"fread data[1] frame->linesize[1] %d,readSize %d \n",frame->linesize[1],readSize);
        readSize = fread(frame->data[2],1,frame->linesize[2]*frame->height/2,fileIn);
		fprintf(stdout,"fread data[2] frame->linesize[2] %d readSize %d \n",frame->linesize[2],readSize);
        //初始化packet
        av_init_packet(&packet);
        /* encode the image */
        frame->pts = frameCount;
		//将AVFrame中的像素信息编码为AVPacket中的码流,成功编码一个packet，将getPacket置位1
        ret = avcodec_encode_video2(codecContext, &packet, frame, &getPacket); 
        if (ret < 0) 
        {
            fprintf(stderr, "Error encoding frame\n");
            return -1;
        }
		fprintf(stdout,"had encode %d frame,and getPacket is %d\n",framenum,getPacket);	//read并encode了22帧，才开始获得一个完整编码帧
        if (getPacket) 
        {
            frameCount++;
            //获得一个完整的编码帧
            printf("Write frame %3d (size=%5d)\n", frameCount, packet.size);
            fwrite(packet.data, 1,packet.size, fileOut);
            av_packet_unref(&packet);
        }
    }
    /* flush buffer */
    for ( getPacket= 1; getPacket; frameCount++) 
    {
		fprintf(stdout,"get flush buffer getPacket %d,frameCount %d\n",getPacket,frameCount);
		fflush(stdout);
        frame->pts = frameCount;
        ret = avcodec_encode_video2(codecContext, &packet, NULL, &getPacket);
        if (ret < 0)
        {
            fprintf(stderr, "Error encoding frame\n");
            return -1;
        }

        if (getPacket) 
        {
            printf("Write frame %3d (size=%5d)\n", frameCount, packet.size);	//
            fwrite(packet.data, 1, packet.size, fileOut);
            av_packet_unref(&packet);
        }
    } 
    fclose(fileIn);
    fclose(fileOut);
    av_frame_free(&frame);
    avcodec_close(codecContext);
    av_free(codecContext);

    return 0;
}

整个工程目录：https://download.csdn.net/download/sishen4199/88522517?spm=1001.2014.3001.5503

YUV视频查看工具：https://download.csdn.net/download/sishen4199/88522520?spm=1001.2014.3001.5503

H264码流查看工具：https://download.csdn.net/download/sishen4199/88522519?spm=1001.2014.3001.5503