YUV420P像素数据编码为JPEG图片

本文的编码器实现了YUV420P的数据编码为JPEG图片。本着简单的原则，代码基本上精简到了极限。使用了2014年5月6号编译的最新的FFMPEG类库。

程序很简单，打开工程后直接运行即可将YUV数据编码为JPEG。本程序十分灵活，可以根据需要修改成编码各种图像格式的编码器，比如PNG，GIF等等。平台使用VC2010。

  * 本程序实现了YUV420P像素数据编码为JPEG图片。是最简单的FFmpeg编码方面的教程。
  * 通过学习本例子可以了解FFmpeg的编码流程。
  */

 #include

 #define __STDC_CONSTANT_MACROS

 #ifdef _WIN32
 //Windows
 extern "C"
 {
 #include "libavcodec/avcodec.h"
 #include "libavformat/avformat.h"
 };
 #else
 //Linux...
 #ifdef __cplusplus
 extern "C"
 {
 #endif
 #include
 #include
 #ifdef __cplusplus
 };
 #endif
 #endif


 int main(int argc, char* argv[])
 {
     AVFormatContext* pFormatCtx;
     AVOutputFormat* fmt;
     AVStream* video_st;
     AVCodecContext* pCodecCtx;
     AVCodec* pCodec;

     uint8_t* picture_buf;
     AVFrame* picture;
     AVPacket pkt;
     int y_size;
     int got_picture=0;
     int size;

     int ret=0;

     FILE *in_file = NULL;                            //YUV source
     int in_w=480,in_h=272;                           //YUV's width and height
     const char* out_file = "cuc_view_encode.jpg";    //Output file

     in_file = fopen("cuc_view_480x272.yuv", "rb");

     av_register_all();

     //Method 1
     pFormatCtx = avformat_alloc_context();
     //Guess format
     fmt = av_guess_format("mjpeg", NULL, NULL);
     pFormatCtx->oformat = fmt;
     //Output URL
     if (avio_open(&pFormatCtx->pb,out_file, AVIO_FLAG_READ_WRITE) < 0){
         printf("Couldn't open output file.");
         return -1;
     }

     //Method 2. More simple
     //avformat_alloc_output_context2(&pFormatCtx, NULL, NULL, out_file);
     //fmt = pFormatCtx->oformat;

     video_st = avformat_new_stream(pFormatCtx, 0);
     if (video_st==NULL){
         return -1;
     }
     pCodecCtx = video_st->codec;
     pCodecCtx->codec_id = fmt->video_codec;
     pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
     pCodecCtx->pix_fmt = AV_PIX_FMT_YUVJ420P;

     pCodecCtx->width = in_w;
     pCodecCtx->height = in_h;

     pCodecCtx->time_base.num = 1;
     pCodecCtx->time_base.den = 25;
     //Output some information
     av_dump_format(pFormatCtx, 0, out_file, 1);

     pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
     if (!pCodec){
         printf("Codec not found.");
         return -1;
     }
     if (avcodec_open2(pCodecCtx, pCodec,NULL) < 0){
         printf("Could not open codec.");
         return -1;
     }
     picture = av_frame_alloc();
     size = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
     picture_buf = (uint8_t *)av_malloc(size);
     if (!picture_buf)
     {
         return -1;
     }
     avpicture_fill((AVPicture *)picture, picture_buf, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);

     //Write Header
     avformat_write_header(pFormatCtx,NULL);

     y_size = pCodecCtx->width * pCodecCtx->height;
     av_new_packet(&pkt,y_size*3);
     //Read YUV
     if (fread(picture_buf, 1, y_size*3/2, in_file) <=0)
     {
         printf("Could not read input file.");
         return -1;
     }
     picture->data[0] = picture_buf;              // Y
     picture->data[1] = picture_buf+ y_size;      // U
     picture->data[2] = picture_buf+ y_size*5/4;  // V

     //Encode
     ret = avcodec_encode_video2(pCodecCtx, &pkt,picture, &got_picture);
     if(ret < 0){
         printf("Encode Error.\n");
         return -1;
     }
     if (got_picture==1){
         pkt.stream_index = video_st->index;
         ret = av_write_frame(pFormatCtx, &pkt);
     }

     av_free_packet(&pkt);
     //Write Trailer
     av_write_trailer(pFormatCtx);

     printf("Encode Successful.\n");

     if (video_st){
         avcodec_close(video_st->codec);
         av_free(picture);
         av_free(picture_buf);
     }
     avio_close(pFormatCtx->pb);
     avformat_free_context(pFormatCtx);

     fclose(in_file);

     return 0;
 }