FFmpeg音视频编解码实践总结

PS:由于目前开发RTSP服务器 传输模块时用到了h264文件，所以攻了一段时间去实现h264的视频编解码，借用FFmpeg SDK实现了任意文件格式之间的转换，并实现了流媒体实时播放，目前音视频同步需要稍加完善，视频编码代码已成功移植到Visual Stdio平台，如有需要的留下邮箱

以下文档来自FFmpeg工程组(http://www.ffmpeg.com.cn/index.php开发事例)

实现转码一个普通视频文件为视频mpeg4,音频mp3的功能的程序

本程序源引自FFmpeg工程组，实现转码一个普通视频文件为视频mpeg4,音频mp3的功能

#include <avcodec.h>
#include <avformat.h>
#include <stdio.h>
#include <avutil.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
main(int argc,char **argv)
{ 
 const char *input_file_name="/root/movies/ddh1.mpg";
 av_register_all();//注册库中所有可用的文件格式和编码器
 AVFormatContext *ic;
 //输入文件处理部分
 ic=av_alloc_format_context();
 if(av_open_input_file(&ic,input_file_name,NULL,0,NULL)!=0)
 {
 printf("can't open the file %s\n",input_file_name);
 exit(1);
 }//打开输入文件
 if(av_find_stream_info(ic)<0)
 {
 printf("can't find suitable codec parameters\n");
 exit(1);
 }//取出流信息
 dump_format(ic,0,input_file_name,0);//列出输入文件的相关流信息
 int i;
 int videoindex=-1;int audioindex=-1;
 for(i=0;i<ic->nb_streams;i++)
 { 
 if(ic->streams[i]->codec->codec_type==CODEC_TYPE_VIDEO)
 {
 videoindex=i;
 //printf("video\n");
 }
 else if(ic->streams[i]->codec->codec_type==CODEC_TYPE_AUDIO)
 {
 //printf("audio\n");
 audioindex=i;
 }
 }
 if(videoindex==-1)
 {
 printf("can't find video stream\n");
 exit(1);
 }//没有找到视频流
 AVCodecContext *vCodecCtx;
 vCodecCtx=ic->streams[videoindex]->codec;//取得视频流编码上下文指针
 AVCodec *vCodec;
 vCodec=avcodec_find_decoder(vCodecCtx->codec_id);
 if(vCodec==NULL)
 {
 printf("can't find suitable video decoder\n");
 exit(1);
 }//找到合适的视频解码器
 if(avcodec_open(vCodecCtx,vCodec)<0)
 {
 printf("can't open the video decoder\n");
 exit(1);
 }//打开该视频解码器
 if(audioindex==-1)
 {
 printf("can't find audio stream\n");
 exit(1);
 }//没有找到音频流
 AVCodecContext *aCodecCtx;
 aCodecCtx=ic->streams[audioindex]->codec;
 AVCodec *aCodec;
 aCodec=avcodec_find_decoder(aCodecCtx->codec_id);
 if(aCodec==NULL)
 {
 printf("can't find suitable audio decoder\n");
 exit(1);
 }//找到合适的音频解码器
 if(avcodec_open(aCodecCtx,aCodec)<0)
 {
 printf("can't open the audio decoder\n");
 exit(1);
 }//打开该音频解码器
//下面为输出文件处理部分
 const char *output_file_name="/root/123.avi";
 AVOutputFormat *fmt;
 AVFormatContext *oc;
 AVCodecContext *oVcc,*oAcc;
 AVCodec *oVc,*oAc;
 AVStream *video_st,*audio_st;
 AVFrame *oVFrame,*oAFrame;
 double video_pts;
 oVFrame=avcodec_alloc_frame();
 fmt=guess_format(NULL,output_file_name,NULL);
 if(!fmt)
 {
 printf("could not deduce output format from outfile extension\n");
 exit(0);
 }//判断是否可以判断输出文件的编码格式
 oc=av_alloc_format_context();
 if(!oc)
 {
 printf("Memory error\n");
 exit(0);
 }
 oc->oformat=fmt;
 pstrcpy(oc->filename,sizeof(oc->filename),output_file_name);
 video_st=av_new_stream(oc,0);
 if(!video_st)
 {
 printf("could not alloc video stream\n");
 exit(0);
 }
 oVcc=avcodec_alloc_context();
 oVcc=video_st->codec;
 oVcc->codec_id=CODEC_ID_MPEG4;
 oVcc->codec_type=CODEC_TYPE_VIDEO;
 oVcc->bit_rate=2500000;
 oVcc->width=704;
 oVcc->height=480;
 oVcc->time_base=vCodecCtx->time_base;
 oVcc->gop_size=vCodecCtx->gop_size;
 //oVcc->pix_fmt=vCodecCtx->pix_fmt;
 oVcc->pix_fmt=vCodecCtx->pix_fmt;
 oVcc->max_b_frames=vCodecCtx->max_b_frames;
 video_st->r_frame_rate=ic->streams[videoindex]->r_frame_rate;
 audio_st=av_new_stream(oc,oc->nb_streams);
 if(!audio_st)
 {
 printf("could not alloc audio stream\n");
 exit(0);
 } 
 avcodec_get_context_defaults2(audio_st->codec,CODEC_TYPE_AUDIO);
 oAcc=avcodec_alloc_context();
 oAcc=audio_st->codec;
 oAcc->codec_id=CODEC_ID_MP3;
 oAcc->codec_type=CODEC_TYPE_AUDIO;
 oAcc->bit_rate=aCodecCtx->bit_rate;
 oAcc->sample_rate=aCodecCtx->sample_rate;
 oAcc->channels=2;
 if (av_set_parameters(oc, NULL) < 0) 
 {
 printf( "Invalid output format parameters\n"); 
 exit(0); 
 }//设置必要的输出参数
 strcpy(oc->title,ic->title);
 strcpy(oc->author,ic->author);
 strcpy(oc->copyright,ic->copyright);
 strcpy(oc->comment,ic->comment);
 strcpy(oc->album,ic->album);
 oc->year=ic->year;
 oc->track=ic->track;
 strcpy(oc->genre,ic->genre);
 dump_format(oc,0,output_file_name,1);//列出输出文件的相关流信息
 oVc=avcodec_find_encoder(CODEC_ID_MPEG4);
 if(!oVc)
 {
 printf("can't find suitable video encoder\n");
 exit(0);
 }//找到合适的视频编码器
 if(avcodec_open(oVcc,oVc)<0)
 {
 printf("can't open the output video codec\n");
 exit(0);
 }//打开视频编码器
 oAc=avcodec_find_encoder(CODEC_ID_MP3);
 if(!oAc)
 {
 printf("can't find suitable audio encoder\n");
 exit(0);
 }//找到合适的音频编码器
 if(avcodec_open(oAcc,oAc)<0)
 {
 printf("can't open the output audio codec");
 exit(0);
 }//打开音频编码器
 /*if(url_exist(output_file_name)) { printf("the output file name %s has exist,please select other\n",output_file_name); exit(0); }//判断该输出文件是否已经存在*/ if (!(oc->flags & AVFMT_NOFILE)) { if(url_fopen(&oc->pb,output_file_name,URL_WRONLY)<0) { printf("can't open the output file %s\n",output_file_name); exit(0); }//打开输出文件 } if(!oc->nb_streams) { fprintf(stderr,"output file dose not contain any stream\n"); exit(0); }//查看输出文件是否含有流信息 if(av_write_header(oc)<0) { fprintf(stderr, "Could not write header for output file\n"); exit(1); }[/i][/i]AVPacket packet; uint8_t *ptr,*out_buf; int out_size; static short *samples=NULL; static unsigned int samples_size=0; uint8_t *video_outbuf,*audio_outbuf;int video_outbuf_size,audio_outbuf_size; video_outbuf_size=400000; video_outbuf= (unsigned char *) malloc(video_outbuf_size); audio_outbuf_size = 10000; audio_outbuf = av_malloc(audio_outbuf_size); int flag;int frameFinished;int len;int frame_index=0,ret; while(av_read_frame(ic,&packet)>=0)//从输入文件中读取一个包 { if(packet.stream_index==videoindex)//判断是否为当前视频流中的包 { len=avcodec_decode_video(vCodecCtx,oVFrame,&frameFinished,packet.data,packet.size);//若为视频包，解码该视频包 if(len<0) { printf("Error while decoding\n"); exit(0); } if(frameFinished)//判断视频祯是否读完 { fflush(stdout); oVFrame->pts=av_rescale(frame_index,AV_TIME_BASE*(int64_t)oVcc->time_base.num,oVcc->time_base.den); oVFrame->pict_type=0; out_size = avcodec_encode_video(oVcc, video_outbuf, video_outbuf_size, oVFrame); if (out_size > 0) { AVPacket pkt; av_init_packet(&pkt); if(oVcc->coded_frame && oVcc->coded_frame->key_frame) pkt.flags |= PKT_FLAG_KEY; pkt.flags = packet.flags; pkt.stream_index= video_st->index; pkt.data= video_outbuf; pkt.size= out_size; ret=av_write_frame(oc, &pkt); } frame_index++; } else ret=av_write_frame(oc, &packet); //img_convert((AVPicture *)vFrame, PIX_FMT_RGB24, (AVPicture*)oVFrame, oVcc->pix_fmt,oVcc->width,oVcc->height); //SaveFrame(vFrame,oVcc->width,oVcc->height,frame_index); if(ret!=0) { printf("while write video frame error\n"); exit(0); } } else if(packet.stream_index==audioindex) { len=packet.size; ptr=packet.data; int ret=0; while(len>0) { out_buf=NULL; out_size=0; if(&packet) samples=av_fast_realloc(samples,&samples_size,FFMAX(packet.size*sizeof(*samples),AVCODEC_MAX_AUDIO_FRAME_SIZE)); out_size=samples_size; ret=avcodec_decode_audio(aCodecCtx,samples,&out_size,ptr,len);//若为音频包，解码该音频包 if(ret<0) { printf("while decode audio failure\n"); exit(0); } fflush(stdout); ptr+=ret; len-=ret; if(out_size<=0) continue; out_buf=(uint8_t *)samples; AVPacket pkt; av_init_packet(&pkt); pkt.size= avcodec_encode_audio(oAcc, audio_outbuf, audio_outbuf_size, out_buf); pkt.pts= av_rescale_q(oAcc->coded_frame->pts, oAcc->time_base, audio_st->time_base); pkt.flags |= PKT_FLAG_KEY; pkt.stream_index= audioindex; pkt.data= audio_outbuf; if (av_write_frame(oc, &pkt) != 0) { fprintf(stderr, "Error while writing audio frame\n"); exit(1); } } } av_free_packet(&packet); } av_write_trailer(oc);for(i = 0; i < oc->nb_streams; i++) { av_freep(&oc->streams[i]->codec); av_freep(&oc->streams[i]); }url_fclose(oc);av_free(oc);av_free(oVFrame);av_free(out_buf);avcodec_close(vCodecCtx);avcodec_close(aCodecCtx);av_close_input_file(ic);}

最近一直很忙  花时间整理了一份  希望大家多多交流ffmpeg视频编解码方面的知识  接下来会抽时间总结一篇RTP传输协议的文章  好了  废话不说  附上链接自己下载

source download:  http://files.cnblogs.com/msopengl/ffmpegh264codec.rar

来源：http://www.cnblogs.com/msopengl/archive/2011/12/25/2301382.html