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: https://files.cnblogs.com/msopengl/ffmpegh264codec.rar
作者：jemmyLiu
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。
