下面的代码是我从网上找来的，并且做了一些改进，主要有：
- 增加命令的选项：
- RTSP url
- 视频文件保存格式
- 要保存的帧数
- 第一帧是I帧
废话少说，上代码：
#include<stdio.h>
#include<libavformat/avformat.h>
#include<libavutil/mathematics.h>
#include<libavutil/time.h>
#include <unistd.h>
#define USAGE "rtsp2x -i <rtsp url> -t [avi | flv | mp4] -n <number of frames you want to save>"
#define OPTS "i:t:n:h"
static void print_usage()
{
printf("Usage: %s\n", USAGE);
return;
}
int main(int argc,char **argv)
{
AVOutputFormat *ofmt = NULL;
AVFormatContext *ifmt_ctx = NULL,*ofmt_ctx = NULL;
AVPacket pkt;
const char in_filename[128] = {0}, out_filename[128] = {0};
int ret,i;
int video_index=-1;
int frame_index=0;
int I_received = 0;
int opt, frames_count = -1;
while ((opt = getopt(argc, argv, OPTS)) != -1) {
switch (opt) {
case 'i':
strcpy(in_filename, optarg);
break;
case 't':
if (strcmp(optarg, "avi") == 0)
strcpy(out_filename, "receive.avi");
else if (strcmp(optarg, "flv") == 0)
strcpy(out_filename, "receive.flv");
else if (strcmp(optarg, "mp4") == 0)
strcpy(out_filename, "receive.mp4");
else {
return -1;
}
print_usage();
break;
case 'n':
frames_count = atoi(optarg);
if (frames_count < 0) {
print_usage();
return -1;
}
printf("frames_count = %d\n", frames_count);
break;
case 'h':
default:
print_usage();
return -1;
}
}
if (strlen(in_filename) == 0 || strlen(out_filename) == 0 || frames_count < 0) {
print_usage();
return -1;
}
av_register_all();
avformat_network_init();
//使用TCP连接打开RTSP，设置最大延迟时间
AVDictionary *avdic=NULL;
char option_key[]="rtsp_transport";
char option_value[]="tcp";
av_dict_set(&avdic,option_key,option_value,0);
char option_key2[]="max_delay";
char option_value2[]="5000000";
av_dict_set(&avdic,option_key2,option_value2,0);
//打开输入流
if((ret=avformat_open_input(&ifmt_ctx,in_filename,0,&avdic))<0)
{
printf("Could not open input file.\n");
goto end;
}
if((ret=avformat_find_stream_info(ifmt_ctx,0))<0)
{
printf("Failed to retrieve input stream information\n");
goto end;
}
//nb_streams代表有几路流，一般是2路：即音频和视频，顺序不一定
for(i=0;i<ifmt_ctx->nb_streams;i++){
if(ifmt_ctx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
{
//这一路是视频流，标记一下，以后取视频流都从ifmt_ctx->streams[video_index]取
video_index=i;
break;
}
}
av_dump_format(ifmt_ctx,0,in_filename,0);
//打开输出流
avformat_alloc_output_context2(&ofmt_ctx,NULL,NULL,out_filename);
if(!ofmt_ctx)
{
printf("Could not create output context\n");
ret=AVERROR_UNKNOWN;
goto end;
}
ofmt = ofmt_ctx->oformat;
for(i=0;i<ifmt_ctx->nb_streams;i++)
{ //根据输入流创建输出流
AVStream *in_stream = ifmt_ctx->streams[i];
AVStream *out_stream = avformat_new_stream(ofmt_ctx,in_stream->codec->codec);
if(!out_stream)
{
printf("Failed allocating output stream.\n");
ret = AVERROR_UNKNOWN;
goto end;
}
//将输出流的编码信息复制到输入流
ret = avcodec_copy_context(out_stream->codec,in_stream->codec);
if(ret<0)
{
printf("Failed to copy context from input to output stream codec context\n");
goto end;
}
out_stream->codec->codec_tag = 0;
if(ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
}
//Dump format--------------------
av_dump_format(ofmt_ctx,0,out_filename,1);
//打开输出文件
if(!(ofmt->flags & AVFMT_NOFILE))
{
ret = avio_open(&ofmt_ctx->pb,out_filename,AVIO_FLAG_WRITE);
if(ret<0)
{
printf("Could not open output URL '%s'",out_filename);
goto end;
}
}
//写文件头到输出文件
ret = avformat_write_header(ofmt_ctx,NULL);
if(ret < 0)
{
printf("Error occured when opening output URL\n");
goto end;
}
//while循环中持续获取数据包，不管音频视频都存入文件
while(1)
{
AVStream *in_stream,*out_stream;
//从输入流获取一个数据包
ret = av_read_frame(ifmt_ctx,&pkt);
if(ret<0)
break;
in_stream = ifmt_ctx->streams[pkt.stream_index];
out_stream = ofmt_ctx->streams[pkt.stream_index];
//copy packet
//转换 PTS/DTS 时序
pkt.pts = av_rescale_q_rnd(pkt.pts,in_stream->time_base,out_stream->time_base,(enum AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, (enum AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
//printf("pts %d dts %d base %d\n",pkt.pts,pkt.dts, in_stream->time_base);
pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
pkt.pos = -1;
//此while循环中并非所有packet都是视频帧，当收到视频帧时记录一下，仅此而已
if(pkt.stream_index==video_index)
{
if ((pkt->flags & AV_PKT_FLAG_KEY) && (I_received == 0))
I_received = 1;
if (I_received == 0)
continue;
printf("Receive %8d video frames from input URL\n",frame_index);
frame_index++;
} else {
continue;
}
if (frame_index == frames_count)
break;
//将包数据写入到文件。
ret = av_interleaved_write_frame(ofmt_ctx,&pkt);
if(ret < 0)
{
/**
当网络有问题时，容易出现到达包的先后不一致，pts时序混乱会导致
av_interleaved_write_frame函数报 -22 错误。暂时先丢弃这些迟来的帧吧
若所大部分包都没有pts时序，那就要看情况自己补上时序（比如较前一帧时序+1）再写入。
*/
if(ret==-22){
continue;
}else{
printf("Error muxing packet.error code %d\n" , ret);
break;
}
}
//av_free_packet(&pkt); //此句在新版本中已deprecated 由av_packet_unref代替
av_packet_unref(&pkt);
}
//写文件尾
av_write_trailer(ofmt_ctx);
end:
av_dict_free(&avdic);
avformat_close_input(&ifmt_ctx);
//Close input
if(ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
avio_close(ofmt_ctx->pb);
avformat_free_context(ofmt_ctx);
if(ret<0 && ret != AVERROR_EOF)
{
printf("Error occured.\n");
return -1;
}
return 0;
}
编译命令：
$ gcc -o rtsp2x rtsp2x.c -lavcodec -lavformat -lavutil
使用举例：
./rtsp2x -i rtsp://admin:NRRMUY@192.168.0.100:554/h264/ch1/main/av_stream -t flv -n 120
执行完成后就会在当前目录下产生一个receive.flv的视频文件。
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