几个RTP命令行小工具结合使用后的妙处

首先分别介绍下几个RTP (Real-time Transport Protocol)命令行小工具的用法.

1. mediastream.exe

mediastream --local <port> --remote <ip:port> --payload <payload type number>
[ --fmtp <fmtpline>]
[ --jitter <miliseconds>]
[ --width <pixels>]
[ --height <pixels> ]
[ --bitrate <bits per seconds>]
[ --ec (enable echo canceller)]
[ --agc (enable automatic gain control)]
[ --ng (enable noise gate)]
[ --ng-threshold <(float) [0-1]> (noise gate threshold)]
[ --capture-card <name>]
[ --playback-card <name>]
[ --infile      <input wav file>] specify a wav file to be used for input, instead of soundcard
[ --outfile <output wav file>] specify a wav file to write audio into, instead of soundcard

mediastream的作用是从声卡捕捉声音, 编码, 然后通过RTP协议发送到远端, 同时接收远端发送过来的RTP报文, 解码, 通过声卡播放.
比如,
主机A IP 192.168.1.100
主机B IP 192.168.1.200
主机A运行 mediastream.exe --local 2000 --remote 192.168.1.200:3000 --payload 110
主机B运行 mediastream.exe --local 3000 --remote 192.168.1.100:2000 --payload 110
这里payload type 110表示payload_type_speex_nb.

2. rtpdump.exe

rtpdump [-F format] [-t duration] [-x bytes] [-f file] [-o outputfile] address/port

rtpdump listens on the address and port pair for RTP and RTCP packets and dumps a processed version to outputfile if specified or stdout otherwise.
rtpdump可以监听地址/端口的RTP报文, 然后输出RTP报文到一个dump文件中. 这一点类似于抓包工具.

3. rtpplay.exe

rtpplay [-T] [-v] [-f file] [-p profile] [-s sourceport] [-b begin] [-e end] destination/port[/ttl] 

rtpplay reads RTP session data, recorded by rtpdump -F dump from either the file or stdin, if file is not specified, sending it to network address destination and port port with a time-to-live value of ttl.
rtpplay可以读取dump文件中的RTP报文, 然后发送到某地址/端口.

上面三个工具, mediastream支持声音的捕获/播放以及RTP协议, 但不支持RTP报文的保存/读取, 而rtpdump/rtpplay支持RTP报文的保存/读取以及RTP协议, 但不支持声音的捕获/播放.

所以, 结合这三个工具就能完成下面的任务:
1. 把你的声音保存到一个dump文件中;
2. 播放一个dump文件中的声音.

这里写了2个批处理, 分别完成上面2个任务.

rtpdump_gen.bat

@ECHO OFF

START "mediastream_test" /MIN mediastream.exe --local 2000 --remote 127.0.0.1:3000 --payload 110
START "rtpdump_test" /MIN rtpdump.exe -F dump -o ./my.rtpdump 127.0.0.1/3000 

ECHO "Press Any Key to Finish the Voice Dump"
PAUSE
TASKKILL /F /FI "WINDOWTITLE eq mediastream_test"
TASKKILL /F /FI "WINDOWTITLE eq rtpdump_test"
EXIT

rtpdump_playback.bat

@ECHO OFF

START "mediastream_test" /MIN mediastream.exe --local 2000 --remote 127.0.0.1:3000 --payload 110
REM Delay for 2 seconds
ping 127.0.0.1 -n 2 > nul
rtpplay.exe -f ./my.rtpdump -s 3000 127.0.0.1/2000 

ECHO "Press Any Key to Finish the Voice Playback"
PAUSE
TASKKILL /F /FI "WINDOWTITLE eq mediastream_test"
EXIT