Tips for recording audio streams

In response to the thread "Recording streaming audio" from 10-02-05 I spent some time experimenting with ways of recording streaming audio from the Internet on a Linux box. Here's what I've learned.

If you want to record streaming audio from a source on the Internet for which you have a URL (e.g. an http or rtsp link) you can accomplish that with MPlayer, realcap or Streamtuner-Streamripper.

1. MPLAYER is an up and coming multimedia player that's loaded with features but is not always easy to install correctly. You can use it on the command line or from within its GUI. You will also need to download codecs for playing a variety of different audio formats, e.g. the "essential" codecs set from

Example (all one long line):

mplayer -noframedrop -dumpfile out.rm -dumpstream rtsp:--real.npr.na-central.speedera.net:80-real.npr.na-central-me-20050314me06.rm

This records the audio stream linked to in RealAudio format in the file out.rm in your current working directory (cwd) until you exit the program (ctrl-Z).

2. REALCAP is a bash shell script that allows you to capture an audio stream from RealPlayer to a file in wav, ogg or mp3 format, with various options for sampling rates and audio quality. To exploit its functionality fully you should have realplay, vsound, lame and oggenc installed. You can get realcap from put it inusr-local-bin.

Example (all one long line):

realcap -c 60 -m 48 -a NPR -t Knuth -d rtsp:--real.npr.na-central.speedera.net:80-real.npr.na-central-me-20050314me06.rm

This command uses vsound and lame to write about half a minute of this stream at 48 kbps in mp3 format to the file vsound.mp3 in your cwd (after first idling for some 30 secs due to connect and buffering time).

3. STREAMTUNER is an internet audio stream directory browser with GUI that allows you to easily access thousands of audio streams from Internet radio stations and from other audio sources on the Internet. It has a "record" option that will capture the audio stream you're listening to in ogg format. This option requires the presence of Streamripper which is a separate command line program (you may have to install it separately). Streamtuner-Streamripper rips shoutcast and icecast compatible audio streams to separate subfolders in a folder in your home dir that will be named after the audio source you're ripping (e.g. the radio station).

STREAMRIPPER is the utility that rips the online audio stream to individual ogg files. You can also use it stand-alone on the command line, e.g.

This command will rip all the songs played to separate tracks in ogg format until you kill the program.

If you want to record streaming audio from a source on the Internet for which you don't have a URL (i.e. direct stream recording), you can use arecord, rawrec-rawplay or Krecord.

4. ARECORD records audio files using the ALSA sound system, e.g.

arecord -f cd -t wav -d 45 -D hw:0,0 capture.wav

This command records 45 sec of the currently playing audio stream in CD quality in wav format to the file capture.wav in your cwd. You can play back that file e.g. with RealPlayer.

arecord -f cd -t wav -d 45 -D hw:0,0 lame -m s --bitwidth

This command records 45 sec of the currently playing audio stream as above, then pipes it to lame to encode it in mp3 format and writes it as a date&time-stamped mp3 file to your cwd. Play it back with xmms or RealPlayer.

5. RAWREC-RAWPLAY is a buffered raw audio recorder-player, e.g.

rawrec -t 30 capture.raw

This command records 30 sec of the current audio stream in raw audio format to the file capture.raw in your cwd. You can play it back with the command "rawplay capture.raw".

rawrec -t 30 sox -t sw -r 44100 -c 2 - -t cdr capture.cdr

This command records 30 sec in raw audio and then uses sox to convert it to a CD quality cdr file. You can play that back with sox or convert it to something else.

6. KRECORD is a program for recording anything that goes through your DSP (the digital signal processor on your soundcard). It's part of the KDE suite and has some nice features such as an input level indicator and a frequency spectrum display. The former is very handy for setting the proper record input level with the "Capture" slider in the alsamixer console.

To direct record audio, open a new file buffer, give it a name with .wav extension, save it, then press the record button. You can watch the record level in the "input level" window. When done, press stop and play back the file e.g. with RealPlayer.

7. AUDACITY is a full-fledged audio editor with a rather complex interface. I have little experience with it. It has a "record" button which I presume allows you to capture in raw audio format whatever audio goes through the soundcard. In fiddling around with this program for a brief length of time, I did manage just once to accomplish just that. But the recording was horribly distorted, and I just don't remember how I got there.

An essential prerequisite for all of this to work is to set up your sound mixer properly. This can be done with the command line utility ALSAMIXER (I use v.1.0.8). It's probably installed in your distro by default. Alsamixer seems to work reliably whereas Kmixer, a KDE program that's designed to do the same thing in a GUI, doesn't always seem to be reliable, i.e. changes you make in Kmixer don't always seem to jive with the settings shown in the alsamixer display. The latter is probably more trustworthy.

In the alsamixer console you can toggle "View" with the tab key, navigate between devices with the forward and backward keys, turn capture on and off with the space bar, toggle muting with the "m" key and change slider settings with the up and down keys.

The mixer setting that I've found to work for direct stream recording with arecord, rawrec etc. has "Capture" and "Mix" turned on to CAPTUR and "Capture" set to about 60%. All other adjustable sliders are set to about 70% save for "Headphones" (100%). "PCM" definitely must be on, i.e. not muted, whereas for recording the other devices may or may not be muted.

Once you have sound playing through your soundcard, you can use the input level meter in Krecord to check the record level in db (use the log option) while you're adjusting the alsamixer sliders and switches. A setting with the moving horizontal bars being red much of the time (i.e. the peak mostly being between -10 and 0 db) seems to work fine.

I'm using the Intel 82801DB-ICH4 AC'97 Audio Controller which is integrated into the motherboard and uses the AD1981A sound chip. With other soundcards the alsamixer console may show device names other than "Capture" and "Mix"; in this case turn on capture for "AC'97" and "AC'97 Cap" and turn up the latter's slider.

Good luck,

Robert