Audio - Looping back your sound card - no cables required

One option for getting loopback is to use two sound cards - setting other applications to run off a second, non-default sound card by specifying the output driver. This is something to be elaborated upon in another issue. So, with a 'virtual audio loopback' whatever you would otherwise hear through your speakers could be recorded, as well as built-in sound card effects, should you have them included.

This article will cover capturing audio from any audio program by directing the audio from one application to another, and how to get around error messages such as "Audio device already in use". There will also be a focus on the use of "merged audio" - combining the output from several programs into one audio stream ready to be recorded. With streaming media and applications such as software synthesisers, samplers and sequencers becoming more popular, the need to perform such tasks has increased.

A shareware program titled VAC (Virtual Audio Cable) is used for this demonstration and is included on this month's cover CD. This program is able to send the output from one audio software program into the input of another. It works on Windows 9x and is designed to work with limited RAM. There are up to 16 "virtual cables" in the full version and a single cable in the demo. VAC installs as if it is an additional sound card - it appears as full-duplex, with its output virtually loopbacked into its input, and can also take input from your existing hardware sound card. This is what allows you to connect several programs, even programs that don't create .wav files. Also included on this month's cover CD is the program Total Recorder, which works in a similar fashion as VAC except that it saves all of its data to a .wav file automatically.

Here's how you go about setting up VAC. In Windows 9x, navigate to Control Panel-Add New Hardware. Select No to the auto search and then select Sound, video and game controllers. Select Have disk and browse to where you unzipped VAC. Find the 9x directory and click OK when you have selected vac.inf. Click OK and select Virtual Audio Cable and click Next to go through the remaining dialogue boxes.

You don't need to restart Windows after completing this setup. VAC is now installed in your device manager.

To check this, right click on My Computer and go to Properties and navigate.

You should now have a new wave device titled Virtual Audio Cable which includes Virtual Cable 1 In for input and Virtual Cable 1 Out for output. If you have DirectSound 5 or higher, you might find that it will read as "Virtual Cable N (Direct Sound)" or similar. In the registered version, all 16 cables are independent and can allow an unlimited number of programs to access each chosen cable at the same time. If multiple audio applications are connected to the same out port, all audio will be merged.

Overall, VAC works like a real cable. If only the output application is opened, the audio data is lost. If only the input (e.g. recording) application is opened then silence will be recorded.

Apart from the uses mentioned, you can, for example, record the outputs of ReBirth (a software synthesiser) and FruityLoops (a software sampler) into GoldWave, all at the same time. This is only a rough example to show you the potential of this utility and there are much wider uses of such techniques.

Say, for example, you are using Re-Birth and FruityLoops (or any audio outputting program) and you want to record it. Using GoldWave (available on this month's cover CD), go to Tools-Device Controls-Properites-Device and select Virtual Cable 1.

In ReBirth go to Edit-Preferences and select Virtual Cable 1 Out. In FruityLoops access the wave configuration by simply pressing .

Press in both FruityLoops and ReBirth and then start a recording in GoldWave. Press and you are recording to a wave file, both Re-Birth and FruityLoops at the same time. To listen to the wave stream you have just completed, stop the recording, ReBirth and FruityLoops, and press . If you are happy with the recording, then you'll want to make sure that ReBirth and FruityLoops are in sync and that you've created a great track first.

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