Audacity 1.3.5 and 1.3.6 Flatlining

[cassam]

Halfway through transferring my cassette collection onto my PC, Audacity appears not to be recording anymore.
I'm getting two flat lines in both left and right channels. I'm transferring using a Citronic USB device from my stereo into a USB port - very sucessfully for the past three months!
PC is Windows XP standard and I've clicked Realtek AC 97 in my Recording and Playback options in Audacity Preferences and the Line In option on the Toolbar.
Have installed 1.3.6 tonight thinking that might make a difference - it hasn't!
Audacity will still play my previously transferred files - just won't let me make new ones.
Would be grateful for any tips.

[steve]

Check that you have plenty of free disk space.
Try rebooting your computer.
Try reinstalling your USB device.

[cassam]

Have 80GB of space. Have reboooted. USB device isn't installed as such. When you buy it they supply it with Audacity 1.2.6 which you then install. I was using this for a while, but upgraded to 1.3.5 because of the improvement in the latency. Also - apologies that I've ended up in this forum. Should I not be in the Windows section of the Audacity 1.3 forums?

[steve]

USB device isn't installed as such.

I see, it uses generic Windows drivers.
In 99% of the times when Audacity flat-lines, it is because it is simply not receiving any audio. This is either because Audacity is not set in its Preferences (Edit menu > Preferences > Audio I/O tab) to the correct audio device, (so it's listening to the wrong device and there's nothing to hear), or there is (usually a configuration) problem with the device and it is not sending any audio (so Audacity is listening, but the device ain't talkin').

USB devices always need to be installed in a manner of speaking, but with the "Plug and Play" USB devices, that simply means that installation occurs when you plug it in using generic drivers that are already included with the operating system.

You know how when you plug in a USB memory stick, there is a short pause, then (sometimes) Windows says that a device has been found, then a short while later Windows may say that the new hardware is ready for use. That is the installation - after Windows has used a device once, it should be a bit quicker at installing the device the next time that it is plugged in as it has the drivers ready and is half expecting the device, in which case it may not inform you that it has installed the device, until you notice that Windows is scanning the memory stick and asks you if you want to play, open or run the contents.

The same thing happens with USB audio devices. Before they are plugged in, as far as the computer is concerned, the device does not exist, so if Audacity is open, the USB device will not appear in Preferences > Audui I/O tab and will not be available for Audacity to use. Audacity only checks for available audio devices at the point that it is being launched. This is why it is essential that Audacity is not opened until the audio device is fully connected and working.

When the device is detected by Windows (the operating system is periodically scanning the USB ports for new devices), it will check to see what sort of device it is, then load the appropriate drivers that make the device available to the operating system and other applications. With audio devices, Windows will usually pass over the entire sound system to the device, making it the default recording and playback device (this is where we get problems with people loosing their playback when they plug in a USB microphone or turntable).

You can usually tell when a USB audio device has been installed by opening (but obviously not applying) the "safely remove hardware" utility that has an icon near the system clock. Another way of testing that USB sound cards have been connected is to play a system sound (such as clicking on the volume control near the system clock, or anything else that is configured to ping or beep). The important thing is not to rush - Windows needs a bit of time to detect, install and connect the device.

Once that is complete, Audacity may be opened and the USB device should now be listed in the Audio I/O tab of Preferences and be available for selection.

That is what happens when everything works, and you can no doubt see many possible trip up points that would stop Audacity from recording at all.

The other important thing about USB devices, is that they require constant attention from the computer CPU (processor). With digital audio, the throughput of data is pretty high, and it has to remain synchronised with the rest of the system at all times. A single momentary lapse of attention from the CPU can mean that the device looses synchronisation and all the data that follows will turn to garbage. As far as I know, there is no error checking on the data, so once the data turns to garbage, there is no going back until the device is disconnected and reinstalled. This is why it is important to not use any CPU intensive programs at the same time, and also one of the reasons why we see so many problems with USB turntables recording half an album perfectly, then suddenly recording loads of static (garbage data), or nothing at all. In the case of USB turntables, I strongly suspect that half of the problem is with poor quality components, but even with good quality sound cards it is not unusually to find that the device is not working correctly when you come to use it, and requires removal and reinstalling to get it going properly.

I have been concentrating on the potential problems with USB audio devices here, which is not to say that they are unusable. As long as they are correctly installed and working before Audacity is opened, and as long as you do not try to have other CPU intensive applications running at the same time, they will usually run reliably, and are a godsend for laptop users. But if they loose sync for just one moment, then there is no other option but to close Audacity, remove/switch off the audio device, reconnect, wait for it to install, and restart Audacity.

If after all of this, Audacity is still flat-lining, you need to find out if the problem is with Audacity, or with the installed device. The easiest way to check this, is to open Windows Sound Recorder and try recording with that. If Windows Sound Recorder has the same problem, then the issue is with either the hardware, or its installation. If it is a sound card issue, then you may find that one of your USB sockets works better than the others, or sometimes you may find that there is an updated driver available for the device. (In the case of some Macs it has been reported that back dating the drivers is required for reliable functioning of certain USB audio devices).

That's about all I know on the subject - good luck