As you work with digital audio, it’s important that you have some understanding of the demands on your computer’s CPU and hard drive. You might at times face problems saying drive corrupted or drive is not accessible, during such times make sure to contact a data recovery specialist with having yourself perform tasks trying to recover the data, as even a single step can lead to the file being completely erased from your system.
In general, the CPU is responsible for running all active processes on your computer. Processes take turns getting slices of time from the CPU so that they can all be making progress in their execution at the same time. You might have processes running on your computer at the same time you’re recording and not even be aware of it. For example, you may have automatic software updates activated. What if an automatic update tries to run while audio capture is in progress? The CPU is going to have to take some time to deal with that. If it’s dealing with a software update, it isn’t dealing with your audio stream.
Even if you make your best effort to turn off all other processes during recording, the CPU still has other important work to do that keeps it from returning immediately to the audio buffer. One of the CPU’s most important responsibilities during audio recording is writing audio data out to the hard drive. To understand how this works, it may be helpful to review briefly the different roles of RAM and hard disk memory with regard to a running program.
Ordinarily, we think of software programs operating according to the following scenario. Data is loaded into RAM, which is a space in memory temporarily allocated to a certain program. The program does computation on the data, changing it in some way. Since the RAM allocated to the program is released when the program finishes its computation, the data must be written out to the hard disk if you want a permanent copy. In this sense, RAM is considered volatile memory. For all intents and purposes, the data in RAM disappear when the program finishes execution.
But what if the program you’re running is an audio processing program like Logic or Sonar through which you’re recording audio? The recording process causes audio data to be read into RAM. Why can’t Sonar or Logic just store all the audio data in RAM until you’re done working on it and write it out to the hard disk when you’ve finished? The problem is that a very large amount of data is generated as the recording is being done – 176,400 bytes per second for CD quality audio. For a recording of any significant length, it isn’t feasible to store all the audio data in RAM. Thus, audio samples are constantly pulled from the RAM buffer by the CPU and placed on a hard drive. This takes a significant amount of the CPU’s time.
In order to keep up efficiently with the constant stream of data, the hard drive needs a dedicated space in which to write the audio data. Most audio recording programs automatically claim a large portion of hard drive space when you start recording. The size of this hard drive allocation is usually controllable in the preferences of your audio software. For example, if your software is configured to allocate 500 MB of hard drive space for each audio stream, 500 MB is immediately claimed on the hard drive when you start recording, and no other software may write to that space. If your recording uses 100 MB, the operating system returns the remaining 400 MB of space to be available to other programs. It’s important to make sure you configure the software to claim an appropriate amount of space. If your recording ends up needing more than 500 MB, the software begins dynamically finding new chunks of space on the hard drive to put the extra data. In this situation, it’s possible for dropouts to happen if sufficient space cannot be found fast enough. The problem is compounded by multitrack recording. Imagine what happens if you’re recording 24 tracks of audio at one time. The software has to find 24 blocks of space on the hard drive that are 500 MB in size. That’s 12 GB of free space that needs to be immediately and exclusively available.
One way to avoid problems is to dedicate a separate hard drive other than your startup drive for audio capture and data storage. That way you know that no other program will attempt to use the space on that drive. You also need to have a hard drive that is large enough and fast enough to handle this amount of sustained data being written, and often read back. In today’s technology, at least a 7200 RPM, one terabyte dedicated external hard drive with a high-speed connection should be sufficient.