File formats
From WikiRecording
There are a variety of file formats associated with computer-based audio production, which can be grouped into a few major categories.
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Audio
Audio files are digital representations of audio waveforms. In audio production, a few common file formats are:
- AIFF
- WAVE (including Broadcast WAVE)
- Sound Designer II (SDII or SD2)
These are usually found as 16 or 24 bit files, with sample rates ranging from 44.1 kHz to 192 kHz. Less commonly, you may find 8 bit or 32 kHz files, especially if the program is associated with low-bandwidth multimedia (such as audio for the web).
Stereo 16 bit, 44.1 kHz files (the format for CD audio) require about 5 MB of disk space per channel per minute. So, for example, 2 minutes of CD audio requires 20 MB of disk space -- 2 channels times 5 MB times 2 minutes = 20 MB. Using a greater bit rate or sample rate will increase the disk space required, and will also increase demands on the computer's hard drive and processor.
These file formats can be imported into & exported from most DAWs, though SDII is a Mac-only format. Many DAWs offer the ability to choose which file format to use when recording or otherwise creating audio files.
Project
Project files are the files in which the software you are using saves information about your project, session, song, etc..
What exactly is contained in these files vary greatly from program to program, though generally speaking, project files for DAWs usually contain information about how many tracks you have, how they're configured, where the audio is placed, what edits you've made, effects that are being used, and so forth; audio data is usually saved separate from the project file as separate audio files, though MIDI data is usually saved within the project file.
Project files from one program generally cannot be opened in another program. However, there are "interchange" formats which allow at least some basic project data from one program to be transferred to another, providing that both programs support the same interchange format.
The most common interchange formats are OMF, AAF, and SMF (Standard MIDI Files -- see MIDI below).
The amount of data that will be retained when moving from one program to another using one of these interchange formats can vary signficantly, so for mission-critical data, check the documentation for each program to see how well the interchange format is supported.
Sampler
Sampler files are files which contain information about the interaction of sample files with a sampler; this includes information like which samples are mapped to which keys, what happens when they're triggered, filters, envelopes, and so forth. Depending on the file format, sampler files may reference audio data found in separate files, or the audio data may be contained directly in the sampler file.
There are a wide variety of hardware and software samplers, each with its own variety of support for the multitude of sampler formats available, so it's best to check with the documentation for the sampler you plan on using to find out if it supports the sampler file format you have.
MIDI
MIDI files contain information that tell MIDI devices how and what to do. MIDI files do not contain any audio, and you cannot hear anything from a MIDI file without a hardware or software MIDI device to interpret the data.
DAWs generally save MIDI data in their project file, though almost all DAWs can also import & export Standard MIDI Files (SMFs). A SMF is a type of MIDI file which can be interpreted by nearly any MIDI device.
