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cs276:jed.tutorial8


Part 1:

AIFF

      Audio Interchange File Format, or AIFF, is an audio file format that was co-developed by Apple Computer in 1988 based on Electronic Arts' Interchange File Format and is most commonly used on Apple Macintosh computer systems. The data in a standard AIFF file is uncompressed pulse-modulation(PCM) which is basically time-based pressure data. This format is lossless and uses about 10MB for one minute of audio at a sample rate of 44.1 kHz and a sample size of 16 bits. In addition to audio data, AIFF can also include loop point data and the musical note of a sample. AIFF files are generally uncompressed, although they do allow for compression. It's unclear, though, what information, if any, is lost in the process.


WAVE

     WAVE files are a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs. They're an application of the RIFF bitstream format method for storing data in “chunks”, and therefore also close to the AIFF format used on Amiga and Macintosh computers. They're the main format used on Windows systems for raw and typically uncompressed audio. The usual bitstream encoding is the Pulse Code Modulation (PCM) format, so again it's time-based pressure data. WAVE files, as well as AIFF, are compatible with Macintosh, Windows, and Linux systems. Though a WAVE file can hold compressed audio, the most common WAVE format contains uncompressed audio. The standard audio file format for CDs, for example, is LPCM-encoded, containing two channels of 44,100 samples per second, 16 bits per sample. The WAV format is limited to files that are less than 4 GB in size, because of its use of a 32-bit unsigned integer to record the file size header. Although this is equivalent to about 6.8 hours of CD-quality audio (44.1 kHz, 16-bit stereo), it is sometimes necessary to exceed this limit. The W64 format was therefore created. Its 64-bit header allows for much longer recording times.


AU

     The AU file format is a simple audio file format introduced by Sun Microsystems. The format was common on NeXT systems and on early web pages. It was originally headerless, being simply 8-bit µ-law-encoded data with an 8000 Hz sample rate. Hardware from other vendors often used sample rates as high as 8192 Hz, often integer factors of video clock signals. Newer files have a header consisting of six unsigned 32-bit words, an optional information chunk and then the data (in big endian format). AU files can store data as lossless, uncompressed pcm or lossy, compressed pcm. Originally, the format was designed to handle an 8-bit sample depth and to use a 64kbit/s bit rate, but this has since changed thanks to the file header.

Part 2:

Pitch Modification

Normalization

Volume Modification

cs276/jed.tutorial8.txt · Last modified: 2009/11/05 23:36 by jdfalcon06