Orinj Audio formats

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Orinj version 3.0.0

Orinj uses wave files and MIDI files.

Wave files

Orinj uses pulse code modulation (PCM) wave files (files with extension ".wav"). There is a large number of wave file types, each with a specific compression code.

The PCM wave file contains uncompressed digital sampled audio data. When a sound signal is recorded digitally with the PCM format, the values of the analog sound signal are taken (sampled) at uniform intervals and the amplitude of the signal at each interval is recorded with numbers that use the same representation.

  • The rate at which the signal is sampled (the number of times the signal is sampled per unit of time) is the sampling rate. The larger the sampling rate, the more precise the recording of the signal.
  • The representation of the numbers used to record the value at each sample is the sampling resolution. Usually, the sampling resolution is determined by the number of bits in used in the computer representation of the recorded numbers (for example, "16-bit"). With more bits, the recorded numbers can represent larger magnitudes. The larger the sampling resolution, the larger the dynamic range of the recorded signal.

Sound quality and dynamic range improve as sampling rates and sampling resolutions increase, but this happens at the expense of speed and disk space.

A standard music CD, for example, uses the sampling rate 44.1KHz and the sampling resolution 16 bits. These are usually good enough for most popular music and will do well in representing the frequencies and amplitude ranges that most people can actually hear.

Orinj supports:

  • The sampling rates: 8 KHz, 11 KHz, 16 KHz, 22 KHz, 32 KHz, 44.1 KHz, 48 KHz, 55.1 KHz, 64 KHz, 66.2 KHz, 77.2 KHz, 80 KHz, 88.2 KHz, 96 KHz, 99.2 KHz.
  • The sampling resolutions: 8, 16, 24, and 32 bits.

These are the the sampling rates and sampling resolutions that can be used in Orinj sessions. By convention, Orinj expects that 8-bit audio files will use unsigned integer bytes, 16- and 24-bit audio files will use signed 2- and 3-byte integers respectively, and 32-bit data will use signed floats. For 8, 16, and 24 bit representations, Orinj uses the compression code 1 (for Microsoft PCM uncompressed) in the wave format. For the 32-bit representation, Orinj uses the compression code 3 (for Microsoft IEEE float). Technically, the 32-bit wave files in Orinj are also PCM files, since they use uniform sampling and sample representations, although a 32-bit wave with the Microsoft PCM uncompressed compression code will normally be expected to use 32-bit integers, not floats. If a file created in different software uses a different convention, this file will not be understood by Orinj.

The sampling rates and sampling resolutions that are actually available in Orinj also depend on the audio devices (i.e., soundcards) on each computer. Some soundcards will not support large sampling rates and resolutions.

Orinj can also open AIF, AU, A-law, and U-law wave files. Orinj will convert these files to wave PCM files and will use these newly created wave PCM files instead. The original files will not be changed.

In general, wave files have been in use for a while and there currently exists a large number of wave file formats. Wave formats usually differ in two main aspects: how and where audio data is stored and what other data is allowed in the file. Some files, for example, are compressed (usually with loss in audio quality). Some files contain other data in addition to audio data, such as the author's name, the title of the file, and the copyright owner. It is always possible to stumble upon a wave file that will not be recognized by Orinj.

MIDI files

MIDI files (files with extension ".mid"), rather than containing sampled audio data, contain actual notes, instruments, and controllers. Similarly to wave files, MIDI files follow standard formats. While the MIDI standard defines the notes and instruments, it does not define how these will sound on different devices. This choice is left to the manufacturer of the device. This means that one and the same MIDI file may sound differently on different soundcards.

Orinj is designed so that any MIDI file will play on the computer's soundcard provided that the sound card can handle the file. However, when modifying and creating files, Orinj treats all MIDI files as type 1 MIDI files. This means that one file can contain multiple tracks, but that all tracks would be considered a part of the same MIDI sequence and will be played together. Orinj does not support the full General MIDI standard (see General MIDI 1 and General MIDI 2). Orinj supports the standard General MIDI 1 instruments, including percussion instruments, and some of the controllers (volume, pan, pitch shift, key pressure, channel pressure).



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