SPC700 sound format

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An SPC700 sound file (or SPC) is a type of video game music file consisting of a copy of a program and music data from RAM used by the SPC700 sound chip on the Super Nintendo Entertainment System or Super Famicom (though such data are usually obtained from a console emulator such as ZSNES or Snes9x, rather than from the system itself). The SPC700 chip (or emulator thereof) produces sound by executing the embedded program, which processes the stored music data and transforms them to a sequence of DSP commands issued to the chip, which in turn produce the audio output in accordance to the DSP commands. The capabilities of the SPC700 DSP commands allow for music synthesis by samples (analogous to MOD or IT music playback), allowing long stretches of audio which would likely take up several megabytes—even hundreds, for particularly lengthy pieces—if stored as a digital waveform (using PCM or similar), to be produced from only 64 kilobytes of data. The SPC700 chip produces 16-bit sound at 32 kHz, but SPC700 emulators generally can be reconfigured to output at a different sampling rate (from 8 to 48 kHz).

SPC plugins (such as SNESAmp) are available for Winamp, XMPlay, foobar2000, portable mp3 players running Rockbox, and other popular players; a few have native SPC support. Some SPC players, including SNESAmp, can even produce higher-quality output than the SPC700 itself by outputting the sound at a higher sampling rate (up to 192 kHz), using more complex sound interpolation methods and using a special "High Quality" enhancement feature (as in SNESAmp). There are also several programs (such as SPC Tool and SPC2MIDI) able to produce MIDI files from SPC files.

Recently, soundtracks are being compressed using the RAR algorithm, with a solid archive format not available with ZIP compression--this archive format generally saves an enormous amount of space because so many samples are usually reused between songs and it remembers the repeating samples instead of storing them over again. The archived files are given the extension RSN, and these are uncompressed directly by the player on play.

A disadvantage of .spc format can be seen in the sets for Tales of Phantasia and Star Ocean, two high-level SNES games that used "streaming" sampling and swapped samples on the fly to overcome the 64KB limit of the SPC700 and to allow additional instruments and vocals. Because the .spc dump only stores the 64KB of the time of the save, rather than updating according to the game's changes, many of the songs in these games go off-tune or sound "scratchy." Most notably, the fully vocal intro to Tales of Phantasia, "Yume-Wa Owaranai," fails to play any vocals at all when loaded in an .spc player, instead either producing squealing noises or complete silence where the vocals should be.