Sample Replay

As memory capacity increases it becomes possible to store and replay arbitrary waveforms rather than lists of approximate pitch and volume for simple pre-set pulses. This 'sample replay' technology has transformed interactive audio. This chapter explains how, and the new techniques it spawned.

Cheetah's minimalist but sonically-convincing £29.95 SpecDrum uncovered: Ferranti DAC, op-amp, TTL glue and analogue filters. This let the 3.5 MHz Sinclair Spectrum's Z80A processor play AM-radio quality 20 KHz audio, packing 8 percussion samples into 20K of RAM (photo by SNG, overmatter from the book)
Cheetah's 1985 minimalist but sonically-convincing £29.95 SpecDrum sample replay hardware uncovered, comprising a Ferranti DAC, an op-amp, TTL glue chip and simple analogue filters. This let the 3.5 MHz Sinclair Spectrum's Z80A processor play AM-radio quality 20 KHz audio, packing eight well-recorded percussion samples in 20K of RAM. Photo by SNG, overmatter from the book.


Concepts: Pulse-width modulation, direct memory access, output filters, tracker modules, MIDI, Moore's Law, multichannel phasing, correlation, combining voices, sample rate optimisation, noise masking, analogue surround phase encoding, block-update rates and latency.

Audio formats: PCM, ATRAC3, VAG, MP3, XADPCM, Opus, Ogg Vorbis.

People: Jay Miner, Allister Brimble, Bobby Prince, Trent Reznor, Lyndon Sharp, Richard Furse.

Products mentioned: Fairlight CMI, SpecDrum, Commodore Amiga, Paula, OctaMED, Doom, Quake, PS1 CXD2922, PS2 SPU, Salt Lake 2002, FMOD, Colin McRae: DiRT, CD, DVD, XM, Dance Factory, PS3 Operation Flashpoint, OPL2.

Further reading

Early Digital Audio Hardware - previous chapter abstract.
Interactive Audio Development Roles - next chapter abstract.
Return to the index of chapters.
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Copyright © 2019 Simon N Goodwin     [';']