Digital audio scrambling system with error conditioning
US4608456A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 27, 1983 |
| Grant date | Aug 26, 1986 |
| Priority date | — |
| Expiry date | May 27, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/802
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
In the scrambling system, an analog audio signal is converted into a digital signal to provide a sequence of digital signal samples corresponding to the analog audio signal. Each digital signal sample is compressed to provide compressed signal samples having a sign bit, three exponent bits and seven mantissa bits. Each bit of each compressed signal sample is exclusive-OR'd with a unique keystream to thereby scramble the audio signal. A Hamming code generator generates code bits for correcting singular errors in a combination of the sign bit, the exponent bits and the code bits; and a parity bit generator generates a parity bit for detecting double errors in a combination of the sign bit, the exponent bits and the code bits and for further detecting an error in the most significant mantissa bit and/or the parity bit. The bits from a plurality of successive compressed, error-encoded signal samples are interleaved and serialized in order to separate the bits from any single sample by at least a predetermined duration associated with an FM discriminator click. The serialized, interleaved, error-encoded, compressed signal samples are combined to provide two-bit digital words. The digita…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.