Shaping of automatic audio crossfade
US4947440A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 27, 1988 |
| Grant date | Aug 7, 1990 |
| Priority date | — |
| Expiry date | Oct 27, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04H60/04
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Shaping of automatic audio crossfade is accomplished by adding a shaping function to the theoretical logarithmic crossfade function to decrease the rate of gain change at the limit of audibility. The gain change at each sample time within a crossfade interval is computed as a logarithmic function of the fractional part of the crossfade interval completed and the gain differential between the sources. The shaping function may be in the form of a cosine function that can be accessed with a look-up table that is added to the fractional part of the crossfade interval so that the gain change is expressed by: ti G.sub.delta =20*log{(k-s(k))*10.sup.(G.sbsp.1.sup.-G.sbsp.2.sup.)/10 } where S(k) is the shaping function, k is the fractional part complete and G.sub.1 -G.sub.2 is the gain differential between sources. The gain change is added to the current gain for the particular audio source and applied to a variable gain element for that source. The outputs of the variable gain elements are summed to produce the resulting output audio mix.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.