Bitrate estimator for selecting quantization levels for image encoding
US5926222A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 28, 1995 |
| Grant date | Jul 20, 1999 |
| Priority date | — |
| Expiry date | Sep 28, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N19/146
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An estimate of the number of bits required to encode a block of transform coefficients at a specified quantization (Q) level is generated without performing the actual encoding. The transform coefficients and the specified Q level are used to generate indices to lookup tables that map to the number of bits contributed to the encoded bitstream by each transform coefficient. lookup table may be used to perform non-linear compression to map Q level, unquantized transform coefficients, and zero runs to degrees of quantizer, unquantized coefficient, and zero run. The degrees of quantizer and unquantized coefficient are used to generate an index to another lookup table that maps to a degree of quantized coefficient. The degrees of quantized coefficient and zero run are then used to generate an index to yet another lookup table that maps to the number of bits contributed to the encoded bitstream.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.