Variance Adaptive Quantization (VAQ) is a video encoding algorithm that was first introduced in the open source video encoder x264. According to Xvid Builds FAQ: "It's an algorithm that tries to optimally choose a

quantizer Quantization, in mathematics and digital signal processing, is the process of mapping input values from a large set (often a continuous set) to output values in a (countable) smaller set, often with a finite number of elements. Rounding and ...

for each

macroblock The macroblock is a processing unit in image and video compression formats based on linear block transforms, typically the discrete cosine transform (DCT). A macroblock typically consists of 16×16 samples, and is further subdivided into transform ...

using advanced math algorithms." It was later ported to programs which encode video content in other video standards, like MPEG-4 ASP or

MPEG-2 MPEG-2 (a.k.a. H.222/H.262 as was defined by the ITU) is a standard for "the generic video coding format, coding of moving pictures and associated audio information". It describes a combination of Lossy compression, lossy video compression and ...

. In the case of Xvid, the algorithm is intended to make up for the earlier limitations in its Adaptive Quantization mode. The first Xvid library containing this improvement was released in February 2008.

References

External links

Implementation of variance-based adaptive quantization in x264

{{Tv-tech-stub Signal processing Video compression