Hi, Can some one help me with deadzone quantization. What is its difference when compared to normal quantization methods? I googled on it resulting unsatisfactory results :( Is there a place on the web I can look for more information regarding the same. -- TIA, jag

# newbie question on deadzone quantization

Started by ●August 30, 2005

Reply by ●August 30, 20052005-08-30

Hi,> Can some one help me with deadzone quantization. What is its > difference when compared to normal quantization methods?There's no "normal" quantization, so to say. A quantizer is a mapping from a continuous set A of "signals" to a discrete set "D" of symbols such that every a in A is assigned a symbol d in D. A dequantizer re-assigns every d a "representative" or "reconstruction value" r in A. The pre-image of a symbol d is called a "bucket". The "easiest" possible quantizer is the scalar equiquantizer: Here "A" is the real line, and the buckets are intervals of a constant size \Delta, for example: (-3 Delta,-2 Delta], (-2 Delta, -Delta], (-Delta,0] (0,Delta] (Delta,2 Delta]... Quantization is here simple: Divide the "signal" a by Delta, round to -infinity and you get the symbol value: 0 -> 0 Delta/2 -> 0 -Delta/2 -> -1 3.5 * Delta -> 3 etc. A "scalar equiquantizer with deadzone" works very similar, the only difference is that the size of the bucket containing the zero-signal has a different size, say Theta. Here is a typical example for an equiquantizer with deadzone with Theta = 2 Delta: (-3 Delta,-2 Delta], (-2 Delta, -Delta], (-Delta,Delta] (Delta,2 Delta], (2 Delta,3 Delta] (Note the difference above). It is often a good idea to introduce a deadzone because a lot of noise is then quantized to zero. A scalar equiquantizer is found in traditional JPEG-1, equiquantizers with deadzone are found in JPEG2000 (as above here Theta = 2 * Delta), scalar equiquantizers with arbitrary deadzone are in JPEG2000-2. Then, we can also consider quantizers where the symbol set A is not the real line, but a higher- dimensional space. These are called "vector quantizers". One nice vector quantizer is the Trellis Quantizer (TCQ) in JPEG2000-2.> I googled on it resulting unsatisfactory results :(Recommended reading on quantizers: Robert M. Gray, David L. Neuhoff: Quantization IEEE Transactions on Information Theory, Vol. 44, No. 6, October 1998 So long, Thomas