Quantization for hybrid video coding

Abstract

Method for coding a video signal using hybrid coding, comprising: reducing temporal redundancy by block based motion compensated prediction in order to establish a prediction error signal; performing quantization on samples of the prediction error signal or on coefficients resulting from a transformation of the prediction error signal into the frequency domain to obtain quantized values, representing quantized samples or quantized coefficients respectively; calculating a quantization efficiency for the quantized values; calculating a zero efficiency for a quantization, when the quantized values are set to zero; selecting the higher efficiency; and maintaining the quantized values or setting quantized values to zero, for further proceeding, depending on the selected efficiency.

We claim: 
     
       1. A method for coding a video signal using hybrid coding, comprising:
 reducing temporal redundancy by block based motion compensated prediction in order to establish a prediction error signal; 
 performing quantization on samples of the prediction error signal or on coefficients resulting from a transformation of the prediction error signal into the a frequency domain to obtain quantized values, representing quantized samples or quantized coefficients respectively, wherein the prediction error signal includes a plurality of subblocks each including a plurality of quantized values; 
 calculating a first quantization efficiency for the quantized values of at least one subblock of the plurality of subblocks; 
 setting the quantized values of the at least one subblock to all zeroes; 
 calculating a second quantization efficiency for the at least one subblock while all of the quantized values are zeroes; 
 selecting which of the first and second quantization efficiencies is a higher efficiency; and 
 selecting, for further proceeding, the at least one subblock with the quantized values prior to setting the quantized values of the at least one subblock to all zeroes if the first quantization efficiency is higher and selecting the at least one subblock with the quantized values set to zero, for further proceeding, if the second quantization efficiency is higher. 
 
     
     
       2. The method according to  claim 1 , wherein:
 the prediction error signal comprises macroblocks, which are subdivided into the plurality of subblocks, 
 performing quantization includes performing quantization on samples of the at least one subblock or the coefficients resulting from a transformation of the at least one subblock into the frequency domain respectively, and 
 calculating the first quantization efficiency; setting the quantized values, calculating a second quantization efficiency; selecting which of the first and second quantization efficiencies is a higher efficiency; selecting, for further proceeding, the at least one subblock with the quantized values prior to setting the quantized values of the at least one subblock to all zeroes if the first quantization efficiency is higher; and selecting the at least one subblock with the quantized values set to zero, for further proceeding, if the second quantization efficiency is higher, and selecting steps are performed for each subblock, the method further comprising:
 calculating an overall quantization efficiency for quantizing all subblocks of one macroblock of the macroblocks; 
 setting the quantized values of the one macroblock to all zeroes; 
 calculating an overall zero efficiency for quantizing while all quantized values of the one macroblock are set to zero; 
 selecting which of overall quantization efficiency and the overall zero efficiency is higher; 
 selecting, for further proceeding, the one macroblock with the quantized values prior to setting the quantized values of the one macroblock to all zeroes if the overall quantization efficiency is higher than the overall zero efficiency; and 
 selecting the one macroblock with the quantized values of the one macroblock set to zero, for further proceeding, if the overall zero efficiency is higher than the overall quantization efficiency. 
 
 
     
     
       3. The method according to  claim 1 , wherein calculating the first and second quantization efficiencies is based on a cost function. 
     
     
       4. The method according to  claim 3 , wherein the cost function is based on rate distortion costs, whereby the rate distortion costs are calculated depending on the a required rate and the a resulting distortion. 
     
     
       5. The method according to  claim 4 , wherein the rate distortion costs are based on the a sum of the a distortion and the a weighted required rate. 
     
     
       6. The method according to  claim 5 , wherein the rate distortion costs C j  are calculated using the an equation C j =D j +L*R j , whereby D j  represents the resulting distortion resulting from the quantization, R j  represents the required rate required for quantization, L is a Lagrange parameter and the Index j depicts the corresponding subblock. 
     
     
       7. The method according to  claim 4 , wherein the resulting distortion is the a sum of the squared quantization errors or the a mean absolute quantization error. 
     
     
       8. The method according to  claim 2 , whereby the overall quantization efficiency of the on macroblock is the a sum of the selected efficiencies of each subblock. 
     
     
       9. A method for decoding a video signal using hybrid coding, wherein the video signal has been coded according to  claim 1 , comprising: decoding coded video data effectively in the frequency domain or the a spatial domain, in accordance with the a coding mechanism used for coding the video signal data. 
     
     
       10. The decoding method of  claim 9 , wherein positions of the prediction error signal samples received in a one-dimensional array are assigned to locations in a two-dimensional arrangement are determined based on a previously received prediction error signal or prediction image. 
     
     
       11. A coder for coding a video signal using hybrid coding, comprising:
 means for reducing temporal redundancy by block based motion compensated prediction in order to establish a prediction error signal, 
 quantization means for quantizinga quantizer that quantizes the prediction error signal in order to establish quantized values representing samples or coefficients, wherein the prediction error signal includes a plurality of subblocks, 
 control means for:
 calculating a first quantization efficiency of at least one subblock of the plurality of subblocks; 
 setting the quantized values of the at least one subblock to all zeroes; 
 calculating a second quantization efficiency for the at least one subblock while all of the quantized values are zeroes; 
 selecting which of the first and second quantization efficiencies is a higher efficiency; and 
 selecting, for further proceeding, the at least one subblock with the quantized values prior to setting the quantized values of the at least one subblock to all zeroes if the first quantization efficiency is higher and selecting the at least one subblock with the quantized values set to zero, for further proceeding, if the second quantization efficiency is higher. 
 
 
     
     
       12. The coder according to  claim 11 , further comprising: transformation means for transforming a frequency transformer that transforms picture elements of the prediction error signal from the a spatial domain into the a frequency domain. 
     
     
       13. A decoder for decoding a coded video signal coded by use of hybrid coding according to the method of  claim 1 , comprising:
 adaptive control means for adaptively deciding whether an input stream of the coded video signal represents the prediction error signal of the coded video signal in the a spatial domain or in the a frequency domain and for decoding the coded video signal into a quantized prediction error signal; and 
 an inverse quantizer configured to inverse quantize the quantized prediction error signal. 
 
     
     
       14. The method according to  claim 1 , wherein the calculating the first quantization efficiency; setting the quantized values; calculating the second quantization efficiency; selecting which of the first and second quantization efficiencies is a higher efficiency; selecting, for further proceeding, the at least one subblock with the quantized values prior to setting the quantized values of the at least one subblock to all zeroes if the first quantization efficiency is higher; and selecting the at least one subblock with the quantized values set to zero, for further proceeding, if the second quantization efficiency is higher are performed for each subblock.