Patent ID: 7106799

Claim:
A digital transcoding system for receiving data bit streams with a first bit rate (R 1 ) and outputting a data bit stream with a second bit rate (R 2 ), which differs from the first bit rate (R 1 ) and in particular is reduced relative thereto, comprising on its input side a decoding device, which has an input buffer and a series-connected variable length decoder, also, on its output side, a coding device, which has a series circuit that includes a quantizer for requantizing with a requantization factor the data that have been dequantized in the decoding device, a subsequent variable length coder, and an output buffer, wherein to adjust the second bit rate R 2 ), the new DCT coefficients QF new , which are to be conducted to the variable length coder, are determined with reference to macro-blocks, in accordance with the following formula: QF new ⁡ [ v ] ⁡ [ u ] = QF old ⁡ [ v ] ⁡ [ u ] · qs old qs new , where qs old stands for the old quantization factors, and qs new for the new ones, and where QF old stands for the DCT coefficients at the output of the variable length decoder.