US Patent 7492822 Compression techniques

In a video encoder a prediction signal at a bit resolution of P is subtracted from an input signal received at a bit resolution of P+Δ, where P is typically 8 bits, and P+Δ, 10 bits. A transform is then performed on the result, the output of which transform being at a bit resolution of at least P+Δ. The transformed signal is quantised, and the quantised signal used to form the prediction signal. The quantised signal is then coded for downstream delivery. At a decoder, the process is inverted, preserving the extra Δ bits input to the encoder.