U.S. Philips Corporation

Petrus J Van Otterloo

Gerrit J Keesman

Marcel Breeuwer

A hybrid waveform and model-based image signal encoder and decoder are described. The image signal is waveform-encoded (11) and decoded (31) so as to approximate the waveform of the original input signal as well as possible after compression. In order to compensate its loss, the noise component of the signal (or, more generally, a signal component which gets lost by the waveform encoding) is model-based encoded (12,13) and separately transmitted or stored. In the decoder, the noise is regenerated (32-34) and added (36) to the waveform-decoded image signal. The invention is particularly applicable to compression of medical X-ray angiographic images where loss of noise leads a cardiologist or radiologist to believe that the image is distorted.

Hybrid waveform and model-based encoding and decoding of image signals

A method of transcoding coded video signals and a corresponding device for implementing this method are described. The device comprises decoding and encoding sub-assemblies (201, 202) and, within the encoding sub-assembly, quantizer (23) and bitrate controller. This bitrate controller comprise, before the quantizer (23), circuit for computing a local target value for encoding each sub-picture of the images to which video signals correspond and circuit for controlling the step size during the quantizing step.

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Eindhoven, Netherlands

Petrus J Van Otterloo