Two stage video film compression method and system

A system for encoding data representative of a sequence of video frames for transmission to a decoder, the system comprising:

• a motion compensated predictive coder which losslessly compresses the data, the motion compensated predictive coder computing a motion vector and forming an intermediate coded representation which includes the compressed data and the motion vector;
• a frame detector which detects frames having a prediction error which exceeds a predetermined threshold;
• a digital storage device, coupled to the motion compensated predictive coder and the frame detector, which stores the intermediate coded representation and stores a representation of the frames having the prediction error which exceeds the predetermined threshold;
• a lossless decoder, coupled to the digital storage device, which losslessly decodes the intermediate coded representation to form a decoded representation;
• a recoder, coupled to the digital storage device and the lossless decoder, which compresses the decoded representation at a compression ratio in dependence upon a selectable bit rate for transmission;
• and
• a preload coder, coupled to the digital storage device, which transmits encoded data representative of high activity frames during a period of low transmission activity.

A method of encoding data representative of a sequence of video frames,the method comprising the steps of:

• losslessly compressing the data by applying the data to a predictive coder to form an intermediate coded representation;
• storing the intermediate coded representation in a digital storage device;
• compressing the stored intermediate coded representation at a selectable compression ratio to form an encoded representation of th data;
• detecting frames having a prediction error which exceeds a predetermined threshold;
• and
• storing in said digital storage device a representation which indicates the frames having the prediction error which exceeds the predetermined threshold.

A system for encoding data representative of a sequence of video frames, the system comprising:

• a first coder which losslessly compresses the data to form an intermediate coded representation and includes a predictive coder which compresses the data to form the intermediate coded representation;
• digital storage device, coupled to the first coder, which stores the intermediate coded representation;
• a second coder, coupled to the digital storage device, which compresses the stored intermediate coded representation at a selectable compression ratio to form an encoded representation of the data;
• and
• a frame detector coupled to the digital storage device which detects frames having a prediction error which exceeds a predetermined threshold, wherein a representation thereof is stored in the digital storage device.