Patent ID: 9143806
Filing Date: 2015-09-22
Classification: H04N

Abstract:
1. A method of encoding a video stream comprising a plurality of frames, each frame comprising a plurality of image portions, the method comprising: for each target image portion to be encoded, selecting a preferred one of a set of encoding modes by optimizing a function comprising an estimate of distortion and a measure of bit rate required to encode the target image portion, the encoding modes comprising at least an intra frame mode which encodes the target image portion relative to a reference image portion in the same frame, and an inter frame encoding mode which encodes the target image portion relative to a reference image portion in a previously encoded frame, the estimate of distortion being based on a contribution from possible loss over a channel comprising possible loss of the target block, and on a contribution from possible past loss over the channel comprising possible loss in a history of the encoded video stream upon which decoding of the target image portion depends; encoding the target image portion into the encoded video stream using the selected encoding mode; and transmitting the encoded video stream over the lossy channel; accumulating the contribution from past loss over time, such that the estimate of distortion grows irrespective of the contribution from new loss, the estimate of distortion comprising a bias term representing an estimate of distortion that would be experienced due to loss over the channel, the bias term being based on the contributions from possible new and past loss, on a second term representing an estimate of the distortion that would be experienced, if the target image portion arrives over the channel, due to non arrival of a reference portion in the target image portion's history from which prediction of the target image portion depends, and on a concealment term representing an estimate of distortion that would be experienced due to concealment; applying a temporal integration factor to the second term of the accumulated contribution; updating an error propagation distortion map after each encoding mode selection; and determining the error propagation bias term from the error propagation distortion map for use in each respective subsequent encoding mode selection, the bias term being based on an entry in the error propagation distortion map comprising the second term and the concealment term.