Patent ID: 7382926
Filing Date: 2008-06-03
Classification: H04N

Abstract:
1. A method for transcoding a compressed image from a first resolution and first bit-rate to a lower or equal second resolution and lower or equal second bit-rate, said compressed image including a collection of sub-bands encoded in one or more coding passes into a compressed bit-stream of quantized sub-band coefficients partitioned into codeblocks of each sub-band and aggregated into packets and further aggregated into a set of layers, said method comprising the steps of: calculating the number of bytes associated with each of the layers at said second resolution to produce a layer byte-count table; estimating a subset of layers to be decoded up to the second resolution at the second bit-rate; extracting compressed data corresponding to each included codeblock, from the packets in the subset of layers, belonging to resolutions up to the second resolution; concatenating the compressed data corresponding to each said included codeblock to produce a compressed codeblock bit-stream for each said codeblock; producing coding pass inclusion information, which represents the coding passes that should be included in a transcoded bit-stream to be generated, utilizing the second bit-rate; and generating the transcoded bit-stream from each said compressed codeblock bit-stream and respective said coding pass inclusion information.