초록 ▼

Error flags are generated for use in source decoding of a source-coded bit stream transmitted through a channel of a communication system. The source-coded bit stream is channel coded using at least one channel code, and the channel code is decoded in a soft-decision channel decoder to generate a re

Error flags are generated for use in source decoding of a source-coded bit stream transmitted through a channel of a communication system. The source-coded bit stream is channel coded using at least one channel code, and the channel code is decoded in a soft-decision channel decoder to generate a received version of the source-coded bit stream and one or more reliability measures associated with a designated portion of the received version of the source-coded bit stream. The reliability measures are processed to generate one or more error flags indicative of the presence of an error in the corresponding portion of the received version of the source-coded bit stream. The invention allows different detection capabilities to be used for different portions of the received version of the source-coded bit stream, and further allows these detection capabilities to be changed dynamically at the receiver. The error flags may be used to trigger an error mitigation/concealment algorithm in the source decoder. Advantageously, the error flags can be matched to frames or subframes of the source-coded bit stream, such that the performance of the error mitigation/concealment algorithm is substantially improved relative to its performance when using error flags generated from a conventional outer block code.

대표청구항 ▼

1. A method of generating error flags for use in source decoding of a source-coded bit stream transmitted through a channel of a communication system using at least one channel code, the method comprising the steps of:decoding the channel code using a soft-decision channel decoder to generate a rece

1. A method of generating error flags for use in source decoding of a source-coded bit stream transmitted through a channel of a communication system using at least one channel code, the method comprising the steps of:decoding the channel code using a soft-decision channel decoder to generate a received version of the source-coded bit stream and one or more reliability measures associated with a portion of the received version of the source-coded bit stream; andprocessing the reliability measures to generate one or more error flags indicative of the presence of an error in the corresponding portion of the received version of the source-coded bit stream, wherein the error flags are utilized in a source decoder in conjunction with source decoding of the received version of the source-coded bit stream. 2. The method of claim 1 wherein the one or more error flags are utilized to trigger an error mitigation/concealment algorithm in the source decoder. 3. The method of claim 1 wherein at least a subset of the reliability measures generated by the soft-decision channel decoder comprise a posteriori probabilities for each of a plurality of bits or symbols in the portion of the received version of the source-coded bit stream. 4. The method of claim 1 wherein at least a subset of the reliability measures generated by the soft-decision channel decoder comprise log-likelihood ratios for each of a plurality of bits or symbols in the portion of the received version of the source-coded bit stream. 5. The method of claim 1 wherein the soft-decision channel decoder implements a forward-backward decoding algorithm. 6. The method of claim 1 wherein the soft-decision channel decoder comprises a soft-decision Viterbi decoder. 7. The method of claim 1 wherein the reliability measures for each decoded bit or symbol in the portion of the received source-coded bit stream are checked against a threshold, and if any one of the bits or symbols have reliability measures below the threshold, an error flag is generated for the portion. 8. The method of claim 1 wherein the reliability measures for one or more designated least reliable bits or symbols in the portion are compared to the reliability measures for one or more designated most reliable bit or symbols in the portion, and an error flag is generated for the portion based on the comparison. 9. The method of claim 1 wherein an error flag is generated for a first portion of the received version of the source-coded bit stream by checking corresponding reliability measures against a first threshold and an error flag is generated for a second portion of the received version of the source-coded bit stream by checking corresponding reliability measures against a second threshold. 10. The method of claim 1 wherein error flags are generated for different portions of the received version of the source-coded bit stream by checking corresponding reliability measures against thresholds which are dynamically adapted to characteristics of the different portions. 11. The method of claim 1 wherein each of the error flags is matched to a frame of the source-coded bit stream. 12. The method of claim 1 wherein each of the error flags is matched to a subframe of the source-coded bit stream. 13. The method of claim 1 wherein the at least one channel code comprises an inner channel concatenated code. 14. The method of claim 1 wherein the at least one channel code comprises inner channel trellis coded modulation. 15. The method of claim 1 wherein the channel code comprises an inner channel convolutional code. 16. The method of claim 1 wherein the source-coded bit stream comprises at least one of audio, speech, image and video information. 17. An apparatus for use in decoding of a source-coded bit stream transmitted through a channel of a communication system using at least one channel code, the apparatus comprising:a soft-decision channel decoder for decoding the channel code to generate a received version of the source-code d bit stream and one or more reliability measures associated with a portion of the received version of the source-coded bit stream; anda source decoder having an input coupled to an output of the soft-decision channel decoder and being operative to process the reliability measures to generate one or more error flags indicative of the presence of an error in the corresponding portion of the received version of the source-coded bit stream, wherein the error flags are utilized in the source decoder in conjunction with source decoding of the received version of the source-coded bit stream. 18. An apparatus for use in decoding of a source-coded bit stream transmitted through a channel of a communication system using at least one channel code, the channel code being decoded in a soft-decision channel decoder to generate a received version of the source-coded bit stream and one or more reliability measures associated with a portion of the received version of the source-coded bit stream, the apparatus comprising:a source decoder operative to process the reliability measures to generate one or more error flags indicative of the presence of an error in the corresponding portion of the received version of the source-coded bit stream, wherein the error flags are utilized in the source decoder in conjunction with source decoding of the received version of the source-coded bit stream. 19. An article of manufacture for storing one or more software programs for use in decoding of a source-coded bit stream transmitted through a channel of a communication system using at least one channel code, the channel code being decoded in a soft-decision channel decoder to generate a received version of the source-coded bit stream and one or more reliability measures associated with a portion of the received version of the source-coded bit stream, wherein the one or more programs when executed implement the step of:processing the reliability measures to generate one or more error flags indicative of the presence of an error in the corresponding portion of the received version of the source-coded bit stream, wherein the error flags are utilized in a source decoder in conjunction with source decoding of the received version of the source-coded bit stream.