Patent ID: 8165224
Filing Date: 2012-04-24
Classification: G06F,H03M,H04L

Abstract:
1. A lost frame concealment method for processing data frames received from transmission over a communications channel, wherein the method comprises: a) determining whether a current data frame is a bad frame; b) performing source decoding on the current data frame with one or more parameters, the one or more parameters being limited by a first set of one or more values if the current data frame is a bad frame; c) performing source decoding on the current data frame with one or more parameters, wherein the one or more parameters are not limited if the current data frame is a good frame; d) determining a value for a channel quality indicator to determine if the condition of the communications channel is good or bad by comparing the value of the channel quality indicator to a threshold if the current data frame is a good data frame and the previous data frame is a bad data frame; e) performing source decoding on the current data frame with one or more parameters, wherein the one or more parameters are not limited if the current data frame is a good data frame, the previous data frame is a bad data frame and the condition of the communications channel is good; and f) performing source decoding on the current data frame with one or more parameters, the one or more parameters being limited by a second set of one or more values if the condition of the communications channel is bad, the current data frame is a good data frame and the previous data frame is a bad data frame, wherein the data frames include speech frames; wherein a state machine is used to indicate the quality of the communications channel, and the method further comprises: q) starting the state machine in state 0; h) incrementing a state counter to enter a subsequent numbered state each time a bad frame is detected, the incrementing being limited to 6; and i) resetting the state counter to zero each time a good speech frame is detected except when in state 6 in which case the state counter is set to 5; and wherein steps (d) to (f) are performed in state 0 or state 5 when the current data frame is a good data frame and the previous data frame is a bad data frame, and step (f) comprises limiting Long Term Prediction (LTP) gain and fixed codebook gain below values used for a last subframe in a last received good speech frame according to:  where g wherein the bad frame is a data frame with an error and the good frame is a data frame with no errors.