Interpolative variable frame rate transmission of speech features for distributed speech recognition

In distributed speech recognition, vector quantization is used to reduce the number of bits for coding speech features at the user end in order to save energy for transmitting speech feature streams to remote recognizers and reduce data traffic congestion. We notice that the overall bit rate of the transmitted feature streams could be further reduced by not sending redundant frames that can be interpolated at the remote server from received frames. Interpolation introduces errors and may degrade speech recognition. This paper investigates the methods of selecting frames for transmission and the effect of interpolation on recognition. Experiments on a large vocabulary recognizer show that with spline interpolation, the overall frame rate for transmission can be reduced by about 50% with a relative increase in word error rate less than 5.2% for clean and noisy speech.