Method and device for hiding throw-away frame

Abstract

The invention is concerned with the losing-frame hiding equipment and the method, it is: gets the current losing-frame pitch period by the last good frame pitch period before losing frame, recovers the current losing-frame excitation signal by the latest good frame excitation signal, reduces the sensation contrast of the receiver, improves the sound quality. The invention can avoid the buzzing effect creating by continuous losing-frame, improve the sound quality; process energy attenuation for the excitation signal, reduce the audition contrast of the receiver.

Description

technical field [0001] The invention relates to the technical field of speech codec, in particular to a frame loss concealment device and method. Background technique [0002] Voice over IP (VoIP) implements voice communication through voice compression and encoding, packetization, distribution routing, storage switching, and unpacking and decompression on the IP network or the Internet. Coding technology is the key technology of IP voice. Coding technology is divided into waveform coding, parametric coding and hybrid coding. When using waveform coding, it is not suitable for occasions with tight bandwidth because it occupies a large bandwidth. [0003] In order to improve the transmission efficiency of voice over IP in the case of limited bandwidth, the industry proposes a low-rate codec method. The Telecommunication Standardization Part of the International Telecommunication Union (ITU_T) published the telephone bandwidth speech signal coding standard in March 1996: In th...

AI Technical Summary

Problems solved by technology

[0005] However, when IP packets are transmitted in the network, they cannot avoid being damaged during transmission, or being discarded due to network congestion, or lost due to network failure, or simply because they arrive at the receiving end too late to be included in the replayed voice. Frame loss is the main reason for voice quality degradation in network transmission

The lost IP frame cannot be reproduced at the decoding end. When one frame or several consecutive adjacent frame codebooks are lost, the CS-ACELP decoder faces two problems: losing all symbols contained in a group of sequentially arranged excitation signals, At this time, it is necessary to calculate the alternative excitation signal that can produce the minimum speech quality distortion and smooth transition; when the frame is lost, all the original adaptive codebook parameters, short-term linear prediction filter coefficients and gains will be lost, due to the adoption of G.729 Adaptive coding method, so when the next good frame is received, it takes a certain period of time for the speech signal to converge

[0021] The method shown in Figure 2 uses the pitch delay of the last good frame before the frame loss to estimate the pitch delay of the current frame loss, and fully uses the adaptive code according to whether the last good frame before the frame loss is speech or non-speech. Using the fixed codebook to restore the excitation signal of the lost frame can achieve better compensation in terms of the physiological characteristics of the speech, but when the network condition is poor, the compensation effect will drop rapidly; at the same time, due to the recovery of the excitation signal Signals only take adaptive codebook excitation or fixed codebook excitation, and the fixed codebook excitation is just a random number. Any frame loss will cause a large deviation in the recovered excitation signal. The higher the frame loss rate, the deviation The larger the , the greater the fluctuation of the signal energy before and after frame loss, which makes the receiver's subjective perception contrast larger

Generally, when the frame loss rate is below 2%, this method can achieve satisfactory results, and when the frame loss rate exceeds 2%, the effect is not satisfactory

Images