Time-scale modification method for digital audio signal and digital audio/video signal, and variable speed reproducing method of digital television signal by using the same method

Abstract

A method capable of ensuring a synchronization between an audio signal and a video signal both of which are modified in time-scale is needed. Solution: When analysis shift Sa = Ss / alpha, where Ss is synthesis shift and alpha is a designated time-scale (variable speed ratio), has a decimal value, two natural numbers which are nearest to the decimal value are selected as a modified analysis shift Sa' and a compensated analysis shift Sa'', respectively. In time-scale modification of source audio samples to vary playback speed by dividing them into overlapped successive analysis windows, the modified analysis shift Sa' and the compensated analysis shift Sa'' are alternately applied whenever a predetermined condition is met. The time difference between an estimated playback time and a real playback time of the time-scale modified audio signal is accumulated. The case that the predetermined condition is met is a case than an accumulated time difference goes beyond an upper threshold or a lower threshold of an allowed error range. In a processing of varying the playback speed of an AV signal, if a real variable speed ratio of a playback-speed-varied video signal is given as a target variable speed ratio of an audio signal to vary the playback speed of the audio signal, a synchronization between the video signal and the audio signal can be obtained. By applying this technology to the digital TV or TV phone, consecutive watch of the broadcasting signal for a phone-break time is possible. Catch-up for the currently received broadcasting signal is also possible through a high speed playback mode after a low speed playback mode initiated from a time of the past or the present.

Description

technical field [0001] The present invention relates to time-scale modification ("TSM") of digital audio signals. In particular, the present invention relates to a timescale modification method in which, after TSM processing, the reproduction time of a digital audio signal can be modified almost precisely in proportion to a predetermined timescale (or variable speed ratio), thereby almost completely Synchronization between video and audio signals is maintained in time-scaled reproduction of multimedia signals. Background technique [0002] Since the introduction of the overlap-add ("OLA") method, a method for modifying the reproduction speed of a digital audio signal in the time domain has been developed into the simultaneous overlap-add ("SOLA") method and based on Superposition and Addition of Waveform Similarity ("WSOLA") methods, both of which are based on OLA. The basic principle of these techniques is to modify the time scale of the original digital audio signal by a...

AI Technical Summary

Problems solved by technology

[0009] However, in the case of timescale modification of a multimedia signal containing video and audio signals, if the timescale of the audio signal is not exactly proportional to the assigned timescale α, the audio and video signals will be out of sync during the reproduction process

The increase in cumulative error in reproduction time will lead to 'lip sync' problems, where the sound does not match the lips

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