US 2007/0168188 A1Published application

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

OwnerWon Choiinventor

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Abstract

Problem: 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/α, where Ss is synthesis shift and α 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.

Claims24

Dependent claims

A time-scale modification method for a digital audio signal, in which an audio sample stream of an input signal is segmented into a plurality of overlapping analysis windows, the length of the overlapping area is changed into a length corresponding to an assigned time-scale α, and the overlapping area is weighted-synthesized to thereby be converted into a time-scaled output signal, the method comprising steps of:

a) defining N+Kmax number of samples starting from the mSath sample (m:
period index) of an input audio sample as an analysis window Wm of current period m, wherein, if a value of a desired synthesis interval Ss divided by the time-scale α is a natural number, the value is assigned as an analysis interval Sa, and if it is a decimal, two natural numbers nearest to the decimal are assigned respectively as a modified analysis interval Sa′ and a compensated analysis interval Sa″, the modified analysis interval Sa′ and the compensated analysis interval Sa″ being alternately applied in place of the analysis interval Sa every time when a certain desired condition is met;
b) calculating a shift value Km of the current period analysis window Wm when exhibiting a highest waveform-similarity between OV number of samples from the end of the output audio sample and OV number of samples of the current period analysis window Wm overlapping therewith, while shifting the starting point of the current period analysis window Wm by a certain predefined number of samples in a search range defined as Kmax number of samples from the OV+1th sample counting from the end of an output signal of previous period m−1;
c) defining N number of samples starting from the Km+1th sample from the front of the current period analysis window Wm as an additional frame to be added to the current period, wherein an output signal of the current period m is synthesized by overlap-adding OV number of samples from the front of the additional frame to OV number of samples from the end of the previous period frame;
and
d) accumulating an error between a real reproduction time of the output signal of the current period m and a computed reproduction time calculated by the time-scale α, wherein, when the accumulated error is deviated from the upper or lower limit of an allowed error range, the certain desired condition is considered as being met.

3 more elements

A time-scale modification method for a digital audio/video signal, in which an input digital audio/video signal is separated into an audio signal and a video signal, each of which is time-scaled with a same time-scale α, the method comprising steps of:

a) calculating periodically a real time-scale of a time-scaled video signal obtained by time-scaling the video signal based on the time-scale α;
b) determining whether a real time-scale of a current period of the time-scaled video signal differs from that of a previous period, wherein, if different, the real time-scale of the current period is provided as a target time-scale α′, the target time-scale α′ becoming a reference for the time-scale modification of the audio signal;
and
c) segmenting a sample stream of the input audio signal into a plurality of overlapping analysis windows, changing the length of the overlapping area into a length corresponding to the target time-scale α′, and weighted-synthesizing the overlapping area, thereby modifying into a time-scaled output audio signal.

1 more element

A method of reproducing a broadcast signal using an apparatus, which receives a transport stream of a digital television broadcast signal compressed and coded in a MPEG mode and reproduces video and audio signals in real-time, the method comprising steps of:

a) storing sequentially a digital television broadcast signal being received in a storage means at least after a user inputs a phone-break key;
b) after the user presses a return key, reading the stored broadcast signal in a FIFO mode and time-scaling the respective retrieved video and audio signals with a predetermine time-scale, wherein, in particular, the time-scaling of the audio signal is performed based on a real time-scale α of the produced video signal, the real time-scale of the video signal obtained by the time-scaling of the video signal being calculated by applying the predetermine time-scale, an audio sample stream of an input signal is segmented into a plurality of overlapping analysis windows, the length of the overlapping area is changed into a length corresponding to the real time-scale α of the video signal, and the overlapping area is weighted-synthesized, thereby converting into a time-scaled output signal;
and
c) outputting the time-scaled video and audio signals in place of a broadcast signal being currently received.

1 more element

a) storing sequentially the broadcast signal in a storage means;
b) when a user's back-and-slow key input is detected, reading the stored broadcast signal in a FIFO mode, starting from a broadcast signal received before a certain period of time from that time point, and time-scaling the respective retrieved video and audio signals with a predetermine time-scale so as to enable a low speed reproduction, wherein, in particular, the time-scaling of the audio signal is performed based on a real time-scale α of the produced video signal, the real time-scale of the video signal obtained by the time-scaling of the video signal being calculated by applying the predetermine time-scale, an audio sample stream of an input signal is segmented into a plurality of overlapping analysis windows, the length of the overlapping area is changed into a length corresponding to the real time-scale α of the video signal, and the overlapping area is weighted-synthesized, thereby converting into a time-scaled output signal;
and
c) outputting the time-scaled video and audio signals in place of a broadcast signal being currently received.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 10/576,519Filed 17 May 2004
Priority: KR 10-2003-007961011 Nov 2003
Published: 19 Jul 2007
Term ends: Not estimatedThe source records don’t support an estimate.

Classification11 codes

G10L 21/04
Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its…:…
G11B 27/005
Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel: reproducing at a different information rate from the…
G11B 27/10
Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel: indexing; Addressing; Timing or synchronising;…
H04N 5/76
Details of television systems: television signal recording