Patent DE548715C successfully refreshed from Google Patents.
Patent EP0681398A2 successfully refreshed from Google Patents.
EP0681398A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Synchronised, variable speed playback of digitally recorded audio and video
Assignee: International Business Machines Corp
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Filing: 1995-04-12
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Granted: —
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Expires: 2015-04-12
Abstract
Abstract Method and system for providing user-controlled, continuous, synchronized variable-speed playback of a previously recorded digital audio/video presentation. The user directly controls the rate of playback and the audio and video remain synchronized. The audio is expanded or compressed using the time domain harmonic scaling method so that the pitch of the audio remains undistorted. Synchronization is maintained by allowing one clock to serve as the master time clock for the system. The clocks which can serve as the master time clock include the audio decoder clock, the video decoder clock, and the system clock. The invention is particularly useful in multimedia display systems designed to display MPEG data. <IMAGE>
Inventors
- 👤 Malcolm S. Ware
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 21:58
CPC Classifications
H; H04; H04N; H04N21/00; H04N21/40; H04N21/43; H04N21/434; H04N21/4341; G; G11; G11B; G11B20/00; G10; G10H; G10H1/00; G10H1/0033; G10H1/36; G10H1/361; G10H1/368; G11B20/00007; G11B20/10; G11B20/10527; G11B27/00; G11B27/005; G11B27/10; H04N21/4302; H04N21/4307; H04N21/43072; H04N21/47; H04N21/472; H04N21/47217; H04N5/00; H04N5/04; H04N5/06; H04N5/067; H04N5/073; H04N5/76; H04N5/78; H04N5/782; H04N5/783; H04N5/91; H04N5/93; H04N5/937; H04N7/00; H04N7/24; H04N7/52; H04N7/54; H04N7/56; G10H2240/00; G10H2240/011; G10H2240/046; G10H2240/066; G10H2250/00; G10H2250/541; G10H2250/571; G11B20/14; G11B2020/10537; G11B2020/10546; G11B2020/10555; G11B2020/1062; G11B2020/10629; G11B2020/10638; G11B2020/10805; G11B2020/10814; G11B2220/00; G11B2220/20; G11B2220/25; G11B2220/2537; H04N5/44; H04N5/60; H04N5/602; H04N5/84; H04N5/85; H04N9/00; H04N9/79; H04N9/80; H04N9/804; H04N9/8042
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
231 words
A method of maintaining synchronization of a stream of digital audio data with a stream of digital video data originally recorded at a specified rate in frames per second, FPS, the digital video data being played back on a variable-speed audio/video display system using a selected scaling factor, RV, which is set to a proportional value of the recorded rate, comprising the steps of: placing at least 2 frames of digital audio in an audio buffering means and at least 2 frames of digital video in a video buffering means; setting an audio scaling factor, C, equal to the selected scaling factor, RV; calculating an amount of time, T, required to play back an audio frame with the selected audio scaling factor C; decoding and displaying, if the video buffering means is not empty, a frame of video from the video buffering means for T seconds; decoding, scaling and playing, if the audio buffering means is not empty, an audio frame from the audio buffering means using the scaling factor C so that playback of the audio frame requires an audio playback time period approximately equal to T; reading, after T seconds, and if the end of the data streams has not been reached, another frame from the stream of digital audio into the audio buffering means and another frame from the stream of digital video into the video buffering means;
Claim 2
Dependent Claim
75 words
The method of claim 1 further comprising the following steps: determining whether the audio playback time period of the audio frame played during the preceding time period T was exactly equal to T seconds; adjusting the value C if the audio playback time period was not exactly equal to T seconds; and recalculating the time T if the time domain harmonic scaling factor C has changed since the beginning of the preceding time period T.
Claim 3
Dependent Claim
126 words
The method of claim 1 further comprising the following steps: determining whether the audio buffering means is approaching an underflow condition because the audio playback time period is less than T seconds; if the audio buffering means is approaching an underflow condition, recalculating the scaling factor C according to an equation C = C - A, where A is an audio adjustment factor which is set to a fractional value of C that is large enough to prevent underflow and overflow of the audio buffering means, and small enough so that changes in playback speed are perceived as gradual by a user; and recalculating the time T if the time domain harmonic scaling factor C has changed since the beginning of the preceding time period T.
Claim 4
Dependent Claim
134 words
The method according to claim 1 further comprising the steps of: determining whether the audio buffering means is approaching an overflow condition because the audio playback time period is more than T seconds; and the adjusting step comprises the following step: if the audio buffering means is approaching an overflow condition, recalculating the scaling factor C according to an equation C = C + A, where A is an audio adjustment factor which is set to a fractional value of C that is large enough to prevent underflow and overflow of the audio buffering means, but small enough so that changes in playback speed are perceived as gradual by a user. recalculating the time T if the time domain harmonic scaling factor C has changed since the beginning of the preceding time period T.
Claim 5
Independent Claim
238 words
A method of maintaining synchronization of a stream of digital video data with a stream of digital audio data originally recorded at a specified rate in frames per second in a variable-speed, digital audio/video playback system having an audio buffering means for storing at least 2 frames of digital audio and a video buffering means for storing at least 2 frames of digital video, and where an audio frame comprises samples recorded in a fixed period of time corresponding to an associated video frame recording rate in frames per second, comprising the steps of: reading a value for a user-selected audio scaling factor, C, where C is a proportion of the originally recorded specified rate; decoding, scaling and playing, if the audio buffering means is not empty, an audio frame from the audio buffering means using the scaling factor C so that playback of the audio frame requires an audio playback time period inversely proportional to C; decoding and displaying, if the video buffering means is not empty, a frame of video from the video buffering means which corresponds to the currently playing audio frame, for a time period equal to the audio playback time period; and reading a frame of video from the video data stream into the video buffering means and a frame of audio from the audio data stream into the audio buffering means if the end of the data streams has not been reached.
Claim 6
Dependent Claim
58 words
The method according to claim 5, further comprising the step of: re-reading the value of the user-selected audio scaling factor C in preparation for scaling and playing another audio frame from the audio buffering means if the user-selected value to be assigned to C has been changed since the start of the immediately preceding audio playback time period.
Claim 7
Dependent Claim
248 words
A digital audio/video playback system for playing digitally encoded, simultaneous audio and video at variable speeds while maintaining synchronization between the audio and video, comprising: means for receiving digital audio data and digital video data from a source; video buffering means capable of holding at least two frames of video, the video buffering means connected to the receiving means; audio buffering means capable of holding at least two frames of audio, the audio buffering means connected to the receiving means; means for displaying a plurality of video frames in succession; means for generating sounds from electronic signals; and apparatus for maintaining synchronization during playback of the audio data stream with the video data stream, where the video data stream is being played using a selected scaling factor, RV, which is set to a proportional value of the originally recorded rate, the apparatus being disposed between the audio and video buffering means and the generating and displaying means, the apparatus including: means for calculating an amount of time, T, required to play back an audio frame with an audio scaling factor C, where C is initially set to equal RV; means for decoding a frame of video from the video buffering means and sending the frame of video to the display means; and means for decoding, scaling and playing an audio frame from the audio buffering means using the scaling factor C so that playback of the audio frame requires an audio playback time period approximately equal to T.
Claim 8
Dependent Claim
103 words
The system of claim 7 wherein the apparatus for maintaining synchronization during playback further includes: means for determining whether the audio buffering means is approaching an underflow condition because the audio playback time period is less than T seconds; and means for recalculating scaling factor C according to an equation C = C - A, where A is an audio adjustment factor which is set to a fractional value of C that is large enough to prevent underflow and overflow of the audio and video buffering means, but small enough so that changes in playback speed are perceived as gradual by a user.
Claim 9
Dependent Claim
102 words
The system of claim 7 wherein the apparatus for maintaining synchronization during playback further includes: means for determining whether the audio buffering means is approaching an overflow condition because the audio playback time period is more than T seconds; and means for recalculating the scaling factor C according to an equation C = C + A, where A is an audio adjustment factor which is set to a fractional value of C that is large enough to prevent underflow and overflow of the audio buffering means, but small enough so that changes in playback speed are perceived as gradual by a user.
Claim 10
Dependent Claim
263 words
A digital audio/video playback system for playing digitally encoded, simultaneous audio and video at variable speeds while maintaining synchronization between the audio and video, comprising: means for receiving digital audio data and digital video data from a source; video buffering means capable of holding at least two frames of video, the video buffering means connected to the receiving means; audio buffering means capable of holding at least two frames of audio, the audio buffering means connected to the receiving means; means for displaying a plurality of video frames in succession; means for generating sounds from electronic signals; and apparatus for maintaining synchronization of a stream of digital video data with a stream of digital audio data originally recorded at a specified rate in frames per second where each audio frame comprises samples recorded in a fixed period of time corresponding to an associated video frame recording rate in frames per second, the apparatus disposed between the audio and video buffering means and the generating and displaying means, the apparatus including: means for reading a value for a user-selected audio scaling factor, C, where C is a proportion of the originally recorded specified rate; means for decoding, scaling and playing an audio frame from the audio buffering means using the scaling factor C so that playback of the audio frame requires an audio playback time period inversely proportional to C; and means for decoding and displaying a frame of video from the video buffering means which corresponds to the currently playing audio frame, for a time period equal to the audio playback time period.
Claim 11
Independent Claim
186 words
A system for providing synchronized display of video and audio data, a synchronized rate being set by a scaling factor input which may be varied, the system for being connected to a source of synchronized digital audio and video data, comprising: means for buffering digital video data received from the source; system clocking means, the system clocking means being controlled by the scaling factor input; means, connected to the digital video buffering means, for outputting the digital video data to a video display, the rate of the outputting being controlled by the system clocking means; means for buffering digital audio data from the source; means, connected to the digital audio buffering means, for scaling and outputting the digital audio data to a sound generating means, the digital audio data outputting means controlling the scaling and the output rate of the digital audio data based upon the system clocking means so that the output of the scaled, digital audio data is in synchronism with the output of the digital video data; means for connection to a sound generating means; and means for connection to a video display.
References Cited (Backward Citations)
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