Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1998-10-08
2001-09-18
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S047320
Reexamination Certificate
active
06292454
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to data reproduction systems, and relates more particularly to an apparatus and method for implementing a variable-speed audio data playback system.
2. Description of the Background Art
Implementing an effective and efficient method for the playback of audio data is a significant consideration of designers, manufacturers, and users of contemporary audio systems. Modem audio playback systems are typically required to accurately reproduce various types of audio data. For example, a digital video-disc device may be utilized to reproduce recordings of motion picture soundtracks that include various combinations of voice, music and background sounds. Current advances in digital audio technology have further increased the importance of preserving high sound quality in any audio playback system.
One special playback technique that may be advantageously used in many audio devices is a variable-speed playback function. For example, a system user may wish to use a program search mode to rapidly shuttle forward at double the normal playback speed in order to quickly locate a particular remote point in the recorded program. To facilitate locating the desired point in the recorded program, the system user typically aurally monitors the audio playback during variable-speed playback mode. The playback sound quality that is available during the variable-speed playback mode is therefore a significant performance factor that can enhance the efficiency and user-friendliness of such an audio reproduction system.
Some audio reproduction systems include variable-speed playback modes that simply provide the audio data to the listener at a higher rate of speed. For example, if such a system featured a double-speed playback mode, then the reproduced audio program would be played back at twice the originally-recorded speed, and the pitch of the audio program would be similarly doubled. This rapid playback speed and the corresponding distorted audio program result in substantially decreased performance for the system user.
Other audio reproduction systems feature variable-speed playback modes that produce the audio program with various types of sound artifacts. For example, some of the sound artifacts present in selected variable-speed audio devices include clicking-type sounds and warbling sound distortion. In spite of the difficulties encountered, variable-speed playback functionality remains a beneficial and important feature for enhanced operation of contemporary audio playback systems. Therefore, for all the foregoing reasons, an improved method is needed for implementing a variable-speed audio data playback system.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus and method are disclosed for implementing a variable-speed audio data playback system. In the variable-speed mode of one embodiment of the present invention, a post-processor initially stores the first two frames (frame
1
and frame
2
) of audio data into a first buffer. Then, the post-processor stores the next two frames (frame
3
and frame
4
) of audio data into a second buffer
2
.
Next, the post-processor analyzes the audio data and locates a maximum crosscorrelation lag “L” between a source frame (initially, frame
2
) and a destination frame (initially, frame
3
). The maximum crosscorrelation lag “L” represents the point of maximum similarity between the source frame and the destination frame. The processor then performs a synchronized crossfading procedure between the source frame and the destination frame starting at the previously-determined maximum crosscorrelation lag “L”. The post-processor preferably performs the synchronized crossfading procedure by decreasing the amplitude of the source frame while simultaneously increasing the amplitude of the destination frame.
Then, the post-processor discards any unnecessary audio data, and outputs those frames that have just completed the synchronized crossfading procedure to a playback system for reproduction. Next, the post-processor determines whether any unprocessed (uncrossfaded) frames of audio data remain for the variable-speed playback mode. If unprocessed frames of audio data remain for the variable-speed playback mode, then the post-processor repeatedly returns and performs another synchronized crossfade on the next two frames of audio data until the variable-speed mode is terminated or all audio data has been processed. The present invention thus efficiently and effectively removes unneccessary audio data to implement a variable-speed audio data playback system and thereby provide high-quality sound reproduction to a system user.
REFERENCES:
patent: 5341432 (1994-08-01), Suzuki et al.
patent: 5543927 (1996-08-01), Herz
patent: 5671318 (1997-09-01), Herz
patent: 0371717 (1990-06-01), None
patent: 0525544 (1993-02-01), None
patent: 09073299 (1997-03-01), None
patent: 2320791 (1998-07-01), None
patent: 9825405 (1998-06-01), None
Salim Roucos and Alexander M. Wilgus, “High Quality Time-Scale Modification for Speech”, Aug. 1985.
Huber Paul W.
Koerner Gregory J.
Simon & Koerner LLP
Sony Corporation
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