Audio reproducing apparatus having voice speed converting function

• US 5,809,454 A
• Filed: 06/28/1996
• Issued: 09/15/1998
• Est. Priority Date: 06/30/1995
• Status: Expired due to Term

• Current Assignee: Godo Kaisha IP Bridge 1 (IP Bridge, Inc.)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Tanaka, Hiroshi, Iida, Masayuki, Okada, Shigeyuki, Yamauchi, Hideki
• Primary Examiner(s): Hudspeth, David R.
• Assistant Examiner(s): MCFADDEN, SUSAN IRIS
• Application Number:
  US08/678,370
• Time in Patent Office: 809 Days
• Field of Search: 395/2.16, 395/2.17, 395/2.19, 395/2.2, 395/2.23, 395/2.24, 395/2.69, 395/2.85, 395/2.87, 395/2.94, 395/806, 395/807, 704/207, 704/208, 704/210, 704/211, 704/214, 704/215, 704/260, 704/276, 704/278, 704/503
• US Class Current: 704/214
• CPC Class Codes: G10L 21/04 Time compression or expansion
• CPC Class Codes: G11B 20/00007 Time or data compression or expansion audio compression based on psychoacoustics G10L19/00; data processing for reproducing audio data at different playback speeds G10L21/04; video compression H04N19/00; data compression per se H03M7/30
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: G11B 2220/20 Disc-shaped record carriers
• CPC Class Codes: G11B 27/005 Reproducing at a different information rate from the information rate of recording for television signals H04N5/783

Abstract

A audio reproducing apparatus includes an audio decoder and a voice speed converting unit. The audio decoder decodes an audio data stream to produce an audio signal. The voice speed converting unit converts the audio signal in such a manner that when a bit rate is higher than a normal bit rate, a pitch of a reproduced sound interval is the same as the pitch of the sound interval in a normal playback mode and a voice speed in the reproduced sound interval approaches a voice speed in a sound interval in the normal playback mode. The voice speed converting unit further performs voice speed conversion on the audio signal in such a manner that when the bit rate is lower than the normal bit rate, the sound interval is not noticeably interrupted.

Claims

1. An audio reproducing apparatus comprising:

an audio decoder for decoding an audio data stream to produce an audio signal, said audio data stream having a higher or lower bit rate than a normal bit rate; and

a voice speed converting unit receiving said audio signal and performing voice speed conversion on said audio signal, wherein said voice speed converting unit performs voice speed conversion on said audio signal such that when said bit rate is higher than said normal bit rate, a pitch of a first reproduced sound interval based on said higher bit rate is substantially the same as a pitch of a second reproduced sound interval in a normal playback mode and a voice speed in said first reproduced sound interval approaches a voice speed in a sound interval in said normal playback mode, and when said bit rate is lower than said normal bit rate, a time length of at least one of a third reproduced sound interval based on said lower bit rate and a soundless interval is selectively adjusted.

2. The audio reproducing apparatus according to claim 1, said voice speed converting unit further comprising:

a memory for storing said audio signal; and

a detector for detecting an amount of said audio signal stored in said memory;

wherein said voice speed converting unit performs voice speed conversion on said audio signal by adjusting a time length of said first and third sound intervals in accordance with said storage amount of said audio signal in said memory.

3. An audio reproducing apparatus comprising:

an audio decoder for decoding an audio data stream to produce an audio signal, said audio data stream having a higher or lower bit rate than a normal bit rate, said signal including a plurality of sound intervals and at least one soundless interval; and

a voice speed converting unit for receiving said audio signal and performing voice speed conversion on said audio signal;

wherein said voice speed converting unit performs first voice speed conversion on said audio signal when said bit rate is higher than said normal bit rate, such that a time length of a sound interval reproduced is expanded and time lengths of individual soundless intervals are shortened, and performs second voice speed conversion on said audio signal when said bit rate is lower than said normal bit rate, said second voice speed conversion being such that individual ones of said sound intervals are linked by eliminating any of said individual soundless intervals that are between said individual ones of said sound intervals and a soundless interval is inserted after a sound interval resulting from said linkage.

4. The audio reproducing apparatus according to claim 3, said voice speed converting unit further comprising:

a memory for storing said audio signal; and

a detector for detecting an amount of said audio signal stored in said memory,

wherein said voice speed converting unit performs voice speed conversion on said audio signal by adjusting one of a compression ratio of said time length of said sound interval and an expansion ratio of said time length of said sound interval in accordance with said storage amount of said audio signal in said memory.

5. The audio reproducing apparatus according to claim 3, said voice speed converting unit further comprising:

a memory for storing said audio signal;

a detector for detecting an amount of said audio signal stored in said memory;

a voice determining circuit for determining a sound interval and a soundless interval included in said audio signal;

a soundless interval deleting/inserting circuit for eliminating and inserting said soundless interval; and

a compressor/expander for performing one of compression of said time length of said sound interval and expansion of said time length of said sound interval in accordance with said storage amount of said audio signal in said memory.

6. An audio/video reproducing apparatus for reproducing an audio signal and a video signal from a system bit stream, comprising:

an audio decoder for decoding an audio data stream contained within the system bit stream to produce said audio signal, said audio data stream having a higher or lower bit rate than a normal bit rate;

a voice speed converting unit for receiving said audio signal and performing voice speed conversion on said audio signal;

wherein said voice speed converting unit performs voice speed conversion such that when said bit rate is higher than said normal bit rate, a pitch of a first reproduced sound interval based on said higher is the same as a pitch of a second reproduced sound interval in a normal playback mode, and a voice speed in said first reproduced sound interval approaches a voice speed in a sound interval in said normal playback mode, and when said bit rate is lower than said normal bit rate, a time length of at least one of a third reproduced sound interval and a soundless interval is selectively adjusted; and

a video decoder for decoding a video data stream contained within the system bit stream to produce a video signal.

7. The audio/video reproducing apparatus according to claim 6, said voice speed converting unit further comprising:

a memory for storing said audio signal; and

a detector for detecting an amount of said audio signal stored in said memory,

wherein said voice speed converting unit performs voice speed conversion on said audio signal by adjusting a time length of said sound interval in accordance with said storage amount of said audio signal in said memory.

8. The audio/video reproducing apparatus according to claim 7, further comprising:

an index adding circuit for adding an index signal as information associated with time to said audio signal before said audio signal is stored in said memory; and

an index detector for detecting said index signal added to said audio signal read from said memory, detecting a signal delay time in said voice speed converting unit from time information acquired from said index signal and current time information, and supplying a signal indicating said signal delay time to said video decoder,

wherein said video decoder controls a self-operation timing based on said signal indicating said signal delay time.

9. The audio/video reproducing apparatus according to claim 7, further comprising:

a control circuit for generating a control signal to synchronize said audio signal undergone voice speed conversion with said video signal in accordance with said storage amount of said audio signal in said memory,

wherein said video decoder controls a self-operation timing in accordance with said control signal.

10. An audio/video reproducing apparatus for reproducing an audio signal and a video signal from a system bit stream, comprising:

an audio decoder for decoding an audio data stream contained within the system bit stream to produce said audio signal, said audio data stream having a higher or lower bit rate than a normal bit rate, said audio signal including a sound interval and a soundless interval;

a voice speed converting unit for receiving said audio signal and performing voice speed conversion on said audio signal;

wherein said voice speed converting unit performs first voice speed conversion on said audio signal when said bit rate is higher than said normal bit rate, such that a time length of a sound interval reproduced is expanded and time lengths of individual soundless intervals are shortened, and performs second voice speed conversion on said audio signal when said bit rate is lower than said normal bit rate, said second voice speed conversion being such that individual ones of said sound intervals are linked by eliminating any of said individual soundless intervals that are between said individual ones of said sound intervals and a soundless interval is inserted after a sound interval resulting from said linkage; and

a video decoder for decoding a video data stream contained within the system bit stream to produce a video signal.

11. The audio/video reproducing apparatus according to claim 10, said voice speed converting unit further comprising:

a memory for storing said audio signal; and

a detector for detecting an amount of said audio signal stored in said memory,

wherein said voice speed converting unit performs voice speed conversion on said audio signal by performing one of compression of said time length of said sound interval and expansion of said time length of said sound interval in accordance with said storage amount of said audio signal in said memory.

12. The audio/video reproducing apparatus according to claim 11, further comprising:

an index adding circuit for adding an index signal as information associated with time to said audio signal before said audio signal is stored in said memory; and

an index detector for detecting said index signal added to said audio signal read from said memory, detecting a signal delay time in said voice speed converting unit from time information acquired from said index signal and current time information, and supplying a signal indicating said signal delay time to said video decoder,

wherein said video decoder controls a self-operation timing based on said signal indicating said signal delay time.

13. The audio/video reproducing apparatus according to claim 11, further comprising:

a control circuit for generating a control signal to synchronize said audio signal after having undergone voice speed conversion with said video signal in accordance with said storage amount of said audio signal in said memory,

wherein said video decoder controls a self-operation timing in accordance with said control signal.

14. The audio/video reproducing apparatus according to claim 10, said voice speed converting unit further comprising:

a memory for storing said audio signal;

a detector for detecting an amount of said audio signal stored in said memory;

a voice determining circuit for determining a sound interval and a soundless interval included in said audio signal;

a soundless interval deleting/inserting circuit for eliminating and inserting said soundless interval; and

a compressor/expander for performing one of compression of said time length of said sound interval and expansion of said time length of said sound interval in accordance with said storage amount of said audio signal in said memory.

15. The audio/video reproducing apparatus according to claim 14, further comprising:

an index adding circuit for adding an index signal as information associated with time to said audio signal before said audio signal is stored in said memory; and

an index detector for detecting said index signal added to said audio signal read from said memory, detecting a signal delay time in said voice speed converting unit from time information acquired from said index signal and current time information, and supplying a signal indicating said signal delay time to said video decoder,

wherein said video decoder controls a self-operation timing based on said signal indicating said signal delay time.

16. The audio/video reproducing apparatus according to claim 14, further comprising:

a control circuit for generating a control signal to synchronize said audio signal after having undergone voice speed conversion with said video signal in accordance with said storage amount of said audio signal in said memory,

wherein said video decoder controls a self-operation timing in accordance with said control signal.

17. The audio/video reproducing apparatus according to claim 14, further comprising:

a delay time detector for detecting a signal delay time in said voice speed converting unit based on a determination result from said voice determining circuit and said bit rate of said audio data stream, and supplying a detection signal indicative of said detected delay time to said video decoder,

wherein said video decoder controls a self-operation timing to synchronize said audio signal after having undergone voice speed conversion with said video signal in accordance with said detection signal.

18. The audio/video reproducing apparatus according to claim 14, further comprising:

a delay time detector for detecting a signal delay time in said voice speed converting unit based on a determination result from said voice determining circuit and a result of processing in said compressor/expander, and supplying a detection signal indicative of said detected delay time to said video decoder,

wherein said video decoder controls a self-operation timing to synchronize said audio signal after having undergone voice speed conversion with said video signal in accordance with said detection signal.