Frame-based audio coding with gain-control words

• US 5,899,969 A
• Filed: 10/17/1997
• Issued: 05/04/1999
• Est. Priority Date: 10/17/1997
• Status: Expired due to Term

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Todd, Craig Campbell, Fielder, Louis Dunn
• Primary Examiner(s): Dorvil, Richemond
• Application Number:
  US08/953,324
• Time in Patent Office: 564 Days
• Field of Search: 704/201, 704/229, 704/230, 704/224, 704/225, 704/203, 704/205, 704/206, 704/211, 704/500, 704/501, 704/502, 704/265, 375/240, 375/242, 375/345
• US Class Current: 704/225
• CPC Class Codes: G10L 19/035 Scalar quantisation
• CPC Class Codes: G11B 27/038 Cross-faders therefor
• CPC Class Codes: G11B 27/10 Indexing; Addressing; Timing or synchronising; Measuring tape travel
• CPC Class Codes: H04B 1/667 using a division in frequency subbands for TV signals H04N19/63

Abstract

Several audio signal processing techniques may be used in various combinations to improve the quality of audio represented by an information stream formed by splice editing two or more other information streams. The techniques are particularly useful in applications that bundle audio information with video information. In one technique, gain-control words conveyed with the audio information stream are used to interpolate playback sound levels across a splice. In another technique, special filterbanks or forms of TDAC transforms are used to suppress aliasing artifacts on either side of a splice. In yet another technique, special filterbanks or crossfade window functions are used to optimize the attenuation of spectral splatter created at a splice. In a further technique, audio sample rates are converted according to frame lengths and rates to allow audio information to be bundled with, for example, video information. In yet a further technique, audio blocks are dynamically aligned so that proper synchronization can be maintained across a splice. An example for 48 kHz audio with NTSC video is discussed.

Claims

1. A method for signal processing comprising:

receiving multiple control signals, each control signal associated with a respective channel of multiple audio channels and representing gain information,

receiving an input signal conveying information arranged in frames, a respective frame comprising encoded audio information for said multiple audio channels,

generating for a respective frame of said input signal a plurality of gain-control words in response to each of said control signals, wherein said plurality of gain-control words represent starting and ending gain levels within said respective frame, and

generating an output signal conveying information arranged in frames comprising said audio information and said gain-control words, wherein said output signal has a form suitable for transmission or storage.

2. A method for signal processing comprising:

receiving a control signal,

receiving an input signal conveying information arranged in frames, a respective frame comprising encoded audio information for multiple audio channels and a plurality of input gain-control words,

obtaining from said input signal one or more input gain-control words and modifying one or more of them according to said control signal to generate one or more corresponding modified gain-control words, wherein said one or more modified gain-control words and those input gain-control words not corresponding to said modified gain-control words represent starting and ending gain levels within a respective frame of an output signal, and

generating said output signal conveying information arranged in frames comprising said audio information, said modified gain-control words and input gain-control words that do not correspond to a respective modified gain-control word, wherein said output signal has a form suitable for transmission or storage.

3. A method for signal processing comprising:

receiving an input signal conveying information arranged in frames, a respective frame comprising audio information for multiple audio channels,

obtaining from a frame of said input signal encoded audio information for a respective audio channel and a plurality of gain-control words associated with said respective audio channel, wherein said gain-control words represent starting and ending gain levels within said frame, and

generating an output signal by decoding said encoded audio information, wherein said output signal is effectively modulated according to an interpolation of said starting and ending gain levels.

4. A method according to claim 3 wherein said frame of said input signal comprises encoded audio information arranged in two or more blocks and said generating an output signal includes applying one or more inverse block transforms and subsequently applying one or more synthesis window functions.

5. A method according to claim 4, wherein said output signal is effectively modulated by modifying said blocks of encoded information before application of said transforms.

6. A method according to claim 4, wherein said output signal is effectively modulated by modifying information available after application of said transforms but before application of said synthesis window functions.

7. A method according to claim 3 wherein said interpolation is substantially logarithmic.

8. A device for signal processing comprising:

means for receiving multiple control signals, each control signal associated with a respective channel of multiple audio channels and representing gain information,

means for receiving an input signal conveying information arranged in frames, a respective frame comprising encoded audio information for said multiple audio channels,

means for generating for a respective frame of said input signal a plurality of gain-control words in response to each of said control signals, wherein said plurality of gain-control words represent starting and ending gain levels within said respective frame, and

means for generating an output signal conveying information arranged in frames comprising said audio information and said gain-control words, wherein said output signal has a form suitable for transmission or storage.

9. A device for signal processing comprising:

means for receiving a control signal,

means for receiving an input signal conveying information arranged in frames, a 10 respective frame comprising encoded audio information for multiple audio channels and a plurality of input gain-control words,

means for obtaining from said input signal one or more input gain-control words and modifying one or more of them according to said control signal to generate one or more corresponding modified gain-control words, wherein said one or more modified gain-control words and those input gain-control words not corresponding to said modified gain-control words represent starting and ending gain levels within a respective frame of an output signal, and

means for generating said output signal conveying information arranged in frames comprising said audio information, said modified gain-control words and input gain-control words that do not correspond to a respective modified gain-control word, wherein said output signal has a form suitable for transmission or storage.

10. A device for signal processing comprising:

means for receiving an input signal conveying information arranged in frames, a respective frame comprising audio information for multiple audio channels,

means for obtaining from a frame of said input signal encoded audio information for a respective audio channel and a plurality of gain-control words associated with said respective audio channel, wherein said gain-control words represent starting and ending gain levels within said frame, and

means for generating an output signal by decoding said encoded audio information, wherein said output signal is effectively modulated according to an interpolation of said starting and ending gain levels.

11. A device according to claim 10 wherein said frame of said input signal comprises encoded audio information arranged in two or more blocks and said generating an output signal includes applying one or more inverse block transforms and subsequently applying one or more synthesis window functions.

12. A device according to claim 11, wherein said output signal is effectively modulated by modifying said blocks of encoded information before application of said transforms.

14. A device according to claim 10 wherein said interpolation is substantially logarithmic.

13. A device according to claim I 1, wherein said output signal is effectively modulated by modifying information available after application of said transforms but before application of said synthesis window functions.