Data framing for adaptive-block-length coding system
First Claim
1. A method for audio encoding that comprises steps performing the acts of:
- receiving a reference signal conveying alignment of video information frames in a sequence of video information frames in which adjacent frames are separated by a frame interval;
receiving an audio signal conveying audio information;
analyzing the audio signal to identify characteristics of the audio information;
generating a control signal in response to the characteristics of the audio information, wherein the control signal conveys segment lengths for segments of the audio information in a sequence of overlapping segments, a respective segment having a respective overlap interval with an adjacent segment and the sequence having a length equal to the frame interval plus a frame overlap interval;
applying an adaptive block encoding process to the overlapping segments in the sequence to generate a plurality of blocks of encoded information, wherein the block encoding process adapts in response to the control signal; and
assembling the plurality of blocks of encoded information and control information conveying the segment lengths to form an encoded information frame that is aligned with the reference signal.
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Accused Products
Abstract
An audio encoder applies an adaptive block-encoding process to segments of audio information to generate frames of encoded information that are aligned with a reference signal conveying the alignment of a sequence of video information frames. The audio information is analyzed to determine various characteristics of the audio signal such as the occurrence and location of a transient, and a control signal is generated that causes the adaptive block-encoding process to encode segments of varying length. A complementary decoder applies an adaptive block-decoding process to recover the segments of audio information from the frames of encoded information. In embodiments that apply time-domain aliasing cancellation (TDAC) transforms, window functions and transforms are applied according to one of a plurality of segment patterns that define window functions and transform parameters for each segment in a sequence of segments. The segments in each frame of a sequence of overlapping frames may be recovered without aliasing artifacts independently from the recovery of segments in other frames. Window functions are adapted to provide preferred frequency-domain responses and time-domain gain profiles.
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Citations
32 Claims
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1. A method for audio encoding that comprises steps performing the acts of:
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receiving a reference signal conveying alignment of video information frames in a sequence of video information frames in which adjacent frames are separated by a frame interval;
receiving an audio signal conveying audio information;
analyzing the audio signal to identify characteristics of the audio information;
generating a control signal in response to the characteristics of the audio information, wherein the control signal conveys segment lengths for segments of the audio information in a sequence of overlapping segments, a respective segment having a respective overlap interval with an adjacent segment and the sequence having a length equal to the frame interval plus a frame overlap interval;
applying an adaptive block encoding process to the overlapping segments in the sequence to generate a plurality of blocks of encoded information, wherein the block encoding process adapts in response to the control signal; and
assembling the plurality of blocks of encoded information and control information conveying the segment lengths to form an encoded information frame that is aligned with the reference signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
a long-long sequence of analysis window functions to a sequence of segments having lengths equal to the maximum segment length;
a short-short sequence of analysis window functions to a sequence of segments having effective lengths equal to the minimum segment length;
a bridge-long sequence of analysis window functions to a sequence of segments having lengths that shift from the minimum segment length to the maximum segment length, wherein the bridge-long sequence comprises a first bridge sequence of window functions followed by a window function for a segment having a length equal to the maximum segment length;
a long-bridge sequence of analysis window functions to a sequence of segments having lengths that shift from the maximum segment length to the minimum segment length, wherein the long-bridge sequence comprises a window function for a segment having a length equal to the maximum segment length followed by a second bridge sequence of window functions;
ora bridge-bridge sequence of analysis window functions to a sequence of segments having varying lengths, wherein the bridge-bridge sequence comprises the first bridge sequence followed by the second bridge sequence.
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7. A method for audio encoding according to claim 6 wherein all segments in the short-short sequence have identical lengths.
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8. A method for audio encoding according to claim 6 wherein all analysis window functions in the short-short sequence have non-zero portions that are identical in shape and length.
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9. A method for audio encoding according to claim 3 wherein the block encoding process constrains the segment lengths to be an integer power of two.
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10. A method for audio encoding according to claim 3 wherein the block encoding process adapts the segment lengths between a maximum segment length and a minimum segment length and, for a respective encoded information frame, applies either:
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a long-long sequence of analysis window functions to a sequence of segments having lengths equal to the maximum segment length;
a short-short sequence of analysis window functions to a sequence of segments having effective lengths equal to the minimum segment length;
a bridge-long sequence of analysis window functions to a sequence of segments having lengths that shift from the minimum segment length to the maximum segment length, wherein the bridge-long sequence comprises a first bridge sequence of window functions followed by a window function for a segment having a length equal to the maximum segment length;
a long-bridge sequence of analysis window functions to a sequence of segments having lengths that shift from the maximum segment length to the minimum segment length, wherein the long-bridge sequence comprises a window function for a segment having a length equal to the maximum segment length followed by a second bridge sequence of window functions;
ora bridge-bridge sequence of analysis window functions to a sequence of segments having varying lengths, wherein the bridge-bridge sequence comprises the first bridge sequence followed by the second bridge sequence.
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11. A method for audio encoding according to claim 10 wherein all segments in the short-short sequence have identical lengths.
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12. A method for audio encoding according to claim 10 wherein all analysis window functions in the short-short sequence have non-zero portions that are identical in shape and length.
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13. A method for audio encoding according to claim 1 that comprises converting the audio information from an input audio sample rate to an internal audio sample rate prior to applying the block encoding process, wherein the reference signal conveys a video information frame rate and the internal audio sample rate is equal to an integer multiple of the video information frame rate.
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14. A method for audio decoding that comprises steps performing the acts of:
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receiving a reference signal conveying alignment of video information frames in a sequence of video information frames in which adjacent frames are separated by a frame interval;
receiving encoded information frames that are aligned with the reference signal and each comprise control information and a plurality of blocks of encoded audio information;
generating a control signal in response to the control information, wherein the control signal conveys segment lengths for segments of audio information in a sequence of overlapping segments, a respective segment having a respective overlap interval with an adjacent segment and the sequence having a length equal to the frame interval plus a frame overlap interval;
applying an adaptive block decoding process to the plurality of blocks of encoded audio information in a respective encoded information frame, wherein the block decoding process adapts in response to the control signal to generate the sequence of overlapping segments of audio information. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
a long-long sequence of synthesis window functions to a sequence of segments having lengths equal to the maximum segment length;
a short-short sequence of synthesis window functions to a sequence of segments having effective lengths equal to the minimum segment length;
a bridge-long sequence of synthesis window functions to a sequence of segments having lengths that shift from the minimum segment length to the maximum segment length, wherein the bridge-long sequence comprises a first bridge sequence of window functions followed by a window function for a segment having a length equal to the maximum segment length;
a long-bridge sequence of synthesis window functions to a sequence of segments having lengths that shift from the maximum segment length to the minimum segment length, wherein the long-bridge sequence comprises a window function for a segment having a length equal to the maximum segment length followed by a second bridge sequence of window functions;
ora bridge-bridge sequence of synthesis window functions to a sequence of segments having varying lengths, wherein the bridge-bridge sequence comprises the first bridge sequence followed by the second bridge sequence.
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20. A method for audio decoding according to claim 19 wherein all segments generated from the short-short sequence have identical lengths.
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21. A method for audio decoding according to claim 19 wherein all synthesis window functions in the short-short sequence have non-zero portions that are identical in shape and length.
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22. A method for audio decoding according to claim 16 wherein the block decoding process is constrained to generate segments having lengths that are an integer power of two.
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23. A method for audio decoding according to claim 16 wherein the block decoding process decodes blocks representing segments of audio information representing segments of audio information having different lengths between a maximum segment length and a minimum segment length and, for a respective encoded information frame, applies either:
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a long-long sequence of synthesis window functions to a sequence of segments having lengths equal to the maximum segment length;
a short-short sequence of synthesis window functions to a sequence of segments having effective lengths equal to the minimum segment length;
a bridge-long sequence of synthesis window functions to a sequence of segments having lengths that shift from the minimum segment length to the maximum segment length, wherein the bridge-long sequence comprises a first bridge sequence of window functions followed by a window function for a segment having a length equal to the maximum segment length;
a long-bridge sequence of synthesis window functions to a sequence of segments having lengths that shift from the maximum segment length to the minimum segment length, wherein the long-bridge sequence comprises a window function for a segment having a length equal to the maximum segment length followed by a second bridge sequence of window functions;
ora bridge-bridge sequence of synthesis window functions to a sequence of segments having varying lengths, wherein the bridge-bridge sequence comprises the first bridge sequence followed by the second bridge sequence.
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24. A method for audio decoding according to claim 23 wherein all segments generated from the short-short sequence have identical lengths.
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25. A method for audio decoding according to claim 23 wherein all synthesis window functions in the short-short sequence have non-zero portions that are identical in shape and length.
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26. A method for audio decoding according to claim 14 that analyzes control information obtained from two encoded information frames to detect a discontinuity and, in response, adapts frequency response characteristics of the block decoding process in recovering first or last segments of audio information in a respective sequence of segments for either of the two encoded information frames.
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27. An information storage medium carrying:
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video information arranged in video frames; and
encoded audio information arranged in encoded information frames, wherein a respective encoded information frame corresponds to a respective video frame and includes control information conveying segment lengths for segments of audio information in a sequence of overlapping segments, a respective segment having a respective overlap interval with an adjacent segment and the sequence having a length equal to the frame interval plus a frame overlap interval, and blocks of encoded audio information, a respective block having a respective length and respective content that, when processed by an adaptive block-decoding process, results in a respective segment of audio information in the sequence of overlapping segments. - View Dependent Claims (28, 29, 30, 31, 32)
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Specification