Human vision based pre-processing for MPEG video compression
First Claim
1. A method of pre-processing an input video signal to generate a pre-processed video signal with reduced bandwidth for input to a video compressor comprising the steps of:
- constructing a Gaussian pyramid from the input video signal;
obtaining a local light level and a global light center from the Gaussian pyramid;
from the local light level and global light center generating a local gain control signal;
multiplying a Laplacian image derived from the input video signal by the local gain control signal to produce a modified Laplacian image; and
subtracting the modified Laplacian image from an equivalent video image derived from the input video signal to produce the pre-processed video signal.
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Abstract
Human vision based pre-processing for MPEG video compression uses light intensity. An input video signal is input to a contrast gain control circuit where a Gaussian pyramid is constructed. The reduced pyramid image serves as a local light level. The reduced pyramid image also is processed to obtain a global light center. The difference between the local light level and the global light center is used as an index to a lookup table that provides a local gain control signal. The local gain control signal and a global gain control signal input to the contrast gain control circuit are used to multiply a Laplacian image derived from the input image, the resulting modified Laplacian image being subtracted from an equivalent lowpass filtered video image to produce a pre-processed output video signal having reduced bandwidth for input to an MPEG2 compressor.
54 Citations
18 Claims
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1. A method of pre-processing an input video signal to generate a pre-processed video signal with reduced bandwidth for input to a video compressor comprising the steps of:
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constructing a Gaussian pyramid from the input video signal;
obtaining a local light level and a global light center from the Gaussian pyramid;
from the local light level and global light center generating a local gain control signal;
multiplying a Laplacian image derived from the input video signal by the local gain control signal to produce a modified Laplacian image; and
subtracting the modified Laplacian image from an equivalent video image derived from the input video signal to produce the pre-processed video signal. - View Dependent Claims (2, 3, 4, 5)
selecting a reduced pyramid image from the Gaussian pyramid as the local light level; and
performing a Q-norm of kth power on the reduced pyramid image to produce the global light center.
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5. The method as recited in claim 1 wherein the generating step comprises the steps of:
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subtracting the global light center from the local light level to produce an index; and
accessing a lookup table using the index to produce the local gain signal.
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6. A method of human vision based pre-processing of an input video signal for reducing bandwidth for MPEG video compression comprising the steps of:
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deriving from the input video signal as a function of light intensity a local gain control signal; and
modifying the input video signal as a function of the local gain control signal and a global gain control signal to produce a pre-processed, reduced bandwidth video signal for MPEG video compression. - View Dependent Claims (7, 8, 9, 10, 11)
generating a local light level and a global light center from the input video signal; and
combining the local light level and global light center to produce the local gain control signal.
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8. The method as recited in claim 7 wherein the generating step comprises the steps of:
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obtaining the local light level from a reduced version of the input video signal; and
normalizing the reduced version to obtain the global light center.
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9. The method as recited in claim 8 wherein the combining step comprises the steps of:
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subtracting the global light center from the local light level to produce a contrast signal; and
converting the contrast signal into the local gain control signal.
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10. The method as recited in claim 9 wherein the converting step comprises the step of accessing a lookup table as a function of the contrast signal to obtain the local gain control signal.
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11. The method as recited in claim 10 wherein the lookup table comprises a positive lookup table for positive values of the contrast signal and a negative lookup table for negative values of the contrast signal.
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12. An apparatus for human based pre-processing of an input video signal to reduce bandwidth for video compression comprising:
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means for deriving a local gain control signal as a function of light intensity from the input video signal; and
means for modifying the input video signal as a function of the local gain control signal and a global gain control signal to produce a pre-processed, reduced bandwidth video signal for MPEG compression. - View Dependent Claims (13, 14, 15, 16, 17, 18)
means for generating a local light level and a global light center from the input video signal; and
means for combining the local light level and the global light center to produce the local gain control signal.
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14. The apparatus as recited in claim 13 wherein the generating means comprises:
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means for obtaining the local light level from a reduced version of the input video signal; and
means for normalizing the reduced version to obtain the global light center.
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15. The apparatus as recited in claim 14 wherein the combining means comprises:
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means for subtracting the global light center from the local light level to produce a contrast signal; and
means for converting the contrast signal into the local gain control signal.
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16. The apparatus as recited in claim 15 wherein the converting means comprises a lookup table accessed as a function of the contrast signal to obtain the local gain control signal.
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17. The apparatus as recited in claim 16 wherein the lookup table comprises:
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a positive lookup table for positive values of the contrast signal; and
a negative lookup table for negative values of the contrast signal.
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18. The apparatus as recited in claim 12 further comprising:
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means for constructing a Gaussian pyramid from the input video signal, the highest level of the Gaussian pyramid being used to derive the local light level and global light center;
means for generating a Laplacian signal and an equivalent video signal from the input video signal, the Laplacian signal being multiplied by the local and global gain control signals to produce a modified Laplacian signal; and
means for subtracting the modified Laplacian signal from the equivalent video signal to produce the pre-processed, reduced bandwidth video signal for MPEG compression.
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Specification