Process for controlling the outflow rate of a coder of digital data representative of sequences of images
First Claim
1. A process for controlling a data output flow rate of a coder of digital data which is representative of a sequence of images, said coder including a quantization stage having a quantization parameter Q, said sequence of images comprising successive groups of images, said process comprising the steps of:
- setting a quantization parameter Q(i+1) for coding an (i+1) group of images at a moment when data of an i group of images is at an output of the coder, said digital data having a flow rate at the output of said coder conforming to a version of a leaky bucket defined by a size M and by a leakage rate λ
; and
setting said quantization parameter Q(i+1) for the coding of the (i+1) group of images in terms of an activity of a scene represented by the i group of images, the scene of said i group of images being active when its open-loop flow rate is greater than the leakage rate λ
of the leaky bucket and being inactive when said open-loop flow rate is less than the leakage rate λ
, said open-loop flow rate of a group of images being the flow rate which said scene of images would have at an output of said coder if it had been quantized with a constant quantization parameter Qo at an average rate D over an entire sequence of images to which said scene of images belongs is equal to the leakage rate of said leaky bucket, the average rate D being an average rate when each group of the images is quantized with a constant parameter.
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Abstract
A process for controlling the output flow rate of a coder of digital data representative of sequences of images, the coding effected by the coder including a quantization stage of quantization parameter Q, the sequences of images being made up of successive groups of images. The process consists of determining, at the moment of the presence of the i group of images at the output of the coder, the quantization parameter Q(i+1) for the coding of the (i+1) group of images so that the flow rate at the output of the coder conforms with a version of a leaky bucket defined by a size M and by a leakage rate λ in terms of the activity of the scene represented by the i group of images.
51 Citations
9 Claims
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1. A process for controlling a data output flow rate of a coder of digital data which is representative of a sequence of images, said coder including a quantization stage having a quantization parameter Q, said sequence of images comprising successive groups of images, said process comprising the steps of:
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setting a quantization parameter Q(i+1) for coding an (i+1) group of images at a moment when data of an i group of images is at an output of the coder, said digital data having a flow rate at the output of said coder conforming to a version of a leaky bucket defined by a size M and by a leakage rate λ
; andsetting said quantization parameter Q(i+1) for the coding of the (i+1) group of images in terms of an activity of a scene represented by the i group of images, the scene of said i group of images being active when its open-loop flow rate is greater than the leakage rate λ
of the leaky bucket and being inactive when said open-loop flow rate is less than the leakage rate λ
, said open-loop flow rate of a group of images being the flow rate which said scene of images would have at an output of said coder if it had been quantized with a constant quantization parameter Qo at an average rate D over an entire sequence of images to which said scene of images belongs is equal to the leakage rate of said leaky bucket, the average rate D being an average rate when each group of the images is quantized with a constant parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification