Stuffing process for reducing waiting time jitter and device for executing the process
First Claim
Patent Images
1. In a stuffing process for reducing waiting time jitter, which process includes the steps of:
- a. supplying a first digital signal (A) with a first bit rate to a synchronizer and writing the first digital signal into an elastic memory (ES) in the synchronizer with a first clock pulse (tA) having a pulse rate which corresponds to the first bit rate of the first digital signal (A);
b. reading a second digital signal (B) at a second bit rate out of the elastic memory (ES) with a second clock pulse (tB) having a pulse rate which corresponds to the second bit rate of the second digital signal (B), whereby the elastic memory (ES) will have a mean loading; and
c. in a frame counter (RZ), generating stuffing frames of the second digital signal (B), controlling reading out of the elastic memory, and performing stuffing as a function of a control parameter supplied to the frame counter, the improvement wherein said process further comprises;
d. determining the mean loading of the elastic memory (ES) at a rate of once per stuffing frame of the second digital signal (B);
e. producing an indication of a difference between the mean loading and a selected loading value for each stuffing frame of the second digital signal (B);
f. deriving a sum of the difference indicated during an existing stuffing frame and all previous stuffing frames for which said steps of determining and producing were performed;
g. deriving, from the difference indicated during an existing stuffing frame and the sum derived in step f, an estimated sum value for the next occurring stuffing frame on the assumption that stuffing will not be performed during the next occurring stuffing frame;
h. comparing the estimated sum value with at least one threshold value and determining, as a function of this comparison, a control parameter value which can control stuffing in a manner such that the sum derived in step f remains at least approximately constant; and
i. supplying the value determined in step h, as the control value, to the frame counter (RZ).
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Abstract
A stuffing process and device for reducing waiting time jitter by: determining the mean loading of an elastic memory as precisely as possible; determining a loading error constituted by a difference between an actual value and a set value of the mean loading; producing a sum of successive loading errors; and determining the manner in which stuffing is to take place in order to keep the error sum as constant as possible.
26 Citations
5 Claims
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1. In a stuffing process for reducing waiting time jitter, which process includes the steps of:
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a. supplying a first digital signal (A) with a first bit rate to a synchronizer and writing the first digital signal into an elastic memory (ES) in the synchronizer with a first clock pulse (tA) having a pulse rate which corresponds to the first bit rate of the first digital signal (A); b. reading a second digital signal (B) at a second bit rate out of the elastic memory (ES) with a second clock pulse (tB) having a pulse rate which corresponds to the second bit rate of the second digital signal (B), whereby the elastic memory (ES) will have a mean loading; and c. in a frame counter (RZ), generating stuffing frames of the second digital signal (B), controlling reading out of the elastic memory, and performing stuffing as a function of a control parameter supplied to the frame counter, the improvement wherein said process further comprises; d. determining the mean loading of the elastic memory (ES) at a rate of once per stuffing frame of the second digital signal (B); e. producing an indication of a difference between the mean loading and a selected loading value for each stuffing frame of the second digital signal (B); f. deriving a sum of the difference indicated during an existing stuffing frame and all previous stuffing frames for which said steps of determining and producing were performed; g. deriving, from the difference indicated during an existing stuffing frame and the sum derived in step f, an estimated sum value for the next occurring stuffing frame on the assumption that stuffing will not be performed during the next occurring stuffing frame; h. comparing the estimated sum value with at least one threshold value and determining, as a function of this comparison, a control parameter value which can control stuffing in a manner such that the sum derived in step f remains at least approximately constant; and i. supplying the value determined in step h, as the control value, to the frame counter (RZ). - View Dependent Claims (2, 3, 4)
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5. In a stuffing device for reducing waiting time jitter, which device includes:
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a. means for supplying a first digital signal (A) with a first bit rate to a synchronizer and for writing the first digital signal into an elastic memory (ES) in the synchronizer with a first clock pulse (tA) having a pulse rate which corresponds to the first bit rate of the first digital signal (A); b. means for reading a second digital signal (B) at a second bit rate out of the elastic memory (ES) with a second clock pulse (tB) having a pulse rate which corresponds to the second bit rate of the second digital signal (B), whereby the elastic memory (ES) will have a mean loading; and c. a frame counter (RZ) containing means for generating stuffing frames of the second digital signal (B), for controlling reading out of the elastic memory, and for performing stuffing as a function of a control parameter supplied to the frame counter, the improvement wherein said device further comprises; d. means for determining the mean loading of the elastic memory (ES) at a rate of once per stuffing frame of the second digital signal (B); e. means for producing an indication of a difference between the mean loading and a selected loading value for each stuffing frame of the second digital signal (B); f. means for deriving a sum of the difference indicated during an existing stuffing frame and all previous stuffing frames for which a mean loading was previously determined and an indication of a difference was previously produced; g. means for deriving, from the difference indicated during an existing stuffing frame and the sum derived by said means for deriving a sum of the difference, an estimated sum value for the next occurring stuffing frame on the assumption that stuffing will not be performed during the next occurring stuffing frame; h. means for comparing a currently derived estimated sum value with at least one threshold value and for determining, as a function of this comparison, a control parameter value which can control stuffing in a manner such that the sum derived by said means for deriving remains at least approximately constant; and i. means for supplying the value determined by said means for comparing, as the control value, to said frame counter (RZ).
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Specification