Communication system and method for sample rate converting data onto or from a network using a high speed frequency comparison technique
First Claim
1. A destination port of a communication network, comprising a sample rate converter coupled to receive phase or frequency difference information between a transfer clock used to transfer data across the network and a sampling clock local to a source port coupled to the destination port via the network.
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Abstract
A communication system, source and destination ports of the communication system, and methodology is provided for transporting data in one of possibly three different ways. Data is transported across the network at a frame sample rate that can be the same as or different from the sample rate or master clock within the source port or the destination port. If the sample rate of the source port is known, the sample rate of the destination port can be created using a PLL within the destination port and simply employing a phase comparator in the source port. The phase comparator forwards the phase or frequency difference of the network transfer rate and the source sample rate to the destination port, which then generates a local clock equivalent to the source which then compiles audio data being played at the same rate in which it was sampled at the source. Where economically feasible, sample rate conversion can be used at the source. However, sample rate conversion at the destination is preferred if the source sample rate is forwarded across the network relative to the frame transfer rate of the synchronous network. The sample rate converter simply produces a play rate from the transmitted information at the destination. Again, however, sample rate conversion compares relative phase difference changes similar to the phase difference compared in the digital PLL mode. As a further alternative, sample rates within the source and destination ports can be derived from the network frame rate using fractional dividers in the source and destination ports.
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Citations
26 Claims
- 1. A destination port of a communication network, comprising a sample rate converter coupled to receive phase or frequency difference information between a transfer clock used to transfer data across the network and a sampling clock local to a source port coupled to the destination port via the network.
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15. A communication network, comprising:
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a source port;
a destination port coupled to the source port by the network;
a plurality of frames of data, each of which are transferred across the network at a frame transfer rate;
a comparator coupled to produce;
a first compare result during a first clock cycle of a phase difference between a transfer clock transitioning at the frame transfer rate and a sampling clock used to sample data at the source port;
a second compare result during a second clock cycle of a phase difference between the transfer clock and the sampling clock; and
a sample rate converter at the destination port coupled to receive a frequency difference corresponding to the first and second compare results for changing coefficients of a digital filter local to the destination port. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. A method for generating a sampling rate local to a destination node of a communication network, comprising:
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calculating a frame transfer rate of a plurality of data sent across the network;
comparing the frame transfer rate to a transition rate of a sampling clock at a source node by determining either a phase difference or a change in phase difference between the frame transfer rate and a rate of the sampling clock; and
forwarding the phase difference or the change in phase difference across a network;
changing a sample rate of the data at a destination port using a clock local to the destination port that is transitioning dissimilar from the transition rate of the sampling clock. - View Dependent Claims (25, 26)
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Specification