Snell Limited

Snell Advanced Media Limited

Jeff Butters

Tim Addy

The respective occupancies of a set of audio buffers are controlled via a common target occupancy value common to all the buffers in the set. This common target may take non-integral values. For each buffer, the difference is taken between the occupancy value of the buffer and the common target occupancy value. A sample is dropped or repeated as the difference exceeds half a sample. A recursive sum is formed of the fractional parts of the difference measures from the set of buffers and the recursive sum is used to adjust the common target occupancy value, within a selected range of values.

Adjusting occupancies of a set of buffers

Apparatus is provided for processing a switched audio signal output received from a crosspoint router having a plurality of inputs and a plurality of outputs, there being a control signal that defines which of the plurality of inputs is to be routed by the crosspoint router to which of the plurality of outputs. A control unit receives the control signal and serves to identify a route change in the control signal. An instantaneous value of the switched audio signal prior to the route change is stored. A signal processing unit then combines the stored value with values of the switched audio signal after the route change to form a processed audio signal that changes smoothly.

Method and apparatus for processing a switched audio signal from a crosspoint router

For re-timing sampled data, input data samples at an input data rate are stored in a FIFO buffer and output at an output data rate according to an output clock that is locked to the input data rate in dependence on a loop-filtered measure of the fill level of the said buffer. The frequency of the output clock is additionally controlled by an estimate of the input data rate.

Re-timing sampled data

The invention concerns digital audio processing and in particular the detection of periods where samples can be deleted or repeated unobtrusively so as to change the average sample-rate or to provide time delay modification. Differences between succeeding sample values are evaluated and compared with a threshold and samples are deleted or repeated where two or more consecutive sample value differences are less than the said threshold value.

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Reading, United Kingdom

Jeff Butters