International Business Machines Corporation

Ronald H Jones, Jr

William W Lawton

Keith C Kelly

Bradley Dale Noe

Bruce D Jobse

Linden Alanso De Carmo

Digitized audio information is compressed by retrieving a first audio sample from a digitized audio signal and storing it in its entire, uncompressed, form. The next audio sample is then retrieved and a signed difference between the first audio sample value and the next audio sample value is computed. If this difference value can be represented in fewer data segments than would be required to represent the next audio sample, the difference value is stored, rather than the value of the next sample, otherwise the next sample is stored. The invention proceeds in this fashion until the entire PCM audio signal is compressed and stored. The compressed data stream is decompressed to generate an output data stream by retrieving a stored sample and examining it to ascertain whether it is a difference value or a flag which indicates that the following data represents a coded amplitude value. If the sample is a difference value it is digitally added to the previous value (taking into account the sign) and the sum is inserted into the output data stream. The sum value is retained in order to be used to compute the next output value if the following sample is also a difference value. Alternatively, if the sample is a flag value it is discarded and the next sample is retrieved and inserted into the output data stream.

Real-time digital audio compression/decompression system

Disclosed are methods and apparatus that facilitate the introduction of filters, converters and effects into an active multimedia stream without interruption of the presentation. A control module or sequence permits such introduction only after verifying the presence of a sufficient supply of buffered presentation data. Responding to a user's request for introduction of a filter, the invention first determines whether its immediate implementation would cause interruption, and either introduces the filter, converter or effect into the data stream as backlogged data continues to be presented, or postpones its introduction until sufficient buffered data does exist.

Method and apparatus for selectably retrieving and outputting digitally

A software reverberator system produces a sequence of 'reverberated' samples from an input digital word sequence where each word in the input sequence comprises a digitized sample of an original analog audio signal. The invention generates the reverberated samples by adding together several scaled and delayed input words to produce a corresponding reverberated output word. The resulting reverberated output word stream can be converted to analog form in sequence to produce a reverberated version of the original audio signal. The delays are produced by clocking the input words through multi-stage first-in, first-out buffers with a number of stages selected to give the desired delay.

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Delray Beach, FL, United States of America

Ronald H Jones, Jr