Asynchronous sampling and reconstruction for asynchronous sample data communication system

Claim 2

Method for reconstructing an analog or voice waveform in an asynchronous sample data communication system wherein there is no direct time relation between the generation of sample data and the transmission thereof and no direct time relation between the receiving of sample data and the use thereof in reconstructing a waveform, comprising: at a sending station, generating sample data of said analog or voice waveform at a substantially periodic or constant rate; storing said sample data; sending said stored sample data over an asynchronous communication system in which time differentials exist between the sending of sequential samples to a receiving station; at said receiving station, storing said sample data in a buffer; extracting sample data from buffer storage for use by a periodic decoder; monitoring said buffer to determine if the amount of stored sample data is above or below a predetermined equilibrium amount; gradually varying the rate at which said periodic decoder uses samples by passing said monitoring information through a lag type filter after which it is used to smoothly vary the triggering rate of said decoder such that said amount of stored sample data tends toward said equilibrium amount; whereby the long term average encoding rate is continuously derived in the periodic decoder by providing a smooth, continuous decoding rate for reconstructing the analog or voice waveform.

Claim 3

Method as recited in claim 1, wherein the step of gradually varying the decoding rate includes: gradually increasing said rate when the monitored amount of stored sample data is more than an equilibrium amount; and gradually decreasing said rate when the monitored amount of stored sample data is less than said equilibrium amount.

Claim 4

Method as recited in claim 1, wherein said generating of sample data of said analog or voice waveform is carried out at a substantially periodic rate which changes gradually.

Claim 5

Method as recited in claim 1, wherein the step of monitoring said buffer comprises continuously detecting whether the amount of sample data stored is either greater or less than said predetermined equilibrium amount.

Claim 6

Method as recited in claim 4, wherein said step of monitoring said buffer comprises counting the number of samples placed in storage and continuously subtracting one count from this number each time a sample is extracted from storage.

Claim 7

Method for sampling an analog or voice wave form at one of a plurality of stations in an asynchronous communication system and for reconstructing the waveform at another one of the stations, comprising: at said one station, sampling said analog or voice waveform at a substantially uniform rate; conveying said samples over said asynchronous communication system to said another station; at said another station receiving and storing said conveyed samples, monitoring the amount of stored samples, and deriving the long term average encoding rate of said conveyed samples by a lag type filter connected to receive said monitoring information; and interpolating a waveform from said derived long term average encoding rate by varying the decoding rate of said stored samples in accordance with said derived long term average encoding rate; whereby said interpolated waveform approximates said sampled waveform without predetermining, centrally controlling or communicating the original sample rate.

Claim 8

Method for sampling an analog or voice wave form at one of a plurality of stations in an asynchronous communication system and for reconstructing the waveform at another one of the stations, comprising: at said one station, sampling said analog or voice waveform at a substantially uniform rate; conveying said samples over said asynchronous communication system to said another station; at said another station receiving and storing said conveyed samples, monitoring the amount of stored samples, and deriving the long term average encoding rate of said conveyed samples by a lag type filter connected to receive said monitoring information; and interpolating a waveform from said derived long term average encoding rate by varying the decoding rate of said stored samples in accordance with said derived long term average encoding rate; whereby said interpolated waveform approximates said sampled waveform without predetermining, centrally controlling or communicating the original sample rate.

Claim 9

Method as recited in claim 6, wherein said sampling of said waveform is carried out at a substantially uniform rate which changes gradually.

Claim 10

A sample data communication system wherein there is no direct time relation between the generation of sample data and the transmission thereof and no direct time relation between the receiving of sample data and the use thereof in reconstructing a waveform, compriSing: an encoder for generating sample data from an analog or voice waveform at a substantially uniform rate; a buffer for storing said sample data; means for sending said stored sample data over a transmission medium to a receiving station; at said receiving station, a second buffer for storing said transferred sample data; a decoder for taking sample data from said second buffer at a substantially uniform rate and reconstructing a waveform therefrom; monitoring means for observing the amount of sample data in said second buffer relative to a predetermined equilibrium amount; a lag type filter connected to the output of said monitoring means for gradually and smoothly varying said output so that abrupt changes in the amount of stored sample data may produce only gradual variations at the output of said lag type filter; and controlling means connected to said lag type filter and said decoder for gradually adjusting said rate at which said decoder reconstructs sample data in a direction that tends to bring the amount of said stored sample data toward said equilibrium amount; whereby said reconstructed waveform is formed by decoding said samples at a substantially uniform rate with gradual variations and approximates said sampled waveform without predetermining, centrally controlling or communicating the orignal sample rate.

Claim 11

A sample data communication system wherein there is no direct time relation between the generation of sample data and the transmission thereof and no direct time relation between the receiving of sample data and the use thereof in reconstructing a waveform, compriSing: an encoder for generating sample data from an analog or voice waveform at a substantially uniform rate; a buffer for storing said sample data; means for sending said stored sample data over a transmission medium to a receiving station; at said receiving station, a second buffer for storing said transferred sample data; a decoder for taking sample data from said second buffer at a substantially uniform rate and reconstructing a waveform therefrom; monitoring means for observing the amount of sample data in said second buffer relative to a predetermined equilibrium amount; a lag type filter connected to the output of said monitoring means for gradually and smoothly varying said output so that abrupt changes in the amount of stored sample data may produce only gradual variations at the output of said lag type filter; and controlling means connected to said lag type filter and said decoder for gradually adjusting said rate at which said decoder reconstructs sample data in a direction that tends to bring the amount of said stored sample data toward said equilibrium amount; whereby said reconstructed waveform is formed by decoding said samples at a substantially uniform rate with gradual variations and approximates said sampled waveform without predetermining, centrally controlling or communicating the orignal sample rate.

Claim 12

A system as recited in claim 8 wherein said monitoring means includes: an up/down counter connected to said second buffer for counting the difference between the amount of said sample data placed in said second buffer and the amount of said sample data taken from said second buffer, whereby the count is the amount of said stored sample data.

Claim 13

A system as recited in claim 9, wherein said controlling means gradually increases said decoding rate when said counter has a count above said equilibrium amount and gradually decreases said decoding rate when said counter has a count below said equilibrium amount, thereby tending to bring said count toward said equilibrium amount.

Claim 14

A system as recited in claim 10 wherein said lag type filter comprises a resistor-capacitor circuit to slowly vary said uniform rate of reconstruction.

Claim 15

A system as recited in claim 8 where said decoder comprises a D/A converter connected to and triggered by a voltage controlled oscillator.