Audio digital recording and playback system

• US 4,472,747 A
• Filed: 04/19/1983
• Issued: 09/18/1984
• Est. Priority Date: 04/19/1983
• Status: Expired due to Fees

• Current Assignee: David M. Schwartz
• Original Assignee: Compusound Incorporated
• Inventors: Schwartz, David M.
• Primary Examiner(s): Canney, Vincent P.
• Application Number:
  US06/486,561
• Time in Patent Office: 518 Days
• Field of Search: 360/32, 360/12, 360/67, 360/68, 360/46, 340/347 M
• US Class Current: 360/32
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 5/012 Recording on, or reproducing or erasing from, magnetic disks G11B17/00, G11B19/00 take precedence

Abstract

A microcomputer system for converting an analog input signal, such as an audio signal representative of sound into a digital form for storing in digital form in a highly condensed code and for reconstructing the analog signal from the coded digital form is disclosed. The system includes reductive analytic means where the original digital data stream is converted to a sequential series of frequency spectrograms, signal amplitude histograms and waveform code tables. Approximately 100 times less storage space than previously required for the storage of digitized audio signals of high fidelity quality is thereby obtained. Additive synthesis logic interprets the stored codes and recreates an output digital data stream for digital to analog conversion that is nearly identical to the original source material.

Claims

1. A microcomputer recording system for recording analog audio signals in digital data form comprising:

converting means for converting an analog audio signal into at least three digital data streams, wherein the first of said digital data streams is a relatively broadband reference signal representative of the amplitude of a preselected range of audio frequencies, and wherein another of said data streams is produced by filtering the analog audio signal to produce a data stream channel indicative of a plurality of discrete frequencies encompassed by the bandwidth represented by said first data stream; and

wherein the third of said digital data streams is a reference signal representative of the amplitude of the audio signal for each of said plurality of discrete frequencies;

sampling means for producing a sequential stream of samples in each of said digital data streams,

selection means for selecting a predetermined portion of the digital data samples produced by said sampling means in each digital data stream;

means for separately storing each of said selected data samples produced by said sampling means;

means for comparing the reference data stream containing amplitude data with the reference data stream containing frequency data to produce frequency spectrogram data representative of the frequency and energy of the original audio signal;

means for transforming data samples selected from said filtered data stream into data representative of a time versus amplitude histogram for each channel;

means for comparing said histogram data with selected waveform parameters and producing addressable data representative of the waveform of the original input data;

means for sequentially assembling and storing the frequency spectrogram data and the amplitude reference data and the addressable waveform data for subsequent use.

2. A microcomputer recording and playback system for recording analog audio signals in digital data form and for playback by decoding the digital data and converting it to analog audio signals comprising:

converting means for converting an analog audio signal into at least three digital data streams, wherein the first of said digital data streams is a relatively broadband reference signal representative of the amplitude of a preselected range of audio frequencies, and wherein another of said data streams is produced by filtering the analog audio signal to produce a data stream channel indicative of a plurality of discrete frequencies encompassed by the bandwidth represented by said first data stream; and

wherein the third of said digital data streams is a reference signal representative of the amplitudes of the audio signal for each of said plurality of discrete frequencies;

sampling means for producing a sequential stream of samples in each of said digital data streams,

selection means for selecting a predetermined portion of the digital data samples produced by said sampling means in each digital data stream;

means for separately storing each of said selected data samples produced by said sampling means;

means for comparing the reference data stream containing amplitude data with the reference data stream containing frequency data to produce frequency spectrogram data representative of the frequency and energy of the original audio signal;

means for transforming data samples selected from said filtered data stream into data representative of a time versus amplitude histogram for each channel;

means for comparing said histogram data with selected waveform parameters and producing addressable data representative of the waveform of the original input data;

means for sequentially assembling and storing the frequency spectrogram data and the amplitude reference data and the addressable waveform data for subsequent use; and

playback means for converting said digital data to analog data for subsequent audio reproduction comprising;

addressing means for selecting the stored waveform data representative of the original waveform detected; and

oscillator means for producing an analog signal responsive to the waveform data and the amplitude data to produce a resultant analog signal suitable for use in an audio reproduction device.

3. The system of claim 2 further comprising:

means for transmitting said frequency spectrogram data, amplitude reference data and addressable waveform data by an rf signal to said playback means.

4. A microcomputer playback system for reproducing an audio signal from stored digital data comprising:

addressing means for selecting stored waveform data representative of audio signal waveforms detected by a recording apparatus; and

oscillator means for producing an analog signal responsive to said selected waveform data and associated amplitude data to reproduce said audio signal.

5. An apparatus for recording audio signals in digital form comprising:

means for providing a analog signal representative of an audio signal;

data acquisition means for sampling and digitizing said analog signal to produce a full spectrum amplified digital signal and filtering said analog signal at a plurality of discrete audio frequencies to produce a filtered analog signal and sampling and digitizing said filtered analog signal to produce audio frequency spectrograms;

buffer means for storing a plurality of amplitude histograms from said filtered analog signal representative of the amplitude of said filtered analog signal versus time for each discrete frequency of said plurality of audio frequencies;

waveform analyzer means for extracting characteristic waveforms from said plurality of histograms and generating waveform tables in the form of a computer readable data base from said characteristic waveforms;

disk record assembler means for generating assembled disk records for storage on a disk read/write module from said waveform tables, said audio frequency spectrograms and said full spectrum amplitude digital signal.

6. The apparatus of claim 5 wherein said waveform analyzer means includes means for generating waveform tables using a Fast Fourier Transform.

7. The apparatus of claim 5 wherein said waveform analyzer means includes means for generating waveform tables using a Fast Delta Hademard Transform.

8. The apparatus of claim 5 wherein said waveform analyzer means includes means for generating waveform tables using the B-splines type of cubic splines transform.

9. A method of recording audio signals in digital form comprising the steps of:

converting an analog audio signal into at least three digital data streams, wherein the first of said digital data streams is a relatively broadband reference signal representative of the sum of the amplitudes of a preselected range of audio frequencies, and wherein another of said data streams is produced by filtering the analog audio signal to produce a plurality of frequency channels indicative of a series of discrete frequencies encompassed by the bandwidth of said first data stream; and

wherein the third of said digital data streams is a series of reference signals representative of amplitude signals of said frequency channels;

producing a sequential stream of samples in each of said digital data streams;

selecting a predetermined portion of the digital data samples produced by said sampling means in each digital data stream;

storing each of said selected data samples produced by said sampling means;

comparing the reference data stream containing amplitude data with the reference data stream containing frequency data to produce frequency spectrogram data representative of the frequency and energy of the original audio signal;

transforming data samples selected from said filtered data stream into data representative of a time versus amplitude histogram for each channel;

comparing said histogram data with selected waveform parameters and producing addressable data representative of the waveform of the original input data;

assembling and storing the frequency spectrogram data and the amplitude reference data and the addressable waveform data for subsequent use.

10. A method of recording analog audio signals in digital data form and converting the digital signals back into an analog audio signals capable of being played in an audio reproduction device comprising the steps of:

converting an analog audio signal into at least three digital data streams, wherein the first of said digital data streams is a relatively broadband reference signal representative of the sum of the amplitudes of a preselected range of audio frequencies, and wherein another of said data streams is produced by filtering the analog audio signal to produce a plurality of frequency channels indicative of a series of discrete frequencies encompassed by the bandwidth of said first data stream; and

wherein the third of said digital data streams is a series of reference signals representative of amplitude signals of said frequency channels;

producing a sequential stream of samples in each of said digital data streams;

selecting a predetermined portion of the digital data samples produced by said sampling means in each digital data stream;

storing each of said selected data samples produced by said sampling means;

comparing the reference data stream containing amplitude data with the reference data stream containing frequency data to produce frequency spectrogram data representative of the frequency and energy of the original audio signal;

transforming data samples selected from said filtered data stream into data representative of a time versus amplitude histogram for each channel;

comparing said histogram data with selected waveform parameters and producing addressable data representative of the waveform of the original input data;

sequentially assembling and storing the frequency spectrogram data and the amplitude reference data and the addressable waveform data for subsequent use;

addressing the stored waveform, frequency and amplitude data representative of the original audio signal; and

converting the resultant signal from digital to analog form.

11. The method of claim 10 comprising the further steps of:

transmitting said spectrogram data, said amplitude reference data and said addressable waveform data by an rf signal.

12. A method of recording audio signals in digital form comprising:

providing a analog signal representative of an audio signal;

sampling and digitizing said analog signal to produce a full spectrum digital amplified signal;

filtering said analog signal at a plurality of discrete audio frequencies to produce a filtered analog signal;

sampling and digitizing said filtered analog signal to produce audio frequency spectrograms;

generating a plurality histograms from said filtered analog signal representative of the amplitude versus time for each discrete frequency of said plurality of audio frequencies;

extracting characteristic waveforms from said plurality of histograms; and

generating waveform tables in the form of a computer readable data base from said characteristic waveforms;

generating assembled disk records for storage on a disk read/write module from said waveform tables, said audio frequency spectrograms and said full spectrogram amplitude digital signal.

13. The method of claim 12 wherein said step of generating waveform tables comprises generating waveform tables using a Fast Fourier Transform.

14. The method of claim 12 wherein said step of generating waveform tables comprises generating waveform tables using a Fast Delta Hadamard Transform.

15. The method of claim 12 wherein said step of generating waveform tables comprises waveform tables using the B-splines type of cubic splines transform.

16. A method of reproducing an audio signal from assembled waveform tables generated from histograms of characteristic waveforms of said audio signal, audio frequency spectrograms and full spectrum digital amplitude signals comprising:

addressing waveform, frequency and amplitude data provided by said histograms, spectrograms and amplitude signals; and

converting said waveform, frequency and amplitude data from digital to analog form.

17. The method of claim 16 further comprising:

transmitting digital data from said assembled waveform tables by an rf signal.