Audio Digitization Sampling Rate Adjustment for Wow and Flutter
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Solution Overview
Problem
Existing audio digitization systems face challenges in maintaining sound quality due to irregular tape or film movement, which causes pitch variations known as 'wow' and 'flutter', and current solutions either require expensive and heavy mechanical stabilization or software-based smoothing processes.
Innovation Solution
The method involves dynamically adjusting the sampling rate of the analog-to-digital converter based on the sensed transportation speed of the recording medium, using a modulator clock signal to compensate for speed variations, thereby ensuring accurate digitization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If highly precise bearings and heavy flywheels are used to stabilize transport speed, then sound quality is improved, but device weight and cost increase
Solution Approach 1:
The patent replaces mechanical stabilization methods (bearings and flywheels) with an electronic solution. A sensor detects the actual transport speed, and this information is used to dynamically adjust the sampling rate of the analog-to-digital converter. This substitution eliminates the need for heavy mechanical components while maintaining sound quality through electronic compensation.
Solution Approach 2:
The patent changes the sampling rate parameter of the analog-to-digital converter based on detected transport speed variations. By dynamically adjusting this parameter in response to actual transport conditions, the system compensates for speed irregularities without requiring mechanical stabilization, thereby improving sound quality without increasing device weight.
2Reliability
If highly precise bearings and heavy flywheels are used to stabilize transport speed, then sound quality is improved, but device cost increases
Solution Approach 1:
The patent replaces expensive mechanical stabilization components with a more economical electronic system consisting of a speed sensor and a controllable analog-to-digital converter. This substitution significantly reduces manufacturing cost while achieving the same sound quality improvement through electronic parameter adjustment rather than mechanical precision.
Solution Approach 2:
The patent adjusts the sampling rate parameter dynamically based on transport speed detection. This software-controlled approach is more cost-effective than manufacturing highly precise mechanical components, as it uses standard components with electronic control to achieve the desired sound quality.
3Reliability
If software-based smoothing is used to remove pitch variations, then sound quality is improved, but workflow complexity and cost increase
Solution Approach 1:
The patent performs pitch correction during the initial digitization process rather than as a subsequent software processing step. By adjusting the sampling rate at the point of analog-to-digital conversion based on real-time speed detection, the system eliminates pitch variations before they are encoded into the digital signal, thereby simplifying the overall workflow while improving sound quality.
Solution Approach 2:
The patent replaces post-processing software smoothing with a real-time electronic compensation method. The analog-to-digital converter's sampling rate is dynamically adjusted during the digitization process itself, eliminating the need for separate software-based pitch correction steps and reducing workflow complexity.
Data Source
AI summary
A method of digitizing an audio track carried on an elongate recording medium, such as a movie film, includes transporting the recording medium containing the audio track past a reader to enable sequential reading of the audio track. The reading of the audio track generates an analog output signal. The method also includes sensing a rate of transportation of the recording medium, and sampling the analog output signal at a sampling rate determined on the basis of the sensed rate of transportation to digitize the analog output signal. A system for digitizing audio is also disclosed.