CD Audio Synchronization Controller for Automated Pianos
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Solution Overview
Problem
Existing automated musical instruments, such as pianos, face challenges in achieving accurate synchronization with prerecorded CDs due to the limited timing resolution of CD sub-channels, which is not sufficient for precise piano sequences.
Innovation Solution
The system utilizes the timing inherent in CD audio data as a time reference, allowing for a higher resolution of 22.7 microseconds, and includes a controller that acts as both a MIDI sequencer and CD playback device, synchronizing music sequences with commercial CDs by using the CD's digital audio stream for timestamping and advancing MIDI events to maintain absolute synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CD sub-channel timing information is used for synchronization, then the system can play automated instruments with CDs, but the timing resolution is limited to 13 milliseconds which is not accurate enough for precise piano sequences
Solution Approach 1:
The patent introduces an intermediary time-stamping mechanism that uses the CD audio data stream itself as a high-resolution time reference. Instead of relying on the low-resolution CD sub-channel timing information, the system inserts time stamps into the audio data stream at a much finer resolution (22.7 microseconds), which then serves as the basis for synchronizing MIDI events with the audio playback.
Solution Approach 2:
The patent changes the timing parameter resolution from the CD sub-channel's 13 millisecond granularity to a much finer 22.7 microsecond resolution by utilizing the CD audio sample rate (44.1 kHz) as the time base. This parameter change enables precise timing for automated piano sequences while maintaining compatibility with standard CD playback.
2Adaptability or versatility
If music sequences are pre-synchronized to digital accompaniment tracks on CD, then synchronization is possible, but the system cannot use off-the-shelf commercial CDs with user-authored music sequences
Solution Approach 1:
The patent applies preliminary action by pre-calculating and inserting time stamps into the CD audio data stream during the authoring process. These time stamps are placed at precise intervals based on the audio sample rate, creating a hidden time reference that will be used later during playback to synchronize MIDI events with the audio without requiring any modification to the commercial CD itself.
Solution Approach 2:
The patent makes the CD audio data stream serve multiple functions: it acts as both the audio signal to be played and as a high-resolution time reference for synchronization. By extracting timing information from the audio data stream itself rather than relying on separate sub-channel timing data, the system achieves both universal CD compatibility and high synchronization precision.
Data Source
AI summary
The invention disclosed is a system for playing a music sequence such as a MIDI file in synchronization with a prerecorded CD. The synchronization is accomplished by using the digital media sample rate as a common time base for progression of the playing of the digital media and the music sequence.