Audio sampling clock synchronization
AssigneeTHAT Corporation
InventorsMatthew S. Barnhill, Roger R. Darr, Matthew Easley
Life of this patent
Estimating the term…
Abstract
Systems, methods, and algorithms for estimating the sample clock difference between an audio playback and recording device are described. The sample clock difference can be determined by sequentially playing the same pseudorandom signal and exploiting the statistical properties of said signal in the recording. An exemplary embodiment utilizes a maximum length sequence (MLS) for the pseudorandom signal. While an MLS sequence is a good choice for clock synchronization, it is possible to use other pseudorandom sequences. The sequence preferably has a sharp correlation peak that is clearly discernable with even a single sample shift and be of sufficient length to support the anticipated clock drift.
Claims18
A system for synchronizing audio playback and record clocks, the system comprising:
- a memory comprising computer-executable instructions;
- and
- a processor coupled to the memory and operative to execute the computer-executable instructions, the computer-executable instructions causing the processor to perform operations comprising:
- a. playing a same pseudorandom sequence repeatedly on an audio system having a clock with a clock rate and one or more speakers, wherein multiple versions of the sequence are played;
- b. recording the played pseudorandom sequences with a recording device having a clock with a clock rate;
- c. calculating a lag at a correlation maximum utilizing multiple versions of the sequence;
- d. using the maximum correlation lag to calculate an estimate of a difference between clock rates of the audio system and the recording device;
- and
- e. resampling the recorded sequence and/or subsequent recorded audio, producing a resampled audio recording, to synchronize the clocks of the audio system and the recording device.
A system for measuring the audio impulse response at a listener position utilizing a maximum length sequence (MLS), the system comprising:
- a. a memory comprising computer-executable instructions;
- and
- b. a processor coupled to the memory and operative to execute the computer-executable instructions, the computer-executable instructions causing the processor to perform operations comprising:
- determining a clock difference between (i) a clock of a playback device playing sequentially recorded nominal maximum length sequences (MLSs), and (ii) a clock of a recording device recording the sequentially recorded nominal maximum length sequences (MLS) played by the playback device.
A method for synchronizing audio playback and record clocks, the method comprising:
- a. playing a same pseudorandom sequence repeatedly on an audio system having a clock with a clock rate and one or more speakers, wherein multiple versions of the sequence are played;
- b. recording the played pseudorandom sequences with a recording device having a clock with a clock rate;
- c. calculating a lag at a correlation maximum utilizing the multiple versions of the sequence;
- d. using the lag to calculate an estimate of a difference between clock rates of the audio system and the recording device;
- and
- e. resampling the recorded sequence and/or subsequent recorded audio, producing resampled recorded audio, to synchronize the clocks.
Dependencies are inferred from the claim text.