If you've been paying attention to this thread you will have seen a little discussion about the possibility of using DSP-type algorithms to capture tapes, rather than the traditional "waveform walking" time-domain based approach.

I've spent the past few weeks experimenting with this idea, pursuing a hunch that a combination of a software phase-locked loop (PLL) for synchronisation and something Fourier-esque to identify frequencies might produce reasonable results. I had intended just to use a full-blooded discrete Fourier transform for the frequency domain portion, but BigEd suggested deploying the Goetzel algorithm instead, so that is what I am using.

I don't have any code to share just yet, but I finally (ten minutes ago) added CSW export to Quadbike, so some results are now starting to emerge:

There are plenty of errors in the capture, but there is still much room for improvement here. In particular, one advantage of this approach is that every bit captured comes with an associated

*confidence level*, which provides various options for automatic (and, indeed manual) correction of bit errors. I have not attempted any error correction yet.

Anyway, I seem to have a total of about six Acorn tapes remaining in my collection. I used to have more, but I don't know what happened to them. Is there a repository of WAV recordings of tapes available online anywhere that I can use to test this? If not, I would be grateful if anyone digitising tapes could keep their WAV or FLAC files, and permit me access to them for testing this.

I will release the code for QB, but I would like to improve its fidelity a little bit first.

Thanks.

D