Рок Восточной Европы (forum "East Rock")

Digital technology in reconstructing Krzysztof Komeda's recordings
We are proud to present, for the first time in the history of phonography, unique, historical recordings done on an amateur tape recorder, at 9.5 cm per second. These recordings, which have preserved some truly remarkable concerts, can now be presented to you as a result of having undergone a complicated process of reconstruction. State of the art digital technology was utilized restore the perfect sound and the dynamics of the original carrier.
There were four basic problems to be tackled in the process of reconstruction:
- the problem of eliminating impulse interference
- the problem of compensating for the frequency distortion caused by the recording devices used
- the problem of reducing the recording medium's broad spectrum noise
- the problem of appropriate digital correction based on analyzing the sound spectrum.
Thanks to the availability of digital technology, a self-tuning filter could be used to record the sound as a set of overlapping memory cells. Our choice of the Fourier transformation and the extent of averaging was a compromise we had to make.
Regaining the compensation filter's proper frequency characteristic and calculating the average spectrum amplitude made it possible to calculate the total characteristic of the adapting filter. The transformation of the recording from analog to digital was achieved by a process of approximation. The analog sound was compared with samples of digital sound.
The digital sound was then transformed by fast operating microprocessors to better mirror the original sound. A memory integrator then calculated the sound field functions.
These technologies made it possible to achieve a remarkable improvement of sound dynamics and tone quality without giving up that "original" sound, and thus being able to fully preserve the artists' interpretation as well as the peculiar timbre and dynamic feel of each of the individual instruments.