By the early 1970s, Thomas Stockham of Sound Stream Digital, created the first practical use of pulse-code modulation, also called PCM digital recording, for high fidelity purposes. The first to be released were rereleased cleaned up versions of acoustic recordings made by the great tenor, Enrico Caruso. Early computer algorithms were used in the process of cleaning up the scratchy old 78 RPM records. The process could not be done in "real time" as the early computers were not very powerful or fast, compared to 2010-era computers. All of the data had to be stored on linear digital tape and then played back, in real time. The actual ingest from the 78 RPM records to the digital tape was also done in real-time. The computer processing to clean up the surface noise, pops and scratches took the early computers quite some time to process.