19-09-2018, 12:03 PM
The BBC's first all-electronic 405 to 625 converter was the CO6/502, which was a version of the analogue line-store converter with circuit constants optimised for 405 to 625. This was required to allow 405-line VT recordings to be replayed into a 625-line environment.
By the early 1980s, this converter was becoming problematic to maintain. One of the engineers in Standards Conversion therefore calculated the coefficients required to perform the conversion on the ACE, and the necessary PROMs were produced in-house. I believe that, in later years, it became standard practice to make a 625-line dub of the material when it was converted, since the original tape was becoming subject to physical degradation. For a number of years, a VR-2000 and the boards to fit it were maintained, initially at Television Centre and later at Windmill Road, against the requirement to replay 405-line material.
When the decision was made to transfer all the analogue VT archive to digital tape, this clearly necessitated conversion of all remaining 405-line material to 625. Once this had been done, it was decreed that there was no further operational need to handle 405-line material and therefore that no arrangements need be made to undertake any further conversions after the ACEs were retired.
I imagine that 405-line material on various tape formats still turns up from time to time: I have no idea how this is handled. Given that even material recorded off-air will be going on for 50 years old, I suggest that satisfactory replay might be challenging in some instances.
By the early 1980s, this converter was becoming problematic to maintain. One of the engineers in Standards Conversion therefore calculated the coefficients required to perform the conversion on the ACE, and the necessary PROMs were produced in-house. I believe that, in later years, it became standard practice to make a 625-line dub of the material when it was converted, since the original tape was becoming subject to physical degradation. For a number of years, a VR-2000 and the boards to fit it were maintained, initially at Television Centre and later at Windmill Road, against the requirement to replay 405-line material.
When the decision was made to transfer all the analogue VT archive to digital tape, this clearly necessitated conversion of all remaining 405-line material to 625. Once this had been done, it was decreed that there was no further operational need to handle 405-line material and therefore that no arrangements need be made to undertake any further conversions after the ACEs were retired.
I imagine that 405-line material on various tape formats still turns up from time to time: I have no idea how this is handled. Given that even material recorded off-air will be going on for 50 years old, I suggest that satisfactory replay might be challenging in some instances.
There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey.
John Ruskin
John Ruskin
