NG
For info, the LWT quad tapes were transferred to the D2 format.
My guess is that the D2 tapes (identical in performance to D3 - both use 4fsc (17.7MHz) sampling and uncompressed 8-bit recording) were then captured via a PAL composite feed rather than a component Y feed, and the D2 has added burst on its composite output as standard, triggering a PAL decoder to try and decode the B&W 625 signal...
At the time no-one knew the best solution to preserving the tapes from a technical perspective, all that was known was that quad hardware was rapidly becoming extinct and something had to be done. In the end it was decided that it was best to make the best digital transfer of the analogue material available at the time. In this way future archivists would have a faithful accurate digital copy of the analogue material to work with. A good decision in my book, and preceded PAL decoding techniques like you’ve described which were unheard of and likely not yet ‘invented’. Of course sourcing D2 machines now is likely very difficult, but ITV may well have anticipated that and transferred the D2 tapes to something else anyway?
Strange to say I have a photo of LWT’s last quad machine as it was being pushed out the building. In the few hours before that we ‘old’ engineers fired it up and tweaked it up to get pictures out of it. We were surrounded by some young engineers who were simply astounded at the technology (and the noise!).
Nothing wrong with the decision to transfer 2" Quad to D2 - it's the post-D2 transfer that is the issue.
Dubbing B&W 625/50 to D2 shouldn't have introduced any artefacts - they're both composite-based formats and as a result no PAL decoder would have been in that chain (same is true of the BBC's decision to dub 2" and 1" to D3).
The issue is the composite capture of the D2 output via a PAL decoder to component. My guess is that ITV have transferred their D2 archive to a component format and have treated B&W and Colour shows identically and used the same workflow, which is not ideal.
The chroma-artefacts introduced by this route to capturing B&W content are nothing to do with not having 'clever PAL' decoders - they are because they have been routed through a PAL decoder at all. There is no PAL chroma there to decode after all...
Of course if ITV has retained the D2 content and can replay it - then their colour shows COULD be re-transferred via a better PAL decoder - which might be a good solution for premium content. If ITV captured their D2 stuff via a reversible PAL decoder (one which can be 'undone' to re-encode to PAL) and retained an uncompressed component copy (as the BBC do with their archive transfers - retaining a v210 mxf) then it could be possible to re-encode and re-decode via an improved software decoder, which would improve the quality of colour shows.
noggin
Founding member
Earliest surviving 2″ quad videotape masters
For info, the LWT quad tapes were transferred to the D2 format.
My guess is that the D2 tapes (identical in performance to D3 - both use 4fsc (17.7MHz) sampling and uncompressed 8-bit recording) were then captured via a PAL composite feed rather than a component Y feed, and the D2 has added burst on its composite output as standard, triggering a PAL decoder to try and decode the B&W 625 signal...
At the time no-one knew the best solution to preserving the tapes from a technical perspective, all that was known was that quad hardware was rapidly becoming extinct and something had to be done. In the end it was decided that it was best to make the best digital transfer of the analogue material available at the time. In this way future archivists would have a faithful accurate digital copy of the analogue material to work with. A good decision in my book, and preceded PAL decoding techniques like you’ve described which were unheard of and likely not yet ‘invented’. Of course sourcing D2 machines now is likely very difficult, but ITV may well have anticipated that and transferred the D2 tapes to something else anyway?
Strange to say I have a photo of LWT’s last quad machine as it was being pushed out the building. In the few hours before that we ‘old’ engineers fired it up and tweaked it up to get pictures out of it. We were surrounded by some young engineers who were simply astounded at the technology (and the noise!).
Nothing wrong with the decision to transfer 2" Quad to D2 - it's the post-D2 transfer that is the issue.
Dubbing B&W 625/50 to D2 shouldn't have introduced any artefacts - they're both composite-based formats and as a result no PAL decoder would have been in that chain (same is true of the BBC's decision to dub 2" and 1" to D3).
The issue is the composite capture of the D2 output via a PAL decoder to component. My guess is that ITV have transferred their D2 archive to a component format and have treated B&W and Colour shows identically and used the same workflow, which is not ideal.
The chroma-artefacts introduced by this route to capturing B&W content are nothing to do with not having 'clever PAL' decoders - they are because they have been routed through a PAL decoder at all. There is no PAL chroma there to decode after all...
Of course if ITV has retained the D2 content and can replay it - then their colour shows COULD be re-transferred via a better PAL decoder - which might be a good solution for premium content. If ITV captured their D2 stuff via a reversible PAL decoder (one which can be 'undone' to re-encode to PAL) and retained an uncompressed component copy (as the BBC do with their archive transfers - retaining a v210 mxf) then it could be possible to re-encode and re-decode via an improved software decoder, which would improve the quality of colour shows.
Last edited by noggin on 30 January 2021 9:38am - 2 times in total