Digital transfer question

[garygraham]

Can any extra picture detail be obtained by going back to 2-inch tapes and making an uncompressed digital transfer at a resolution greater than the standard 720x576? For example 960x720 or 1440x1080. 

Or is it the case that a transfer of the 1990s D3 archive tape (in the case of the BBC) provides everything it's possible to get? 

On another note I noticed a D3 tape drop out on a Good Life episode on iPlayer recently. 

[RWels]

But they are still 625 lines, right? So, perhaps, more bitrate, but one assumes that even that has its limits?

[garygraham]

I'm not an expert and not clear exactly on how the pixels and analogue lines interact. I just wonder if having a much greater number of pixels would capture more from the 625 lines? Although there are 625 lines from top to bottom what about horizontally?

[Peter Stirling]

D3 does not use compression - in audio terms, it is more of a WAV file than an MP3.
Not an expert either but the scaling ie. 720 x 576 is more to do with the display equipment you
will show it on -I think?

So, in theory, it should record and playback exactly what it sees, of course the original recording was made with lines but these can be dealt with soft/hardware.

However, some circuits have been improved since the 90s on the original 2' machines which means the D3s recordings will not have them.

[garygraham]

It depends on what you're starting with. 1440x1080 will capture more detail than 720x576 if there is more there in the original to get. With a digital frame you're effectively imposing a grid of pixels over the analogue image?

[Peter Stirling]

Nov 9, 2021 22:33:20 GMT garygraham said:

It depends on what you're starting with. 1440x1080 will capture more detail than 720x576 if there is more there in the original to get. With a digital frame you're effectively imposing a grid of pixels over the analogue image?

I think that applies to an image sensor that would be used to record a film, this would be H/V pixel counted at whatever era or technology it was made in, obviously improving in leaps and bounds over the years.

I do not think it applies to tape to tape, which records the bandwidth and if the bandwidth rating is higher (which digital obviously is) it will record everything from the play-out tape.

[markboulton]

Quantization is the key here. Circuits to do that, as found in any Analogue-Digital Converter, have steadily improved over the years, especially when it comes to handling sharp edges or trailing/dragging from overload (over peak white) and underload (below black shelf level). Also colour subcarrier demodulation is able to be done better now I believe, which benefits from a higher sample rate than the luminance because it's the sidebands that suffer the most from Quantization than the absolute value at any point in time does.