backing up bbc documentary

[johnmckee]

Hello I am creating a backup of some BBC documentaries such as "Life of Birds" and "Blue Planet". I am pretty successful using avisynth like this:

...
qtgmc(...)
srestore()
...

This gives me a nice progressive video at 25 fps. What I am wondering is if I should then do some further processing to "stretch" it to 24 fps. Is there a way to know if this should be done? My understanding is that most PAL video is 24 fps that has been "sped up". Or do most BBC documentaries get mastered at 25 fps? My computer does not like 25fps (unless I use reclock) but my Philips TV does not seem to care..
What should I do? Or is it simply a matter of taste?

[Asmodian]

It seems "Blue Planet", at least, was mastered at 50i. (http://www.broadcastermagazine.com/news/bbc-s-the-blue-planet-goes-high-definition/1000111965/)

From the article:
"The motion compensation was of particular importance to us for archive and BBC delivery specifications," said King. "The series was always going to be mastered at 625/50i. Making the seamless conversion to 1080/59.94i was extremely important, and we are delighted with the results."

[johnmckee]

so it is a matter of happening to have read an article somewhere? is there no technical way to determine this? I know google is my friend but sifting results can be very time consuming.. is there any unified resource for finding this info?

[Asmodian]

Not that I know of. There is only a 4% difference and you would need to know if the audio was just sped up or also pitch-corrected if you wanted to change it back. Some people can hear the difference but I am not one of them. :(

[smok3]

Not that I know of. There is only a 4% difference and you would need to know if the audio was just sped up or also pitch-corrected if you wanted to change it back. Some people can hear the difference but I am not one of them. :(

this one is 50i master, so there was no speedup/slowdown of audio in the chain.

edit: quote from http://www.bbc.co.uk/guidelines/dq/pdf/tv/tv_delivery_of_programmes_to_worldwide_v1.0-2011.pdf
Programmes should be delivered on HDCamSR:
• 1920 x 1080 pixels in an aspect ratio of 16:9
• 25 frames per second (50 fields) interlaced - now known as 1080i/25.
• colour sub-sampled at a ratio of 4:2:2
The HD format is fully specified in ITU-R BT.709-5 Part 2.

[Asmodian]

Of course "Blue Planet" was mastered in 50i (I already stated that) I meant for other 25 fps material that really was mastered at 24.

I personally wouldn't do a 25->24 slow down because it is hard to figure out which method to use for each source even if you know what it was mastered in. Reclock after the fact works well for me too, though this would change if targeting non-PC playback.

Happily, given the PDF you linked smok3, it looks like anything from the BBC, 2011 or newer at least, should be mastered at 50i. This is probably true for everything from the BBC before 2011 too but I don't know how to be sure.

[smok3]

British Broadcast Corporation = PAL land.

[minaust]

What I am wondering is if I should then do some further processing to "stretch" it to 24 fps. Is there a way to know if this should be done? My understanding is that most PAL video is 24 fps that has been "sped up". Or do most BBC documentaries get mastered at 25 fps?

AssumeFPS (24, sync_audio=true) will do a simple slowdown.