Skip to main content
sandeepthefourth
sandeepthefourth
Participant
July 9, 2018
Answered

Converting 1080/50i --> 720/50p (and keeping slow-motion!)

  • July 9, 2018
  • 3 replies
  • 6350 views

Hi there,

How can I convert 1080/50i footage to 720/50p footage?

I had a shoot day over two days filming with a C300. The first day the camera shot at 720p (50fps) as we need slow-motion from both days. The second day the footage was shot at 1080i (50fps). Is there any way to cleanly convert the second day footage to match the first day, and therefore being able to interpret the footage at 25p for slow-motion?

Thanks!

This topic has been closed for replies.
Correct answer SAFEHARBOR11

Your issue with your slow-mo is not video resolution, but rather is temporal - having to do with time. When shooting 50p, the camera captures a complete frame 50 times per second. When shooting 50i, the camera only captures frames 25 times per second (via 50 fields 50 times a second, but frames are what matters here). Thus you cannot expect the same smooth motion at 25p as you get with 50p, as you have only half the temporal resolution.

So what format do you really need to deliver at, the 720p25 or 1080p25? Either way, just drop the 1080i footage into the 720p or 1080p sequence and it should work out automatically.

Thanks

Jeff

3 replies

sandeepthefourth
sandeepthefourthAuthor
Participant
July 16, 2018

Thanks for the help all! I ended up doing as you suggested SAFEHARBOR11​ which has worked a charm. It looks like PP is intelligent enough to realise I want the fields combined into a single frame - so essentially a 25p sequence with no interlacing artifacts.

Re the slow-motion - I am aware of Twixtor but I usually default to Optical Flow first. I've seen pretty decent results all the way down to 50% so will give that a go.

Got pretty detailed in this thread at one point but good to have the technical background. I feel like I'm now pretty well-versed should this issue ever come up in the future!

D
Community Expert
DeanUtianCommunity Expert
Community Expert
July 9, 2018

As Jeff mentioned - the 1080i is fields (odd and even) so is half full frames.

Here's a bit more to the explanation.


The 'i'  refers to interlace - and saves in fields.
'p' refers to progressive - saves full frame information.

Generally, it's better to record in progressive mode.

For more details on progressive vs interlace, see the article below:
https://photography.tutsplus.com/tutorials/choosing-progressive-versus-interlaced-video-recording--cms-22302

S
SAFEHARBOR11
Participating Frequently
July 9, 2018

Your 1080i footage is NOT 50fps, it is only 25fps. The "50" refers to fields, each of which is only half a frame. So will not be able to equal the slow-mo quality if 50p with your 25p (from 50i source), sorry.

Thanks

Jeff

sandeepthefourth
sandeepthefourthAuthor
Participant
July 10, 2018

Ah, I was hoping sacrificing resolution (1080 -> 720) may have meant there was some way of going to 50p.

But as there's not, can I convert my 1080/50i footage to 1080/25p without quality loss?

S
SAFEHARBOR11Correct answer
Participating Frequently
July 10, 2018

Your issue with your slow-mo is not video resolution, but rather is temporal - having to do with time. When shooting 50p, the camera captures a complete frame 50 times per second. When shooting 50i, the camera only captures frames 25 times per second (via 50 fields 50 times a second, but frames are what matters here). Thus you cannot expect the same smooth motion at 25p as you get with 50p, as you have only half the temporal resolution.

So what format do you really need to deliver at, the 720p25 or 1080p25? Either way, just drop the 1080i footage into the 720p or 1080p sequence and it should work out automatically.

Thanks

Jeff

Terms & ConditionsAccessibility statement
Using the community Terms of use Privacy Cookie preferences Do not sell or share my personal information ad choicesAdChoices