720p50 or 720p25 to SD DVD?

[Steve Sykes]

I sometimes need to use 720p50 because I like to see smooth motion and record footage with fast motion. I would like to know if there is improvement in picture quality when converting this to SD DVD. I have already converted 720p25 to SD but I would like some advice on the correct method to convert 720p50 to SD DVD.

For 720p50 I presume the footage has to be interlaced to go on to DVD PAL. However for 720p25 I did not select interlacing in any settings when converting 720p25 to DVD. I presume 720p25 footage is progressive on the DVD and the player itself interlaces for my CRT TV. Is this true, if so how does it do it, repeating frames? If I pause my DVD footage it does look like a progressive frame, so does this mean my DVD player can actually play 720p50?

I don't want to use 720p50 if I end up loosing every other frame. However if I interlace by weaving two frames together correctly then will my footage of fast motion be better than using 720p25?

I hope someone can shed some light on my questions! (Sorry if I have not worded this very well, it's very late now after hours of search on this topic)

Thanks

Steve

[Steve Sykes]

I would love some answers to my questions!

I have just read about "Pure Interlacing". This process supposedly involves taking full advantage of the 50 or 60 individual fields a second that are used in PAL and NTSC video to get the smoothest looking video possible when shown on a CRT TV. If I understand this correctly then I can use 720p50 to SD DVD.

How do I interlace in this way?

In my current workflow for 720p25 I don't know where the interlacing occurs or how it does it:

In my current workflow I don't know where the interlacing happens!?

ATM I import into Vegas choose 1280x720, PAR 1, 8 Bit, Edit in HD, (still not sure whether I colour in 8 bit mode or 32 bit!),
Frameserve to virtualdub, resize to 720x576, not ticking interlaced, Lanczos3 filter,
From virtualdub to TMGEnc, selecting non-interlace, 16:9 625 line (PAL),
The mv2 file I bring into TMPEnc DVD Author.

I feel I need to understand how the interlacing works with this method before trying 720p50. I notice there is no project setting for 720p50 in Vegas unless I change the framerate to double PAL.

I would love some feedback before I wander on guessing, I will try the above workflow with 720p50 and see what happens! Its just nice to know if I'm doing it correctly! I'm also not sure if I have to change PAR settings from square at any point.

[Paul Kellett]

Hi Steve.
I also use Vegas pro 8.
Make your own project preferences.
Then i use the same render template wether i shot in 1080/50i or 720/50p.
You're right about 50p being super smooth,however not that much smoother than 50i.
When downconverting to dvd,ie SD,i can't really see much difference between what was originally 1080/50i and 720/50p.
720/50p is a lot easier to edit with though in vegas,seems smoother on the 2nd monitor,even when adding effects.

Paul.

[Matt Davis]

Originally Posted by Steve Sykes

I would love some answers to my questions!

Briefly, I now shoot 720p50 if I need interlaced SD or footage that will cut well with other shoots.

Assuming Final Cut Pro 6.0.2...

I edit as normal, output 720p, then here's the bit that sucks a little: I pump it through Adobe After Effects to scale down and re-interlace. Either to DVCPro50 or to DV (and then onto tape for the client).

There's a sneaking suspicion that an FCP native plug-in to reinterlace may be available soon, but right now the AE workflow gives me footage that sits VERY well with (if not looking a little better than) DSR-450 footage.

[Bob Grant]

As far as I can see 50p will not give you smoother motion than 50i and for SD PAL you have to deliver 50i. However coming from 50p there's no no need to de-interlace prior to downscaling like there is with 50i so there could indeed be an advantage to shooting 720p50.
With Vegas there shouldn't be any need to go outside of Vegas to make it work either. You should be able to convince Vegas to downscale each frame to 720x576 and then extract one field from each frame. Getting it to happen in that sequence is the clue. If I can find the time I'll see if I can fathom out how to make this work as it's an interesting idea.

[Steve Sykes]

Thank you for all your replies so far.

I can see several advantages for shooting in 720p50: no need to interlace, therefore easier to change to SD resolution, footage can be easily edited for HD and SD both giving smooth motion.

I am still unsure of how / where my footage will be purely interlaced when converting to SD. I can see three options in the project settings in Vegas that I could use....

1) Create a custom template: 1280x720 selecting 50fps (double PAL option)
2) Import into 1080/50i
3) Import into 720/50i

I would prefer option 1 so the footage is kept progressive if outputting for Blue-ray. Paul if you are importing into option 2 above isn't that going to stretch the footage unnnecessarily into a bigger frame? Surely the resolution is also going to be reduced vertically by the interlacing as well? I may have misunderstood what is happening in Vegas but it makes more sense to use option 3 than option 2. Please can you explain further.

I am in the process of up-grading my computer but will be trying these templates soon!

Bob: looking at other threads epecially the "SD DVD from EX1: Horrible" thread; it seems to me that virtualdub's resizing algorithm produces better results than Vegas'!

[Paul Kellett]

Steve.
For 720/50p footage,i make my own project preferences template,1280x720,as you describe,then when finished editing i render as main concept mpeg for dvd-a.
If i've shot some 1080/50i footage and have that on the timeline and want to add some 720/50p onto it then i just put it on,it doesn't seem to me that the project preferences make any difference to the finished product,only to the view at the time of editing.
I've got a lot of coasters now from all my experimenting.
The best quality from dvd that iv'e got is from shooting with Bill PP,detail on,then not adding any sharpening or blurring or whatever in editing.
I've watched many of my experiment coasters on a CRT tv and an LCD tv,both show the same results.

Paul.

[Bob Grant]

Originally Posted by Steve Sykes

Bob: looking at other threads epecially the "SD DVD from EX1: Horrible" thread; it seems to me that virtualdub's resizing algorithm produces better results than Vegas'!

I'm having no problems at all. There's a couple of tricks to get Vegas to do it properly if you're starting with interlaced footage. You must set a de-interlace method, Blend works best for me. I add a tiny amount of sharpening after downscaling. The trick again is to watch the sequence in which Vegas is doing things. Get it wrong and you'll get a mess for certain. There's a control in all FXs that determine where in the chain the FX works, makes a huge difference to the outcome. Look for the triangle next to the FX name at the bottom of the FX window next to the keyframe T/L in the FX window. If you can't find it I'll post a screenshot.

[Steve Sykes]

My new computer should be arriving very shortly and I can try these methods out. Thanks for all your suggestions so far.

I would still love for someone with some knowledge about how / where my footage gets interlaced in my workflow to explain it to me! Can anyone confirm that 50p will get interlaced to exactly 50 individual fields? i.e. a one to one mapping from frame to field. Looking in the help section of the programs I use in my workflow I cannot figure out if this happens!

[Bob Grant]

Steve,
I've been trying to build some tests using generated media to conclusively convince myself that Vegas is downscaling and then interlacing but it's trickier than I thought.
In the interim here's a screenshot that shows the FX toggle I was refering to previously, it's the little triangle before the word "Sharpen".