Progressive Scan and Rendering

DavidPJ wrote on 6/12/2004, 5:13 AM
I'm still in the dilemma of recording in progressive scan vs. interlace. I've read a lot of the threads, but I still need help. For the last several projects I've used progressive scan. When I render to AVI, I've been choosing interlace.

My reasoning for this was I wanted my source material to be the best possible recording. My finished product is DVD to be played on a standard interlace TVs or one progressive scan Pioneer Elite TV and Pioneer Progressive Scan DVD player. Per instructions from Pioneer, the DVD player is set up for interlace, and the Elite upconverts it to progressive. Supposedly the progressive scan electronics in the Elite are much better than in my low-end Pioneer progressive scan player.

So the bottom line is that I need to produce a DVD that's playable mostly on interlace DVD players and TVs. Do I lose anything by having Vegas convert from progressive scan to Interlace when I render to AVI? Do I gain anything?

If there's nothing to be gained for me by recording in progressive scan, I guess I should just go back to recording in standard interlace format.

Finally, will all new non-progressive scan DVD players still play a progressive scan DVD? Or is it a case by case basis?

Thanks.

Comments

B_JM wrote on 6/12/2004, 6:04 AM
well there is progressive 24p with pulldown and allmost all films on dvd are this way and all dvd players play this fine ... progressive dvd players will output this as 24p ..

then there is 29.97 progressive .. you can encode to this and most players will play it but it will look jerky on many interlaced sets ..


farss wrote on 6/12/2004, 7:34 AM
The bottom line is unless your source material in progressive then I think you're loosing quality converting from interlace to progressive.
But as you haven't stated what your source material is it's a bit hard to know. Sometimes just what the source is can be hard to determine.
For example although all SD TV broadcasts are interlaced if they're showing something off film then it will be progressive, in which case nothing will be lost by converting to 24p. This should mean you can squeeze more onto a DVD and the players will then convert to 60i if needed or playout at 24p if the TV and they can handle it as far as I know.
If it wasn't off film though it's interlaced and converting to progressive could cause problems if something tried to play it out as progressive, it's going to have interlace artifacts unless some intelligence is being applied to the process. Vegas can sure do that but unless you're specifically after a 'film look' then you're actually lower the res for nothing.
John_Cline wrote on 6/12/2004, 9:01 AM
David,

Well, I guess it depends on what you consider the "best possible recording." There is spatial resolution and there is temporal resolution. Progressive video has less than half the temporal resolution of interlaced video. I wrote a rather lengthy "rant" abut this subject here:

Progressive Scan vs. Interlaced

John
Spot|DSE wrote on 6/12/2004, 9:04 AM
That was a *rant?* You need to rant more often. It's a post I've bookmarked because it's very articulate on a topic that's not eloquent to explain.
DavidPJ wrote on 6/12/2004, 1:58 PM
Thanks for the replies. I know this topic is beat to death so I appreciate everyone's insight. To be clear, the source material is progressive, at least according to the info on the Canon Elura. However, I don't know if it's 24p or 29.97.

John Cline, thanks for the link to your progressive explanation. I think I'm beginning to understand temporaral and spatial resolution. However, your discussion centers mostly around Vegas converting from interlaced to progressive. My interest is Vegas converting from progressive to interlace. What happens to the temporaral and spatial resolution in this case?

If my cameral didn't have progressive scan mode I wouldn't even think about this. I think I'll go back to shooting in interlace mode unless someone can give me good reasons to continue with progressive and Vegas converting it to an interlaced AVI.

Thanks again.
Guy Bruner wrote on 6/12/2004, 2:42 PM
If you shoot in progressive, most cameras capture both fields at the same time then output the two fields as interlaced to tape. This maintains the NTSC standard for TV video of two interlaced fields/frame. If you convert progressive video to interlaced, you aren't going to change the original material. The two fields in each frame were captured at the same time, the software divides the frame into two fields and outputs them one at a time. It does this anyway whether you use a progressive or interlaced template at 29.97 fps. So, I would say if you like the look you are getting recording in progressive, keep it.
farss wrote on 6/12/2004, 3:31 PM
I see nothing on the Canon site to indicate that the Elura can shoot true progressive scan at either 24 or 30fps. It probably does have a progressive mode much like the PD150 etc however the frame rate drops very dramatically. Sole purpose on these cameras seems to be for extracting better quality still images. So in a nutshell, leave the camera in interlace for video.
B_JM wrote on 6/12/2004, 5:12 PM
one thing to consider - and its overlooked a lot ...

is that the "compliant" mpeg2 settings for DVD's are frame based -- i.e. progressive ..

field based encoding will make your dvd's look better from an interlaced source (like DV) .. but a lot of players (and even some authoring programs) will not play or author correctly... and therefore not recommended ..

you also can of course get better quality encoding with 24p + pulldown as you have 25% more room for bits ..

so even if interlaced footage has higher temporal quality -- the encoder is still encoding it as progressive frame but interlaced playback of course..


now on the flip side - and whats been pointed out -- if your source is interlaced and playback is interlaced .. well it is a simple choice .

my problem is that my material is allmost all film based , BUT 30-48-60 frame per second often times ... so if i make a 30fs progressive dvd ... it will look jerky on tvs ... if i make it 30fps interlaced , im really only double the same frame ..

depends on what the final playback is going to be is how i work out the frame rate and interlacing and in many cases (ive mentioned this before here) i will interpolate a higher frame rate and then "bring it back down" ..same for slow mo .in many cases ..
DavidPJ wrote on 6/12/2004, 5:12 PM
Found on the web that Canon Elura's progressive mode is 30fps. Here's the exact text from their original brochure:

"The Elura's Digital Motor Drive amazes photo hobbyists and professional photographers by recording an incredible 30 full frame images per second continously. Select this mode when you plan to capture superior quality frames from video for either viewing on TV, printing or downloading to a DV compatible computer."

And from another document: "This mode [progressive scan] also produces high resolution still images from video."
B_JM wrote on 6/12/2004, 5:31 PM
john -- read your rant and its very well explained .. great job ..

but -- DVDs are a trade off for a number of reasons in the encoding stage -- i listed one of them below and there is some additional issues.

Now our company DOES use a min. of 30fps film (70mm) and often higher and larger film sizes (5/70 - 10/70) .. and i couldn't agree more about 24fps for film OR video looking bad to my eye (i cant stand some motion picture theaters - specially if the bulb is flickering bad and not set up right added to the 24p -- which now days seems the norm (along with crappy audio) ) ..
In fact i would rather watch HD at 24fps P , than a lot of film movies -- but in my business - i got no choice in the mater , I got to watch a lot of film ..

back to the DVD -- if you need to pack a lot info on one -- its generally considered to use 24p as it uses less room -- well yes but and interesting fact is that it also (adding pulldown) effects bit rate and if adding pulldown , one should lower the bit rate from your interlaced max (which i say is about 8500 - but depends on the encoder used)

but (and i just proved this on another forum) you CAN go real low in bit rate on a interlaced source also ... in fact i made up 2 samples at 1390 and 1 at 1850 from a DV tape shot right by my house with standard settings in a off the shelf encoder. Not perfect by any means - but at that bit rate you can hold a lot of material on a dvd .. I guess I'm rambling here so i will shut up ////

those clips are posted at http://www.videohelp.com/forum/viewtopic.php?p=944634#944634

http://www.videohelp.com/forum/viewtopic.php?p=944647#944647


Catwell wrote on 6/12/2004, 8:11 PM
In movie theatres you see flicker if there is too much light The more light on the screen the more obvious the flicker. Movie projectors actually show each frame twice to increase the flicker rate to 48 images per second. In the 1960s there was a process called Todd AO (Michael Todd and American Optical) that used 70 mm film running at 30 frames per second. OT I have one of these projectors where I work that has gearing to shift from 30 fps to 24 fps. American Optical provided special lenses for these films both for the cameras and the projectors.

In the 1980s, Douglas Trumbell (I think that's right) came up with the show scan system running 70 mm film at 60 fps. This was a spectacular presentation but suffered from problems in keeping the equipment running at high speeds.

My point is that there is always a better way, but the standards are hard to overcome.