Why doesn't iMovie export at 1920*1080?

Jon, just a small clarification - for anyone who's confused by this (..I don't know if we're all going round in circles here, making amendments to each other's comments..)

"..QT employs a simple "drop frame" algorithm, most "HD" fanatics are not that happy with the result.."

NTSC uses a "drop frame rate" method for describing the number of frames shown per second. And QT also uses this description when handling NTSC video.

But no frames are actually dropped when using "drop frame rate" frame counting. It's just that some numbers are dropped when counting frames, so that the equivalent of, say, 29.97 frames can be timed per second.

It's like February. It's got only 28 (or 29) days instead of 30 or 31. But no days are missing or dropped between Feb 28 and March 1. They are just renumbered: after Feb 28 comes March 1. And some years there's a Feb 29 counted. There's never a Feb 30.

Same with drop frame rate: in NTSC, every minute - unless it's the 10th, 20th, 30th minute, etc - two frame numbers are dropped from the count. No frames are dropped. Similarly with any 23.98 frame-count; no frames are actually dropped.

(..For anyone who may be interested, here are a couple of extended descriptions of this.. by Andrew Duncan, and by " chambinator"..)

WHY limit to 960x540?

Watching interlace HD as one edits in 08 -- it's clear that 1080i source files after import remain interlaced. You know this because you can see the "combing" on fast movement. This is unique to 08 -- you don't see it in FCP. (With FCP, each 540-line field is processed separately. Fields are never combined and shown mixed together -- hence no "combing.")

Seeing combing is a clear sign that both fields are combined into a single 1080-line frame. FX are then performed on this frame. Why? Because graphics processors work with frames, not fields, when they generate FX.

So, 08 in order to always have realtime FX -- uses the graphics processor to do FX. That requires fields be combined into frames. The 1080-line result will have almost full vertical resolution on static shots. On motion, vertical resolution is decreased and combing appears.

Combing during editing is acceptable, but not in an exported movie. To get rid of combing, a filter is applied to the 1080-line frame. After filtering, the edges are nicely blurred and the combing covered-over. And, the frame is now only 540-lines. Which is why we have a 540-line maximum frame.

Given square pixels -- the horizontal axis is filtered to 960-pixels.

So the NATIVE export is 960x540. It can then be scaled-down or scaled-up.

Hi Steve,

Thanks. Good question too. Why limit? Apparently we iMac, MacBook, MBP and other users who lack a display that can display it cannot achieve it and there is no default "virtual machine" to use. I am hoping it is a matter of finding and installing one. Apparently if our machines can't display it we may be out of luck because the Mac renders from the graphics card and determines it's limits by the size of our display. Is there anyone who connects to a display that supports 1080i (Apple's 30" Cinema) and doesn't get that same error message? Our other option for 1080i is the H.264 as it is scalable by design but I am not sure at how it would handle it. You will know when you get it to work as the OS is resolution independent so when you do get it to work you will not see the entire image as it will be beyond the limits of the screen.

There are a couple of command lines you can try that are global so I want to read a couple more thing before I post them (they effect everything) and there are a couple of things that don't appear to be what they are supposed to be. Can you set up iMovie for a PAL project of the same and copy and paste that as well? I should be online later this afternoon and should have a better answer or hopefully a solution tonight.

But the limit of your display is why.

Sweet Polly

"But the limit of your display is why."

I really hope this is not the case, because that would be an odd decision: to limit the viewing on the machine where the editing was done.
What if I have an 100 inch TV? (kidding...)

Hi altero,

Unfortunately it is. But-.. all is not hopeless. Often times in logs you will see VM. Many people think it is Virtual Memory but is actually indicating a "Virtual Machine" or hardware that simply does not physically exist in your machine. If you can add a virtual display that supports this resolution and your graphics card supports the same you will be able to do so but viewing the content on your machine at actual size will go outside the bounds of your display. As for viewing your Desktop like this turning on Zoom in the Universal Access preferences may let you drag it around to see all the bounds I'm not sure. So limiting the viewing[/i} is beyond Apple's control, i.e. viewing 1080i at actual size on an ipod will only show a very small portion of the movie. The limiting of the rendering is where the issue is a concern. Scaling down to view usually results in an acceptable image while scaling up isn't always so grand.
You can try this but I think the resulting error still applies unless you change the settings globally and I am not sure if these commands will even do anything as they may need to write to HIMoviewView or something else in 8.
defaults write com.apple.iMovie QuartzComposerDefaultMovieWidth 1920
defaults write com.apple.iMovie QuartzComposerDefaultMovieHeight 1080
Before wasting time to do this someone would want to verify that an iMac or MB's graphics card can support this many lines of resolution.
So can anyone confirm?:
If you follow the steps in the post above while connected to a 1080 display do you still get the error message, "Selecting Full on this computer may result in degraded movie playback"?
The other question is is if playback on "this computer"is all that is effected or is the actual file set to these dimensions? If your create it at the 540 does the file actually contain all the data for 1080?
Sweet Polly

I can try writing the commands, but only if you tell me the "antidote", the reversing command 🙂.

But I don't have an 1080 display.

Hi altero,

If it doesn't work set it to 960 and 540 or your preferred movie size. Setting it any differently will result in an anamorphic effect i.e. if you set it to your display size.

This command will only effect iMovie if it will do anything at all 8 I'm not certain as if this command has been removed it does nothing. The only way you will know if it worked is buy playing back the created movie and it will not fit you screen and appear to be cropped.

Do you have an Apple Store Nearby? Sometimes just connecting to a supported display will keep the display's parameters available to the graphics card. What the goal is is to have a display you can select in System Preferences > Displays > Resolution: you want 1920 x 1080 to show up in the list. Learning the macros or keyboard shortcut will help you out as you will always only be able to see 900 of the 1080 actual lines on a Macbook and will need to navigate around your Desktop when portions of it may not be visible and I'm not certain if universal access will move enough

Sweet Polly

The resolution of the DISPLAY I'm sure has no role in the 960x540 limitation. When I say the graphics processor is used for FX, I mean the GPU itself. The GPU uses system RAM and VRAM. The GPU could care less what physical display is connected to the VRAM. Only if the VRAM is too small could image resolution be affected. I have 256MB of VRAM, more than enough for 1920x1080 computations.

Using the GPU for FX was started by Matrox for FX. It's not a new idea. The GPU is borrowed to compute FX while also driving your display.

To try to avoid speculation, and to supply a bit of practical testing, I've just swapped my Samsung 1280x768 monitor for an Apple 23" 1920x1200 Cinema Display on this quad G5 PowerMac.

I've just played back the video I previously 'Shared' from iMovie (see several posts above) which now almost completely fills the screen, instead of overflowing it. The quality of the 1888x1062 exported movie looks even better (clearer, sharper, slightly better contrast) than the original footage. But it looks exactly the same as it did on the Samsung, except that I can now see more of it.

I imported the same footage with the 1920x1200 Cinema Display connected, still got the..



.."Selecting Full on this computer may result in degraded video playback" message, though my graphics card's (Nvidia GeForce 6600) display settings are now 1920x1200 instead of 1280x768, and then Shared (exported) it, as before.

There is absolutely NO difference between the footage imported and exported with the lower pixel count Samsung 1280x768 monitor connected, compared with the footage imported and exported with the Apple 23" 1920x1200 Cinema Display connected.

As mentioned above, it'd be rather odd if the editing and exporting results were of different quality depending on what monitor, or video settings, you had.

Speculation and guesswork doesn't often help very much. If we want to understand the encoding, or decoding, or anything else which goes on inside iMovie, it's really better to actually test what happens (..e.g; by creating HDV-compatible 16:9 dimensioned two-field frames from, say, Photoshop files of odd (white) and even (black) lines, and then see if iMovie de-interlaces or combines them or discards a field and doubles a field or whatever..) or to actually measure the dimensions of material imported into, or handled within, iMovie, or to go to the Developer Discussions and to see how the actual programmer(s) of iMovie have configured its behaviour.

Just guessing about its import and export capabilities or features doesn't really get us anywhere. If we have real, demonstrable, helpful evidence of what it does, and how it actually handles video, then let's say so.

But if we're just surmising, I don't see that it's worth bothering.

This is all very confusing. If I am an amateur and I want to watch HD footage from my HD camcorder on my HD set, can I use iMovie?

@ Sweet Polly: I tried your commands, but the result is the same: "curent" is 960x540, and the resulting movie is, of course, 960x540.
The closest Apple Store is more than 2000 km (kilometers, for Americans 🙂 ) away; but I could test with the larger display, asking some of the colleagues of my forum. But I strongly doubt it makes a difference.

@David Babsky: I metioned in several posts/topics here that it makes no sense to me the explanation that the resolution of the exported movie is related to the video card. The video card is heavelly involved in editing (in displaying the results of editing, to be more precise) through Quartz Extreme. But several esteemed members of this forum told that, after experimenting with files and diferent machines, the conclusion is that export is dependent on video board.
Because I can not believe just like that, and I have to see for myself, I asked one of my forum member to test it on his (enhanced) Mac Pro. The result: 960x540. Q.E.D.

@miniDVD: the short answer is NO.
HD specifications are: 720p, 1080i, and 1080p. iMovie 08 can not deliver that (the higher options you see in "Size" panel represent upscaling, not real HD).
Now, there are people saying that 960x540 movies send to a HDTV through Apple TV looks very good. That I can not test, but nevertheless, it's not what it's called HD.
P.S. It looks that there is a way to export real HD, through "Export Final Cut XML". Then Final Cut will export it to real HD. But it's Final Cut exporting, not iM08. Did not tested yet.

Message was edited by: altero

The answer is YES! The problem was that given the title of the first post -- there was an assumption that 08 is limited to 960x540. My first tests seemed to show that was true even though much earlier I thought these comments about 08 were wrong.

I then discovered by accident that before export, 1920x1080 was internally be processed as 1920x1080. After more work I became convinced all this talk about graphics card limiting video was false. I'm not sure where it came from -- and why so many believe it to be true. As did the thread starter.

So I went back to my original belief that one could indeed export to QT at 1920x1080 using just the method David posted. I imported an AIC 1920x1080i movie as FULL. I then compare the 1920x1080 source with the 1920x1080 08 exported AIC movie. There was no difference!

So simply ignore the export message that the video is PROGRESSIVE at 960x540 and choose the AIC codec with a size of "1920 x 1080 HD" and you will get an interlace HD movie. Of course, you still need to find something to do with the movie.

With all due respect, I can not dismis what my eyes see and mind think.

Unfortunatelly, I cannot attach pictures here. I did the following:
- Exported from iM08 to AIC, size changed from "current" to 1920x1080 HD;
- Open in QuickTime and took a screen shot of a part of the window, one at normal size, the second when the movie was double size;
- Open the same movie from iMovie folder (the original captured movie file), and took the same screen shots.

The difference is visible, the movie exported through iM08 is lower quality. I'm sure that if I repeat several times the export, the difference in quality will be more visible.

So, I have to stick to my oppinion.

Well, I did another test:
Open a HD movie in QT, select few seconds, and export as QT, choosing as codec None;
Import that in iM08, and export it as well as QT, witn None on codec (you will see already that the "current" size is 1920x1080).

The resulting movie is 1920x1080, as the original movie, so it is HD! iMovie 08 can export as HD!
The only downside is that the files are huge: Data Rate about 1700 mbits/s, one second and half weighting about 225 MB.

Thanks Guys!