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Level 2

171 points

Export process _adds_ stuttering to movies with frame-rate change

SYNOPSIS: When I playback a certain movie project, called VFT, in iMovie 9.0.4, the motion is smooth. If I export it, and then view the export, the motion is jerky. I haven't found a way to view it where the motion is not jerky except to view it as a "project" in iMovie itself. There is a uniform stuttering exhibited in the exports. It looks like the film stops briefly several times a second. (For a very clear alternate example of this, get the Ren and Stimpy episodes "Black Hole" and "Space Madness". The title sequence background (with the moons, planets, etc. moving from right to left) is exactly the same, but appears to run smoothly in "Black Hole" and jerkily (5 jerks per second) in "Space Madness". Can anyone here explain this?) Note: The film VFT is characterized by a lot of moving scenery.

EXAMPLES OF THE STUTTERING: I picked the two parts of the movie (called "Visuals for Timesteps" (VFT)) that best exhibit the stuttering and put them in their own project. I exported the project from iMovie using "None" for compression and "Best" for quality. I then processed them through MPEG Streamclip according to smugmug.com's recommendations and posted it. You can see it at

http://betaneptune.smugmug.com/Movies/Stuttering-examples/26311872_Sh5Kz7#!i=219 2123682&k=mr9Vckn

THE FULL STORY: I made some Super 8 movies at 18 fps in the 70s and 80s. I had them transferred to digital. I received files from the transfer company in the form of QuickTime movie files. The format: Apple Motion JPEG A, 1440 x 1080, Millions. This was a high-definition scan. No interlacing. No blended frames. Each and every frame in the file is a digital copy of each and every frame in the film.

I imported these movie files into iMovie. Ideally one would edit them at 18 fps, but that's not an option with iMovie. So I created projects using 24 fps. To preserve the speed, iMovie doubles every third frame to "stretch" each 18 frames to 24. Why did I choose 24 fps? Easier editing, smaller files, and the hope of making 24 fps progressive DVDs or even BluRays one day. Furthermore, it was recommended by two independent sources, and it taxes the computer less. I was concerned that the 3:4 pulldown would give jerky motion, but playback in iMovie looked perfectly smooth. This surprised me, but it seemed fine, so I went with it.

One of the movies is called "Visuals for Timesteps" (VFT). This is a highly unusual film in that there is a lot of motion of the entire scene a lot of the time. While this looks fine when playback is done from the project browser, there is a uniform stuttering when playing exports. It looks like the movie stops several times a second, just what you might expect from the 3:4 "pulldown", so I assume it is. (My other films mostly look okay.) And it doesn't matter what app or hardware I use to view the export: QuickTime 7, QuickTime 10, MPEG Streamclip, iPod, iPad -- it matters not. (I'm talking about _local_ playback. The Net is not involved, though I get the same effect there, too, in Firefox and Safari.)

I tried different forms of compression: Cmd-E and "Export using Quicktime" with default settings, no compression, and AIC -- all to no avail, which didn't surprise me. I even imported the AIC back into iMovie just to see if there would still be stuttering. There was.

The original 18 fps files from the transfer company play back quite smoothly, with barely a hint of jitter in certain scenes, in QuickTime 7 and 10. The import in the project browser is just slightly more jittery, and again noticeable only upon careful scrutiny of certain shots. Also, the jittering doesn't make the film look like it stops several times a second. The motion appears quite uniform in time. This is far more acceptable (and I'm fine with it) than the stuttering in the exports.

What is going on? What "magic" is iMovie doing when viewing from the project browser that can't be done in exports?

And how can I fix this? I can redo the entire project at 30 fps, which would lessen the stuttering, I would think. But this would be a tremendous amount of work! There are 45 clips, each painstakingly timed, trimmed, and speed-adjusted to match the music. Many required single-frame precision! Many had to be individually cropped to crop out conspicuous defects in the form of dust, splotches, splice gaps, and splice sprocket holes. Also, a few clips needed color correction.

Is there a way to eliminate or at least lessen the stuttering other than a redo at 30 fps? Or an easier way to convert to 30 fps? Or could I create a small virtual disk, add the raw footage and project files, modify file names and folders if needed, and post it for, or send it to, those individuals who have iMovie? Any helpful comments and suggestions are welcome.

Running iMovie 9.0.4 on OS X 10.6.8.

Thanks!

AEF

iMovie '11, Mac OS X (10.6.8)

Posted on Nov 3, 2012 1:38 PM

26 replies

Nov 13, 2012 6:13 AM in response to betaneptune

I may be looking at this wrong, but I see no advantage in going to uncompressed.

A good analogy would be starting with an MP3 music file, and then converting it to an uncompressed WAV file. The file will be much larger, but you do not regain any material that was compressed out to make the MP3. Another analogy would be starting with a RAW file in Aperture. Then create a JPEG. Through the compression to JPEG you lose some detail. Then take the JPEG file and convert to uncompressed. You just get a larger file that includes all the info in the JPEG file. But maybe I am missing something.

betaneptune Author

Level 2

171 points

Nov 13, 2012 8:57 AM in response to AppleMan1958

OK, here's an outline of the process:

1. Transfer Super 8 film to digital file in Apple Motion JPEG A, 1440x1080, Millions.

2. Import into iMovie. This results in an internal copy in AIC format.

3. Export.

4. Compress via MPEG SC according to smugmug's recommendations.

Since steps 1 and 2 are given, I need to start after step 2 with the movie in AIC format in iMovie. Now, don't I lose some information (quality) if I do step 3 with compression? That's why I exported to uncompressed. I put this question to smugmug and am awaiting a response. I didn't ask them about what I'm including below, though.

Alternatively I could try to apply smugmug's settings using iMovie's "Export using QuickTime" function, but the same settings aren't available. The smugmug instructions show a screenshot of MPEG SC's Settings pane and it shows "Better Downscaling" checked. The MPEG SC "guide" says this is for converting to a smaller size in a different way (see the guide). But smugmug recommends not changing the size. But the size in the AIC file in the iMovie Events folder is 1440x1080. So unless I do a 1080p export I will have to change the size. iMovie doesn't offer the "Better Downscaling" option. Does this matter? Come to think of it, I did the uncompressed export at 640 x 480, so I'm already losing some information (quality) from that (and still ended up with a huge file: 20 GB!). But wouldn't I still lose more video information than if I used no compression for the same size?

This is why I did step 3 using no compression.

And I can't duplicate their sound recommendations. Smugmug says for sound: MPEG-4 AAC, Stereo, 48 kHz 128 kbps; but iMovie has two variants of MPEG-4 AAC and neither can be set to 48 kHz. Why? And which variant would I want: "high efficiency" or "low delay"?

AEF

Nov 13, 2012 12:45 PM in response to betaneptune

I would suggest sharing your movie in Apple Intermediate Codec rather than uncompressed.

For sound, the standard for audio on a camcorder is 48khz. The standard for a music CD is 44.1khz. The standard for a DVD is 48khz. iMovie seems to automatically mix to 44.1khz. I don't know why, but I would guess that it is easier to resample the low resolution voice track from a video to match the high resolution music track than vice versa.

My guess is that Smugmug could handle 44.1 audio as long as it is 128kbps AAC, but you could test.

My further guess is that they would take whatever you send them, but then they would have to process it on their end to meet their bandwidth requirements. This is what YouTube does. They take what you send them and then compress it to their internal standards. My theory for YouTube is to give them the highest quality file that I can, so that when they compress it, they have a lot to crunch on. With the SmugMug specs, it would already be highly compressed.

Your size in the Events folder is 1440x1080, but the size of your finished movie should be 1920x1080 assuming you used FIT to make it fit within the 1920x1080 frame by letterboxing.

betaneptune Author

Level 2

171 points

Nov 18, 2012 1:17 PM in response to AppleMan1958

So why AIC over H.264? I only did uncompress as an intermediate step between iMovie and MPEG SC to avoid quality loss due to recompression. Smugmug has since informed me that it should make little difference, so that it is not worth the trouble.

Upon some reflection, I think you're right about the sound. Smugmug doesn't explicitly mention 48 kHz, but they do mention 128 kpbs AAC, so I think, like you say, that that's quite satisfactory. Actually, they say "MPEG-4 AAC, Stereo, Auto HZ, 128kbps". So AAC 128kpbs seems fine.

Now, it would be easier to do this directly from iMovie. The main problem is the MPEG-4 AAC. IMovie has 2 versions: High efficiency and low delay. Do you know which one MPEG SC does? Its "user's guide" doesn't say.

As far as size, if I were to max it out I'd go to 1920x1080 with black bars. I hate incorrect aspect ratios. Stretch-o-vision as a friend once called it. But does anyone ever actually get to watch 1080p on the Net without problems? I have 10 Mbps download speed (13 when measured) and still 1080p doesn't play smoothly a lot of the time.

Thanks again.

Nov 18, 2012 2:28 PM in response to betaneptune

I suggested AIC because you wanted to use MPEG Streamclip for compression. If it was me, I would do the whole thing in iMovie (and go straight to h.264), because I do not see a benefit of using MPEG Streamclip in your case.

The advantage of using 1920x1080 with black bars is that you can fit the 1440x1080 footage into a 1920x1080 frame with no scaling. My 8mm footage came back as 1560x1080 Motion JPEG, which is an odd size, so I wanted to preserve the individual pixels without scaling.

I have 50 Mbps internet download speed and 10Mbps up. I try to watch YouTube in 1080P and most of the time it works. But if there is congestion on the internet between me and YouTube, it doesn't play smoothly sometimes.

lhaw

Level 1

0 points

Nov 23, 2012 3:29 PM in response to betaneptune

Hi there,

After a week of playing with settings and smugmug uploads I realized that you don't really need to use the recommended MPEG converter (or any other 3rd party program) to get the videos in the right format. Like you I was sharing from imovie (30 minutes), converting in MPEG (30 minutes) and then uploading to Smugmug (something less than 30 minutes).

I started playing with the 'Export Movie using Quicktime' option in iMovie instead and after many failed attempts finally got a combo that is suitable for upload to Smugmug (now we just need something that goes direct from iMovie to Smugmug but at least this is something of a good start).

Here's the options I used;

Share / Export using Quicktime

Choose the file name and location

Click 'Options'

In the Video box, click 'Settings'

Compression Type: H.264

Frame Rate: Current

Data Rate: Restrict to 3200 kbits/sec (I tried to mimic the MPEG setting recommended by smug mug so chose the restriction based on the resolution to restriction chart they had)

Encoding: Faster encode (Single-pass)

Click 'OK'

Still in the Video box, click 'Size'

Dimensions: 1280 x 720 HD (that's what I needed, if you choose something else you'll need to change your data rate too I think)

Click 'OK'

In the Sound box, Click 'Settings'

Format: AAC (not sure if this is the best one but it worked for me. i tried with one of the others and got zero sound)

Rate: 48 (again tried to mimic smugmug recommendations)

Quality: Normal

Encoding Strategy: Average Bit Rate

Target Bit Rate: 128

After saving the file this way direct from imovie I was able to upload direct to smugmug (as long as I remembered to keep the file under 20 minutes! just for the record, 20:01 will not work - yep, I tried it 😟)

betaneptune Author

Level 2

171 points

Nov 25, 2012 2:40 PM in response to lhaw

Greetings,

Thanks for experimenting with this.

I recently tried a 640x480 with and without the 1200 bps limit. The former looked out of focus relative to the latter. The latter also showed the grain of the original Super 8 film, which means resolution is better. There was also a little less banding in the latter. I will ask smugmug why I need to use the limit. Either way, by the way, the smugmug versions looked worse than the local versions. No surprise. And the same happens on YouTube.

Did you use "faster encode" just to speed up the experiment? I've been leaving it at double, but the two clips I've been working with are only about a minute each.

Sound. Here's the big revelation you provided. AAC! Previously I thought I'd need either MPEG 4 High Eff. AAC or MPEG 4 Low Delay ACC (because smugmug said MPEG 4 AAC, not AAC). The former didn't offer 128 kbps. Neither offered 48 kHz, but now I think that's because my soundtrack is from a music CD. Anyway, I tried AAC and it comes up as MPEG 4 AAC LC, which is what's on another smugmug webpage, http://help.smugmug.com/customer/portal/articles/84563-video-details-and-specs. So AAC is it! That page also says 48 kHz sampling rate, but I think I'm stuck with 44.1. (The page http://help.smugmug.com/customer/portal/articles/84569 says at the bottom "Auto HZ", so I think 44.1 should be okay.)

My previous efforts, which used iMovie's default, Linear PCM, gave good sound. I will try AAC next time I upload the entire 14 minute film (VFT). (Unfortunately, iMovie doesn't copy any sound when you copy and paste excerpts to another project! So my short excerpts have no sound.) Then there's "average bit rate". There is no mention of this at smugmug.com, but YouTube says to use "constant bit rate". Of course that's for YouTube. Still, I suppose "average bit rate" is okay. I'll ask them.

Then there's the "frame reordering"/B-frames bit. I'm guessing it's better to leave this unchecked, just to be safe. YouTube says to not use it and the MPEG SC screenshot on smugmug's help page shows B-frames unchecked.

One problem I found that I haven't mentioned is the effect of Finder. I recently found that Finder uses as much as 90% CPU when focused on my external drive (tends to hover around 70 - 80%, with brief periods as low as 10% and as high as 90%). Huh? Why is that? Anyway, that may have caused some problems, like QT not being able to keep up with my largest-size exports, or long pauses when watching over the Net. But even when Finder is not on my external drive, I get the same uniform stuttering with local viewing of local exports, which is the chief topic of this thread. And I pass my blind test every time, regardless. So it's definitely not that.

Thanks for your help. (I'd click "this helped me", but you only get two of them per thread, and they're both used up.)

AEF

KROlsen

Level 1

0 points

Nov 26, 2012 12:09 AM in response to betaneptune

betaneptune,

I'm perplexed by the ability to choose the "NO Compression" option in the QuickTime compression box. I read in my Missing Manual for iMovie 11 that this is an option BUT it is not an availible choice when I walk through the Quicktime compression choices. I don't get the ability to get to "None" as you have outlined.

Share > Export using QuikTime...> Options > Settings > Set Compression Type to None

I only have the following options undr the Set Compresion type..

Animation

Apple Intermediate Codec

DV - PAL

DV/DVCPRO - NTSC

DVCPRO - PAL

DVDPRO50 - NTSC

DVCPRO50 - PAL

H.264

MPEG-4 Video

Photo - JPEG

I actually want the "None" option but it is not there. So, what is the secret to getting to the "None" setting?

I'm running an iMac 2011,10.7.5 and QuickTime 10.1

Appreciate your help. Thanks.

betaneptune Author

Level 2

171 points

Nov 26, 2012 4:10 PM in response to KROlsen

KROlsen,

Share > Export to QuickTime... >
Did you set Export to QuickTime Movie as shown above?

Then Options > Settings > Compression Type arrows yields

Does this work? I have 2008 iMac, OS X 10.6.8, iMovie 9.0.4, QT 7 and QT 10. QT 10 is in my Applications folder, but when I double-click a .mov file, QT 7 comes up. Not sure if that means anything with iMovie. I had to get QT 7 so that I could upgrade QT to the Pro version. It took a fair amount of hunting on the Web to find the secret to get a version of QT Pro working. And it was also a struggle finding it and installing it.

I see my list looks much like yours except that you're missing None and I have PNG. Maybe yours doesn't have the none. I'm sorry if it doesn't.

AEF

betaneptune Author

Level 2

171 points

Nov 26, 2012 6:39 PM in response to betaneptune

I have to mention here an important correction to one of my assertions above:

I said that pointing Finder to my external drive pushes the CPU usage up to very high percentages. I just found the reason. I had "Calculate all sizes" checked, and that apparently is "attached" to the drive. I unchecked its box and the CPU came way down to normal levels. OK. Learned my lesson! (^_^)

betaneptune Author

Level 2

171 points

Nov 28, 2012 5:56 PM in response to betaneptune

Smugmug says to use their recommended data rate limits when you make exports because that's what data limit they use on your video, and there's no point sending them a file with a higher data rate when they're going bring it down to their level anyway, and that way you can upload a smaller file. However, I found that the picture looks a little better if you send them an export that doesn't have their data limit applied.

As far as the stuttering goes (the topic!), I'll just have to redo the whole thing at 30 fps. And for the best quality, copy the project to portable drives and send them to people who have iMovie.

A big thanks to AppleMan1958 for putting in so much effort to help and to Ihaw for his clues regarding the audio settings. I just wonder, now, if Average Bit Rate is the best encoding to use as far as video/audio sync goes.

Thanks!

(^_^)

Export process _adds_ stuttering to movies with frame-rate change