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Compression question - easy answer?

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Preston Hull
Compression question - easy answer?
on May 16, 2013 at 1:25:08 am

Hi all,

I don't know much about video, so I'm hoping my problem has an easy answer that I'm just too much of a newbie to figure out.

I successfully ran the (latest) FCPX Trial in OS 10.6.8 to create a music video (I'm an audio guy) for YouTube. I exported the project at what I thought were the most lossless settings (as my trial is expired, I can't now check). The resulting Quicktime file is 1.17 GB, and the "more info" is as follows: 640x480, ProRes 422, Linear PCM, SD (6-1-6) color profile, bit rate 42,750. The source footage was 640x480, so to my eye everything is in order.

I do however need to make one change - the file I created has "widescreen" bars, and I didn't realize YouTube was gonna add bars to the sides as well. So I imported my video to iMovie '11 (9.0.4) (again, FCPX trial is over) and cropped the bars.

Here's my dilemma: When I export from iMovie using H.264 at the highest settings (file is down to about 2-300 MB), by the time the video is further compressed by YouTube it looks truly crappy (lots of noise, especially in under-exposed footage). So I figured I could just export from iMovie using "none" as the compression setting, because my original 1.17 GB file is under the YouTubes limit and looks fine (except for the widescreen bars).

But exporting with "no" compression somehow creates an *8GB* file!

Am I missing something? All I can think of is that I had to "split" my video when I did the cropping in iMovie, because I didn't have the cropped region in the same place for every scene. Does that create some sort of redundancy? Other than that, I can't think what would increase the file size by that much - I didn't "add" anything... to my mind I'm "subtracting" video by cropping!

Is there another compression format I should be looking into, or a setting I'm overlooking? Again, my goal at this point is simply to retain the video quality of my original FCPX export and also keep my cropping job from iMovie.

Also, please don't infer that I'm trying to be cheap here (FCPX trial and all - I wanted to give myself a 30-day deadline for this project!). I will gladly pay for the right compression software if necessary.

Thanks in advance!


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Craig Seeman
Re: Compression question - easy answer?
on Jun 3, 2013 at 4:16:18 pm

640x480 sounds like 4:3. cropping to 16:9, assuming you have black bars, would probably get you to 640x360. If iMovie exports to 1280x720 or 1920x1080 there's going to be significant scaling.

YouTube makes the following recommendations knowing that they will be recompressing your source.
It includes data rate and frame sizes.
http://support.google.com/youtube/bin/answer.py?hl=en&answer=1722171



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Craig Seeman
Re: Compression question - easy answer?
on Jun 3, 2013 at 4:31:07 pm

Thinking about this, you might consider doing this in MPEGStreamclip (free) rather than iMovie. You'd have much better export settings control.



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Preston Hull
Re: Compression question - easy answer?
on Jun 3, 2013 at 4:50:20 pm

Craig,

Thank you for your responses. I was ultimately able to resolve this issue - I had misidentified my problem.

FWIW: The raw footage was an odd size (640x424) that became 640x480 with the addition of the letterboxing. Though I thought "recompressing" was my problem, it was actually the fact that I was cropping out the letterboxing and returning it to 640x424.

I didn't realize that YouTube uses the vertical resolution to determine playback quality - so the fact that I didn't have a full 480 pixels forced it to downgrade even further, to 360 or whatever - which was the dramatic difference I was noticing.

Ultimately I was able to upsample it to trick youtube into thinking it was 480p, which was good enough for my homemade video.

Thanks again!!!


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