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Why is my 27s video file 4GB?

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Michael McCarthyWhy is my 27s video file 4GB?
by on Jan 14, 2012 at 8:21:20 pm

I made a 27 second video clip using chroma key on a Sony HDXR150. I converted that footage to AppleProRes using iMovie and saved it on a portable hard drive WD Scorpio Blue 250 GB - 300 MBps - 5400 rpm the film as around 2GB's then. When I went to my local community college to work on the footage in After Effects to create a keyed out template of the footage it got to 4GB's? The computer can't handle it and the amount of RAM it uses to just preview is rediculous. Why is such a short file so large? And how can I reduce it to a more managable size without losing any resolution? What am I doing wrong?


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Tudor "Ted" JelescuRe: Why is my 27s video file 4GB?
by on Jan 15, 2012 at 10:11:23 am

What resolution are you working at- is it HD 1080, frames per second (24, 29.97 p or i)?
What codec are you using to render out of AE?

When rendering uncompressed with alpha out of AE it is normal to get large size files. Also, the playback in AE is not real time - you need to load into RAM for preview. For large uncompressed files, if you try to preview them in QT, it will play choppy on most computers.

Tudor "Ted" Jelescu
Senior VFX Artist


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Kevin CampRe: Why is my 27s video file 4GB?
by on Jan 16, 2012 at 4:35:47 pm

[Michael McCarthy] "When I went to my local community college to work on the footage in After Effects to create a keyed out template of the footage it got to 4GB's? The computer can't handle it and the amount of RAM it uses to just preview is rediculous."

the size of the file usually won't effect ae's ability to handle it. for ae to process a frame, no matter how much it is compressed, it will have to decompress it, so when that frame is stored in ram it will be the same size whether it was and hdv frame or an uncompressed frame...

there are several ways to effectively work and preview in ae on systems with limited ram. one way is to set the magnification level lower than 100% (it a lttile drop down menu in the lower left corner of the preview window). reducing from 100% to 50% will allow ae to hold 4 times the number of frames in ram for previews.

also, shift-preview (with default settings) will process the preview at half resolution (note, resolution is different from magnification in ae) while skipping every other frame. skipping every other frame will fit 2 times the duration into ram. so combining a magnification setting of 50% and a shift-ram preview will fit 8x the duration into ram. setting for the shift-ram preview are in window>preview.

there is alos a 'region of interest' option (an option at the bottom of the preview window (looks like rectangle in a rectangle). this will allow you to section off just a portion of the frame to preview. this can reduce both processing time and ram preview duration based on the size of the 'region of interest' that you define.

you can also define the work area within the timeline, dragging the handles at the top of the timeline or typing 'b' to set the work area 'beginning' at the current time, or 'n' to set the 'end'. this allows you to preview short sections of your comp.

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW


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