iMovie export file size is larger than the source file.
Source File - 570MB
what I did was trim the last 30 minutes off of 4 hour lecture
Export File (est)
High - 35.93GB
Medium - 24.11GB
Small - 12.28GB
Best(ProRes) - 266.34GB
The source file itself was converted to MP4 from AVI (1.5GB) using handbrake
MacBook Air
Hi,
You get a larger export size than the source because the source file likely
was more highly compressed or lower bitrate than the exported product. Your
source file was 570 mb for a 4 hour lecture, and that is very highly
compressed. From the high, medium, and small export options that you posted you
can see the various file sizes that result when that compression is released
upon export, as determined by your settings.
Things that affect the file size are the codec, the bitrate, the frame rate,
the compression rate, the duration of the movie, the resolution, the complexity
of the edits, and your overall export settings. Faster compression, higher
compression, lower quality, lower resolution = smaller file size. So if you
want to reduce the export size you can tinker with the above items. A lecture
video does not have much motion in it so you wouldn't need the high bitrate,
thus high file size, of pro res. Probably having a lower compression rate
wouldn't matter that much either. You can do a few test exports, experimenting
with the settings, to see what level of quality is satisfactory for your
purposes.
-- Rich
Hi,
You get a larger export size than the source because the source file likely
was more highly compressed or lower bitrate than the exported product. Your
source file was 570 mb for a 4 hour lecture, and that is very highly
compressed. From the high, medium, and small export options that you posted you
can see the various file sizes that result when that compression is released
upon export, as determined by your settings.
Things that affect the file size are the codec, the bitrate, the frame rate,
the compression rate, the duration of the movie, the resolution, the complexity
of the edits, and your overall export settings. Faster compression, higher
compression, lower quality, lower resolution = smaller file size. So if you
want to reduce the export size you can tinker with the above items. A lecture
video does not have much motion in it so you wouldn't need the high bitrate,
thus high file size, of pro res. Probably having a lower compression rate
wouldn't matter that much either. You can do a few test exports, experimenting
with the settings, to see what level of quality is satisfactory for your
purposes.
-- Rich
Thank you for your reply, how can I change the bit rate of the video? There are some youtube videos explaining how to manually fine tune the bit rate but those seem to be an older versions of iMovie.
Edit - I found the slider, but is there like a rule of thumb for quality and bit rate ?
even if I lower the slider to the minimum (3.33Mbps) quality the file size is still more than 5GB, even if I reduce the resolution to 720p and lower the slider to 2Mbps (lowest) the file size is 3.7GB. way more than source.
To be sure we are on the same page, the slider you are referring to is located in the "Quality" option drop down in the share box under the Custom setting.
There really is no rule of thumb other than that the higher the bit rate the larger the file size and the better the quality. It is in the eye of the beholder. Take a small 30 second representative piece of your video and place it in a newly created project. Share it out at various Mbps settings and see what settings give you satisfactory results.
-- Rich
So what is the question?
3 or 4 hours of video exported normally will be many GBs in size, as you discovered but if you want to make it smaller by reducing the bit rate . . . use HandBrake.
export file size is bigger than the source file
