I recently recorded numerous screencasts using Quicktime. The .mov files produced by Quicktime are 2876x1748.

To goal was to upload the files to YouTube and so I wanted to convert to the recommended format. Since I had to merge 3 clips into one, I used a tool called iSkySoft iMedia Converter Deluxe to merge and convert.

The settings selected were optimised for YouTube (Settings were H.264 and resulting video was scaled down to 720P)

Interestingly, the MP4 files produced were significantly larger than the original .mov files! The .mov files combined were ~ 1.5GB at a higher resolution and the merged & converted MP4 file was 2.2GB.

Is this to be expected? Or could there be something wrong with the conversion tool being used?

  • What Codec is the QuickTime recorded in? Mar 11, 2016 at 10:04
  • More specifically: H.264 MPEG4 AVC (part 10) (avc1). And the MP4 for output by iSkySoft iMedia Converter Deluxe uses exactly the same codec & but has a higher frame rate. 50 vs 60. Could the frame rate account for such a difference in file size, despite the resolution being more than halved.
    – Prembo
    Mar 11, 2016 at 10:34
  • Ultimately, it comes down to bitrate, whether expressly set or determined by other factors, such as framerate, resolution, quality setting. What does mediainfo say about your source files?
    – Gyan
    Mar 11, 2016 at 12:20

1 Answer 1


I don't think it's the framerate. Maybe check with mediainfo to see more specific settings of each Codec. Apart from the bitrate, there are plenty of settings that can influence file size, even when using the same Codec.

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