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1/2 the FPS makes minimal diff
I have a movie that’s about 1.63G. I’m using Compressor to encode it using the h.264 codec. All other things being equal, I made two diff settings. One had the Frame Rate set to 30fps and the other at 15fps. Here are my results.
30fps – 27.4M
15fps – 27.2MI could easily not be understanding how this setting works but I figured it should have a much bigger impact on the file size.
The data rate is restricted to 500 kbits/sec and I’m doing a Faster encode (single pass). Again, all these things are the same for the two encodes. Only the fps is different.
Any help would be appreciated.
Thanks in advance,
Paul
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4 Replies
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If the two files have the same length and the same data rate, the file size will be the same.
In the 15fps clip, each picture will have double data than the picture in the 30pfs clip.
If you want that a clip have the half size, you need to set half data-rate.
rafael -
Thanks Rafael.
So that begs the question, what is the reasoning to cut the fps in half? What is the purpose?
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Hi Paul,
With the old codecs (CinePack, Sorenson,..) was very difficult to get small files keeping the quality of the picture. A very common practice was to reduce the fps reducing at the same time the data rate.
Of course if the clip was video would play choppy. But there are many things that works very well with less than 25 or 30fps. Animations works well. For example video-tutorials made capturing the computer screens could work (I’ve never don it) with something like 1fps. The only thing that moves is the mouse.
Today with compressors like H264 is easy to get the file size you need without need to drop frames.
Rafael -
Rafael,
Thanks very much for your insight. Very helpful.
Paul
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