Over the years I've collected loads of video clips and they're all in differing formats like WMV, MP4, AVI, MPG etc.
I've converted them all to MPG using Any Video Converter and I've loaded them into Video ReDo and trimmed off the bits I don't want, mainly from the beginning and ends and sometimes in the middle as well so I now have a smaller MPG file with only the content that I want.
What I do next is run them through Gordian Knot (GK) and convert them into AVI files with the XviD codec - not currently interested in any other output container/codec.
To get started I followed a PDF ripping/encoding guide I found on a torrent site that I found very helpful. In there the sizes of source video was listed along with "scene" target sizes:
23mins -> 175MB
30mins -> 233MB
45mins -> 350MB
60mins -> 466MB
90mins -> 700MB
Going by the cited video sizes (624x336) I've worked out that 1 minute of video is about 7.78MB
I can see that in GK when I change the output video size I can see the bitrate changing and for 702x400 video I've been outputting to a bitrate of around 1,000 is required - again, this will be lower with a smaller picture size.
As my video sources are all varying width and height, I have to reduce this magic figure but I don't know how much to retain video quality.
I mean, if I halve the video size from 624x336 to 312x168 I'm actually quartering the dimensions of the picture - do I quarter my magic number or does it not work like that?
I've tried to work this out myself but have so far had no luck.
The only inputs I can see I'll be needing are frame width, frame height, FPS (either 25 or 29.97 after going through Any Video Converter) and video length.
I only want to use AVI so I can master this before tackling anything else like H.264 and as I have Asperger's, I need things explained in very basic terms please otherwise I get completely lost.
Thanks thanks for reading.
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Thread: Converting MPG to AVI (XviD)
Changing video height/width does not itself affect quality if the bitrate stays the same. The bit rate is changing since a smaller frame does not need a higher bitrate for the video to look 'ok'. But try watching that video at twice the size or full-screen and you will see what I mean.
So if you do reduce frame size better to keep the bitrate.
You may find it easier to use GK's little brother autogk. There you can set a target size, a bitrate and/or the frame size and the program does the rest.