[quote name='anllover' date='12 October 2010 - 04:36 PM' timestamp='1286894166' post='211203']
Big THANKS for the one click RS link.
Question for those with computer skills/knowledge...
With these HD wmv files I have been trying to re-encode them with SuperC. I am changing the dimensions to 50% of original, and encoding as divx or xvid to reduce the filesize to something more manageable. Since I am not burning to dvd to play on a huge tv screen what is the point of having a 2 gig file?
anyway the file is lacking in quality but the filesize is dramitially reduced (1.8g -> 250mb)... what am I doing wrong, or what can I do better? Should I be making the framerate a lot higher than the default of 29fps?
[/quote]
First of all: don't touch the original framerate. (In case of this video, 25fps)
If you want to end up with 50% of the original (widht and height), means you encode to 960x540 pixel resolution. That is, in pixel count, the quater (25%) of the original picture.
All you have to set is the right compression quality value OR the right max. bitrate. That all depends on the used codec and/or behaviour oft the encoding application. (Note: I don't know your "SuperC")
If you can only set the compressin quality (mostly a per cent value), 65-70% is recommended for modern codecs like H264, for good quality.
If you have to specify the max. bitrate (which is a different approach, but, simple spoken, equivalent to the quality setting), the following formular is a recommended starting point:
(hight x width x framerate x 0.00025 = max. fixed bitrate)
Example: 960px x 540px x 25fps x 0.00025 = 3240 kb/s
To know what filesize you have to expect for this example, simply do the math:
The final bitrate is 3240 kb/s (video) + 128 kb/s (audio) (that all are examples!)
The video is 30min = 1800 seconds
So, 3368 kb/s / 8bit = 421 kbyte/s --> x 1800 seconds = 757800 kbyte (which is 740 MB)
Please note, the above rules are VERY simplified, the reality of encoding and it's options is much more complicated and differs from codec to codec.
One last note: You may have noticed, that due to the pixel count of 25% of the original, mathematical, the resulting file size should be 25% (1800MB / 4 = 450MB instead of the 740M in our example)
The reason for that difference: The files from NoRestNetwork are very compressed (way too much in my opinion)
My little math example is for very good quality (means moderate compression).
So maybe it is a starting point for better understanding.
Good luck!
