compression trivia

A

adumb

Active member
i don't completely understand how it works so i have a example of what i am talking about. say you have a video that is 4 minutes long with no effects then you have htat same exact video that you put lots of effects and titles on. you go to output both of them will they be the same file size with the same quality or does you file size get bigger as you add effect,title, and such.


if they are different sizes wouldn't it be a good idea to export to tape then re import the file into the computer as one continous movie file which should make it easier for the computer to compress better.


if i am crazy and making no sense just let me know

adam
 
While I am a computer professional who has written many data compression schemes in the past, I have to admit my knowledge of video specific compression is limited.

However, if I understand your question correctly I can tell you that going to tape and back to digital will have no effect. The reason, as I understand it, is that the compression algorithms look only at hue and saturation (color & light) levels. It is on the basis of the change in these levels from frame to frame that the compression makes its "adjustments".

Hope this helps,
Larry
 
so like i said then a 4min video that uses say 8 video tracks for different mattes, titles and picture effects should have the exact same file size as a video that used just one clip on one track the whole time with no effects. i guess ya learn something new everyday
 
There's a wide range of different codecs to use for compression and each of those has multiple settings. Some have max bit rates you can set and how often a keyframe image is.
In your example some codecs will create more data with more complex images and some limit it per frame or simply provide more detail if there's not small detail.
Some, such as MPEG-2, allow variable compression so tehy adjust accordingly to the amount of detail and the amount of motion.

Don't save out, re-import and then resave. Everytime you load and then resave with different settings you'll add more compression artifacts.

Every compression is a tradeoff. Do you want it super small for fas loading on the web? Highest quality on a CD?
 
it is going to be a video for the web. i want to use quicktime but most poeple don't have that so i will be using windows media player.

are you familiar with ppro. there are like four codec options in there but no where in my books or on the internet can i found out what the differences are between them.
 
and for the record i usualy have pretty good luck getting my file sizes down but this video seems to be floating around 40-50 megs which is like three times the size i usually have
 
Actually most people do have quicktime. Certainly it's not much of an issue to download if they don't have it. Lot more options and better quality overall.

To reduce file size: reduce size of image, reduce number of colors, reduce frame rate, lower quality settings, lower max bit rate
 
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