Hi,
Can someone tell me the difference between,
variable & constant bitrates?
What is the difference?
Which produces the best quality video?
Variable vs. Constant Bitrates?
Moderator: Ken Berry
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Trevor Andrew
Hi
This is a big subject, have a read at the ulead learning centre, link below.
Have a look at General Video Info / Frames and Fields
http://www.ulead.co.uk/learning/learning.htm
http://www.ulead.co.uk/learning/video3/page1.htm
Hope this makes good reading.
Trevor
This is a big subject, have a read at the ulead learning centre, link below.
Have a look at General Video Info / Frames and Fields
http://www.ulead.co.uk/learning/learning.htm
http://www.ulead.co.uk/learning/video3/page1.htm
Hope this makes good reading.
Trevor
High bitrate = High quality = Big file = Low compression.
Low bitrate = Low quality = Small file = High compression.
If you have a half-hour video, you can simply use the highest constant bitrate for the best quality.
If your video won't fit on a DVD, using a lower bitrate will help compress it to fit.
Variable bitrate means a lower average bitrate... A high bitrate where you need it (lots of action/movement), and a low bitrate where you can get-away with it.
If you must reduce the bitrate, a variable bitrate should give better results than a constant bitrate... Assuming the same average bitrate.
Low bitrate = Low quality = Small file = High compression.
If you have a half-hour video, you can simply use the highest constant bitrate for the best quality.
If your video won't fit on a DVD, using a lower bitrate will help compress it to fit.
Variable bitrate means a lower average bitrate... A high bitrate where you need it (lots of action/movement), and a low bitrate where you can get-away with it.
If you must reduce the bitrate, a variable bitrate should give better results than a constant bitrate... Assuming the same average bitrate.
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rwindeyer
To answer the question simply: if you encode at Constant Bitrate, it means just what it says - you are using the same bitrate for the whole movie. This has theoretical disadvantages: if there are parts of the movie where nothing much is happening you are coding at a higher quality than necessary, and in high movement or rapid action scenes you are coding at less than ideal rate.
Variable Bitrate (sort of) overcomes this. The coding engine scans the movie first (so coding takes longer) and automatically applies a higher or lower bitrate where it is needed, consistent with the average or maximum that you have specified.
Because it is more efficient, you may get a little more video on the disc overall.
Don't expect a lot at this level (Video Studio is for home consumers); it uses a 2-pass system. I have read on this forum that professional studios (eg Hollywood) use a 25-pass system - the VBR on commercial DVDs is really efficient.
For what it's worth I use VBR. You won't notice any quality difference.
Variable Bitrate (sort of) overcomes this. The coding engine scans the movie first (so coding takes longer) and automatically applies a higher or lower bitrate where it is needed, consistent with the average or maximum that you have specified.
Because it is more efficient, you may get a little more video on the disc overall.
Don't expect a lot at this level (Video Studio is for home consumers); it uses a 2-pass system. I have read on this forum that professional studios (eg Hollywood) use a 25-pass system - the VBR on commercial DVDs is really efficient.
For what it's worth I use VBR. You won't notice any quality difference.
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Trevor Andrew
Hi Ray
Have a look at this page, some info and a calculator, may come in useful.
http://dvd-hq.info/Calculator.html
Have a look at this page, some info and a calculator, may come in useful.
http://dvd-hq.info/Calculator.html