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Render Quality issue…
Hiya, im having a problem with rendering a clip with intros & keeping quality…
After adding the intros (text, music, audio quote) i render the whole thing as mp4 for ipod, when the clip starts (after the intro) its a bit fuzzy & jumpy for about 10 seconds then evens out, where as if i render just the clip (no intro) its not fuzzy at all.
So i guess im wondering why when i have an intro it effects the quality of the rest of the clip?
There must be a way round this because if i render with just the clip & no intro its fine, but its the same clip & rendering in the same format so i really dont get it?
Thanks in advance for any help im really stuck on this, otherwise its an ace program!!!
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3 Replies
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If this is what I think it is, this is normal. MPEG4 uses interframe compression and macroblocking. Interframe compression means that one or more earlier or later frames in the sequence are used to compress the current frame. This makes the quality of the current frame dependent on how much it has changed from the previous frame.
Macroblocking means that compression is performed on square-shaped groups of neighboring pixels. When a block of pixels doesn’t change much, the video looks very smooth, but when there is a drastic change like going from a title frame to a movie frame, all of the pixels change and the blocks may become noticeable which causes the picture to look a bit fuzzy or like it’s breaking up.
The last part to this equation is bit-rate. Given all the bits in the world, the codec can hide the macroblocks by regenerating the whole frame using all of the bits it needs. The problem is that people use MPEG4 because they want to use a low bit-rate. When the change in the image exceeds the number of bits that you have to represent it, something has to give and picture quality falls apart while all of the macroblocks are updated over the course of a few frames.
This would explain why the images gets a bit fuzzy for a few seconds and them smooths out when you add the opening title but does not without it. Hope that’s understandable.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
Thanks for your reply, i kind of understand, so the intro is effecting the video because of a few factors, but is it possible to change it so the intro doesnt effect the video?
Do i somehow increase the bitrate?
Before i would just render the whole thing as mpg then convert that with an iPod convertor but of course that way gave me quality issues too.
I think its best for me to go straight to iPod from Vegas i just need to figure out how to make the intro not effect the main video?
When i render JUST the video and leave the intro out it plays fineThanks…
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Try increasing the bit rate and see if it lessens the effect. You might also try a crossfade transition so that the cut the the title to the video isn’t so abrupt.
~jr
http://www.johnrofrano.com
http://www.vasst.com
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