Video Bitrate

[Alienz]

When i encoded Forrest Gump to fit 1 cd using SBC, the quality was not that good. I tried re-adjusting the video bitrate of the encoded Divx to a higher one hoping that the marcroblocks would go away in fast-motion scences but that didnt happen. I tried encoding the whole dvd again this time with with a higher bitrate and the quality was perfect. My question is:
Are Divx similar to mp3's where u can change the quality of mp3 file by changing the bitrate?....It seems that i cant change the quality of the Divx after it has been encoded with a specific video bitrate.

Help Please.
thnx

[mega5]

Don't forget ,Forrest Gumb is almost 3 hour movie so would be very wise if you will apply more bitrate for better quality

[Dave B]

Many people claim to be able to improve perceived quality by adding filters (in TMPGENC or Virtualdub) which have no direct effect on filesize or bitrate.

In my experience the only way to get a substantial improvement in quality is to crank up the bitrate.

Either way you'll have to re-encode.

[mpack]

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On 2001-11-16 08:29:06, Dave B wrote:
Many people claim to be able to improve perceived quality by adding filters (in TMPGENC or Virtualdub) which have no direct effect on filesize or bitrate.
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It isn't just a claim, it's fundamental to how MPEG and similar algorithms work.

MPEG basically encodes edge information - I-frames care about edges in the spatial axes (so salt and pepper noise is a killer), while P/B frames care more about edges on the temporal axes (ie. caused by moving objects). The more edges there are the more bits you need to encode them for a given quality, and if these edges derive from noise then most of that effort is wasted.

Careful spatial (smoothing) and temporal filtering can reduce the edginess and noise in the source, allowing MPEG to use all its bandwidth on important information.

If you look at a commercial quality VCD you can easily see that a light spatial filter (at least) has been applied.

[Dave B]

I completely agree mpack, I find spatial filters (especially when encoding from a capture source) are a big help to the mpeg algorithm.

The forums are however full of arguments as to which processes provide the best quality. One persons trash is indeed anothers treasure.