Applying a filter without recompressing in VDub

[chrisr34000]

Hi!

I have a few movies in divx format and I want to apply a denoising filter (Neat Video) on them. How do I do this in VDub without reencoding, or in other words: how do I apply the filter without any quality loss a second encoding would bring?

Thanks for your help and time.

Chris

[redwudz]

Not possible. If you filter or crop or alter the video, you have to re-encode it. If you start with a high quality video and raise the re-encode bit rate a little, you should be able to minimize the losses.

And welcome to our forums.

[chrisr34000]

Hi!

Thanks for your answer. So, if the video has a bitrate of 1600, reencoding it to, for instance, 1800 will minimize the quality loss, right?

Chris

P.S.:Glad to be on these forums

[redwudz]

There's no simple way to know exactly how much to increase the bitrate to minimize loss vs filesize. What I generally do is make up a short representative clip, even as short as ten seconds, though a minute or two would be better. Do your filtering, then try several different bitrates. Remember the higher the bitrate, the larger the file. A bitrate calculator can tell you how big it will end up being fairly closely.

You may have to trade off quality/bitrate for encoded size.

One easy way in VirtualDub, using Divx, is to set the codec to '1-pass-quality based' and set the 'Target quantizer' to about 2. That should give you about the same quality as the original at a larger filesize. Xvid can be set up similarly. But you don't have much control over the filesize with this method.

Just experiment a little.

[chrisr34000]

Alright, thanks!

[guns1inger]

The efficiency of an encoder and the quality a given bitrate can produce is heavily influenced by the actual video itself. A filter that reduces noise can make a encoder more efficient because there is less change frame to frame. An effects filter, on the other hand, might have the opposite effect and require a much higher bitrate to maintain the image quality.