To resize or not to resize?

[plokm]

I've been encoding DVD rips at the native 720x480 resolution, then setting the aspect ratio in mkvtoolnix to 4:3. It occurs to me that I can get an automatic 11% decrease in filesize at the same quality by resizing it to 640x480 first. Is there any good reason to leave it at 720x480?

Also, what would you recommend for (down) resizing in AviSynth for highest quality? I've been using BilinearResize, but I see other, fancier ones there...

[Irakli]

Also, what would you recommend for (down) resizing in AviSynth for highest quality? I've been using BilinearResize, but I see other, fancier ones there...

Well, I know that BilinearResize softens the original picture (i.e it is more suitable for lower bitrates). I personally think that LanczosResize may be good option as it provides sharp picure and good quality IMHO; it is not very good at low bitrates though, as it makes blocking more visible.

[Dr.Khron]

I've been encoding DVD rips at the native 720x480 resolution, then setting the aspect ratio in mkvtoolnix to 4:3. It occurs to me that I can get an automatic 11% decrease in filesize at the same quality by resizing it to 640x480 first. Is there any good reason to leave it at 720x480?

A very good point.
I've been debating myself wether its a good idea to resize or not. I posted a question about it in the MeGUI forum and didn't get a response, so I'll repeat it here and see if someone will chime in on the noob forum. Here is my take:

Having tried it both ways, I'm still debating wether or not to resize my 4:3 TV episode encodes. I'm making MKV files, so I have the choice of resizing in AVS before encoding, or not resizing and setting the DAR flag instead.

It seems to me like it would be better to leave the video alone and encode at 720x480, relying on MediaPlayerClassic (MPC) to resize the video during playback... Encoding quality is best when you don't have to resize before hand, right?

On the other hand, when making video files for PCs, why not resize to square pixels once, instead of everytime you play the video? After all, we do de-interlace television content before encoding.

Furthermore, I recently discovered that you need to be using the "overlay mixer" option in MPC in order for the embeded DAR flag to work properly... without the Overlay, you get straight 720x. Then again, why would anyone use anything other then Overlay?

Are there any other hidden drawbacks to resizing during playback instead of doing it in the AVS before encoding?



As for which resizing filter to use...
The best thing to do is test them in AvsP or Vdubmod, and see which ones LOOK the best. This will depend on: type of source material, quality of source material, bit rate used, other filters...
I generally find Lanczros to be the best for high bit rate encodes, but Spline36 is also popular. Here is a short list of fliters you should try (output from MeGUI AVS maker):

BicubicResize(640,480,0,0.5) # Bicubic (Neutral)
LanczosResize(640,480) # Lanczos (Sharp)
Spline36Resize(640,480) # Spline36 (Neutral)

Edit: oh yeah, I really DON'T like the Bilinear resizer you've been using. One of the 3 I listed above always works better for me, but as always, you milage may vary.