not resize?

[boombastic]

I'm wondering what are the disadvantages of not use a resize filter at all during a conversion dvd to avi with dgindex-avisynth-xvid.
What do you think about?If i only crop and give a sufficient bitrate(space) to the codec to manage the high resolution it must deal with,what are the possible problems?

[Skywalkerjen]

This may be of help - a previous Doom9 forum topic that I started about resizing (http://forum.doom9.org/showthread.php?t=85220&highlight=skywalkerjen)

I asked a while ago about resizing and there was a lot of feedback - some of which may be applicable to you.

[Teegedeck]

...and to cut it short: You've got the right idea there; by resizing you either loose detail (downsizing) or create 'artificial' detail that wasn't there before (upsizing). Upsizing could make sense if you want to devote an entire DVD-R to one single movie but, as that points out, generally it requires far higher bitrates than just NOT resizing - and without much visible improvement. So, yes, many people (including me) don't resize but just crop.

The disadvantage is that you'll want to keep your resolution a multiple of 16 and thus you'll oftentimes have to crop quite far into the picture.

[boombastic]

So apart of multiple of 16-related problem there are no other disadvantages,and the speed gain is very high to me.Thanks!

[scharfis_brain]

if you convert to a format not well standarized for TV playback (such as AVI, MKV etc.) you can grop away black borders.

It has been prooven, that cropping in mod16 steps will increase compressibility, because the blocks are in-place from the already encoded source with the new encoding.

[Teegedeck]

In mod-16-steps, like crop(32,16,656,544)? That sounds a bit like rather a big loss in flexibility for a minor gain in compressibility to me, does it not?

[scharfis_brain]

It is extreme, for sure.
But It seems to improve compressibility more than an encoded border.
(depends on the source)
one may go for mod8 cropping, but that will cut th chroma-blocks of the source in half.

There currently is no access to the discussion regarding this issue, because forum.gleitz.info is unavailable ATM.

[boombastic]

I need a clarification:
finally i decided to not resize during my encodings but if i just call the .d2v file in my script with Mpeg2Source with no other filter i don't get a 16:9 picture but a vertically stretched one,why?
My final target is a xvid encoded-avi file to play in my standalone player that doesn't support corrections made with MpegModifier....

[Teegedeck]

A vertically 'stretched' picture is a 16:9 picture, it is the complete picture as stored on a DVD. It's supposed to be stretched horizontally on playback so you keep the full vertical resolution. If you want to watch the result on a player that doesn't support aspect-ratio signalling then encoding anamorphic aspect ratios is not for you.

Has been talked about a lot; please research 'anamorphic'.

[boombastic]

I know that anamorphic encoding has been treated a lot but after a lot of reading i still miss some "operative" points.
Do you mean that if my SAP doesn't support aspect-ratio signalling i ALWAYS must use a resize filter to have the correct AR?
How would you do an encoding without resizing?
1)create the .d2v file with default options in dgindex
2)create avisynt script with just
mpeg2source + crop
3)encode with xvid with default setting(or should i change something in the Aspect Ratio tab?)

are these step correct?

And mainly the "encoding without resize" i talk about is an "anamorphic encoding"?

[Teegedeck]

Do you mean that if my SAP doesn't support aspect-ratio signalling i ALWAYS must use a resize filter to have the correct AR?Yes, or you won't get a correct AR. It doesn't make sense to use a technique that your player doesn't support! IF you absolutely must use that player.
3)encode with xvid with default setting(or should i change something in the Aspect Ratio tab?)Yes indeed you should! Set it to 'Pixel Aspect Ratio' 16:9 (PAL or NTSC of course).

[imcold]

What do you think about this: I crop only few pixels from sides - let's say 4, that's 712px and then I resize back to 720px?

[Blue_MiSfit]

There is no real reason to do that...