What is a scale factor?

[rocky12]

As I remember one of my recent AIM conversations with DigitAl56k from DivX Corp (No I don't have a copy of the message). He said he uses BlackmanResize or LanczosResize. I asked him what he use more. He replied depending on a scale factor. I didn't ask him but in DivX Corp what is a factor scale? If I remember that name right?

[redwudz]

I'm guessing he's referring to upscaling or downscaling of the frame size. Some filters work better in one direction than the other. I think Lanczos works better for upscalling, but other members may give you better info.

[rocky12]

I'm guessing he's referring to upscaling or downscaling of the frame size. Some filters work better in one direction than the other. I think Lanczos works better for upscalling, but other members may give you better info.

Thank you for your reply.

I use 720x400 for 16:9 and 720x544 for 4:3. Not sure if those are upscaling or downscaling?

[jagabo]

I suspect by "scale factor" he meant how much he was resizing. So downsizing from 720x480 to 320x240 is a larger scale factor than scaling to 640x480.

BlackmanResize() is supposed to produce less ringing at sharp edges than Lanczos4Resize().

http://avisynth.org/mediawiki/Resize

[rocky12]

I suspect by "scale factor" he meant how much he was resizing. So downsizing from 720x480 to 320x240 is a larger scale factor than scaling to 640x480.

BlackmanResize() is supposed to produce less ringing at sharp edges than Lanczos4Resize().

http://avisynth.org/mediawiki/Resize

I still dont understand of what dimensions I gave is suppose to be up or downscaling. I also don't understand is what to use of up or downscaling between LanczosResize and BlackmanResize.

The dimensions I gave are again: 720x544 for 4:3 and 720x400 for 4:3.

[guns1inger]

And what are you doing with the video ?

Are you resizing for DVD, or for Divx playback ?

Are you resizing from these resolutions to something, or from something to these resolutions ?

You have asked a question that requires a context to answer, but you have not provided that context.

Describe exactly what it is you are doing. What is your source, what is your target and how are you getting there ?

[jagabo]

I still dont understand of what dimensions I gave is suppose to be up or downscaling. The dimensions I gave are again: 720x544 for 4:3 and 720x400 for 4:3.

We don't know if you're upscaling (making bigger) or downscaling (making smaller) unless you tell us what the source size is. But guessing it's 720x480 DVD, going to 720x400 is downsizing, 720x544 is upscaling. The differences between Lanczos4 and Blackman are very subtle.

[rocky12]

Either keeping the video on my machine for my Philips player.

DivX playback. I prefer DivX over XviD.

Just the resolutions I gave. Let's say this, if my movie was XviD or DVD set at 16:9 then I use 720x400 or if the XviD is 4:3 then 720x544.

And what are you doing with the video ?

Are you resizing for DVD, or for Divx playback ?

Are you resizing from these resolutions to something, or from something to these resolutions ?

You have asked a question that requires a context to answer, but you have not provided that context.

Describe exactly what it is you are doing. What is your source, what is your target and how are you getting there ?

[guns1inger]

For the very small amount of scaling you are doing, you won't notice a difference between Lanczos, Blackman or Bilinear. The scale factor covers whether or not you are going up or down, and also by how much. As a general rule, I use Lanczos for most upscaling, as I don't upscale by large amounts. For scaling down, Bilinear is usually good enough. Again, I don't tend to down scale by large amounts.

You will usually get better quality from NTSC 4:3 if you go to 640 x 480, as you are only adjusting for the non-square pixels, and not actually scaling the video. If you go to 720 x 544 then you are scaling the video, and run a higher rick of introducing artifacts and problems.

[rocky12]

For the very small amount of scaling you are doing, you won't notice a difference between Lanczos, Blackman or Bilinear. The scale factor covers whether or not you are going up or down, and also by how much. As a general rule, I use Lanczos for most upscaling, as I don't upscale by large amounts. For scaling down, Bilinear is usually good enough. Again, I don't tend to down scale by large amounts.

You will usually get better quality from NTSC 4:3 if you go to 640 x 480, as you are only adjusting for the non-square pixels, and not actually scaling the video. If you go to 720 x 544 then you are scaling the video, and run a higher rick of introducing artifacts and problems.

Thank you. OK 640x480 for 4:3, right? 640x576 for 16:9, right? If I don't want problems. 4:3 in this case is downscaling, right?

[jagabo]

Why don't you leave the frame at 720x480 and use the Divx aspect ratio setting. See if your player handles it properly.

[guns1inger]

16:9 is a different kettle of fish because the pixels are different shape to 4:3.

For 4:3 it is simple. The horizontal size of the pixels is slightly wider than they are tall. When your TV plays them back, it squashes them slightly to get the image right. When you resize to 640 x 480, you are simple squeezing the pixels back to square.

For 16:9 you have two different complications. The first is that the pixels are shaped differently to 4:3. The 1:1 equivalent for NTSC 16:9 is 854 x 480. If you resize to 640 wide, then you have to resize to 360 high.

But : 16:9 is not a film aspect ratio. Film aspect ratios cover a very wide range. The film equivalent of 16:9 is 1.778:1. However if you put a film shot at 1.85:1 or 2.35:1 in a 16:9 frame, you get black bars in the image. If you simply resize to 640 x 360 (or 720 x 400) then you keep these bars and encode them needlessly. So working with widescreen involves correctly cropping off all the bars, then resizing to maintain the correct display aspect ratio.

Are we having fun yet ?

This is why many use something like AutoGK, which takes care of all of these decisions.

[rocky12]

Why don't you leave the frame at 720x480 and use the Divx aspect ratio setting. See if your player handles it properly.

Alright that is fine but let's say this. What if I have an XviD that is either NTSC 4:3 or 16:9 or a PAL that is 4:3 or 16:9 then what do I set it when I want to encode to DivX?

[guns1inger]

Why don't you leave the frame at 720x480 and use the Divx aspect ratio setting. See if your player handles it properly.

And therein lies the problem - too many players still do not observe the AR flags in AVI files.

[rocky12]

Yes I am having fun. It's better then synch. What should PAL 4:3 and 16:9 resolutions should be?

16:9 is a different kettle of fish because the pixels are different shape to 4:3.

For 4:3 it is simple. The horizontal size of the pixels is slightly wider than they are tall. When your TV plays them back, it squashes them slightly to get the image right. When you resize to 640 x 480, you are simple squeezing the pixels back to square.

For 16:9 you have two different complications. The first is that the pixels are shaped differently to 4:3. The 1:1 equivalent for NTSC 16:9 is 854 x 480. If you resize to 640 wide, then you have to resize to 360 high.

But : 16:9 is not a film aspect ratio. Film aspect ratios cover a very wide range. The film equivalent of 16:9 is 1.778:1. However if you put a film shot at 1.85:1 or 2.35:1 in a 16:9 frame, you get black bars in the image. If you simply resize to 640 x 360 (or 720 x 400) then you keep these bars and encode them needlessly. So working with widescreen involves correctly cropping off all the bars, then resizing to maintain the correct display aspect ratio.

Are we having fun yet ?

This is why many use something like AutoGK, which takes care of all of these decisions.

[guns1inger]

PAL 4:3 is 720 x 768 (the pixels are taller than wider for PAL 4:3). Widscreen is even wider than NTSC - 1024 x 576.

Personally, I let AutoGK do all the hard work for me. I am happy with a 640 width, and 10MB/m bitrate. For true PAL 16:9 (i.e. digital broadcasts) I get 640 x 368 resolution 1:1 PAR. However if I were encoding a PAL DVD that was wider, the resolution would be different (e.g. 2.35:1 is 640 x 272 1:1 PAR)

[rocky12]

PAL 4:3 is 720 x 768 (the pixels are taller than wider for PAL 4:3). Widscreen is even wider than NTSC - 1024 x 576.

Personally, I let AutoGK do all the hard work for me. I am happy with a 640 width, and 10MB/m bitrate. For true PAL 16:9 (i.e. digital broadcasts) I get 640 x 368 resolution 1:1 PAR. However if I were encoding a PAL DVD that was wider, the resolution would be different (e.g. 2.35:1 is 640 x 272 1:1 PAR)

No AutoGK and no plain GK. I am happy with the hard work. I learn more. What is PAL 16:9? Just a note, you know I am talking about DivX resolutions? Alright 720x768 is 4:3? What is PAL 16:9? After that between NTSC 4:3 and 16:9 and PAL 4:3 and 16:9 I have to figure out which upscaling and downscaling....I love this! I love hard work besides sych.

[jagabo]

Why don't you leave the frame at 720x480 and use the Divx aspect ratio setting. See if your player handles it properly.

Alright that is fine but let's say this. What if I have an XviD that is either NTSC 4:3 or 16:9 or a PAL that is 4:3 or 16:9 then what do I set it when I want to encode to DivX?

What is the point of reencoding Xvid to Divx? They are both MPEG4 part 2 codecs. The only reason to reencode is if your player can't handle some features used in the Xvid file (note Divx has almost all the same features). Reencoding will reduce the quality. If you have to reencode just leave the resolution as it is.

[rocky12]

Why don't you leave the frame at 720x480 and use the Divx aspect ratio setting. See if your player handles it properly.

Alright that is fine but let's say this. What if I have an XviD that is either NTSC 4:3 or 16:9 or a PAL that is 4:3 or 16:9 then what do I set it when I want to encode to DivX?

What is the point of reencoding Xvid to Divx? They are both MPEG4 part 2 codecs. The only reason to reencode is if your player can't handle some features used in the Xvid file (note Divx has almost all the same features). Reencoding will reduce the quality. If you have to reencode just leave the resolution as it is.

I just want to know what is the resolution for PAL 16:9? I rather DivX not XviD. Also I rather do the dirty work and not leave it the same.

[jagabo]

If you're using square pixel encoding the the aspect ratio is the same as relative frame dimensions. There is no single "right" frame size. You can use the same 720x400 or 640x368 you use for NTSC.

Divx and Xvid are happiest with frame sizes that are multiples of 16. That's why the above listed frame sizes are not exactly 16:9 ratios.

Or, as I said earlier, leave the frame size at 720x576 and use the DAR flags to set the AR. Most newer players respect the DAR flags.

If you're going to reencode an Xvid file to Divx it is probably already using square pixel and the right aspect ratio so there's no need to resize.

[rocky12]

If you're using square pixel encoding the the aspect ratio is the same as relative frame dimensions. There is no single "right" frame size. You can use the same 720x400 or 640x368 you use for NTSC.

Divx and Xvid are happiest with frame sizes that are multiples of 16. That's why the above listed frame sizes are not exactly 16:9 ratios.

If you're going to reencode an Xvid file to Divx it is probably already using square pixel and the right aspect ratio so there's no need to resize.

guns gave me a different size for NTSC 16:9. He gave me 854x480. So use 720x400 for PAL 16:9?

[rocky12]

I said I rather change it.


Is 854x480 upscaling or downscaling? Is 640x480 up or downscaling? Is 720x768 upscaling or downscaling and is 720x400 upscaling or downscaling?

[jagabo]

guns gave me a different size for NTSC 16:9. He gave me 854x480. So use 720x400 for PAL 16:9?

Use whatever 16:9 frame size you want. There is no single perfect size.

I said I rather change it.

Then you're making a stupid pointless mistake.

Is 854x480 upscaling or downscaling? Is 640x480 up or downscaling? Is 720x768 upscaling or downscaling and is 720x400 upscaling or downscaling?

Nobody can tell you if it's upscaling or downscaling unless you say what size the source size is. If you are making the frame size bigger it's upscaling. If you are making the frame size smaller it's downscaling. What's so hard to understand about that?

[rocky12]

Nobody can tell you if it's upscaling or downscaling unless you say what size the source size is. If you are making the frame size bigger it's upscaling. If you are making the frame size smaller it's downscaling. What's so hard to understand about that?

I am making the bitrate of 1600kbps for all my encodes so how do I tell if I am upscaling or downscaling? I thought I tell by the resolutions I gave in my previous post?

[jagabo]

bitrate has nothing to do with upscaling or downscaling.

[Midzuki]

about this thread:

*shakes head*

[rocky12]

bitrate has nothing to do with upscaling or downscaling.

Does the resolutions has something to do with upscaling and downscaling?

[jagabo]

Changing the resolution is the DEFINITION of upscaling and downscaling.

Upscale: Scale up, make bigger, increase the frame size
Downscale: Scale down, make smaller, decrease the frame size

[rocky12]

Changing the resolution is the DEFINITION of upscaling and downscaling.

Upscale: Scale up, make bigger, increase the frame size
Downscale: Scale down, make smaller, decrease the frame size

Oh ok. So 854x480 is upscaling? 640x480 is downscaling? 720x768 is upscaling? 720x400 is downscaling?

[jagabo]

As I've said several times now, nobody can tell you if those are upscaling or downscaling unless you specify what the source frame size is.