Mod-16 & Croping black stripes

[bmnot]

I have been reading this tutorial of yours (http://www.doom9.org/index.html?/gknot-main4.htm)

wont cropping (because of the 2px black bars around the video which, as I understood it, won't allow the codec to compress it properly) in Step 1.4 screw up the mod-16-thingy? or is mod-16 only important for the output resolution?



Furthermore I was wondering wether I should resize the video of dvd to something like 720x400 or keep the original 720x576 (the video itself is 16:9)? Size is not that much of a problem (the DVD itself is about 7,12GB, I'd be happy enough to go up to 5,10GB for the ripped AVI as long as the quality is fine)

Also I get a value of 0.083 for the compressibility test (as described in that tutorial, which is about 580 about the Byte/Pixel value) - what should id do, the tutorial said to not go below 0.17?


(the DVD is PAL, codec is the latest DivX, I am using the latest Guardian Knot)

Thanks!

[LoRd_MuldeR]

wont cropping (because of the 2px black bars around the video which, as I understood it, won't allow the codec to compress it properly) in Step 1.4 screw up the mod-16-thingy? or is mod-16 only important for the output resolution?

Mod-16 only matters for the final resolution that you feed into the encoder...

Furthermore I was wondering wether I should resize the video of dvd to something like 720x400 or keep the original 720x576 (the video itself is 16:9)?

720x576 is PAL anamorphic. It can be either 4:3 or 16:9. You can keep it anamorphic and encode it at it's native resolution -or- convert it to "square pixels" (none-anamorphic).

The proper none-anamorphic resolution for 720x576 video would be either 1024x576 (16:9) -or- 768x576 (4:3).

[bmnot]

720x576 is PAL anamorphic. It can be either 4:3 or 16:9.

The video itself is 16:9


You can keep it anamorphic and encode it at it's native resolution

Yes, That would've been my first choice, but since I'll only watch the video on pc, I was wondering wether there's a way (maybe a 16:9 flag, as DVDs have it?) for the player/codec (winamp/ffdshow) to recognize that this video is supposed to be played in 16:9?


-or- convert it to "square pixels" (none-anamorphic).

The proper none-anamorphic resolution for 720x576 video would be either 1024x576 (16:9) -or- 768x576 (4:3).

Since it's 16:9, it would be 1024x576 - but then the width would be bigger than 100% of the original size - isn't that a problem (at least the field in GK turns red as soon as the value goes above 100%)?


And one more thing, about the cropping: I should cut the black border around the image right? That is 2 px on the left and right side and 4 px at the bottom - but then the aspect ratio isn't 100% 16:9 - is that a problem?
(As said earlier, size is not that much of a concern as is quality)


Also, what about the results of the compressibility test? when I use Xvid I get a value of 0.19 - Is it a DivX bug or does that mean that DivX is way better at compressing things?

Thanks!

[CWR03]

The video itself is 16:9
The video itself is not 16:9. It's using DAR signaling to display at 16:9.

Yes, That would've been my first choice, but since I'll only watch the video on pc, I was wondering wether there's a way (maybe a 16:9 flag, as DVDs have it?) for the player/codec (winamp/ffdshow) to recognize that this video is supposed to be played in 16:9?
If you crop and size the video properly, you don't need to worry about it for PC playback. This issue is more important for standalone playback.
Since it's 16:9, it would be 1024x576 - but then the width would be bigger than 100% of the original size - isn't that a problem (at least the field in GK turns red as soon as the value goes above 100%)?
No, it's just not necessary. It only turns red to warn you that you're exceeding one or both of the parameters of the original.

And one more thing, about the cropping: I should cut the black border around the image right? That is 2 px on the left and right side and 4 px at the bottom - but then the aspect ratio isn't 100% 16:9 - is that a problem?
No. Gordian Knot is pretty good at getting the AR right. You should only have to select 16:9 or 4:3 in the resolution tab, then look at the Aspect Error % and keep it within a reasonable percentage. My own preferences are to keep 720 width if no width cropping is needed, or reduce the width and use height cropping to keep the Aspect Error close to zero.

Also, what about the results of the compressibility test? when I use Xvid I get a value of 0.19 - Is it a DivX bug or does that mean that DivX is way better at compressing things?
Did you use the same video for the compressability test?

[bmnot]

The video itself is not 16:9. It's using DAR signaling to display at 16:9.

Yes, that's what I meant


If you crop and size the video properly, you don't need to worry about it for PC playback. This issue is more important for standalone playback.

So you are suggesting that I should crop more than just the black borders? But if I leave the Video in it's original resolution, then not all players (like winamp) display it in 16:9 (VLC though for some reason detects that it's supposed to be 16:9)

My own preferences are to keep 720 width if no width cropping is needed, or reduce the width and use height cropping to keep the Aspect Error close to zero.

Yes, as said earlier, the black border is 2px left and right and 4 px at the bottom - So what should I do? crop it any further? What output resolution should I choose for the encoder if I'm interested in maintaing a high quality at a reasonable filesize (that is up to 72% of the original filesize)


Did you use the same video for the compressability test?

Yes, it's the same video, but I guess the problem occurs because I selected "Multipass, 1st pass" for the crompressibilty test in dhe codec settings (the codec settings for the encoding are Two-pass), when chosin only "1-pass" it returns normal values (0.18, just like xvid)


Again, thanks a lot for your replies!

[LoRd_MuldeR]

So you are suggesting that I should crop more than just the black borders? But if I leave the Video in it's original resolution, then not all players (like winamp) display it in 16:9 (VLC though for some reason detects that it's supposed to be 16:9)

If you set the PAR properly, then all players will display it at the 16:9 DAR. Otherwise the player/splitter/decoder/renderer is borked ;)

Note that the correct PAR for 720x576 video is 64:45 to make it display at 16:9 DAR. For 720x576 and 4:3 DAR the correct PAR would be 16:15.
Also note that cropping does not change the PAR, but may change the DAR of course!

[bmnot]

If you set the PAR properly, then all players will display it at the 16:9 DAR. Otherwise the player/splitter/decoder/renderer is borked ;)

Where can I set the PAR in Gordian Knot? I can only select the "Input Pixel Aspect Ratio" - but when I set this to 16:9 then I can't set the output resolution to 720x576

[LoRd_MuldeR]

Where can I set the PAR in Gordian Knot? I can only select the "Input Pixel Aspect Ratio" - but when I set this to 16:9 then I can't set the output resolution to 720x576

I got no idea, since I don't use Gordian Knot. But it should be able to set the output PAR in any useful encoder front-end ;)

Maybe there is an option to add "custom" parameters to the x264 command-line. You'd need to add this:
--par 64:45

[squid_80]

Been a long time since I've used Gordian Knot, but it can make anamorphic encodes:
- Set the input pixel aspect ratio to 1:1
- Set the output PAR in the codec specific configuration. I don't know exactly where to look for the latest DivX, but start by going to the Options tab and clicking the "Nth Pass" button in the DivX codec settings section; or if you're using XviD, click "Second Pass" in the XviD codec settings section, click More next to Profile@Level, go to the Aspect Ratio tab, select the appropriate PAR from the dropdown box under Pixel Aspect Ratio. Use OK to close the dialogs and save the changes.

[bmnot]

I got no idea, since I don't use Gordian Knot.

So what are you using? (What should I be using?)


Yes, DivX seems to have a Input-PAR and Output-PAR setting in the codec setting but i'm not sure if it works (I set input-par to 1:1 and output-par to 16:9 PAL (16:11) and still only VLC plays the video in 16:9)

[LoRd_MuldeR]

So what are you using? (What should I be using?)

I'm using Avidemux (http://forum.doom9.org/showpost.php?p=1006659&postcount=1) all night long. You should use whatever makes you happy :)

[bmnot]

hm... ok, I think this is more of a player/decoder issue so I'll start a new topic about it in the Mpeg4-ASP forum...