Resize/aspect settings needed for Divx -- SVCD conversion

[duck712]

I want to convert a Divx movie (size 720x448) to SVCD. The source is 23,976 fps so it's going to have to be an NTSC format with size 480x480.

Now, on the original Divx the black bars (66 pixels on top and bottom) are encoded along with the movie so I want to cut them off for best result. After that I'll have to add new black bars. So the actual vertical size of the source would be 448-(2x66)=316 (I think).

I want to use the following tools to encode the video-part:
- Virtualdub
- CCE 2.50

I know I'll have to frameserve from Virtualdub to CCE to resize it.

-What settings do I have to use for resizing and cropping?
-What do I fill in for aspect ratio in Vdub and CCE?

I tried using the 'smart resize filter' in Virtualdub and using the cropping function at the same time but I end up with a too narrow picture and to big black bars. (The picture looks squashed on my DVD-player/TV and things look fatter than they should). The preview on Vdub looks fine.



<font size=-1>[ This Message was edited by: duck712 on 2001-08-23 15:11:18 ]</font>

[duck712]

Come on....anyone? Sefy?

[flaninacupboard]

um, actually, ive read here on the forum you're best to leave the bars there. they make a certain amount of "dead space" which means more bits to go around for the actual image. make sense?

[Cart Wheel]

Assuming the source was a 720x480 DVD, you should add whatever black bars are necessary to bring the frame size to 720x480 and then resize directly to 480x480. This will produce the correct aspect ratio.

-Cart
http://www.geocities.com/lukesvideo/index.html

[duck712]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2001-08-23 19:20:24, flaninacupboard wrote:
um, actually, ive read here on the forum you're best to leave the bars there. they make a certain amount of "dead space" which means more bits to go around for the actual image. make sense?
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>
Hmm, no this makes little sense to me. It seems a waste of space to me. But anyway, virtualdub adds the bars also so the result is more or less the same (just with better looking bars I would assume because the new bars haven't been Divx'ed).

[duck712]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2001-08-23 19:56:58, Cart Wheel wrote:
Assuming the source was a 720x480 DVD, you should add whatever black bars are necessary to bring the frame size to 720x480 and then resize directly to 480x480. This will produce the correct aspect ratio.
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>
I'm not sure if we can assume this source-size of 720x480 exactly since the Divx is now 720x448.
But anyway, what should I fill in for aspect ratio in Virtualdub and CCE? In my first attempt I used 1/1 in Vdub and 4:3 in CCE.

[Cart Wheel]

If the video is a 720x448 movie, it's more than likely that the source was a 720x480 DVD. The guy who compressed it probably cropped off 32 lines trying to get rid of the black borders. If you don't make an assumption like that one, then there's no way of determining the (possibly) correct aspect ratio.

What kind of aspect ratios are you talking about? Input or output? Does VirtualDub even have an aspect ratio option?
Anyways, here's how I would obtain the (hopefully) correct aspect ratio in your situation:
1) Use VirtualDub to add blacks borders (letterbox) so that the video has a frame size of 720x480.
2) Resize the video (in VirtualDub) to 480x480.
3) Open the video in CCE, doing whatever is necessary to prevent it from resizing or cropping the input 480x480 video. (I don't use CCE, but maybe you could achieve this by setting the input aspect ratio to 1:1).
4) Set the output aspect ratio to 4:3 because that's how it will be played on a TV.

Assuming the source DivX was cropped from a standard 720x480 video, the final aspect ratio should be correct.

-Cart
http://www.geocities.com/lukesvideo/index.html

[duck712]

Thanks for the info but I gave it another try and it looks alright now. What I did is cut of all black borders in Vdub and at the same time using the 'Smart Resize Filter' (http://sauron.mordor.net/dgraft/index.html) to resize and letterbox it to 480x480, setting the aspect ratio to 3/4 (don't know why, but it was in the filter docs). The result looks good.

Now for some questions on your answer, if you don't mind:
<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2001-08-24 10:16:40, Cart Wheel wrote:
If the video is a 720x448 movie, it's more than likely that the source was a 720x480 DVD. The guy who compressed it probably cropped off 32 lines trying to get rid of the black borders. If you don't make an assumption like that one, then there's no way of determining the (possibly) correct aspect ratio.</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>
That seems logical. Ok, let's assume 720x480. Then what would the aspect ratio be? 720/480 equals 1.5. Is that it?

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>What kind of aspect ratios are you talking about? Input or output? Does VirtualDub even have an aspect ratio option?</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>
The Smart Resize does have a ratio setting, that's the one I meant.
<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
1) Use VirtualDub to add blacks borders (letterbox) so that the video has a frame size of 720x480.
2) Resize the video (in VirtualDub) to 480x480.</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>
How can you do this at the same time?

[Cart Wheel]

Standard NTSC 720x480 ITU-R BT.601 has a pixel aspect ratio of 11/10 (height width). If you convert the video to square pixels, it has a frame aspect ratio of ~1.3636 (which is not exactly 4/3).

I just looked at the documentation for Smart Resize, and I can't understand why Donald Graft keeps talking about a pixel aspect ratio of 10/9 (width/height) for 720x480 (NTSV DV) video. I'll send him some e-mail about this.

Personally, I just use VirtualDub's built-in resize filter. You can use two instances of the filter to do what I suggest. First, crop off the 2x66 pixels you mentioned, bringing the video to 720x316. Then in the first resize filter, set the new image size to the current size (720x316), check "expand frame...", and enter a frame size of 720x480. In the second resize filter, simply resize to 480x480 with no letterboxing.

-Cart
http://www.geocities.com/lukesvideo/index.html

[duck712]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2001-08-25 14:38:57, Cart Wheel wrote:
Personally, I just use VirtualDub's built-in resize filter. You can use two instances of the filter to do what I suggest. First, crop off the 2x66 pixels you mentioned, bringing the video to 720x316. Then in the first resize filter, set the new image size to the current size (720x316), check "expand frame...", and enter a frame size of 720x480. In the second resize filter, simply resize to 480x480 with no letterboxing.
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>
Thanks Cart, I did a small sample using these settings and the seem to work fine. My next Divx I'll convert like this. I would think this method applies to all divx-movies with similar height/width?

[Cart Wheel]

That method should apply to most 720x480 video when creating a SVCD. It doesn't apply when creating a VCD or when the source video is a wide-screen DVD.

By the way, if you ever see a 720x480 DivX movie, it more than likely means the person who encoded it didn't know what he was doing. Standard 720x480 video does not have square pixels and therefore won't have the right aspect ratio on a monitor.

-Cart
http://www.geocities.com/lukesvideo/index.html