Questions about cropping when DVD authoring...

[angelleye]

I've been using Divx for quite some time to encode my captures and I'm quite familiar with the steps involved in this process.

I am now trying to get into using Adobe Encore for DVD Authoring and I'm having a few issues which presents a couple of different questions...but kinda the same.

Mainly, am I actually losing quality by using the MPEG-2 method vs. Divx when I encode my captures? I capture using Huffy YUV 720x480. When I capture off my High Def channels there are bars that I would like to remove in order to allow the bitrate to focus on the picture...not solid black. However, doing so changes the resolution of the video file and I can no longer use it in Encore. (side question...is this the same with all DVD authoring packages?) Do I no longer have this option when trying to create DVDs and am I losing quality because of it?

This leads me into my next question. I just capture some video at 720x480. It's almost perfectly fine except that there is a very small gray line that comes in at the bottom of my captures. I've always simply cropped this out...but again this changes my resolution and I can no longer use my clips with Encore. How can I get rid of the gray line w/o upsetting Encore?

Finally, what about de-interlacing or IVTC? Need this be done or do I not worry about it since I'm making a DVD? However, my computer is a media center and it is my TV as well...so I do have a computer monitor...will I see the interlacing lines?

Any information on these questions would be greatly apprecaited. Thanks!

[The Geek]

Mainly, am I actually losing quality by using the MPEG-2 method vs. Divx when I encode my captures?

No, of course not. Just use a high bitrate and you're all set.

When I capture off my High Def channels there are bars that I would like to remove in order to allow the bitrate to focus on the picture...not solid black.

What bars ? Are you referring to the black bars above and underneath a cinemascope footage ? You can't remove them if you want a video DVD. A Video DVD only allows 4:3 or 16:9. And if the footage is something else, black bars have to be added.
DVD also doesn't support HD, so you have to downsize your HD captures.

However, doing so changes the resolution of the video file and I can no longer use it in Encore. (side question...is this the same with all DVD authoring packages?)

If you - what I think - have a wrong aspect ratio, then you can't use it.

This leads me into my next question. I just capture some video at 720x480. It's almost perfectly fine except that there is a very small gray line that comes in at the bottom of my captures. I've always simply cropped this out...but again this changes my resolution and I can no longer use my clips with Encore. How can I get rid of the gray line w/o upsetting Encore?

So you changed the resolution to 720x479 ? That's not possible. It has to remain at 480. If you want to remove a line, fill it with black.

Finally, what about de-interlacing or IVTC? Need this be done or do I not worry about it since I'm making a DVD? However, my computer is a media center and it is my TV as well...so I do have a computer monitor...will I see the interlacing lines?

Don't deinterlace, you'll mess up the quality. Keep it interlaced, as the TV displays interlaced, and PC DVD playback programs are able to deinterlace during playback anyway, so you won't see the interlacing lines on the PC.

The Geek

[angelleye]

What bars ? Are you referring to the black bars above and underneath a cinemascope footage ? You can't remove them if you want a video DVD. A Video DVD only allows 4:3 or 16:9. And if the footage is something else, black bars have to be added.
DVD also doesn't support HD, so you have to downsize your HD captures.

Yes, I am referring to the bars above and below the cinemascope footage. On my actual TV display it's edge to edge of course...but when I use capture software it leaves bars because I'm capturing 720x480. Even with a high bitrate though...isn't a lot of that bitrate being wasted in the black areas?

So you changed the resolution to 720x479 ? That's not possible. It has to remain at 480. If you want to remove a line, fill it with black.

Actually I used Null Transform and cropped off the gray bar which gave me a 720x476 file. With Divx this was fine...but apparently not with DVD. Simply filling it with black isn't what I'm trying to accomplish...I'd like to get rid of this line entirely so that the picture itself will be edge to edge on a standard 4:3 television. Right now it's edge to edge all except the bottom...which shows the gray line. It gives it a non-professinal look.

Thanks again for the information! Any more would be great.

[The Geek]

Yes, I am referring to the bars above and below the cinemascope footage. On my actual TV display it's edge to edge of course...but when I use capture software it leaves bars because I'm capturing 720x480. Even with a high bitrate though...isn't a lot of that bitrate being wasted in the black areas?

The black areas don't require much bitrate, so don't worry. After all, it's not really a waste at all coz you need bitrate for the whole 720x480, like you always do even if you didn't have cinemascope footage.

Actually I used Null Transform and cropped off the gray bar which gave me a 720x476 file. With Divx this was fine...but apparently not with DVD. Simply filling it with black isn't what I'm trying to accomplish...I'd like to get rid of this line entirely so that the picture itself will be edge to edge on a standard 4:3 television. Right now it's edge to edge all except the bottom...which shows the gray line. It gives it a non-professinal look.

DivX is just a video compression technology, as is MPEG-2. You can do what you want, no problem, with MPEG-2, you just can't use it for DVD, as DVD doesn't only require MPEG-2, but requires certain parameters. It's 352x480, 704x480 and 720x480.
So, you can't get rid of that line really, you have to fill it up with something, like a black line. You could resize your footage, but that would mean quality loss, so better don't do it.

The Geek

[angelleye]

DivX is just a video compression technology, as is MPEG-2. You can do what you want, no problem, with MPEG-2, you just can't use it for DVD, as DVD doesn't only require MPEG-2, but requires certain parameters. It's 352x480, 704x480 and 720x480.
So, you can't get rid of that line really, you have to fill it up with something, like a black line. You could resize your footage, but that would mean quality loss, so better don't do it.

So how do I make the gray line black with VirtualDub? And is there way I could actually move the video part down just slightly so that there's a black line of equal size on both the top and bottom...I don't think that would bother me as much as just on the bottom.

Thanks for all the info!

[mic]

Personal opinions and all that...

Your DVD authoring prog. wants 720 x 480 video (DVDLab may be the only exception). One alternative that might work is to use something like AVestensione to generate fake mpg2 headers, another might be to feed your authoring program a temporary mpg2, at the correct size, then re-mux in your desired mpg2 file using IFOEDIT. Done that -- in fact can use that method to create menus etc. in cheaper authoring prog. without having to use their encoders. If you're only cropping a pixel or two from the height, and using a separate encoder, encode to 480 height anyway -- shouldn't notice the stretch.

RE: cropping... The more correct way to do it would be to resize your video after cropping height and width. You'll get 480 lines of picture, but your'll also lose a few on both sides. Again, if you're just losing a few off the bottom, might be able to just resize without noticing the aspect stretch. Either way unfortunately you'll lose some quality from the extra resize -- a good reason to let the encoder do it.

The downside is that if you upsize interlaced video too much, you stand a risk of creating a huge mess on a std TV screen, so depending on how much you enlarge, you might want to deinterlace or do IVT. Each field is made up of a picture as many lines. Eventually displayed on a std TV, it's divided up, the first one pixel row being sent to the first line of the TV screen. If you make a one pixel row two pixels tall for example, you've now created a new 2nd line on your TV, one that belongs to the other field, and shoved the 2nd line down to the 3rd and 4th positions.

Because of the above, the best answer might be just coloring the gray line black if that looks better to you. Use the V/Dub resize filter, crop off the line, keep the frame size the same, and use the letterboxing opion.

RE: the gray line itself.... do you have the option to capture cropped, or to another format? If so, try those. My AIW for example will capture garbage at the bottom of the frame using any avi format, but loses it capturing mpg2.

RE: deinterlacing... At the least you're re-rendering frames so you'll take a quality hit. Otherwise, IMHO depends on the content, source, hardware, final format, DVD player etc... I'm not sure what your HD content is, actual specs or anything, or what your TV's specs are, so please take the following with a grain of salt, as generalities...

If your TV is standard, it expects interlaced, and your DVD player will send it interlaced. The picture your DVD player sends the TV might look worse - it has to re-generate the interlacing. When you deinterlace you merge fields -- both odd and even are effected. The DVD player simply can't send the original fields to your TV any longer.

The same thing goes for IVT to a certain extent. Frames are repeated to act as fields by your DVD player when you encode 24 fps video - some encoders will insert the pulldown flags for you, or the player will do it, but either way a std TV will get 29.97i video. One of my players handles SVCDs with 24 fps captured video extremely well, while the other does only fair. Neither likes IVT'd captured video on a DVD. And both will do the 24 fps video off a re-authored DVD.

The advantage of 24 fps video is it takes less room, allowing higher bandwidth encoding. If you have a progressive TV, then most or all the above doesn't really apply -- just have to see what looks best on your equipment to your eyes.

Most every current PC will display interlaced video as progressive, so I doubt you would see the difference if you filtered (deinterlaced) it. IVT on the other hand you will likely notice. Removing added frames you'll see a reduction in smoothness of motion on your PC. Now, this is not all bad -- some prefer the film look.

About the only thing I can think of to add is about anamorphic. If your HD content is wide screen to start with, you may want to read up on it a bit. Very basically, widescreen on a NTSC DVD is resized to 720 x 480, then spread back out by the DVD player. If all you can capture is 720 x 480, there might not be much you can do other then capture the letterboxed content.

If you wanted to go anamorphic from a 720 x 480 capture, you'll have to deinterlace or IVT, crop, and resize - without all the explanations, you crop 112 pixels off the height (split top and bottom), resizing to 720 x 480, encoding with the 16:9 mpg2 flag. A DVD player will expand and letterbox the video for you.

[angelleye]

i appreciate your response. thanks!

I'm actually using an AIW card as well. Again, I've never had to worry about the extra garbage at the bottom when capturing AVI because I've simply cropped it off.

I did actually go ahead and simply use the resize filter in VDub and cropped it away within that filter. It gave me 720x480 and just barely had to stretch at all so it looks great.

I'm going to read into the anamorphic stuff and I thank you for leading me onto another path.