horizontal frame size

rlsnyder wrote on 8/11/2004, 8:53 AM
The Sony VX1000 camcorder apparently has a horizontal frame size of 704. The Vegas DV standard is 720. This discrepancy results in two narrow black stripes on the left and right edges of the Vegas captured VX1000 frame. Because of overscan, these stripes are not visible on the TV screen, but they are visible in a computer screen window. One also wonders if these stripes in some way degrade the rendering process.

Is it possible to work in Vegas with a nonstandard DV frame size of 704 x 480? Can this frame size be maintained throughout the entire capture, edit, render (to mpeg2), and DVD production cycle - filling the frame without distorting the aspect ratio of this frame and without interpolating from one pixel grid to another?

If so, how does one configure Vegas (capture and edit) and DVD Architect to achieve this?

Comments

Bill Ravens wrote on 8/11/2004, 8:59 AM
yikes!!!! this sounds like a similar and well-acknowledged problem with the Canon XL1s in which a black bar appears in the overscan area of the frame, on the right side. This, seemingly, innocous black bar wreaks havoc on compression algorithms, driving up render time and affecting noise of mpeg compressed files because the discreet cosine transform has difficulty with radical and sudden changes in contrast..
rlsnyder wrote on 8/11/2004, 9:17 AM
I thought I read somewhere that the DV algorithm used a block size of 8 x 8. If so, it may be that the stripes are well located to do minimum damage. (I guess this would depend on how much influence one block has on neighboring blocks.) Nonetheless, why waste time and effort transforming a block that is uniformly black, particularly when you really don't want this block included in the resulting frame?
riredale wrote on 8/11/2004, 10:49 AM
If true, I wouldn't worry about it, unless it really bothers you.

For one thing, no one is going to notice it. I'd bet that, even on a PC monitor, no one points to the very narrow black bars and says, "What's that?" However, if you really want to, you can completely resample your project to expand the width out to 720 pixels. It will take a while to render and you'll lose a bit of resolution in the process, though. Perhaps you would want to do this if you were cutting this camera's output in with other video footage that did not show the same effect.

One some of my projects I noticed that one of the camcorders used had an annoying habit of turning the very top scan line on and off at random times. This "flicker" was easily noticed, so I simply rerendered the final output with a very narrow mask on all four sides. Issue gone.
rlsnyder wrote on 8/11/2004, 12:24 PM
If I could eliminate the stripes without distorting the aspect ratio of the embedded video and without resampling (interpolation), I would do so. Otherwise, this elimination is probably not worth it.

My guess is such elimination presupposes working with a DV frame size that matches that of the VX1000, namely 704 x 480. Is this possible? If so, how does one configure Vegas to achieve this?
Chienworks wrote on 8/11/2004, 12:32 PM
You can tell Vegas to use any frame size you wish. Set up the project properties (File / Properties) to whatever you want it to be and Vegas will use it. However, be aware that some output formats have specifically defined parameters. You cannot write a DV .avi file at 704x480; only 720x480 (for NTSC) will work. So, if you go this route, you will still end up with 720x480 output. You can choose whether Vegas leaves the image the same aspect and adds 8 black pixels on each side, stretches the image to fill 720, or crops to have 704x469.3 fill the 720x480 frame (thereby losing about 5 pixels from the top and bottom), or any combination thereof.
rlsnyder wrote on 8/11/2004, 4:14 PM
Sounds like I can't do what I would like to do.

Do you know whether the restriction of DV .avi frame size to 720 x 480 is specific to Vegas or a general restriction characteristic of all NLEs?

Thanks to all for your comments.
Chienworks wrote on 8/11/2004, 8:40 PM
It's the DV spec. All NTSC DV files will be 720x480.