Rendering to less than full DV size

Videot wrote on 6/16/2004, 12:39 AM
Whenever I have rendered out a file it's always been to full PAL DV settings of 720 x 576. If I were to render to a small size I would expect the file size to se smaller & that the rendering would be done more quickly. If I were to do this would the resulting DVD be payable on any DVD player & would the picture fill the entire TV screen?

If the original source for the video was an old VHS tape of poor quality,
would rendering to smaller size no be noticed too much or would the
resulting file look worse than if I had gone for the full size?

Comments

Chienworks wrote on 6/16/2004, 4:51 AM
There are no smaller frame sizes for DV. It is fixed at 720x576 for PAL and 720x480 for NTSC. Those are the only choices for DV. If you want a smaller frame size you'll have to render to something else, such as uncompressed or MPEG. Of course, if your final output is DVD then rendering straight to MPEG may be what you want to do anyway.

The rendering time will probably be faster when using a smaller frame size. However, for MPEG the file size is not determined by the frame size. All other things being equal, a 360x288 MPEG file will be the same size as a 720x576 MPEG file. The same number of bits per second will be used in either case. Therefore, what matters is the bitrate, and you can use a lower bitrate on a full frame size file. However, that being said, you may be able to get away with a lower bitrate on a smaller frame size than you could on a full size frame.
TheHappyFriar wrote on 6/16/2004, 5:42 AM
He's right. :) With mpeg (and divx & wmv I think) the bitrate affects file size. However, a smaller frame size with a "decent" bitrate can look better then a bigger frame size (more bitrate for less pixels).
Videot wrote on 6/16/2004, 6:52 AM
Basicly it seems that you saying that bit rate is more important than frame size. Does the fact that the source is of poor quality mean that doing this might be a good thing or not?
wdormann wrote on 6/16/2004, 7:07 AM
The bitrate of a video determines the file size. Nothing else.
Using a lower resolution lets you get away with a lower bitrate. If you cut the resolution in half in one dimension, you can use half the bitrate and still have the same bits per pixel
Chienworks wrote on 6/16/2004, 7:48 AM
And since old VHS probably only has a usable resolution of quarter-frame (327x240 or so), you probably won't lose anything by going to this resolution. At this frame size you can use a lower bitrate than would be acceptable for a full size frame.

"The bitrate of a video determines the file size. Nothing else."   Well, this holds true for compressed video, which is what most of us work with most of the time. In uncompressed video the bitrate is determined by the frame size, as well as the bit depth and frame rate. Just a little technical distinction, but it's worth noting.
erratic wrote on 6/16/2004, 7:58 AM
352x240 NTSC and 352x288 PAL are DVD compliant resolutions, but the video is no longer interlaced. If the source video is interlaced I would keep it interlaced. In that case 352x480 NTSC and 352x576 PAL are DVD compliant resolutions.