This page is just a quick collection of notes on for The Movie Project.
There are several different standard sizes that might be chosen from. The information on frame sizes supported under DVD gives us a good starting point.
First of all, the number of vertical scan lines on a TV display is fixed. The horzontal pixel count is not. That led to all sorts of fun things back when signals were still mainly analog.
There are two general standards for TV frames. NTSC and that junk the other people use ;-)
| Standard | Vertical lines | Hz |
|---|---|---|
| PAL/SECAM | 625 | 50 |
| NTSC | 525 | 60 |
Given these, it's easier to understand the different frame sizes.
| lines | Width | Height |
|---|---|---|
| 525 | 720 | 480 |
| 704 | 480 | |
| 352 | 480 | |
| 352 | 240 1 | |
| 625 | 720 | 576 |
| 704 | 576 | |
| 352 | 576 | |
| 352 | 288 1 |
1 Only frame sizes allowed for MPEG-1
Given all this, it seems off-hand that the horizontal resolution should be either 704 or 352. The vertical resolution would probably depend on the desired aspect ratio.
If we were going for the standard 16:9 aspect ratio for a nice letterboxed effect, then we could get the following:
| lines | Width | Height |
|---|---|---|
| 525 | 720 | 360 |
| 704 | 360 | |
| 352 | 360 | |
| 352 | 180 1 | |
| 625 | 720 | 432 |
| 704 | 432 | |
| 352 | 432 | |
| 352 | 216 1 |
Oh, yes. To confuse things further, the standard for width on computer screens is 640, not 720. I believe that mainly the 720 width was chosen because of signal quality issues, whereas 640 was chosen to get square pixels for computer displays. Since the purpose of IMP is to end up with something for the general public, I feel that we should focus on the TV friendly sizes.
For initial test and such, we should probably start with 352x240 and about a 1.17 aspect ratio. This will also help with distributing the tests in MPEG format. If letterboxing is desired, the top 30 and bottom 30 lines can be blacked.
For tests on computer displays, we should go for 320x240, with an aspect ratio of 1:1. For the more accurate test, the left 13 and right 13 columns could be blacked, leaving 294 width used.