Generally, you really want to record either 240 or 480 lines, though I guess you can go below 240 because once you convert to 240 you no longer have interlacing issues the same way. 240 lines is considered the resolution of VHS tapes, but good broadcast has the full 480 (interlaced) and a DVD has the full 480 progressive if you have the right setup.
*sigh*... here we go again. I suggest you do a little research on the meaning of "lines of resolution" as it refers to analog video. The NTSC spec *DEFINES EXACTLY* 525 scanlines/frame, of which 480 (483, actually) are visible. VHS tape does *not* remove those lines, but rather has a low "lines of resolution" as refered to in analog video. It actually refers to the *horizontal* resolution, not the vertical... vertical is fixed by the standard (at 480 for ntsc).
Analog "lines of resolution" are measured as the largest number of alternating black and white vertical lines that can be drawn on the screen before they muddle together and cannot be individually resolved. At's also based on a "per-picture-height," so a different aspect ratio TV affects "lines of resolution." Strictly speaking, a DVD with a widescreen aspect ratio has lower "lines of resolution" than one with fullscreen resolution (720/16*9=405 lines vs. 720/4*3=540 lines).
Thus, for a VCR that has a generally-accepted "240 lines", that translates into an effective capturable resolution of 240*4/3 = 320. The capture resolution that reflects this is:
SP: 320x480, 29.97Hz interlaced.
For EP (which apparently has 2.6MHz luminance bandwidth instead of 3.0MHz for SP), it's (2.6*80)*4/3 = 277 \approx 280, so it is:
EP: 280x480, 29.97Hz interlaced.
A quickie search found: http://www.doom9.org/index.html?/capture/introduction.html http://www.ee.washington.edu/conselec/CE/kuhn/vcr/vcr.htm
There... I feel better
-Cory
************************************************************************* * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * *************************************************************************
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