DVL-Digest 601 - Postings: Index Progressive Scan for easier mi Progressive Scan for easier mi - "Perry" There are cleverer ways of doing it, but most standards conversions from PAL to NTSC make up 6 new fields from the original 5. The result is a little jerky but acceptable to most folk. If you shot progressively with current kit you are looking at then needing to make up 6 new frames from 5 PAL frames, and the resultant jerkiness would be much worse. It is a similar situation with telecine pull down, if you wanted progressive video you'd need to mix 3:2 frames vs. fields that are used with interlaced video. This would also result in unacceptable jerkiness. What Alon calls fields-hell is actually the secret to getting acceptable motion interpolation. In answer to his other points, DV is inherently an interlaced format although you can 'cheat' and record pseudo progressive scan information. Nearly all CCD chips operate a progressive scan every field, but if you used this raw information on the interlaced DV format you would get unacceptable 'interfield twitter'. In practice the camera averages line pairs which also improves sensitivity and noise. Pseudo progressive scan video interpolates a frame from a single field. PAL and NTSC cameras have different CCD chips, so it is not possible to use them to record both standards. The DV data structure is very similar between PAL and NTSC, and apparently a few DV cameras will play the opposite standard into the viewfinder (but not out of the camera). Perry Mitchell Video Facilities http://www.perrybits.co.uk/ (diese posts stammen von der DV-L Mailingliste - THX to Adam Wilt and Perry Mitchell :-) [up] |
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