As I Understand:
Raghuvir wrote:
And is it true that a field averaged video has lesser bit rate than a progressive one??
No. They are independant.
When you make a digital copy or copy or transfer from one system to another, it's copyer's choice, what bit rate they use. You can have a 10th gen VHS copy transferred to Blu Ray bit rates of 20, 30 mbps, but video quality will not be any better than the original.
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I think companies like Shemaroo keeps on making copies of the video which spoils the quality, adds fuzziness, frames disappear, speed shift takes place and the end result is INTERLACED video -- correct me if I'm wrong.
Copying a digital video is not the same as copying VHS to VHS where quality degrades every generation. Digital Video is copied "exact Code' or 'Compressed Data'. Obviously, Orig Code is exactly same as Orig and in Compressed copy, obviously some info is lost. Digital copying does not alter Interlace/ Progressive.
NTSC DVD: 24 fps Progressive: Record 24 individual frames per sec and write a code to put each frame into two fields (alternate lines) and repeat every 5th frame. (Saves 20% data space)
Pseudo-Prog: Record 24 film frames into 60 fields, where every 5th field is a repeat of 4th field. As you are storing infi in 5th field that did not need to, you are wasting 20% bit space. Progressive players can/ may detect this repeat pattern and regroup the video to original 24 fps and discard the un-neccessary 5th fields. Film to NTSC telecine are Pseudo-Prog. Depending on noise level or quality of video, 2-3 pattern may or may not be recognized by Prog Scan players/ converters.
Field Averaged: 24 fps into 60 or 24 into 50 and then into 60 or any combo where video fields keep recording at their speed and film at their speed, thus resulting in one video field containing info from more than one film frame.
PAL DVD:Film to PAL telecine is done by recording 24 film frames into 48 video fields. Any Prog player can put the two video fields together to give original film frames back. Note that in one sec, now you see 25 film frames and hence the 4% speed up.
NTSC to PAL or vice versa: Usually, player and recording machine keep playing at their speeds and hence no distinct copying of orig film frames. Eacxh video field contains info from more than one film frames. And hence, Field Averaged.
It's possible to keep track manually, or by some programming, how the film frames are individually stored and then keep them separate. Muz got some PAL VHSs transferred to NTSC this way. 4% speed up PAL VHSs were converted to 24 fps NTSC DVD that now has the original 24 fps original film speed.
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BTW, flicks like Pyasa by Ultra shows me speed shift in some parts (not sure about the rate of shift) but not in all parts and I don't find any fuzziness and combing. Then why the speed shift?
Ultra Pyasa DVD: I haven't seen the DVD, so can't comment. But, the state of Indian DVD industry is, many DVD writers don't know what they are doing. For example, I have one DVD that's half in NTSC and the other half in PAL. Another film that has alternating Giga Bytes in 24 FPS Progressive and 60 fields per sec Interlaced. Another DVD Author (EVP) said he has no idea why some of his DVDs are Progressive and other are Interlaced (some even Field Averaged). He said, he gave the same treatment to all.
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Does Shemaroo use a PAL telecine? And then they convert it to NTSC by field averaging ??
I think they have both types. Some of their DVDs are direct Film to NTSC but most are Film to PAL Telecine and then converted to NTSC. See, India is a PAL country, so their Telecine machines are normally PAL. But, the DVD market is NTSC, so they use PAL to NTSC converters to make NTSC DVDs. PAL to NTSC converter (or vice versa) does not know that the info originally was 24 fps. So, they just convert 50 into 60 for which easiest way is field averaging. (Yes, just like what Muz did, one can keep track of film frames in PAL and then re-distribute them into 24 fps NTSC and getting the 4% speed correction in the process).
Also see:
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