Converting PAL to NTSC wil the duration be longer?
by Caropillar
on
Nov 9, 2007 at 9:16:23 pm
I just recently converted some Mini DV footage I digitized from 4 PAL tapes. I converted all the footage from the tapes into NTSC and am in the process of lay them back to tape. It seems that what once took 4 tapes now needs 5. Is this possible? Or did I make some type of mistake?
Re: Converting PAL to NTSC wil the duration be longer? by Caropillar on Nov 9, 2007 at 9:32:08 pm
I used Compressor to convert to NTSC. I have done it this way before with footage off a digibeta and they looked great and the duration stayed the same. I am still pretty new at doing this but it looks like the duration changed on these videos...
Re: Converting PAL to NTSC wil the duration be longer? by cofe on Nov 9, 2007 at 10:25:26 pm
could it be that you recording to tape in dvcam format and not mini dv?
dvcam and mini dv are the same codecs - dv - but the tape runs at different speed. the idea was that through wider spacing on the tape dvcam is less error prone and therefor better for professional applications. some dv decks play back mini dv and dvcam recorded tapes, but only record in dvcam. Like the the dsr40 which i have. a 60 min dv tape will only record about 40 min in dvcam mode.
i doubt that it is a frame conversion issue as the only possibility of a changed duration would be if you converted the 25 fps from pal 1 to 1 to ntsc's 30 (29.98) but his would mean you running time would be shorter as you pack 25+5 pal frames into the 30 frames per second ntsc.
that's all i can think of right now.
cheers
carsten
Re: Converting PAL to NTSC wil the duration be longer? by k i pugh on Nov 10, 2007 at 1:18:25 am
The tape duration, yes.
I believe that although 1 second of PAL = 1 second of NTSC, it takes more tape to play this second, as NTSC contains around 30 frames a second instead of 25. That's why a 30 minute Beta SP tape is actually 33 minutes in PAL land, but only 30 minutes in NTSC. So yes - you may need 5 tapes instead of 4 if the tapes were full.
Re: Converting PAL to NTSC wil the duration be longer? by rafalaos on Nov 10, 2007 at 2:36:33 am
One minute is one minute whereever in the world you are.
I think as Cofe. You have recorded 4 hours of MiniDV and you are pringting to video as DVCam. In DVCam the tape runs a 25% faster than in MiniDV. So to acomodate 4 hours of footage in DVCam fashion, you need 5 tapes.
rafael
Re: Converting PAL to NTSC wil the duration be longer? by Rennie on Nov 10, 2007 at 3:03:45 am
I believe it is a tape speed issue like Ken suggested. I remember with my panasonic AG -AW1 format converter you had to watch it because one of them uses more tape phyically. The tape runs past the heads faster so more tape is used. The running time of your programe stays the same of coarse but more linear feet of tape is used. I don't remember which one uses the most but it sounds like ntsc is the one that cranks the tape faster therefor using more tape.
Re: Converting PAL to NTSC wil the duration be longer? by rafalaos on Nov 10, 2007 at 3:15:05 am
There are not MiniDV tapes for NTSC and for PAL. They use the same tapes and in one hour tape you can record one hour footage in the two systems. The tape runs at the same speed.
Only the drum works different. In NTSC spins 30 times per second and in PAL 25 per second.
rafael
Re: Converting PAL to NTSC wil the duration be longer? by Rennie on Nov 10, 2007 at 6:28:10 am
Couldn't find my old manual but this from wikipedia
{The tape speed is 3.335 cm/s for NTSC, 2.339 cm/s for PAL. A cassette holds a maximum of about 430 m of tape at the lowest acceptable tape thickness, giving a maximum playing time of about 3.5 hours for NTSC and 5 hours for PAL at "standard" (SP) quality}
They basically are saying if you have a cassette tape of a given size you will get 30% more pal on it than ntsc. This is regarding vhs tape but I don't see why a similar scenario wouldn't exist for dv cassettes.
Re: Converting PAL to NTSC wil the duration be longer? by rafalaos on Nov 10, 2007 at 9:29:32 am
When we are in the analoge world, PAL and NTSC are two signals with diferent band-with (higher in PAL) and diferent time-base (lines and frames per second). When we are in digital NTSC DV and PAL DV are two very similar streams of 25Mbps.
VHS is a very old system that record analog in cheap tapes. MiniDV tapes are a much modern technologie and you only record bits (zero or one).
rafael
Re: Converting PAL to NTSC wil the duration be longer? by k i pugh on Nov 11, 2007 at 12:37:09 am
The Panasonic AJ-HDX400 DVCPRO deck runs the tape at 67.640 mm/s in NTSC and 67.708 mm/s in PAL. The speeds are close, but clearly different, and surprisingly the NTSC is slower, not faster.
However - A European E120 VHS tape is 570 feet in length and will give 2 hours of playing time on a PAL VCR. The same tape used on an NTSC VCR will give only 1 hour & 26 minutes of play time.
So it does seem that while NTSC and PAL had big differences in tape speed when recording analogue, ie with BetaSP and VHS, the differences in tape speed are much smaller, practically speaking insignificant, in DV recording (although I've not done the maths!).
Re: Converting PAL to NTSC wil the duration be longer? by rafalaos on Nov 11, 2007 at 4:03:04 am
[k i pugh]"The speeds are close, but clearly different, and surprisingly the NTSC is slower, not faster." In magnetic recording, the range of frecuencies you can manage depends on the tape speed and the wide of the 'gap" of the magnetic head. If you want to record higher frequencies you need to pass the tape faster or make the gap smaller.
The speed in the PAL tape is higher because in PAL you need to record higher frecuencies than in NTSC (4.5 Mhz vs 5.5Mhz if I can remember).
When you are recording analoge, you are recording a much complex signal with a wide range of frequencies from the lower to the higer. You need that the track that you set in the tape are clearly separated to avoid inter-modultion of the magnetic fields, and mistracking of the video heads when reading. In digital you are laying a serie of "0" and "1" that are much easier to recover when reading. So in this sense, digital is less critic even if you are recording very high bit rate.
Sorry if my English is not good enough to explain this properly.
Rafael
Re: Converting PAL to NTSC wil the duration be longer? by Rennie on Nov 11, 2007 at 6:22:44 pm
Interesting, it would seem the original tapes were dvcam and they were laid back to ntsc dv would more than likely be the answer although Caropillar should have ended up with 6 tapes from 4 dvcam originals unless they were not full tapes.
Re: Converting PAL to NTSC wil the duration be longer? by rafalaos on Nov 12, 2007 at 2:09:28 am
[Rennie]"it would seem the original tapes were dvcam and they were laid back to ntsc dv" I think the opposite. They recorded 4 MiniDV tapes (four hours) but now are recording as DVCam, so they need 5 tapes to fit 4hours.
rafael
