... a little lesson in fundas:
1. Film to NTSC Master is always the same length -- True?
2. Film to PAL Master is always 4% faster -- True?
3. NTSC Master to PAL is --- ??
4. PAL Master to NTSC is --- ??

As I understand:


Almost same length. 59.97 vs 60.0
@ NTSC broadcast frequency there can be 59.97---- fields of 525 lines per second and not 60.0.
Normal practice is to record 24 film frames (per sec) into 60 fields (and not 59.97).
24 into 60 can be achieved splitting first frame into 2 fields and the next frame into three fields (or the three field one can be two fields and the third one exact repeat; Pseudo-Prog).
EROS et al record 2nd frame into three fields and thre third field has complimentary info and not the exact repeat. Don't know if it's in DVD encoding or in Telecine.
Another way of changing 24 into 60 or into 59.97 can be by averaging (Field Averaging). Should not be done but can be done.

(In case of Digital media, they need record 24 frames into 24 or 48 blocks and output to NTSC by repeating every 4th block into 5th).


Not a must, but that's the case 99% of the time.

As PAL freq is 50 (not sure if it's exact 50.0000 or aprox), and film rate is 24 fps, normal practice is to record each film frame into 2 fields. Hence 24 frames info gets into 48 PAL fields (default progressive) and hence 4% faster. It was judged that 4% speed up audio pitch was not noticeable. Moreover pitch an be corrected even if audio goes 4% faster.

Another way to convert 24 into 50 is by splitting each frame into 2 fields and to make up for 4% speed up, repeat one field after every 24 fields. Or, by field averaging 24 into 50. There must be some machines doing this, as occasionally I see some DVDs like this.


Depends:

If NTSC master is at normal speed, usually it's PAL conversion will be normal speed too. Mostly it's done by field averaging 60 into 50 (not 48).

Technically it's possible to find a 2:3 pattern in NTSC master and ignore the repeat info giving you the orig 24 film frames from where you can get a 4% speed up default progressive PAL DVD.


Again it depends:
If PAL master is 4% speed up default progressive, it's easy to detect original 24 film frames and then convert it to NTSC using any of the methods used for Film to NTSC. So, the "Film to PAL to NTSC" may or may not be 4% speed up, and it may or may not be Field Averaged or Progressive or Pseudo-Prog.
(Some EVP Hindi DVDs had every 6th field a repeat of 5th field, indicating it to be a "Film to PAL to NTSC" transfer @ 4% speed up.)

If PAL master is 24 into 50 Field Averaged or if it's every 24th field repeated, NTSC conversion too will be field averaged.

PAL to NTSC conversion: If there is a 4% speed up in PAL, normal PAL to NTSC converters will not slow it down back to orig speed. Why should they ?? Normal PAL TV is not 4% speed up.

It just happens that Film to PAL transfer is simpler if they speed up the running by 4% so that 25 film frames make up 50 PAL fields. When converting from PAL to NTSC, transfer routine does not know, & how would it know, that the PAL program was speed up 4%.

Once known that PAL is coming from a direct film source and 25, instead of 24, film frames have taken up 1 sec of run time, some programs can separate out 25 orig frames (1 sec) and then re-record them in NTSC @ 24 fps (24P), the original film speed will be restored.
I think, some EVP Hindi DVDs were really Film to PAL to NTSC converted this way and hence remained orig speed.