Agamemnon's questions on DivX encoding - The 3:2 pulldown and how to remove it.

There I was last night looking for files to delete off my hard drive when I
discovered an NTSC torrent of ST Enterprise which I downloaded last year
because for some reason or other my VCR failed to record the start of the
episode (along with an entire episode of Stargate) thanks to the Freeview
EPG clock being put back by an hour in the middle of February. Damn them the
flocking barstools.

Anyway this episode had defeated all my efforts to put it on DVD as a PAL
recording because WinDVD could not convert it properly without it jerking
all over the place. Even the original file played back as NTSC looked
jerkey. Anyway since I'd come across it again, today I decided to have
another go at fixing it, this time using VirtualDub.

After looking at the preview it looked like it was interlaced, which I was
not expecting it to be since I seem to remember that when I last saw
Enterprise it was progressive. So off I went and set my favourite
deinterlacer on it and set VirtualDub it to convert the frame rate to 25fps
and resized it to 576 lines, after cropping it out of the 16:9 letter box it
was sitting in, but what it came back with after I encoded it in DivX was
garbage. Ok I said, lets take another look at this, so I set the
deinterlacer to show what was being deinterlaced and what was not and going
through it frame by frame I discovered it was a 3:2 pulldown. Worse still
the person who had put it together had not re-synchronised it properly when
he/she edited out the commercial breaks. When I tired to used VirtualDub's
3:2 pulldown remover on it, set to adaptive I found out that it some places
it would not sync properly and left the pseudo-interlace still there in
scenes where there where bright flashes, so I had to set it to manual, work
out the offset by trail and error at the start and then fix the offset on
all the commercial break edits so that the initial interlaced frames
repeated every 5 frames.

The output it then came up with was perfectly smooth, in fact smoother than
the NTSC source from UPN but was at 23 frames per second. It was then that I
realised the reason for all the crappily encoded torrents of Battlestar
Galactica S3 which I had previously downloaded, which looked like they had
been resized without being deinterlaced properly, but were also at 23fps.
Whoever did this must have been using VirtualDub on adaptive to removed the
3:2 pulldown and it failed to sync properly in places where the image became
too bright.

So the question is, what is going on? ST Enterprise and Battlestar Galactica
are made on video tape so why aren't they being filmed at 30fps interlaced
but at 23 fps progressive and then converted to 30fps using 3:2 pulldown?
And why 23fps and not 24?

"Agamemnon" wrote

So the question is, what is going on? ST Enterprise and Battlestar
Galactica are made on video tape so why aren't they being filmed at 30fps
interlaced but at 23 fps progressive and then converted to 30fps using 3:2
pulldown? And why 23fps and not 24?

Because NTSC isn't 30 frames per second or 60 fields per second. By a
historical and technical quirk to do with adding colour to the original
monochrome 525-line standard , it's 59.94 fields per second.

So if you have a frame-based show like the ones you mention or any cinema
films, you actually run them at a frame rate of 23.98 frames per second and
apply 3:2 pulldown to get to 59.94 fields per second.

Both shows are shot on progressive HD video at 24fps and so the VTR plays
them out slightly slow at 23.98, down-converts them to standard def and adds
3:2 pulldown at the same time and this is recorded onto an SD format
(probably Digital Betacam) to produce the standard def release master.

Steve

"Steve Roberts" wrote in message
.uk...

"Agamemnon" wrote

So the question is, what is going on? ST Enterprise and Battlestar
Galactica are made on video tape so why aren't they being filmed at 30fps
interlaced but at 23 fps progressive and then converted to 30fps using
3:2 pulldown? And why 23fps and not 24?

Because NTSC isn't 30 frames per second or 60 fields per second. By a
historical and technical quirk to do with adding colour to the original
monochrome 525-line standard , it's 59.94 fields per second.

So if you have a frame-based show like the ones you mention or any cinema
films, you actually run them at a frame rate of 23.98 frames per second
and apply 3:2 pulldown to get to 59.94 fields per second.

Both shows are shot on progressive HD video at 24fps and so the VTR plays
them out slightly slow at 23.98, down-converts them to standard def and
adds 3:2 pulldown at the same time and this is recorded onto an SD format
(probably Digital Betacam) to produce the standard def release master.

And then some idiot encodes it at 30fps (progressive) and uploads it to the
internet and the result is totally unwatchable on a stand-alone player )

(kim)

"kim" wrote in message
...
"Steve Roberts" wrote in message
.uk...

"Agamemnon" wrote

So the question is, what is going on? ST Enterprise and Battlestar
Galactica are made on video tape so why aren't they being filmed at
30fps interlaced but at 23 fps progressive and then converted to 30fps
using 3:2 pulldown? And why 23fps and not 24?

Because NTSC isn't 30 frames per second or 60 fields per second. By a
historical and technical quirk to do with adding colour to the original
monochrome 525-line standard , it's 59.94 fields per second.

So if you have a frame-based show like the ones you mention or any cinema
films, you actually run them at a frame rate of 23.98 frames per second
and apply 3:2 pulldown to get to 59.94 fields per second.

Both shows are shot on progressive HD video at 24fps and so the VTR plays
them out slightly slow at 23.98, down-converts them to standard def and
adds 3:2 pulldown at the same time and this is recorded onto an SD format
(probably Digital Betacam) to produce the standard def release master.

And then some idiot encodes it at 30fps (progressive) and uploads it to
the internet and the result is totally unwatchable on a stand-alone player
)

(kim)

Oh! I'm so glad I'm in PAL land!

On Thu, 17 May 2007 23:30:58 GMT, "Steve Roberts"
wrote:


"Agamemnon" wrote

So the question is, what is going on? ST Enterprise and Battlestar
Galactica are made on video tape so why aren't they being filmed at 30fps
interlaced but at 23 fps progressive and then converted to 30fps using 3:2
pulldown? And why 23fps and not 24?

Because NTSC isn't 30 frames per second or 60 fields per second. By a
historical and technical quirk to do with adding colour to the original
monochrome 525-line standard , it's 59.94 fields per second.


The original standards for PAL, NTSC, Secam etc. were linked to the
Mains Frequencies for domestic power supplies (50Hz Europe, 60 Hz
North America). As the standard frame rate for film was 24 frames per
second, broadcast material had to be modified to accommodate the
working frequencies of the equipment, Film source material was
broadcast in Europe at the slightly higher rate of 25 fps, but in
north America, it was necessary to repeat frames in order to add the
extra material required by the broadcasting standard.

There are several detailed accounts of the process available on the
Decomb and Doom9 sites. The important thing to remember is that most
Ntsc videos and Dvds carry this extra material (NTSC video is recorded
at the higher frame rate), and for a successful conversion to PAL,
that material needs to be removed,

As most European sets and DVD players will now operate quite happily
with both standards it's unnecessary to do so; but with your PC it's
necessary to adjust the operating frequency of older graphics cards to
a multiple of the appropriate frame rate (ie 60, or 75 Hz) in order to
achieve smooth playback. Most multi synch monitors will handle this.

So if you have a frame-based show like the ones you mention or any cinema
films, you actually run them at a frame rate of 23.98 frames per second and
apply 3:2 pulldown to get to 59.94 fields per second.

Both shows are shot on progressive HD video at 24fps and so the VTR plays
them out slightly slow at 23.98, down-converts them to standard def and adds
3:2 pulldown at the same time and this is recorded onto an SD format
(probably Digital Betacam) to produce the standard def release master.

Steve


= IF

On 2007-05-17, Agamemnon wrote:
There I was last night looking for files to delete off my hard drive when I
discovered an NTSC torrent of ST Enterprise which I downloaded last year
because for some reason or other my VCR failed to record the start of the
episode (along with an entire episode of Stargate) thanks to the Freeview
EPG clock being put back by an hour in the middle of February. Damn them the
flocking barstools.

Anyway this episode had defeated all my efforts to put it on DVD as a PAL
recording because WinDVD could not convert it properly without it jerking
all over the place. Even the original file played back as NTSC looked
jerkey. Anyway since I'd come across it again, today I decided to have
another go at fixing it, this time using VirtualDub.

Why not just record it as NTSC?
IIRC UK DVD players are required to be able to play NTSC material, as
Europe and Japan are both region 2.

"Paul Murray" wrote in message
m...
On 2007-05-17, Agamemnon wrote:
There I was last night looking for files to delete off my hard drive when
I
discovered an NTSC torrent of ST Enterprise which I downloaded last year
because for some reason or other my VCR failed to record the start of the
episode (along with an entire episode of Stargate) thanks to the Freeview
EPG clock being put back by an hour in the middle of February. Damn them
the
flocking barstools.

Anyway this episode had defeated all my efforts to put it on DVD as a PAL
recording because WinDVD could not convert it properly without it jerking
all over the place. Even the original file played back as NTSC looked
jerkey. Anyway since I'd come across it again, today I decided to have
another go at fixing it, this time using VirtualDub.

Why not just record it as NTSC?

I just told you that the NTSC version was all jerky. The 3:2 pulldown is the
reason why. Get rid of it and the motions becomes smooth.

IIRC UK DVD players are required to be able to play NTSC material, as
Europe and Japan are both region 2.

"Steve Roberts" wrote in message
.uk...

"Agamemnon" wrote

So the question is, what is going on? ST Enterprise and Battlestar
Galactica are made on video tape so why aren't they being filmed at 30fps
interlaced but at 23 fps progressive and then converted to 30fps using
3:2 pulldown? And why 23fps and not 24?

Because NTSC isn't 30 frames per second or 60 fields per second. By a
historical and technical quirk to do with adding colour to the original
monochrome 525-line standard , it's 59.94 fields per second.

If NTSC is 59.94 Hz how were they able to build stable enough oscillators in
the 50's without using expensive crystals and phase locked loops, when the
mains frequency was 60Hz and how was live NTSC converted to 50Hz PAL in the
60's when the nearest common multiple which is a whole number is 2997 and I
am not aware of there being digital frame buffers back then and certainly
not ones of that capacity so that sync could be maintained?


So if you have a frame-based show like the ones you mention or any cinema
films, you actually run them at a frame rate of 23.98 frames per second
and apply 3:2 pulldown to get to 59.94 fields per second.

Both shows are shot on progressive HD video at 24fps and so the VTR plays
them out slightly slow at 23.98, down-converts them to standard def and
adds 3:2 pulldown at the same time and this is recorded onto an SD format
(probably Digital Betacam) to produce the standard def release master.

Thanks.


Steve

"Ignis Fatuus" wrote in message
...
On Thu, 17 May 2007 23:30:58 GMT, "Steve Roberts"
wrote:



The original standards for PAL, NTSC, Secam etc. were linked to the
Mains Frequencies for domestic power supplies (50Hz Europe, 60 Hz
North America).

Ehem, Europe power frequency = 100Hz not 50Hz, if you stick your finger in a
socket you'll notice the difference.

"Ignis Fatuus" wrote in message
...
On Thu, 17 May 2007 23:30:58 GMT, "Steve Roberts"
wrote:


"Agamemnon" wrote

So the question is, what is going on? ST Enterprise and Battlestar
Galactica are made on video tape so why aren't they being filmed at
30fps
interlaced but at 23 fps progressive and then converted to 30fps using
3:2
pulldown? And why 23fps and not 24?

Because NTSC isn't 30 frames per second or 60 fields per second. By a
historical and technical quirk to do with adding colour to the original
monochrome 525-line standard , it's 59.94 fields per second.


The original standards for PAL, NTSC, Secam etc. were linked to the
Mains Frequencies for domestic power supplies (50Hz Europe, 60 Hz
North America). As the standard frame rate for film was 24 frames per
second, broadcast material had to be modified to accommodate the
working frequencies of the equipment, Film source material was
broadcast in Europe at the slightly higher rate of 25 fps, but in
north America, it was necessary to repeat frames in order to add the
extra material required by the broadcasting standard.

The easy way would be to run the camera at 30fps so it can be scanned in
1/30 of a second and every fourth frame is shown twice by using some sort of
special rack which lets the frame sit there for 1/30 of a second more than
the other frames. The way 3:2 puldown is done on STE is by scanning frams 1,
2, and 3 as progressive then interlacing material from the third frame with
the fourth and the fourth with the sixth to give frame 5 and then scaning
the fifth frame as progressive. This would requite some sort of digital
buffer to store 24 frames and these things did not exist in the 50's and
60's as far as I'm aware, maybe not even in the 70's and 80's.

This is making me think, how were they able to convert live PAL to NTSC and
back again in the 60's when the only thing that the have in common is that
the frequency of each horizontal scan line is the same (I think). The
problem is that there are different numbers of them every second so some
sort of buffering would be required. Just look at the mess you get you your
TV capture card defaults to NTSC_M and not PAL.


There are several detailed accounts of the process available on the
Decomb and Doom9 sites. The important thing to remember is that most
Ntsc videos and Dvds carry this extra material (NTSC video is recorded
at the higher frame rate), and for a successful conversion to PAL,
that material needs to be removed,

As most European sets and DVD players will now operate quite happily
with both standards it's unnecessary to do so; but with your PC it's
necessary to adjust the operating frequency of older graphics cards to
a multiple of the appropriate frame rate (ie 60, or 75 Hz) in order to
achieve smooth playback. Most multi synch monitors will handle this.

So if you have a frame-based show like the ones you mention or any cinema
films, you actually run them at a frame rate of 23.98 frames per second
and
apply 3:2 pulldown to get to 59.94 fields per second.

Both shows are shot on progressive HD video at 24fps and so the VTR plays
them out slightly slow at 23.98, down-converts them to standard def and
adds
3:2 pulldown at the same time and this is recorded onto an SD format
(probably Digital Betacam) to produce the standard def release master.

Steve


= IF