Jump to content


Photo

Canon 24F No Longer?


  • Please log in to reply
7 replies to this topic

#1 Adam Davis

Adam Davis

    New

  • Basic Members
  • Pip
  • 7 posts
  • Other

Posted 05 August 2008 - 11:17 PM

When I first started using the XH-A1 in 24F mode, the output footage would read as 23.98fps. Lately however, most editors and playback software say all my 24F footage is really 29.97fps. Any reason for the change? I haven't done anything new or out of the ordinary.
  • 0

#2 Phil Rhodes

Phil Rhodes
  • Sustaining Members
  • 11941 posts
  • Other

Posted 06 August 2008 - 07:28 AM

As far as I know all the Canon stuff has always shot 24F (properly 23.98) but put it to tape as 29.97 with 3:2 pulldown. Confusion over this may explain the discrepancy. I doubt anything has actually changed.

P
  • 0

#3 Adam Davis

Adam Davis

    New

  • Basic Members
  • Pip
  • 7 posts
  • Other

Posted 06 August 2008 - 11:26 AM

As far as I know all the Canon stuff has always shot 24F (properly 23.98) but put it to tape as 29.97 with 3:2 pulldown. Confusion over this may explain the discrepancy. I doubt anything has actually changed.

P



That's exactly what confused me, as the raw .m2t files originally read as 23.98 when I would check the properties (I use Media Player Classic to view just about everything).
  • 0

#4 Johan Malmsten

Johan Malmsten

    New

  • Basic Members
  • Pip
  • 1 posts
  • Other

Posted 18 August 2008 - 04:53 PM

That's exactly what confused me, as the raw .m2t files originally read as 23.98 when I would check the properties (I use Media Player Classic to view just about everything).

As the HDV standard only can record in 50i/60i there are two ways of putting in progressive frames into the stream.

1. PAL-mode shooting 25p and record it even-field as 50i.

2. NTSC-mode shooting 24p(or 23.98p) and record it with 3:2 pulldown to the 60i stream.

The stream is then "flagged" by a bit that tells it that the stream is indeed progressive. If the player or NLE don't know about this flag they can't read it and thus it will play and edit in it's normal interlaced way.

So, in your case, MPC seems to recognize the flag properly. The editors NLE however isn't. Is that an issue? well yes and no. No, in that if you are using PAL the frames are already on the appropriate fields so normal edits are no problem, NTSC however run a frequent risk of ghosting fields and errant half-frames during edits because of the mixed frame. And in both formats, one should stay clear of anything that manipulates the clips framerate since fields will start to show and show up and just become a mess that won't even look good on interlaced TV's...

All in all, your footage are probably correctly 24p in a 3:2 60i stream. Your editor though needs to make sure that his NLE is set up correctly to avoid the issues that can occur.

Also, there exists conversion tools to make 3:2 free 24p video out of the stream. I haven't used these myself though so I cannot judge the quality of the results.
  • 0

#5 Phil Rhodes

Phil Rhodes
  • Sustaining Members
  • 11941 posts
  • Other

Posted 18 August 2008 - 05:40 PM

> As the HDV standard only can record in 50i/60i

Not quite true; the JVC stuff will do 24/25/30/50/60, albeit at 720p.

Under Windows, I'd look into Virtualdub or perhaps better (if a bit more complex) AVIsynth. Either have tools to unwind 24p from 3:2 pulldown. From HDV originals, the automated modes should make few enough mistakes that correcting them manually is no big deal.

P
  • 0

#6 Thomas Worth

Thomas Worth
  • Basic Members
  • PipPipPipPip
  • 372 posts
  • Director
  • Los Angeles

Posted 19 August 2008 - 04:24 AM

That's exactly what confused me, as the raw .m2t files originally read as 23.98 when I would check the properties (I use Media Player Classic to view just about everything).

I've noticed the same thing not only from the XL H1, but the XH A1. I noticed this on Wikipedia:

Canon 1080i50 and 1080i60 can play on Sony HDV cameras and decks. Canon's 24f, 25f, and 30f are not cross-compatible with Sony's implementation of HDV.

Can someone confirm this?

If this is true, then 24F, 25F and 30F are most likely NOT 50i/60i. If they were, they'd play just as peachy as the 50i and 60i modes (because they would be the same). My suspicion is that Canon is recording these modes progressive, using a tricky method to perhaps maximize the HDV bandwidth for the slower frame rates. This would explain why FireWire capture is not interlaced (3:2 applied) after capturing 24F footage, and why these modes are incompatible with Sony HDV even though interlaced modes are.

I can confirm that SDI output does not work when playing back 24F from tape, but analog component does. Perhaps the 3:2 is being performed during D to A.

Any thoughts? Phil?
  • 0

#7 Phil Rhodes

Phil Rhodes
  • Sustaining Members
  • 11941 posts
  • Other

Posted 19 August 2008 - 09:14 AM

Well, it would make a lot of objective sense for it to be as Mr. Worth proposes; I believe the JVC stuff does vary its data rate per frame at various taking speeds and if I'm right it has been done before. It is fairly trivial to apply 3:2 pulldown in a frame buffer.

You have the gear to test this - what's the SDI output do while shooting 24F live? 60i, I assume.

P
  • 0

#8 Adam Davis

Adam Davis

    New

  • Basic Members
  • Pip
  • 7 posts
  • Other

Posted 20 August 2008 - 11:33 AM

On a whim I tried re-installing Vegas, and oddly enough it worked. It's now reading 24F files as 23.98. Don't ask me to explain what was wrong before. I can't explain it.


As the HDV standard only can record in 50i/60i there are two ways of putting in progressive frames into the stream.

1. PAL-mode shooting 25p and record it even-field as 50i.

2. NTSC-mode shooting 24p(or 23.98p) and record it with 3:2 pulldown to the 60i stream.

The stream is then "flagged" by a bit that tells it that the stream is indeed progressive. If the player or NLE don't know about this flag they can't read it and thus it will play and edit in it's normal interlaced way.

So, in your case, MPC seems to recognize the flag properly. The editors NLE however isn't. Is that an issue? well yes and no. No, in that if you are using PAL the frames are already on the appropriate fields so normal edits are no problem, NTSC however run a frequent risk of ghosting fields and errant half-frames during edits because of the mixed frame. And in both formats, one should stay clear of anything that manipulates the clips framerate since fields will start to show and show up and just become a mess that won't even look good on interlaced TV's...

All in all, your footage are probably correctly 24p in a 3:2 60i stream. Your editor though needs to make sure that his NLE is set up correctly to avoid the issues that can occur.

Also, there exists conversion tools to make 3:2 free 24p video out of the stream. I haven't used these myself though so I cannot judge the quality of the results.


  • 0


rebotnix Technologies

Willys Widgets

Paralinx LLC

Rig Wheels Passport

FJS International, LLC

Tai Audio

Glidecam

Abel Cine

Opal

Gamma Ray Digital Inc

Aerial Filmworks

Technodolly

Visual Products

Metropolis Post

The Slider

Media Blackout - Custom Cables and AKS

Ritter Battery

CineTape

Wooden Camera

Broadcast Solutions Inc

CineLab

Glidecam

rebotnix Technologies

Paralinx LLC

Media Blackout - Custom Cables and AKS

Willys Widgets

Wooden Camera

Visual Products

Technodolly

Broadcast Solutions Inc

Opal

Metropolis Post

Abel Cine

Aerial Filmworks

Rig Wheels Passport

Ritter Battery

FJS International, LLC

CineLab

The Slider

CineTape

Tai Audio

Gamma Ray Digital Inc