29.97 / 23.98 timecode question

[Gohanto]

I just finished working on a short done on the RED, shot at 23.98. Following some advice I read here a week or two ago I converted the mp4 video I received into 29.97 .dv file. One thing I quickly notice though was that the timecode burn on the video was set in 24 fps, while my timeline was in 29.97 (and altering a 2nd ruler to 23.98 was way off).

The sync in the end was fine, but just a minor inconvenience for working.

Searching I found partial answers but just want to clarify for the future, if I'm going to receive or convert video to 29.97, is it pretty simple for video editors to burn just 29.97 timecode to 23.98 video? Or is there a step I'm just missing somewhere?

Thanks,

[Postman]

You do not have to change the video frame rate when transcoding a movie, you could have kept it at 23.976. A 23.976 dv movie will play out of Pro Tools into an NTSC display, even through a Canopus or MOJO. Pro Tools handles the 2:3 frame rate conversion on the fly. You set the session frame rate to match video and use the main counter as you would like to.

A 23.976 ruler should stay in sync with a 23.076 burn-in, though, even when you transcode the video to 29.97 (assuming you transcode to interlaced video, NOT progressive video). The absolute time might be different (or might not, depending on other factors), but there shouldn't be any drift between the ruler time and burn-in.

If the editor is working at 23.976, you should also. You can introduce sync ambiguity when transcoding from one frame rate to another, and there are playback ambiguities as well. This is because there can be differences of a video field, 1/2 frame, between the two frame rates. 1/2 frame ambiguity is not a big issue, but there can be another 1/2 frame error when you still-frame or scrub video. The two errors are additive. It is possible to mark a scene change, for instance, based on what you see when you scrub the image, yet the actual cut can be (but not necessarily) 1/2 frame earlier. Same thing when cutting sound effects.

When you still-frame an NTSC or PAL image, most programs these days including Pro Tools show you only one of the two fields. An interlaced frame of video is made up or two video fields. If the scene cut is on the field you do not see when still-framed, you have to step to the next video frame to see it. That is 1/2 frame of error when still-framed, with no error in realtime playback. Things get slightly more sloppy if you transcode from 23.976 into 29.97 progressive, which "locks in" ambiguity, so you will never see exactly the same sync as with 23.976 video! These errors will generally not happen if you maintain a 23.976 frame rate.

[hef]

Originally Posted by Postman

You do not have to change the video frame rate when transcoding a movie, you could have kept it at 23.976. A 23.976 dv movie will play out of Pro Tools into an NTSC display, even through a Canopus or MOJO.

For the MOJO- even when converting quicktimes in media station to MXF format you can keep them at 23.976? I remember not having success with this in the past. or are you just talking about using a quicktime (.mov or .dv) through the mojo?

[Audio_Vision]

Originally Posted by hef

For the MOJO- even when converting quicktimes in media station to MXF format you can keep them at 23.976? I remember not having success with this in the past. or are you just talking about using a quicktime (.mov or .dv) through the mojo?

I have completed projects that were 23.976 using Avid converted MXF video out the Mojo to an NSTC monitor; the real time 2:3 always worked fine. The video was usually Quicktime with the H.264 codec and I would then convert it in Xpress or now Media Composer to some flavor of MXF at the same frame rate. Pro Tools sessions were also set to 23.976 (I really had no reason to work at 29.97, so I can't comment on that, but what Postman said, as usual is the right advice regarding 29.97 compatibility). What issues were you having specifically?

[Gohanto]

Thanks for the tips. Is there anyway to get a 23.98 .dv files from Quicktime Pro? (From looking at the setting it looks like it only can export NTSC 29.97)

[C]

Grab MPEG Streamclip from Squared5.com.

It will output to any QuickTime codec, accurately and will write a file that Pt recognises as 23.976. Something that I've never managed to get QuickTime to do consistently.

[kd_special]

When I work with projects at 23.97 frame rates. We capture the video in using SonyVegas with SDI canopus(From HDSR deck or HDDV Deck at 29.97DV Or convert from QT) . Then just use a 29.97fps video in a 23.97fps PT session so it will play out on the the Canopus.

I think becasue 29.97 and 23.97 are divisable by 6? The code still lines up. But that is one thing I remember from college and it might not be right. those times were pretty foggy.

The code burn in slips in and out but the audio stays in sync. Always check the two beeps..

Its the best workaround for are facility.

kd