Frame Rate Converstion Techniques

[ensignrickyto]

I'm working with a number of older DSP100 media blocks which are very fussy with the frame rates that they are fed. We do a large number of film festivals where most of the content is provided in either H.264 MP4, ProRes or Bluray and can be any number of frame rates. I'm trying to come up with a standardized method of doing the frame rate conversion of the source material to 24fps without affecting the pitch of the sound and without introducing choppiness into the video. I've tried Handbrake and Acrok video converters with no luck and wondered if there was a solution that anyone's found to do it effectively. I'm willing to employ a paid solution but the UI needs to be something a theatre manager can use. We can't afford to employ post production services for the task. Any help or suggestions would be greatly appreciated.

[Carsten]

My first suggestion would be to use the 25->24fps slow-down approach built-into DCP-o-matic - like anyone else does. This is a standard technique used in professional broadcast and for DVD as well. Re-pitching audio can be done if you think it's necessary. Even Audacity is now good enough for this.
Honestly, I wouldn't put too much effort into this. If someone submits 25fps footage to a film-festival, the first error is done on his side. Same for 29,97/30fps.

And a DSS100/DSP100 really is the worst equipment for this application. High quality framerate conversion IS expensive. And slow. Premiere and AfterFX, Twixtor, etc will yield nice results with most footage, but I don't know any 'click and run' software that can do it. And I would never let a theatre operator do jobs like this in a festival situation.

You may want to give this a try, I did not have the time so far:

http://research.microsoft.com/en-us/um/ ... eapps/#pro

I don't know if it supports basic frame rate conversion as well.

- Carsten

[jite]

Hi,
I don't agree with this thinking that cinema must be in 24fps. This was the first standard adopted by the DCI, for sure, but they aren't alone in the world. I'm convinced that the best way to project a movie is to do it at the frame rate it was shot. A TV movie can be shot in 29,97 or 25 fps or in the corresponding HFR. As the SMPTE did, I can accept that a 29,87 movie is screened in 30.
At my opinion, this mess comes because a few industries, like Qube and others, have limited their first cinema servers to be only DCI compliant. I guess those in the American Studios had a big laugh at that time !
Doremi is the one that understood that and their serveurs were rapidely compatible with many frame rates. They were "a bit too far" when they made their Cineasset tool permit a kind of DCP in 23,98 (24000:1001 is read in the cpl), which is not even a SMPTE standard and is only readable by their Doremi servers.
Carl, you have given a wonderfull tool to us. Many many thanks. If you think it is possible to fix the pitch change in audio when adapting the frame rate, it would be wonderfull.
Regards
Jean

[Carsten]

There is a problem with this approach: Usually, the people creating a DCP from their own work will have no knowledge about the equipment the DCP is projected on, and the limitations imposed by this equipment. There are too many variations in the field. 24fps and 48fps(3D) are the only frame rates that do work on EVERY server. It is important that the DCP creators know about these limitations. A festival situation is the worst scenario for arbitrary frame rates. Very often, content is grouped into themed categories. You can not assign DCPs to different locations, one being capable of higher frame rates, one not, if you follow theme grouping. They need to be played in groups at the same location using the same equipment, and having different frame rates in a group can cause serious problems. Yes, it would be nice if all festivals would have HFR capable IMB/IMS equipment, but that is not the case.

Another issue is that people do fantastic work with whatever equipment they have. It is totally acceptable if they use 30fps, 50fps or 60fps for this. Most of the time, these people have no reason to think of presentation frame rate limitations, because presentation at a cinema through DCPs was never their intent. Now, if they submit their work to a festival, and the festival chooses to prefer or convert to DCP, is when the problems arise. Essentially, the festival should either cater for a HFR capable system (Sonys are very good at this), or skip DCPs and show native files at their native frame rates with common media players.

So, sorry to insist, but cinema IS 24fps.

- Carsten

[Aswippe Johnson]

The motion picture industry has always been 24 fps (at least, since the late 1920s). That is a worldwide standard. It's global.
Any deviation from that standard (Todd-AO, HFR, etc.), and the producer is responsible for getting requisite changes made in the theatres. It's not the industry's responsibility to cater to amateurs who are ignorant of, or who refuse to adhere to, standard practice.

Digital Cinema has allowed videomakers ready access to motion picture venues... not vice-versa.