F35: F23 and Odyssey 7Q variable frame rates

[steve phillipps]

So what happens when you hook up an F23 or F35 to an Odyssey and select off-speed frame rates? Say you set project frame rate at 25P and select 45fps on the camera for example, do you get slow motion? Or do you need to set say 60P on the Odyssey and camera to get 60fps then conform for slow motion? Never had the 2 units together to try it, and not been able to find an answer online.
Steve

 

[yachacha]

I have done high speed with F23 to 7Q. Sorry I do not have everything with me to test right now.

Setting F23 at 60P 422 output via the dual link to the 7Q recording at 23.98P, the footage will playback as slow motion.
Setting F23 at 60P 422 output via the dual link to the 7Q recording at 60P, the footage will playback at real time.

You also have the option to reset the 7Q file to 23.98 if you recorded as 60P when you use the CD Transfer Utility.

Basically it comes down to what the project rate of the 7Q file is. My method is the first, shoot 60P out of camera and record 23.98 in 7Q for already slowed down footage.

I haven't really answered your questions about off speeds. Need to experiment more, i really have only tried 60P on F23 and 50P on F35. It is my feeling that the dual link won't output off frame rates like 45fps without a special recorder like the SRW1 or Codex.

 

[steve phillipps]

Thanks for that, that's in part what I needed to know at least - getting 60fps slow motion played back properly without having to conform is the main thing. I am curious as to what happens with the off-speed settings though. Sony touts the F23 as a proper "variable speed sensor" - somehow saying that it's different to how others work, ie others scan at 60fps and remove frames.
Steve

 

[Viddovation]

Thanks for that, that's in part what I needed to know at least - getting 60fps slow motion played back properly without having to conform is the main thing. I am curious as to what happens with the off-speed settings though. Sony touts the F23 as a proper "variable speed sensor" - somehow saying that it's different to how others work, ie others scan at 60fps and remove frames.
Steve

So, there's two different things we could discuss here. The first is recording at one frame rate (50p,60p) and reinterpreting that footage as something else (23.98p,29.97p) resulting in fast or slow motion.

The F23/F35 are capable of an additional thing though: they can at non standard frame rates, from 1fps to 50fps(F35)/60fps(F23). They can even ramp while recording between speeds. This is where I beleive Sony is touting the variable speed sensor. This is where the camera flags output SDI frames as either good for recording, or to be ignored (only for monitoring). However, you're going to need an SRW1 or Codex to use these modes. The Odyssey doesn't support this record mode.

 

[steve phillipps]

This is where the camera flags output SDI frames as either good for recording, or to be ignored (only for monitoring).

See that's not how I understood it, as most cameras that do variable frame rate, ie Varicam, do it that way, recording all 60 frames and flagging those that are needed or not. I took it to mean that F23 / F35 actually runs the sensor at the precise frame rate, like 37fps for instance, and lays only that amount down. It is hard to see exactly how that would work though...
Steve

 

[Viddovation]

See that's not how I understood it, as most cameras that do variable frame rate, ie Varicam, do it that way, recording all 60 frames and flagging those that are needed or not. I took it to mean that F23 / F35 actually runs the sensor at the precise frame rate, like 37fps for instance, and lays only that amount down. It is hard to see exactly how that would work though...
Steve

I can't personally speak for the implementation on cameras other than the Sony F23 and F35, but speaking to the F23/F35:

Think of it as a two step process. There's image capture from the sensor in step one, and in step two there is image output via SDI. That's a vast simplification, but it will serve this discussion fine.

Given this model, the image capture can be run on one timebase, and the image output on a separate one. In terms of sensor capture, it should be taking the user selected variable frame rate per second, and sampling the sensor that number of times per second, at equally distributed intervals.

In image output however, it would cause a great many problems to output a genuinely variable number of frames per second. While it could perhaps be accomplished, it would be a completely proprietary signal, and would take a great deal of work to code on both the sender and receiver side. So Sony went the more practical approach - conform to one of the SDI standards for output, and use ancillary packets to flag which frames ought to be recorded and which ignored. The key here is that there is a delay of some minute amount between image capture and image output, and in this delay are hidden the timebase difference. So you see, it's completely possible to capture - for example - 5 evenly spaced frames per second - and conform them into a 23.98fps output signal.

We reach a third step though, in regards to your thinking that all frames are recorded, and only some are played back. To my understanding this isn't how it works with the F23/F35 and the SRW1 or Codex recorder. The SRW1/Codex would read the incoming stream, and would only record the frames flagged for capture. For the Codex, being hard drive based, this wasn't a huge challenge. For the SRW1, it required a upgrade memory cache board. You'd imagine that with videotape it's not practical to record just three or five frames per second, it would be hard on the heads and turning the tape at the right rate, etc. The SRW1 overcomes this by caching the frames, and when the cache filled up, it would record the cached frames to videotape, taking a few seconds of video roll at regular speed.

Does that make more sense?