50fps audio recorder - sync

[humbuk]

Hi, is there any reason why any portable audio recorder from Sound Devices, Aaton, Zoom doesn't have the option to record at 50fps? Likewise, no sync box and TC slate that I looked at, there is no 50fps option. Quite often 50fps is required on the camera, but it is not possible to synchronize via timecode.

[The Immoral Mr Teas]

Hi, ahoj, Humbuk,

 

I may be wrong / missing the point, but since the TC is just a TC Stamp on both the recorder(s) and (most probably) camera, could you choose 25fps then there will be at least a valid 'start' reference for sync (or the equivalent 'normal' framerate for whatever double speed rate you use)?

 

Have you searched for previous posts, especially in 'Cameras...' section for high framerates?

 

Best, Jez

[humbuk]

I'm not dealing with how to sync a 50fps camera with 25fps audio, but I'm wondering if there's a reason why portable audio recorders, TC sync boxes, and TC slates can't handle 50fps?

[rich]

27 minutes ago, humbuk said:

I'm not dealing with how to sync a 50fps camera with 25fps audio, but I'm wondering if there's a reason why portable audio recorders, TC sync boxes, and TC slates can't handle 50fps?

my poorly educated guess is that there is no SMPTE standard for it yet.

i dimly remember reading some time ago that there was an updated standard being drawn up by SMPTE, but cant help any more than that.

i believe that the Betso sync boxes have settings for framerates above 30fps, as ive seen that setting on mine. but i have never used it as i always have them synced to my SD recorder.

[humbuk]

 

12 minutes ago, rich said:

my poorly educated guess is that there is no SMPTE standard for it yet.

i dimly remember reading some time ago that there was an updated standard being drawn up by SMPTE, but cant help any more than that.

i believe that the Betso sync boxes have settings for framerates above 30fps, as ive seen that setting on mine. but i have never used it as i always have them synced to my SD recorder.

 

Yes, you can set 50fps on Betso, but it's not 50fps, but 25fps once faster.

from Betso manual:

Standard rate TC: 30, 30DF, 29.97, 29.97DF, 25, 24, 23.976

2x multiplied rate TC: 60, 60DF, 59.54, 59.54DF, 50, 48, 47.952 

[rich]

ok then. is there a camera that when set to 50fps that will allow incoming timecode to see if those settings on the betso will work?

what is the difference between the 2x multiplied rate of the betso at 25fps and 50fps?
does it behave like an Alexa mini when you put it to 50fps, and the timecode runs twice as fast?

[humbuk]

I don't think this will work, but I don't know if the camera records 50 frames per second, so the timecode runs at 50 or 25 - 2x faster. If I subsequently receive the edited video, the timecode is normally at 50 frames. If you are doing audio post production in Protools, Nuendo you are working in a 50 frame project. The only thing is that it is not possible to record sound in 50 - I don't understand why.

[rich]

i am guessing that if the camera base rate is 25fps, then 50 fps goes at double speed.

i dont know the camera settings well enough to know wether it is possible to set its base rate to 50fps, so that on playback 50 frames takes 1 second, which i am thinking is what you are talking about.

 

i do not understand why. that is well beyond my knowledge level, and what i am prepared to try and understand.

 

i wonder if projects like the Hobbit, which they filmed at 48fps hadnt looked so odd to moviegoers, the situation might be different, and there would have been more urgency to develop a new SMPTE standard for the higher framrates.

[Bouke]

12 hours ago, humbuk said:

The only thing is that it is not possible to record sound in 50

You record in audio frames, and that are samples, so you probably record 48000 'frames' per second.
There is no tc stored in BWF, only a number of samples that can be calculated to tc, and sometimes a metadata flag telling at what speed the tc generator was running.
The only question you need to aks is if the cam able to slave to 25 tc when it is set to record at 50.

 

[Mungo]

8 hours ago, Bouke said:

The only question you need to aks is if the cam able to slave to 25 tc when it is set to record at 50.

 

All cameras I tried so far (all from Sony: FS7, FX9, several ENG models) would accept 25fps TC even when recording 50fps without complaining.

 

I experimented with the various options of the Ambient Lockit ACL204. The manual says:

"As with firmware 6.xx Lockits now support double project rates to be synchronized via ACN and automatically select double frame sync settings with genlock/PPF activated. However, as not part of the SMPTE specification, this will have no effect on timecode frame rate and also cannot be transferred via cable."

[humbuk]

21 minutes ago, Mungo said:

All cameras I tried so far (all from Sony: FS7, FX9, several ENG models) would accept 25fps TC even when recording 50fps without complaining.

Thanks, I tried with FS7 and it didn't want to read 25fps if it was recording at 50 frames. Maybe it depends on the camera's other image settings, but I tried everything available for the TC settings and it didn't read the 25fps timecode.

[Mungo]

23 hours ago, humbuk said:

Thanks, I tried with FS7 and it didn't want to read 25fps if it was recording at 50 frames. Maybe it depends on the camera's other image settings, but I tried everything available for the TC settings and it didn't read the 25fps timecode.

 

I guess. I just tried out: FS7 (MK1) syncs to all Timecodes regardless if it records 25p or 50p. It doesn't accept Genlock at 50p, only 25p/50i.

 

But when it is set to Slow&Quick Motion (which can be 50fps too), no incoming timecode is recognized. Maybe that's the case. You can easily see if it's enabled since audio is not recorded also. There is a red prohibit sign visible on the audio level meters in the viewfinder.

[Bash]

There are no SMPTE 'standards' for TC for camera/sound frame rates greater than 30fps.

 

Cameras can run at frame rates greater than 30fps, but because there are no standards it all gets a bit freestyle with regards to TC and sync.

 

I think what needs to be asked here is why the camera is running at 50fps. If the camera is running at 50fps because they want to play the video back at 50fps, ie the 'motion' will be real time, like 25fps video, but with twice the amount of frames in the same second, so perhaps a different video quality, or....... is the camera running at 50fps but the video will be played back at 25fps, so the motion will be at half real time, ie slow motion. If the former then the motion is real time so the sound will also be expected to be in realtime (ie 1second = 1 second), whereas the latter will be at half speed so maybe the sound will be played in at half speed, either pitch corrected, or an octave lower than usual because of the 'varispeed', ie 1 sec of action = 2 secs of screentime.