GH1 is 24 not 23.98...

nandanrao

nandanrao

Member
So I have read everywhere for quite a while that the GH1 is recording in 23.98, but recently I started realizing that after performing the inverse telecine in JES deinterlacer and coming up with 23.98 footage, my audio starts to drift after a while (dual system). Using a 17 minute clip as a test I realized that, like many people say, it was necessary to set my audio to 99.97% of the duration. Then I tried setting JES to output as 24P and it worked perfectly with the audio straight out of the recorder (Sound Devices 544), the audio wasn't drifting at all.


To me this is pretty indicative, unless I'm misunderstanding something (granted I'm probably misunderstanding a lot), that the camera is actually recording an even 24 frames per second.

Any thoughts? I actually am in a difficult situation as I just finished shooting a feature on the GH1 and had been logging/transcoding 30 hours of footage only to realize that I will need to do it over again now as 24... So I would actually love to learn that I'm wrong. But I can't seem to see it any other way.
 
I noticed this too when I had my chance to test the GH2 but I have not toyed with one since. Many of the .mts clips I downloaded to examine the cams performance and codec issues were also at an exact 24 and not 23.976
 
Since I am from PAL region, why is 23.98p so important?
Can't you just play 24p on TV?

I mean, if you play it as it is, do you see any Serious Problems?
 
OKAY, some clips sync at 24p, some clips sync at 23.98. My only conclusion is that this camera erratically drops or adds frames sometimes and that it was a fluke that it synced at 24 and that it is attempting to shoot 23.98...Which is what one expects from DSLR's I guess.
 
could it be JES? I can't say I've seen this problem as I hardly ever use the camera's audio for anything but syncing external audio recorders but I've not noticed anything suspicious either.
 
nandanrao said:
So I have read everywhere for quite a while that the GH1 is recording in 23.98, but recently I started realizing that after performing the inverse telecine in JES deinterlacer and coming up with 23.98 footage, my audio starts to drift after a while (dual system). Using a 17 minute clip as a test I realized that, like many people say, it was necessary to set my audio to 99.97% of the duration. Then I tried setting JES to output as 24P and it worked perfectly with the audio straight out of the recorder (Sound Devices 544), the audio wasn't drifting at all.
Click to expand...


You say you are using a dual system. So, what device are you using to record the audio? This is important, as the crystals used to generate the digitization rate in the audio recording device are not sync'ed up with the camera, and, further, the components in both devices may have a certain 'tolerable', engineeringwise, drift, such that by the time 17 minutes have passed, both are 'out of sync' with each other.

The Zoom H4 for example has been noted for 'drift' over time. A quick check of the Zoom's specs do not mention 1) parts per million tolerance of the fundamental crystals involved in the time generation circuits, nor 2) temperature dependencies of drift.

So, the suggestion is... don't make long takes using a device like this... or accept that one will have to adjust the timing of the audio by perhaps 0.03% (or whatever...) with a system where there is no common sync.

Back in the olden days, the camera would generate a sync pulse based on its actual transport mechanism, which would then feed into a phased lock loop to control the actual timing of the audio recorder.

Time Code is also used in this way in 'big' productions. In production houses, there would be a great amount of care to provide common clocking signals throughout the facility...
 
The GH1 shoots at a locked 23.98 not 24p. JES is an awesome application for what it is, but it is freeware. It simply screws up a lot.
 
Ok i figured it out. I feel like a fool but it definitely wasn't the camera, nor was it JES, it was the audio. I recorded on two devices, one was a FOSTEX FR2-LE which I had used before and new had decent time recording, the other was a SOUND DEVICES 552, which is a super-nice device that I had never used on a project I was involved with in post. Turns out the Sound Devices records Metadata into the WAV files that will sometimes include a Frame Rate (even if you are recording without timecode). Luckily you can change this metadata with a Sound Devices piece of software called Wave Agent. So i went through and changed the metadata frame rate to 29.98 and it synced up perfectly...

I mean, probably no one else will ever be dumb enough to get into this situation, but if they do, it's now on the internet. I guess I had always thought you were either recording timecode, or you weren't.

Thanks for the thoughts.
 
BY the way I thought you were talking about a GH2.. GH1 def records 23.976. There were some issues with the early native hack that changed this a little but now it is fixed.
 
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