Camera drift: audio goes out of sync…

Viewing 15 posts - 1 through 15 (of 29 total)
  • #758

    imagetemps
    Participant

    Hi to the community!

    Did some of you have experienced troubles while trying to sync sounds in FCP after shooting at 25fps with the Kinemini? I had a long shot (49min) it gradually goes out of sync in FCP.

    I convert my images via Kinestation, images at 25fps. I then do a proxy with Da Vinci, session set up and playback speed at 25. FCP set on 25. It goes out of frame.

    Any idea?

    Erwan Kerzanet

    #1088

    aspirepro
    Participant

    Hey again Erwan,

    I have had that problem in the past with DSLR audio sync… if its the same problem and the audio goes out of sync gradually and notice obvious difference after 5 min or so, then it could be the sample rate of the audio which should always be at 48K… which sometimes it was left on 44.1K, which is the other main setting on my Tascam DR100Mkii.

    If it happens gradually after about a minute, then it is probably the project frame rate in camera that might be set to 24FPS… which would mean that if the sensor FPS was 25 and the project FPS is 24 then all you have to do is modify the footage to conform to the right frame rate( I forgot how to do this in FCP, but in Premiere it is as simple as right clicking the original clip in the project finder and chose “Modify” and assume the frame rate to be”…” BTW- this is not neccesarity interpolating the footage (if the Sensor FPS is 25 then the footage is 25 FPS regardless of what the Project FPS says)

    Just to make it clear-the “project FPS” is a piece of metadata that tells the NLE what the playback rate is(even transferring the metadata through Kinestation)…that does not mean that the frame rate is actually what the “project FPS” says it is… the “sensor FPS” is constant and does not change and is locked in the file despite what the metadata says.

    #1089

    imagetemps
    Participant

    Hi (… and happy new year!)

    Thank you for your reply.

    The thing is : the duration of the .krw file matches the duration of the converted file at 25 in Cineform.

    It matches also the duration of the ProRes Proxy I insert in FCPro.

    BUT

    When I put the CineformRaw in FC Timeline the file length is 13’08 while the original audio file delivered by the camera is only 13’07″20f !! That means that kinestation may cancel 4 fps during conversion. Unefortunatly I can’t check speed with the original .krw files. Could it be possible that the kinemini cam stamps at 25 but doesn’t record a real 25? so everything deals with a “fake” 25??

    Erwan

    #1090

    aspirepro
    Participant

    It looks like quite the mystery to me…

    I would probably try and recreate the problem and see if it happens again, checking how many frames are unaccounted for and probably rely on an external audio recorder for safety(personally I don’t really trust the pre-amps on the KineMINI)

    If you have checked the slate info and everything matches and still the problem persists… then you should probably report the problem with Kinefinity and keep on knocking on their door until they respond… Either they will offer you a solution or they will take care of the problem in a future firmware update( I hope)

    Happy New Year to you to man!

    #1091

    imagetemps
    Participant

    Happy new year!

    I recorded a new 5-minutes test file with a slate every minute.

    The drift is 1 frame every minute. Even if I record directly in DNG (ie, I don’t use neither Cineform features nor Davinci).

    It might be my computer a Macbook Pro… but with an AppleProRes workflow I never experienced such drift!

    To me it looks it is not a location production sound compatible camera… if this problem comes from the camera.

    Did anyone experience sync sound in a professional context with the Kinemini in OS 3.2?

    Best regards,

    Erwan

    #1092

    imagetemps
    Participant

    Hi

    I just got news from Kinefinity. They say the actual firmware is set to guarantee a maximum time drift of 6 frames for 10000 frames. At 25FPS that means a professional external audio recording with a high quality quartz may be 6 frames out of sync every 6min 45 (!) It looks like what I have experienced on my time line. It is very much noticeable. I would rather say it is impossible.

    They say they could reduce the drift to 1 frame every 10000 fps in a future firmware.

    To be continued…

    regards

    EK

    #1093

    Calomile
    Participant

    I’ve had the sync issue and it was around 5-6 frames over the 6 minute 45 second time period that imagetemps has mentioned.

    Personally it’s unacceptable, even 1 frame in every 10000 is unacceptable as it means you’ll be noticeably out on a recording longer than 18 minutes.

    As it stands right now, even doing sync sound is out of the question unless you like having gaps in your audio as you have to shuffle the sync back. Completely unprofessional.

    #1094

    George A.
    Participant

    Thanks for you guys sharing this. It is really useful. I don’t understand how camera companies still manage to mess up audio even though it seems to the simplest part to the camera! I don’t see mics developing nowhere near as quick as sensors.

    #1095

    imagetemps
    Participant

    They don’t mess with audio… they messed with the camera itself!

    #1096

    George A.
    Participant

    I did a small test to see how bad it gets.

    #1097

    imagetemps
    Participant

    Yes it is like that… Thanks for the video.

    #1098

    George A.
    Participant

    Totally not cool.

    #1099

    Calomile
    Participant

    Does this imply that the footage isn’t actually in the timebase it says it is, when compared to real time?

    #1100

    imagetemps
    Participant

    Yes. Exactly.

    In the real world, a second is a second. In the digital audio world a sample is a 48000th of a second. In the digital camera world a second is 23.98, 24th or … 30th of a second. In the real world a second is always a second but if your filming speed drift, when you play back your frames one after the other at 24 FPS, a second is no more the second of the real world. The fact is that in the camera, a second of the “Image block” is slower than a second of the “audio bloc”. It sounds unreal to make a camera that don’t record at the exact same speed sound and image!

    By the way, don’t forget that timecode is camera speed when timecode on an audio recorder is only a stamped reference. The audio speed is always is sample rate.

    The precision of a sound recorder should guarantee that they can play 48000 samples every second while they should basically be able to read 25 or 24 frames in a second. In terms of milliseconds the drift allowed by audio is more critical than for images. That’s why sound recorded by Kinemini remains in sync with an external recorder.

    Let’s say that we are speaking of 5, 10 or 22min shooting tests. When you record interviews, in the last ten years (how many cameras?) we recorded full flash cards, P2 cards, HD etc… of one or two hours non-stop interviews.

    I have filmed gently first footage for my documentary. On the NLE it is umbearable!!!

    You can’t — as they recommend to us — resample the sound, and you can’t slice audio like a sausage every minute to keep your audio in sync!

    Let’s hope they’ll find a solution.

    All the best

    I AM CHARLIE TOO!!!!!!!

    Erwan Kerzanet (from France)

    #1101

    Calomile
    Participant

    The only saving grace I have in all of this is that my camera is being predominantly used on a drone so therefore audio isn’t as big of a deal, but I do also use it for corporates, which can have up to 20 minute takes while people work on the delivery of their lines. I seriously hope kinefinity sort this out as the more work I get with this camera on the ground the more it’s going to make me resent it.

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