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OT - image stabilizer & changing frame rates

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Paul DoughertyOT - image stabilizer & changing frame rates
by on Apr 6, 2015 at 12:50:24 am

I posted earlier about getting 7 interview files, each with a different frame rate (and all from the same session!). Ht Davis had a very good theory on why that would be (thanks!) He suggested that the image stabilizer on a camera might be responsible for the changing frame rates.

One particular file was so problematic (24.33) re. sync, it makes me ask this question… If a image stabilizer is doing this.. is it (can it) changing the frame-rate dynamically on the fly?

If so, no wonder it would drive editing software nuts! Nest is there software, a utility, a feature that could measure or monitor such a thing? Providing data or diagnostics?



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Ht DavisRe: OT - image stabilizer & changing frame rates
by on Apr 6, 2015 at 3:13:23 am

On camera, no. But in computer playback, try VLC and show the inspector, and frame rates.

Alternatively, let premiere pro show you where frames are dropped (it will detect them as they are marked in the original stream, and will show you them by color coding the preview render notifier bar).

Other than that, I haven't seen any direct utility that will detect it and do something about it (asking you if you want to blend the frames and output a new file). I simply accept that there are both technological and human factors that can create this problem; and I work around it by treating every video as suspect, even my own. I transcode every ingest.

Sync problems can also occur due to clock problems in cameras. SO to account for it, I always capture a mid-line audio source (something right in the middle of the whole scene if possible). It helps to have a single clock to rely on that oscillates at 48 or 96 thousand beats per second (any inconsistent beats are such a small increment that it's extremely improbable for any human to notice). Aligning by sound is more likely to find common points if your mid-line is double or triple the rate of your camera audio.

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Paul DoughertyRe: OT - image stabilizer & changing frame rates
by on Apr 6, 2015 at 3:27:28 pm

Thanks Ht, in VLC I don't see an "Inspector" in the window Media Information (same deal I guess) it does mention one frame being dropped.

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Ht DavisRe: OT - image stabilizer & changing frame rates
by on Apr 10, 2015 at 4:03:10 am

go to ame, and transcode, turn on "Use Frame Blending". This will fix the missing frame with a blended one.

ame or AME are Adobe Media Encoder

you can use any transcoder really; handbrake, compressor, ffmpeg, mpegstreamclip; it really doesn't matter. Just leave no setting on automatic. Set everything but the retiming. Any setting that says retiming should be avoided, left to 100%. The frame rate setting should be altered, and set to a definitive. Most will sense a frame drop and fix it, or have a setting for a Constant Frame Rate (do not confuse with CBR or constant bit rate, leave any of the Bit Rate settings on Variable Bit Rate).

Media encoder uses standard frame rate from the original video, but will conform it to a constant frame rate and fix any missing frames (1 or two over a few seconds), if you turn on frame blending and set your desired frame rate.

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