23.98 TC Metadata Question

I have a question regarding TC metadata

When working at 23.98 FPS, if I export a file starting at 00:59:50:00 the timecode embedded in the files is 00:59:53:16 and no frame rate is to be found int the metadata.

I have checked the files in Wavelab Pro and Sound Devices Wave Agent and get similar results.

Wavelab shows a speed of 24000/1001 which gives us 23.976 but no actual 23.98 or 23.97 stamp as such.

I’m guessing Nuendo bases the TC position off the 00:59:53:16 and calculates a pulldown of 24000/1001

When I drag the file into ProTools it shows a file start time 00:59:53:14 and pastes is to that TC.

Why does this happen? Is this how 23.98 is calculated universally? Is there a way to embed a start time of 00:59:50:00 into a BWAV that can be accurately read universally?

What kind of file?
WAV files have no frame rate. It is pure audio.

Good question. Broadcast Wave Files. Even when I insert the iXML chunk and use the Wave Extensible format I still can’t get an accurate 00:59:50:00 start time using 23.976 FPS TC

Broadcast WAV records a timestamp, “the number of samples since midnight” as opposed to a SMPTE timecode. So how you turn that into time code depends on the framerate you calculate the timestamp against, which BWAV doesn’t record.

The iXML chunk can, but application support is questionable. AVID has their own “dark metadata” chunk they insert into WAVs which contain timecode; I’m not sure if ProTools cares about iXML enough to pull the SPEED tag. A lot of applications will just assume the framerate of the project you’re importing it into.

That said, your timecode of 00:59:53:14 could be the timestamp calculated at 24.0fps, while 00:59:53:16 would probably be at 30.0fps (there are rounding errors in all cases so it just depends on who’s calculating.)

SamplesSinceMidnight / (Samplerate / Framerate) = Num of frames at Framerate

At 48Khz, 00:59:50:00 is 172492320 samples as exported from Nuendo, so you can plug in various framerates and convert the frame count to HH:MM:SS:FF

1 Like

Thanks for this great info!