Is there a way to encode continuous time onto an audio track?

[Peter Holt]

OK; thank you Richard, again.

This comes down to whether my FDR-1000V camera actually records any kind of timecode.

The spec suggests it does if the higher rate format, X-AVC-S, 50mbits/sec (at 50FPS 1080P), is selected. It isn’t clear whether this records a timecode into the file, or just burns it into the video like the old Hi-8 camcorders used to do (which would be stupid). But in any case in that format I get just 5hrs of recording at most, which is not enough unless I turn it on and off.

The other way would be to burn a fake SMPTE timecode into the mp4 file afterwards, with some bit of software. That obviously won’t be the exact time; it will at best be the file date/time incremented by 20ms for every frame encountered. And it will have to assume the recording was continuous. But this defeats the point of timecoding… which (in my case) is having *discontinuous* video and still having the audio clips synced.

[Peter Holt]

“That Tascam page is talking about “genlock” (locking the RATE of the video camera frame clock with the rate of the audio recorder sample clock. ”

How does that enable the sync of audio clips with video clips, if the camera video has no timecode on it?

Or does that process assume the video does actually have timecode on it, but the DR701 doesn’t use it and just uses the frame rate from the HDMI signal? I guess the latter may have been their only option since a DSLR is probably not outputting the video anywhere, so the only way to get any timing info from it is by looking at the HDMI and that doesn’t contain the timecode either, but obviously you can count the frames… and it probably extracts the date/time of the start of each clip from HDMI as well.

I trid to phone Tascam UK (Teac) but there is just an answering machine on their tech line # they gave me! And they don’t return calls.

I think every DSLR records in .mov (all those I have used did, including my Pentax K3) and that is Quicktime and that contains SMPTE as default, as far as I can find out.

So that is probably how all this hangs together.

But unless the camera itself is adding SMPTE to the video, none of this audio stuff will be of any use.

[Richard Crowley]

How does that enable the sync of audio clips with video clips, if the camera video has no timecode on it?
The Tascam recorder derives the RATE from the HDMI video (amateur “genlock”). Some recorders even start/stop automatically when the camera is started/stopped. Dunno whether that Tascam DR701 does or not?

But since there is no timecode via HDMI, it is left to the user to work that out. This is typically done with a clapstick/slate where you can slate the scene/angle/take, etc. on the board (and announce it verbally for the audio) and then snap the sticks together to establish simultaneous video and audio sync point. That has been the tradition for 100 years, and it continues to be almost universal to this day. Of course, that is impractical for you, but then you have a very “far out” application there.

I have to wonder, if you are starting/stopping the camera (remotely) why can’t you simply start/stop the audio recorder at the same time? Maybe I’m still not understanding your operation.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Peter Holt]

No; a perfectly good point.

It is however difficult to do that accurately, because the remote control of the camera is over wifi (using a clumsy phone app) while the recorder I currently use (a low end Tascam one) needs two button presses.

The simplest thing would be to control the camera on/off as required (if only to get the required 7+ hours out of its X-AVCS mode in which the timecode appears available, but which runs for a max of 5 hours) while run the recorder unattended.

I will investigate the camera timecode options further and report on any progress.

[Richard Crowley]

Doesn’t the camera write a separate video file each time you start it? What does the date stamp on the file say?

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Peter Holt]

Yes; if you stop the camera and restart it, it will close the current file and open a fresh one, whose date stamp is the time it was started.

It then continues to write into that file, until 4GB is reached, and then it closes that one and immediately starts another one whose date stamp is the time *that* one was started.

IOW, what you would expect.

[Richard Crowley]

So, with knowledge of the starting time of the first “take”, you effectively have rough “time code” for each clip. Doesn’t that get you what you are looking for? You aren’t needing genlock/lip-sync for your application, you just need some rough way of correlating a video clip with an audio clip. So even a tolerance of 1 or 2 minutes would be perfectly adequate to match up video and audio files.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Trevor Asquerthian]

Assuming:
a. that you have video that does not record a TC track (but does record a date/time stamp for file)
b. that your audio is continuously recorded
c. that the video stop/starts

Best thing is to get the video TC track to match the date/time stamp

https://www.videotoolshed.com/product/qtchange/ — does this, I think

Then to string out videos so that there is black where there was no recording (Avid does this with ‘autosequence’ – other NLEs you have to do it manually, although you may be able to do it by stringing all clips in one timeline, exporting an EDL or XML and copying the source timecode to the record timecode)

Then add the audio (continuous recording) to this. Timecode or date/time stamps may help get you close.

Now slide all the video (or the audio) to get sync… should be reasonably consistent across a few hours, likely to drift a bit as nothing is locked.