Rename files using metadata without changing timestamp?

[Bouke Vahl]

Hi Tangier,
I think it’s you, not WA.

If you turn ON ‘Preserve start TC’, a new timestamp will be created based on the Frame Rate and Sample rate you have set. And if that does not match the original, it will indeed mess things up.

Just a rename will do nothing to the timestamp, but if you want to exit, WA might bitch that you have changed the metadata, and will ask you if you want to save that. Just say DISCARD.

Note that a BWF file has a TIMESTAMP, not TC.
What is important is the ‘Samples Since Midnight’, that number should not change unless you know what you are doing!

Bouke
http://www.videotoolshed.com

[Tangier Clarke]

Thanks. I gave it a try and believe it or nor WA was inconsistent. I tired two WAV files, had “preserve TC” unchecked. The first go round the creation date was maintained. The second time I had WA rename all of the WAV files for the shoot day which included copies of the original clips again. This time it did not maintain the same timestamp for same file that it did the first time. Digging a little further on the original files. The accurate created timestamp is the Date Modified timestamp. The Date Created is Dec 31 1969 at 4:00 pm for every single file.

In each test only one WAV was renamed while keeping correct information and it wasn’t the same file.

[Bouke Vahl]

Date creation time timestamp, I don’t give a rats ass.
What does the Samples After Midnight say? THAT is your time stamp!

But, if you don’t want WA, no sweat, I can build something like this in my BWF Toolbox (that you want anyways now or in the near future.) What kind of formats do you need on renaming?

Bouke
http://www.videotoolshed.com

[Ty Ford]

Hello Tangier, and welcome to the Cow Audio Forum.

And if you’re wondering if Bouke can do this, yes he can. ☺

It’s nice to have really smart friends.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford\’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford\’s Blog

[Tangier Clarke]

Thanks Bouke and Ty. I am not sure Bouke if you’re upset or not and if you’re approachable, but I appreciate the help you’ve given. Via the forum and personal email I’ve gotten “I don’t give a rats ass” comment and in my neck of the woods that’s usually a phrase of contention with the emotion of tension; essentially eluding to not wanting to be bothered further.

In any case, I am not sure if by “samples after midnight”, what is meant is other WAV files or the actual sampling of the audio file itself. That being said, I am not sure what I am supposed to be looking for. The last clip before midnight was at 11:30 pm, then the next was at 3:50 am (after midnight). The recorder was set on a 12 hour time so the timecode wouldn’t go to zero according the the boom operator/recordist.

[Bouke Vahl]

Hi Tangier,
My remark was about the file properties, not about something else, so no worries, I’m very much approachable!

It’s a strange way of thinking, but once you grasp the logic, it all makes sense. (And it sucks that a lot of terminology is used double / wrong / badly rounded, that does not help…)

Wave Agent displays the SAM somewhere in the middle of the lower part of the interface.
What it means with ‘keep start TC’, is that the TC numbers will stay the same even when you change the TC rate:
This is in general a VERY bad idea to do, as then the numbers have no relation anymore with the internal clock.
So, as I told you, renaming ‘should’ be fine, but be VERY VERY afraid if WA tells you it needs to update the metadata.
UNLESS you are very sure, do NOT press ‘save’, and in all cases, UNCHECK ‘keep start TC’, as it will keep the start TC, but might change the actual timestamp. Confusing? Not so much, read on.

Samples after midnight means EXACTLY what it says. But, it is midnight when the TC generator of your BWF recorder is reset to 00:00:00:00
(And luckily nowadays close to anyone shoot TOD, so it sorta kinda matches the wall clocks.)
Oh, I call it Samples AFTER midnight, Sound Devices calls it Samples SINCE midnight. It’s the same.)

Now, SAM is the same as TC, but not in HH:MM:SS:FF format, but as an absolute frame number.
(Hence I call it time STAMP, not time CODE.)

In your case, on renaming, the file has also a Time Stamp for being a digital file. (Actually, it has two, ‘created’ and ‘modified’.) This is confusing, and probably the ‘modified’ will update / change after WA renamed it (as it was indeed modified) but has nothing to do with the internal BWF SAM.

And, if you record @ 48K, you have 48.000 ‘audio frames’ per second.
Thus, if you start recording when your recorder displays 00:01:00:00 (one minute after midnight), the SAM as written in the file is 2.880.000 (60 seconds times 48K samples)
This in not very well human readable of course, especially when it gets later.
At 23.00 PM, the number is
23 hours * 60 minutes * 60 seconds * 48000 samples per second makes
39.744.000.000
This sucks for humans, so any device / software will calculate it back to TC, that you can read in the blink of an eye
(23:00:00:00)

Now, as you know, the number of video frames as well as the play speed differs between the video frame rates.
You like to shoot 23.976, so to divide the large number back to TC, there is a 0.1% difference, making some 83 seconds difference.
The speed as recorded (thus, how the math should be done to show you the TC numbers as intended, is most of the time baked into the BWF file. But it is up to the device / software if it will do the math based on that value, or another one. (Depending on what you want to do with the file / will solve problems.)
In theory, editing software will NOT use the calculated TC, but the samples itself. This way you can sync up / place your audio on the timeline sample accurate instead of frame accurate. (That makes a big difference.)

So, depending on the setup:
The file is the same, the actual values are the same, but the TC displays are different, making up for lots of stress sometimes ☺

(And I’m only touching the surface of more fun that can be had with these relative very simple file format…)

Hth,

Bouke
http://www.videotoolshed.com