Hello,
can one of the audacity gurus pls give a quick answer to a stupid question:
Audacity recordings work with time relative to the beginning. Is there a way to get the absolute time of a point in a recording?
Is there a recording option doing this?
(Application: alarm recordings)
thanks
Audacity doesn’t make a very good surveillance recorder.
– As you discovered, there’s no good way (outside of SMPTE Time Code) to record time of day.
– We can’t do Rolling Recording (erase the old while you’re recording new).
– There’s no good way to custom Timed Recording. There’s Sound Activated Recording, but we can’t go into full record for a defined period.
– Audacity doesn’t Play Well With Others, so for best stability you can’t have any other applications running on the machine. This brings you immediately to buying a real Surveillance Recorder instead of trying to cross-purpose Audacity.
– Audacity doesn’t have guaranteed process integrity. Search the forum for “holes or gaps in my recording.”
– There’s no company here. It’s a bunch of volunteers and we can’t do law enforcement, traceable surveillance or certified evidence.
Koz
That’s not to say you can’t do this cheaply. Run a video camera watching a clock and recording the sound event. That may take you straight back to buying a surveillance system rather than trying to wing it.
Koz
thanks for your reply, Koz. I understand, this is not the purpose of audacity.
Actually, we are a bunch of glider pilots and want to monitor our frequency. The sound triggered recording would be perfect, if only we knew when it was triggered.
thanks again for your great program!
Sound Activated Recording only activates when the sound is there. You can’t use the trigger to start and then tell it to record the next ten minutes.
SMPTE is not a dreadful way to do this. There are SMPTE generators/readers. It will take up one channel of a stereo recording for time and you can do whatever you want with the other.
~~
Never mind. They’re all in the high hundreds of dollars.
http://www.markertek.com/product/es-453u/ese-es-453u-smpte-ebu-timecode-displays
The attached clip is of SMPTE sound. It was designed to go on the low quality cue track of early tape machines…and survive. Early tape had your problem. No time.
http://kozco.com/tech/audacity/clips/SMPTETimeCode-59-00-00MonoShort.wav
Cover your ears.
In fact, if you snugged a time code reader up to your computer and played that track, the reader would tell you the exact time I recorded it down to television frames, 1/30 second.
Maybe there are software versions of these generators/readers. DV Home tape machines didn’t use the full timecode. They used frame-code, a simplified version. So that’s another possibility.
None of this is going to work if you need both stereo sound tracks.
Koz
There are silly/stupid ways to do this, too. Record a radio tuned to NBS Fort Collins.
“National Bureau of Standards, Fort Collins, Colorado. When the tone returns, the time will be Four Hours, Thirty Minutes.”
Boop…Boop…Boop
If they even still do that.
I know there used to be a Canadian one—in French, thankyouverymuch. I used that one because the reception was better.
You can work the recorded time back from there.
Koz
Still there. See, I wasn’t joshing. My radio only picks up the 15MHz broadcast and I live in a festival of overhead wires and electrical interference. But still.
https://en.wikipedia.org/wiki/WWV_(radio_station)
So, you put that as a mono recording on one Audacity track and you put your work on the other. As long as the “show” lasts longer than one minute, WWV will be happy to time-tone align you.
~~
There’s the Canadian one.
https://en.wikipedia.org/wiki/CHU_(radio_station)
I can’t hear that one because my receiver won’t tune all the utility short wave frequencies.
Koz
The next version of Audacity is due to be released around the end of the year, and has an option to automatically add the date and time to the name of newly recorded tracks. (The “start time” of the recording). The setting will be in: “Edit menu > Preferences > Recording” and the feature will be documented in the manual.
Is there a new time window on the bottom that reads forward from that tagged time? Ver 2.1.4? Where does it get the time from and can I set it?
Koz
It’s in Recording Preferences. It will be in 2.1.3 when released.
It gets system date and time and writes it in ISO format (file name safe, not configurable).
Gale
Window on the bottom? Point to a place on an hour recording. How hard is it to figure that time?
So export the work, read the time and figure the differential offset.
I think Casio made my time calculator. I remember having to save up for it. It’s really cool. It will calculate directly in television drop-frame time code for those countries so afflicted.
You can’t figure time on a regular calculator.
Maybe there’s an App…
Koz
Wasn’t there a thing about not being able to get seconds or fractional seconds from Windows? It’s the reason you can’t reconstruct your show from the _DATA folder.
Koz
If you mean while it is recording, just look at the “Length”.
When writing to disk, the precision (granularity) of the time stamp depends on the file system.
NTFS (Windows) has a maximum (at best) resolution/ranularity of 100 ns.
FAT had a granularity of 2 seconds
For ext4 (Linux) it’s 1 ns
The new timestamp feature in Audacity 2.1.3 gives: hh-mm-ss
Date is as: yyyy-mm-dd
Date and time as: yyyy-mm-dd_hh-mm-ss
So you still have to add manually the cursor position(s relative time) to the start time extracted from the name ?
No way to see the absolute time of the cursor as you scan through the recording ?
No.
Attached a valuable tool in this quest.
Apparently, there was a FrameMaster II.
http://mathcs.albion.edu/~mbollman/CI/FrameMaster2.htm
The Producer was scribbling notes from the clock on her phone during the shoot. Here’s a list of the cuts she thinks might work.
Once you pass basic recording your guitar, bookkeeping is a really big deal.
Koz
I haven’t done this in a long time, but you can “record” a standard offset and then keep recalling it to rapidly convert back and forth.
Are you sure there isn’t an APP for that?
Koz
Even if Audacity doesn’t obsessively track every nsec, it would be insanely handy to be able to set one of those timers on the bottom.
“See that cursor? That cursor is sitting at 16:30:00 GMT. Work from that.”
Koz
I moved this to “Adding Features”.
Gale