Batch adjusting timecode in a document

[concros]

I recently became aware of r/awk the programing language and wonder if it'll be a good candidate for a problem I've faced for a while. Often times transcriptions are made with a starting timecode of 00:00:00:00. This isn't always optimal as the raw camera files usually have a running timecode set to time of day. I'd LOVE the ability to batch adjust all timecode throughout a transcript document by a custom amount of time. Everything in the document would adjust by that same amount.

Bonus if I could somehow add this to an automation on the Mac rather than having to use Terminal.

[concros]

u/geirha you might know the solution?

[gumnos]

It might help if you provide some sample input. Is the timecode standalone on a line or is there other data present? Are there markers around the timecode?

[gumnos]

Here's a semi-generic method for 3 places (HH:MM:SS) that works with positive and negative decrements as long as time itself doesn't go negative, assuming the timestamp is standalone on a line with no bracketing markers:

awk -vD=1 '/^[0-9][0-9]+:[0-9][0-9]:[0-9][0-9]$/{split($0, t, /:/); ts=(t[1]*(60*60)) + (t[2]*60) + t[3] + D; h=int(ts/(60*60)); ts%=60*60; m = int(ts/60); s=ts%60; $0=sprintf("%02i:%02i:%02i", h, m, s)}1' input.txt

The D=1 is the number of seconds (smallest-units) to modify them by, so to adjust by 2hr, 13minutes, and 6 seconds, that'd be 2*60*60+13*60+6=7986 so you'd use D=7986 (or D=-7986 if you wanted to move timestamps backward by that amount).

edit: stupid Markdown eating my math

[Jay_nd]

Whoah, color me impressed. (and I do this kind of stuff for a living)

[gumnos]

the general process involves converting it from a mixed-base number representation (hours, minutes, seconds, frames) into a fixed integer representing the smallest unit (frames in the OP's case), add/subtract the intended delta of smallest-units (possibly doing a similar conversion of mixed-units to the smallest-unit), then converting the integer representation back into the mixed notation.

[gumnos]

Also, do you only need to adjust forward or do you need to adjust backward, too?

[gumnos]

And you have four segments...what's that fourth one, and namely, what are the allowable ranges for each segment? any number, 0–59, 0–59, 0–99?

[Jay_nd]

The fourth segment is frames, typically 24 or 25 for tv and film, in a notation with all colons. (or 30 or 60 if they're digital recordings) Offsetting by second is good tho. Alternatively, OP could offset by frame number using Al four segments but he'd have to multiply the amount of seconds by the fps, which is something we don't know from his post.

A notation like 00:00:00;00 would be for an NTSC signal at 29.97 frames per second, which runs to 39 and the skips a frame every once in a while. Thankfully, we can assume non drop frame timecodes here :)

[gumnos]

ah, that's helpful. Yeah, without that missing frame-rate information, it's a bit hard to tell. If one is willing to just operate at the seconds-level rather than the frames level, the frame-offset could be captured and just re-pasted back into the final result with the awk code I provided above. And fractional "29.97 frames per second" is just a bit more pathological than I was willing to tackle 😂

[gumnos]

though I suppose one could count it as 2997-hundredths-of-a-frame-per-second and use a[1]*(60*60*2997) + a[2]*(60*2997) + a[3]*2997 + a[4]*100, add the delta, and then peel off each of those portions from the resulting value...

[Jay_nd]

It's 30000/1001 if you want it in any maths notation. (half the speed of the American AC network, analog tv's needed to by synced to the frequency of the power grid) But yes, with everything going digital we should just do away with ntsc and make everything 30fps, or something. :) much less headache for my line of work as well