how to convert datetime-like string into milliseconds-CodePudding

I have a user-defined function (return_times) that takes json file and returns two datetime-like strings.

time_1, time_2= return_times("file.json")
print(time_1, time_2) # outputs: 00:00:11.352 00:01:51.936

By datetime-like string I mean 00:00:11.352 which suits '%H:%M:%S.%f' formatting. However, when I try to convert them into milliseconds, I get negative values.

from datetime import datetime

dt_obj_1 = datetime.strptime(time_1, '%H:%M:%S.%f')
start_ms = dt_obj_1.timestamp() * 1000

dt_obj_2 = datetime.strptime(time_2, '%H:%M:%S.%f')
end_ms = dt_obj_2.timestamp() * 1000

print(start_ms, end_ms ) # outputs: -2209019260648.0 -2209019160064.0

If I success I would like to trim a video with the following command:

from moviepy.video.io.ffmpeg_tools import ffmpeg_extract_subclip
ffmpeg_extract_subclip("long_video.mp4", start_ms, end_ms, targetname="video_trimmed.mp4"), so just delete ` * 1000` part.

Note that ffmpeg_extract_subclip requires its t1 and t2 parameters to be in seconds, not in milliseconds as I initially thought.

Because of those negative integers I am not able to successfully run the trimming process. I searched the web that mainly discusses several formats for the year, month and day, but not '%H:%M:%S.%f'.

What may I be overlooking?

CodePudding user response：

What may I be overlooking?

time.strptime docs

The default values used to fill in any missing data when more accurate values cannot be inferred are (1900, 1, 1, 0, 0, 0, 0, 1, -1).

whilst start of epoch is 1970. You might get what you want by computing delta between what you parsed and default strptime as follows:

import datetime
time1 = "00:00:11.352"
delta = datetime.datetime.strptime(time1, "%H:%M:%S.%f") - datetime.datetime.strptime("", "")
time_s = delta.total_seconds()
print(time_s)

output

11.352

CodePudding user response：

You need to add the year date (year, month, day) to datetime, else this will default to 1 January 1900.

What you do is this:

from datetime import datetime
s = "00:00:11.352" 
f = '%H:%M:%S.%f'
datetime.strptime(s, f) # datetime.datetime(1900, 1, 1, 0, 0, 11, 352000)

One way to do this is to append the date-string to the time-string you receive from return_times

CodePudding user response：

From https://stackoverflow.com/a/59200108/2681662

The year 1900 was before the beginning of the UNIX epoch, which was in 1970, so the number of seconds returned by timestamp must be negative.

What to do?

It's better to use a time object instead of a datetime object.

from datetime import time

time_1 = "00:00:11.352"
hours, minutes, seconds = time_1.split(":")

print(time(hour=int(hours), minute=int(minutes), second=int(float(seconds)),
           microsecond=int(float(seconds) % 1 * 1000000)))

CodePudding user response：

You can split the time string into hours, minutes, seconds and miliseconds and with some simple math calculations, you get the whole time in miliseconds