Fix garbled duration in info() output for files of 10 minutes or longer

[sungbin1015]

repr(sf.info(file)) prints the duration in scientific notation as soon as the minutes or hours field reaches 10, and never zero-pads the seconds:

import numpy as np
import soundfile as sf

sf.write('x.wav', np.zeros(900 * 8, dtype='int16'), 8)   # 15 minutes
print(sf.info('x.wav'))

length	current master	with this PR
61 s	01:1.000 min	01:01.000 min
600 s	1e+01:0.000 min	10:00.000 min
900 s	2e+01:0.000 min	15:00.000 min
3599 s	6e+01:59.000 min	59:59.000 min
3661.5 s	1:01:1.500 h	1:01:01.500 h
11707.5 s	3:2e+01:7.500 h	3:15:07.500 h
36000 s	1e+01:00:0.000 h	10:00:00.000 h
119.9996 s	01:60.000 min	02:00.000 min

(soundfile 0.14.0 at 3503941, libsndfile 1.2.2, Python 3.11, Linux x86_64)

Cause

_SoundFileInfo._duration_str formats hours and minutes with .0g. g with precision 0 means one significant digit, so every value >= 10 is rounded to one digit and switches to exponent notation (format(15.0, '02.0g') == '2e+01'). The seconds use 05.3f, but d.ddd is already five characters wide, so the zero padding never applies; the width has to be 6.

The 4e+01 in the output quoted in #443 (6e+10:4e+01:3.719h) is this formatting; the frame count reported there is a separate matter.

Change

• Use .0f / 02.0f for hours and minutes and 06.3f for seconds.
• Round the duration to milliseconds before splitting it. Otherwise a value such as 119.9996 s is split into 1 min + 59.9996 s and then printed as 01:60.000 min.

The samples and s branches are unchanged, and so is the duration attribute itself.

Tests

info() had no test for the duration line. Added a parametrized test_info_duration covering all four branches; 6 of its 8 cases fail on master. python -m pytest: 339 passed. pyright soundfile.py reports the same two errors (line 188) before and after.

Related work

• The duration of the audio read by the soundfile library is incorrect #443 (open issue) is about a wrong frame count for an mp3 and was redirected to libsndfile. Its quoted output shows this formatting bug, but the formatting was never raised there. This PR does not touch frame counts or the duration attribute, so it does not resolve The duration of the audio read by the soundfile library is incorrect #443.
• Do not yield stale frames from blocks() when out= is longer than the file #495 (open) fixes blocks() with out=; it changes other lines of soundfile.py.

I found no issue or PR about the info() duration format (searched duration, _duration_str, e+01, info repr, scientific notation, open and closed).

🤖 Generated with Claude Code

[bastibe]

Thank you!