Get length of .wav from sox output

Question

I need to get the length of a .wav file.

Using:

sox output.wav -n stat

Gives:

Samples read:            449718
Length (seconds):     28.107375
Scaled by:         2147483647.0
Maximum amplitude:     0.999969
Minimum amplitude:    -0.999969
Midline amplitude:     0.000000
Mean    norm:          0.145530
Mean    amplitude:     0.000291
RMS     amplitude:     0.249847
Maximum delta:         1.316925
Minimum delta:         0.000000
Mean    delta:         0.033336
RMS     delta:         0.064767
Rough   frequency:          660
Volume adjustment:        1.000

How do I use grep or some other method to only output the value of the length in the second column, i.e. 28.107375?

Thanks

Solution 1

The stat effect sends its output to stderr, use 2>&1 to redirect to stdout. Use sed to extract the relevant bits:

sox out.wav -n stat 2>&1 | sed -n 's#^Length (seconds):[^0-9]*\([0-9.]*\)$#\1#p'

Solution 2

There is a better way:

soxi -D out.wav

Solution 3

This can be done by using:

• soxi -D input.mp3 the output will be the duration directly in seconds
• soxi -d input.mp3 the output will be the duration with the following format hh:mm:ss.ss

Solution 4

This worked for me (in Windows):

sox --i -D out.wav

Solution 5

I just added an option for JSON output on the 'stat' and 'stats' effects. This should make getting info about an audiofile a little bit easier.

https://github.com/kylophone/SoxJSONStatStats

$ sox somefile.wav -n stat -json

View more solutions

Comments

[joshu]

I've got no idea how you constructed this, but it works like a charm. Thank you!

[MrCranky]

For what it's worth, using sox v14.0.0 on Windows, the $ (EOL) marker caused this answer to fail to give the result expected (instead of parsing to the end of line, it simply parses till it finds something which isn't a digit or period.

[Ivan Kochurkin]

Unfortunately it returns wrong duration, distinguish from sox output.wav -n stat method in my case.

[Ivan Kochurkin]

Unfortunately it returns wrong duration, distinguish from sox output.wav -n stat method in my case.

[Andrew Kuklewicz]

I have never seen it to be wrong - can you distinguish in what situation this is incorrect?

[Ivan Kochurkin]

I've cropped the audio with mp3cut.net and got the warn from sox: WARN mp3-util: MAD lost sync with wrong duration. On the other hand sox output.wav -n stat execution returns correct duration in error output thread (see my answer for explanation). Also windows explorer shows correct duration.

[Andrew Kuklewicz]

FWIW - I've used this method on linux and mac for years without any such issue - sounds windows specific.

[Ruprecht von Waldenfels]

I think the two differ in that soxi uses the header info, while sox looks at the body, too. SO if the header is wrong, the two give different outpu.

[Matthias]

@RuprechtvonWaldenfels Interesting theory. Can anyone confirm this? I can't see anything on a quick glance at the man pages.

[Hubbitus]

Why theory? Man directly states it for soxi (sox --info): "Displays information from the header of a given audio file or files.", for sox stat: "Display time and frequency domain statistical information about the audio. Audio is passed unmodified through the SoX processing chain." You could read further how it statistics collected and calculated also.

[ed22]

stat returned 139.389388 and this returned 139.407007. For my purposes it's OK. Thanks.

[WestCoastProjects]

This is more reliable than soxi: this one involves traversing the audio file to calculate the length whereas soxi simply reports what is in the header - regardless of accuracy