How do you trim the audio file's end using SoX?

Question

Using Sox, how do I shorten an audio file by 5 seconds, trimming from the end?

For example, this is how to trim a file from the beginning:

    sox input output trim 5000

This is how to add 5 seconds of silence to the end:

    sox input output pad 0 5000

Answer 1

The syntax is sox input output trim <start> <duration>

e.g. sox input.wav output.wav trim 0 00:35 will output the first 35 seconds into output.wav.

(you can know what the length is using sox input -n stat)

From the SoX documentation on the trim command:

Cuts portions out of the audio. Any number of positions may be given; audio is not sent to the output until the first position is reached. The effect then alternates between copying and discarding audio at each position. Using a value of 0 for the first position parameter allows copying from the beginning of the audio.

For example,

sox infile outfile trim 0 10

will copy the first ten seconds, while

play infile trim 12:34 =15:00 -2:00

and

play infile trim 12:34 2:26 -2:00

will both play from 12 minutes 34 seconds into the audio up to 15 minutes into the audio (i.e. 2 minutes and 26 seconds long), then resume playing two minutes before the end of audio.

Per dpwe's comment, the position values are interpreted as being relative to the previous position, unless they start with = (in which case they are relative to the start of the file) or - (in which case they are relative to the end of the file).

So, trimming five seconds off the end would be sox input output trim 0 -5

Answer 2

Above command is wrong, it will get you last 5 seconds only. You actually need to use:

sox input output reverse trim 5 reverse 

which will cut 5 seconds from end of the file.

Answer 3

I'm new to SoX but have noticed this page frequently shows up in search results for audio trimming and will be seen by many trying to do similar things.

As such I wanted to provide what I have found to be the best solution personally.

I experienced the same 'click' at file end which John Smith Optional had mentioned. This suggested a brief fade out could remove any glitching artefacts as the audio finishes and sure enough it works. It's acceptance of a negative value for the fadeout position parameter to indicate the time before the end of audio is the key.

So I can see no better way to achieve the OP's aim than this:

sox full_length.wav trimmed.wav fade 0 -5 0.01

Parameter 1 is '0' so there is no fade in. Parameter 2 removes the last 5 seconds Parameter 3 uses a 10ms fade