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
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
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.
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
Related
I want to detect silence or delay in audio for a given duration file and remove it. For example, if someone started speaking and then paused for some duration to think.
There's this question but it only detects the silence at the end and doesn't remove it. My colleague suggested sox but I'm not sure if it's the best tool for the job nor how to use it frankly, moreover, the project died in 2015.
The Sox man page describes this in detail.
silence [-l] above-periods [duration threshold[d|%]
[below-periods duration threshold[d|%]]
if we start with a sample command:
sox input.mp3 out.mp3 -S silence -l 1 0.2 1% -1 0.2 1%
`-S` - show progress
`silence` - the filter
`-l` - leave x amount of each silence in tact
`1` - trim from 1st silence [above-periods]
`0.2` - amount of each silence to leave untouched [duration]
`1%` - test for near absolute (0%) silence [threshold]
`-1` - trim silence from the middle of the file [below-periods]
`0.2` - amount of each silence to leave untouched [duration]
`1%` - test for near absolute (0%) silence [threshold]
The detail courtesy of Sox:
silence [-l] above-periods [duration threshold[d|%]
[below-periods duration threshold[d|%]]
Removes silence from the beginning, middle, or end of the audio. `Si‐
lence' is determined by a specified threshold.
The above-periods value is used to indicate if audio should be trimmed at
the beginning of the audio. A value of zero indicates no silence should
be trimmed from the beginning. When specifying a non-zero above-periods,
it trims audio up until it finds non-silence. Normally, when trimming si‐
lence from beginning of audio the above-periods will be 1 but it can be
increased to higher values to trim all audio up to a specific count of
non-silence periods. For example, if you had an audio file with two songs
that each contained 2 seconds of silence before the song, you could spec‐
ify an above-period of 2 to strip out both silence periods and the first
song.
When above-periods is non-zero, you must also specify a duration and
threshold. duration indicates the amount of time that non-silence must be
detected before it stops trimming audio. By increasing the duration,
burst of noise can be treated as silence and trimmed off.
threshold is used to indicate what sample value you should treat as si‐
lence. For digital audio, a value of 0 may be fine but for audio
recorded from analog, you may wish to increase the value to account for
background noise.
When optionally trimming silence from the end of the audio, you specify a
below-periods count. In this case, below-period means to remove all au‐
dio after silence is detected. Normally, this will be a value 1 of but
it can be increased to skip over periods of silence that are wanted. For
example, if you have a song with 2 seconds of silence in the middle and 2
second at the end, you could set below-period to a value of 2 to skip
over the silence in the middle of the audio.
For below-periods, duration specifies a period of silence that must exist
before audio is not copied any more. By specifying a higher duration,
silence that is wanted can be left in the audio. For example, if you
have a song with an expected 1 second of silence in the middle and 2 sec‐
onds of silence at the end, a duration of 2 seconds could be used to skip
over the middle silence.
Unfortunately, you must know the length of the silence at the end of your
audio file to trim off silence reliably. A workaround is to use the si‐
lence effect in combination with the reverse effect. By first reversing
the audio, you can use the above-periods to reliably trim all audio from
what looks like the front of the file. Then reverse the file again to
get back to normal.
To remove silence from the middle of a file, specify a below-periods that
is negative. This value is then treated as a positive value and is also
used to indicate that the effect should restart processing as specified
by the above-periods, making it suitable for removing periods of silence
in the middle of the audio.
The option -l indicates that below-periods duration length of audio
should be left intact at the beginning of each period of silence. For
example, if you want to remove long pauses between words but do not want
to remove the pauses completely.
duration is a time specification with the peculiarity that a bare number
is interpreted as a sample count, not as a number of seconds. For speci‐
fying seconds, either use the t suffix (as in `2t') or specify minutes,
too (as in `0:02').
threshold numbers may be suffixed with d to indicate the value is in
decibels, or % to indicate a percentage of maximum value of the sample
value (0% specifies pure digital silence).
Finally, a python sample code, to enable monitoring of the output:
try:
self.comm = Popen(['sox', self.orig_file, self.new_file, '-S', 'silence',\
'-l', '1', '0.1', '1%', '-1', str(self.secs.GetValue()), '1%'],\
stdout=PIPE, stderr=STDOUT, universal_newlines=True)
except Exception as e:
......
It's worth pointing out that ffmpeg has the filters silencedetect and silenceremove.
While I do use silencedetect e.g.:
ffmpeg -hide_banner -stats -i interview.wav -af silencedetect=noise=0dB:d=3 -vn -sn -dn -f null -
silenceremove e.g.:
ffmpeg -hide_banner -v quiet -i interview.wav -af silenceremove=stop_periods=-1:stop_duration=2:stop_threshold=-3dB -vn -sn -dn -f wav - | ffplay -hide_banner -v quiet -autoexit -i -
I've found to be less dependable.
It should also be pointed out, that silence is notoriously difficult to pin down, except on an individual/ad-hoc basis, due to background noise.
I've a couple of recordings where at the end of the track there's silence and the start of a new track (fraction).
I tried to remove the start of the new track from the end of the file.
My command (*nux)
sox file_in.mp3 -C 320 file_out.mp3 silence 1 0.75 0.2% -1 0.75 0.2%
Preferably keep the silence at the end or just add some new. Any help appreciated
Probably you can use the below period parameter without the above period.
A bit of silence can optionally be kept with the -l parameter (or you can just use pad with a fixed amount).
For example:
sox input.mp3 -C 320 output.mp3 silence -l 0 1 0.5 0.5%
Sample input:
Result:
Note, if the beginning of some new tracks has long silence periods inside, it may be tricky - but usually possible - to find appropriate duration and threshold parameters (the general case, apparently, it is not tractable at all by simple processing, one needs a machine learning approach to reliably mark inner periods of silence that belong to a track).
Also, if it is just a couple of files, opening an editor e.g. Audacity is the quickest and the best outcome approach.
I need to split mp3 file into slices TIME sec each. I've tried mp3splt, but it doesn't work for me if output is less than 1 minute.
Is it possible do do with:
sox file_in.mp3 file_out.mp3 trim START LENGTH
When I don't know mp3 file LENGTH
You can run SoX like this:
sox file_in.mp3 file_out.mp3 trim 0 15 : newfile : restart
It will create a series of files with a 15-second chunk of the audio each. (Obviously, you may specify a value other than 15.) There is no need to know the total length.
Note that SoX, unlike mp3splt, will decode and reencode the audio (see generation loss). You should make sure to use at least SoX 14.4.0 because previous versions had a bug where audio got lost between chunks.
There are two use case trim in sox:
sox file_in.mp3 file_out.mp3 trim START LENGTH
and
sox file_in.mp3 file_out.mp3 trim START =END
In last example you need to know the END position instead of LENGTH
I’d like to change the volume level of a particular time range/slice in an audio file using SoX.
Right now, I’m having to:
Trim the original file three times to get: the part before the audio effect change, the part during (where I’m changing the sound level), and the part after
Perform the effect to change the sound level on the extracted “middle” chunk of audio, in its own file
Splice everything back together, taking into account the fading/crossfading 5ms overlaps that SoX recommends
Is there a better way to do this that doesn’t involve writing a script to do the above?
For anyone who stumbles across this highly ranked thread, searching for a way to duck the middle of an audio file:
I've been playing with SoX for ages and the method I built uses pipes to process each part without creating all those temporary files!
The result is a single line solution, though you will need to set timings and so, unless your fade timings will be the same for all files, it may be useful to generate the line with an algorithm.
I was pleased to get piping working, as I know this aspect has proved difficult for others. The command line options can be difficult to get right. However I really didn't like the messy additional files as an alternative.
By using mix functionality and positioning each part using pad, then giving each section trim & fade we can also avoid use of 'splice' here. I really wasn't a fan.
A working single line example, tested in SoX 14.4.2 Windows:
It fades (ducks) by -6dB at 2 seconds, returning to 0dB at 5 seconds (using linear fades of 0.4 seconds):
sox -m -t wav "|sox -V1 inputfile.wav -t wav - fade t 0 2.2 0.4" -t wav "|sox -V1 inputfile.wav -t wav - trim 1.8 fade t 0.4 3.4 0.4 gain -6 pad 1.8" -t wav "|sox -V1 inputfile.wav -t wav - trim 4.8 fade t 0.4 0 0 pad 4.8" outputfile.wav gain 9.542
Let's make that a little more readable here by breaking it down into sections:
Section 1 = full volume, Section 2 = ducked, Section 3 = full volume
sox -m
-t wav "|sox -V1 inputfile.wav -t wav - fade t 0 2.2 0.4"
-t wav "|sox -V1 inputfile.wav -t wav - trim 1.8 fade t 0.4 3.4 0.4 gain -6 pad 1.8"
-t wav "|sox -V1 inputfile.wav -t wav - trim 4.8 fade t 0.4 0 0 pad 4.8"
outputfile.wav gain 9.542
Now, to break it down, very thoroughly
'-m' .. says we're going to mix (this automatically reduces gain, see last parameter)
'-t wav' .. says the piped command that follows will return a WAV (it seems the WAV header is being lost in the pipeline)
Then.. the FIRST piped part (full volume before duck)
'-V1' .. says ignore warnings - there will be a warning about not knowing length of output file for this specific section as it's piping out, but there should be no other warning from this operation
then the input filename
'-t wav' .. forces the output type
'-' .. is the standard name for a piped output which will return to SoX command line
'fade t 0 2.2 0.4' .. fades out the full volume section. t = linear. 0 fade in. Then (as we want the crossfade's halfway point to be at 2 seconds) we fade out by 2.2 seconds, with a 0.4 second fade (the fadeout parameter is for when the fade ENDS!)
'-t wav' .. to advise type of next part - as above
Then.. the SECOND piped part (the ducked section)
'-V1' .. again, to ignore output length warning - see above
then the same input filename
'-t wav' .. forces output type, as above
'-' .. for piped output, see above
'trim 1.8' .. because this middle section will hit the middle of the transition at 2 seconds, so (with a 0.4 second crossfade) the ducked audio file will start 0.2 seconds before that
'fade t 0.4 3.4 0.4' .. to fade in the ducked section & fade back out again. So a 0.4 fade in. Then (the most complicated part) as the next crossfade will end at 5.2 seconds we must take that figure minus trimmed amount for this section, so 5.2-1.8=3.4 (again this is because fadeout position deals with the end timing of the fadeout)
'gain -6' .. is the amount, in dB, by which we should duck
'pad 1.8' .. must match the trim figure above, so that amount of silence is inserted at the start to make it synch when sections are mixed
'-t wav' .. to advise type of next part - as above
Then.. the THIRD piped part (return to full level)
'-V1' .. again - see above
then the same input filename
-t wav' .. to force output type, as above
-' .. for piped output, see above
trim 4.8' .. this final section will start at 5 seconds, but (with a 0.4 second crossfade) the audio will start 0.2 seconds before that
'fade t 0.4 0 0' .. just fade in to this full volume section. No fade out
'pad 4.8' .. must match the trim figure above, as explained above
then output filename
'gain 9.542' .. looks tricky, but basically when you "-m" to mix 3 files the volume is reduced to 1/3 (one third) by SoX to give headroom.
Rather than defeating that, we boost to 300%. We get the dB amount of 9.542 with this formula 20*log(3)/log(10)
If you copy & paste the single line somewhere you can see it all easily, it's a lot less scary than the explanation!
Final though - I was initially concerned about whether the crossfades needed to be logarithmic rather than linear, but in my case from listening to the results linear has definitely given the sound I expected.
You may like to try longer crossfades, or have the point of transition happening earlier or later but I hope that single line gives hope to anyone who thought many temporary files would be required!
Let me know if more clarification would help!
audacity waveform
Okay, with ffmpeg and filters it's all quite simple.
Imagine that you have 2 tracks, A and B. And you want to crop ones and do something about the volume. So the solution would be:
ffmpeg -y -i 1.mp3 -i 2.mp3 i f454495482c151aea8761dda.mp3 -i f5544954796af4a171f11b57.mp3 -i f754495448788e35e6123679.mp3 -i f754495448788e35e6123679.mp3 -i f85449545e646dea98e5dd19.mp3 \
-filter_complex "[0]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=stereo,volume='if(between(t,129.00,129.20),0.15000*(t - 129.00) + 0.03,1)':eval=frame,volume='if(between(t,129.20,181.50),-0.00057*(t - 129.20) + 0.06,1)':eval=frame,volume='if(between(t,181.50,181.60),0.40000*(t - 181.50) + 0.03,1)':eval=frame,volume='if(between(t,181.60,183.50),-0.03684*(t - 181.60) + 0.07,1)':eval=frame,volume='if(between(t,183.50,188.00),0.00000*(t - 183.50) + 0.00,1)':eval=frame,atrim=0.00:56.00,adelay=129000|129000|129000|129000,apad[0:o];[1]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=stereo,volume='if(between(t,0.00,134.00),0.00000*(t - 0.00) + 0.06,1)':eval=frame,atrim=0.00:134.00,apad[1:o];[0:o][1:o]amix=inputs=28,atrim=duration=185.00" -shortest -ac 2 output.mp3
which will take 2 input files, transform both of the streams to the appropriate aformat and then apply volume filters.
The syntax for volume is simple: if time t is between some start and end time - then apply the volume filter, based on the desired start volume level plus by some coefficient multiplied by difference between the start time and current time t.
This will increase the volume linearly from initial volume to desired value on a range.
atrim will trim the audio chunk after the volume has been adjusted on all ranges.
ffmpeg is just amazing, the expressions could be very complex and many of math functions may be used in the expressions.
I am trying to output the begin-timestamps of periods of silence (since there is background noise, by silence I mean a threshold) in a given audio file. Eventually, I want to split the audio file into smaller audio files, given these timestamps. It is important that no part of the original file be discarded.
I tried
sox in.wav out.wav silence 1 0.5 1% 1 2.0 1% : newfile : restart
(courtesy http://digitalcardboard.com/blog/2009/08/25/the-sox-of-silence/)
Although, it somewhat did the job, it also trimmed and discarded the periods of silence, which I do not want happening.
Is 'silence' the right option, or is there a simpler way to accomplish what I need to do?
Thanks.
Unfortunately not Sox, but ffmpeg has a silencedetect filter that does exactly what you're looking for:
ffmpeg -i in.wav -af silencedetect=noise=-50dB:d=1 -f null -
(detecting threshold of -50db, for a minimum of 1 seconds, cribbed from the ffmpeg documentation)
...this would print a result like this:
Press [q] to stop, [?] for help
[silencedetect # 0x7ff2ba5168a0] silence_start: 264.718
[silencedetect # 0x7ff2ba5168a0] silence_end: 265.744 | silence_duration: 1.02612
size=N/A time=00:04:29.53 bitrate=N/A
There is (currently, at least) no way to make the silence effect output the position where it has detected silence, or to retain all of the silent audio.
If you are able to recompile SoX yourself, you could add an output statement yourself to find out about the cut positions, then use trim in a separate invocation to split the file. With the stock version, you are out of luck.
SoX can easily give you the timestamps of the actual silences in a text file. Not periods of silence though, but you can calculate those with a simple script
.dat Text Data files. These files contain a textual representation of the sample data. There is one line at the beginning that contains the sample
rate, and one line that contains the number of channels. Subsequent lines contain two or more numeric data intems: the time since the beginning of
the first sample and the sample value for each channel.
Values are normalized so that the maximum and minimum are 1 and -1. This file format can be used to create data files for external programs such as
FFT analysers or graph routines. SoX can also convert a file in this format back into one of the other file formats.
Example containing only 2 stereo samples of silence:
; Sample Rate 8012
; Channels 2
0 0 0
0.00012481278 0 0
So you can do sox in.wav out.dat, then parse the text file and consider a silence a sequence of rows with a value close to 0 (depending on your threshold)
necroposting:
You can run a separate script that iterates all of the sox output files, (for f in *.wav), and use the command; soxi -D $f to obtain the DURATION of the sound clip.
Then, get the system time in seconds date "+%s", then subtract to find the time the recording starts.