Crop MP3 to first 30 seconds

Original Question

I want to be able to generate a new (fully valid) MP3 file from an existing MP3 file to be used as a preview -- try-before-you-buy style. The new file should only contain the first n seconds of the track.

Now, I know I could just "chop the stream" at n seconds (calculating from the bitrate and header size) when delivering the file, but this is a bit dirty and a real PITA on a VBR track. I'd like to be able to generate a proper MP3 file.

Anyone any ideas?

Answers

Both mp3split and ffmpeg are both good solutions. I chose ffmpeg as it is commonly installed on linux servers and is also easily available for windows. Here's some more good command line parameters for generating previews with ffmpeg

• -t <seconds> chop after specified number of seconds
• -y force file overwrite
• -ab <bitrate> set bitrate e.g. -ab 96k
• -ar <rate Hz> set sampling rate e.g. -ar 22050 for 22.05kHz
• -map_meta_data <outfile>:<infile> copy track metadata from infile to outfile

instead of setting -ab and -ar, you can copy the original track settings, as Tim Farley suggests, with:

• -acodec copy

I also recommend ffmpeg, but the command line suggested by John Boker has an unintended side effect: it re-encodes the file to the default bitrate (which is 64 kb/s in the version I have here at least). This might give your customers a false impression of the quality of your sound files, and it also takes longer to do.

Here's a command line that will slice to 30 seconds without transcoding:

ffmpeg -t 30 -i inputfile.mp3 -acodec copy outputfile.mp3

The -acodec switch tells ffmpeg to use the special "copy" codec which does not transcode. It is lightning fast.

NOTE: the command was updated based on comment from Oben Sonne

If you wish to REMOVE the first 30 seconds (and keep the remainder) then use this:

ffmpeg -ss 30 -i inputfile.mp3 -acodec copy outputfile.mp3

try:

ffmpeg -t 30 -i inputfile.mp3 outputfile.mp3

This command also works perfectly. I cropped my music files from 20 to 40 seconds.

> -y : force output file to overwrite.

ffmpeg -i test.mp3 -ss 00:00:20 -to 00:00:40 -c copy -y temp.mp3

you can use mp3cut:

cutmp3 -i foo.mp3 -O 30s.mp3 -a 0:00.0 -b 0:30.0

It's in ubuntu repo, so just: sudo apt-get install cutmp3.

You might want to try Mp3Splt.

I've used it before in a C# service that simply wrapped the mp3splt.exe win32 process. I assume something similar could be done in your Linux/PHP scenario.

I have got an error while doing the same

Invalid audio stream. Exactly one MP3 audio stream is required.
Could not write header for output file #0 (incorrect codec parameters     ?): Invalid argumentStream mapping:

Fix for me was:

ffmpeg -ss 00:02:43.00 -t 00:00:10 -i input.mp3 -codec:a libmp3lame out.mp3

My package medipack is a very simple command-line app as a wrapper over ffmpeg.

you can achieve trimming your video using these commands:

medipack trim input.mp3 -s 00:00 -e 00:30 -o output.mp3
medipack trim input.mp3 -s 00:00 -t 00:30 -o output.mp3

you can view options of trim subcommand as:

srb@srb-pc:$ medipack trim -h
usage: medipack trim [-h] [-s START] [-e END | -t TIME] [-o OUTPUT] [inp]

positional arguments:
  inp                   input video file ex: input.mp4

optional arguments:
  -h, --help            show this help message and exit
  -s START, --start START
                        start time for cuting in format hh:mm:ss or mm:ss
  -e END, --end END     end time for cuting in format hh:mm:ss or mm:ss
  -t TIME, --time TIME  clip duration in format hh:mm:ss or mm:ss
  -o OUTPUT, --output OUTPUT

you could also explore other options using medipack -h

srb@srb-pc:$ medipack --help
usage: medipack.py [-h] [-v] {trim,crop,resize,extract} ...

positional arguments:
  {trim,crop,resize,extract}

optional arguments:
  -h, --help            show this help message and exit
  -v, --version         Display version number

you may visit my repo https://github.com/srbcheema1/medipack and checkout examples in README.