Some program to change the bpm of a track?

Someone knows some program in Ubuntu to change the bpm of a track, retaining the tone. I've tried with Audacity, but when changing the bpm, it also changes the tone. Any idea? Maybe whit LMMS?

Thanks.

2 Answers

Actually, you can in Audacity.

Referring from the manual, you can access it by Effect > Change Tempo.

Playback changes (rather than permanent changes to the track itself) can be accomplished quite easily using the command line MPlayer and the 'scaletempo' filter. Typical syntax is (halving the playback speed in this case):

mplayer -af scaletempo -speed 0.5 input.mp4

From here playback speed can be adjusted during playback using the default '{' and '}' keys. This filter is unfortunately not available in the best gui for MPlayer: SMPlayer.

Permanent changes to a track's speed can be accomplished with the use of FFmpeg: using the 'setpts' video filter and the 'atempo' audio filter. The following syntax doubles both audio and video speed without altering pitch:

ffmpeg -i input.mp4 \
-filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" \
-map "[v]" -map "[a]" \
output.mp4

And increments are possible for both speeding up and slowing down a track...

References:

• Top 10 Tricks and Tips for the svn MPlayer My own page :). Have a look at Tip 1: Using 'scaletempo'...
• How to speed up / slow down a video Solid information on the subject from the FFmpeg Trac site...