Does anyone know of a way, in ruby, to render an mp3 into a waveform graphic? Like you'd see in audio editing tools like Audacity, Soundforge etc. Just a jpeg as the end result is fine. Hoping there might be a gem out there for this... thanks max
on 2008-07-24 17:35
on 2008-07-24 20:34
2008/7/24 Max Williams <firstname.lastname@example.org>: > Does anyone know of a way, in ruby, to render an mp3 into a waveform > graphic? Like you'd see in audio editing tools like Audacity, > Soundforge etc. Just a jpeg as the end result is fine. Hoping there > might be a gem out there for this... I don't think there's a Ruby gem to allow direct decoding of mp3 files, however it should be doable using mpg123 or some other program callable from the shell which can decode mp3's. The command 'mpg123 -O file.raw file.mp3' produces raw 16bit stereo PCM data (I think sampled at 22KHz) from the .mp3 file and stores it in the .raw file. So for every 4 bytes you read the first two bytes would be the signal strength of the one channel and the second two bytes would be the signal strength of the second channel. You could then use String#unpack (I think 'ss' will unpack to shorts, which were signed 16bits last I checked) to decode these bytes and get the values you need. You could then plot these values using a gem like RMagick. I haven't executed this code but it could look like: File.open('file.raw') do |file| while !file.eof? first_channel_data, second_channel_data = file.read(4).unpack('ss') # Plot data here end end Farrel
on 2008-07-25 10:40
Ah, that's useful, thanks farrel.