How to reduce voice-audio file size?

WindowBreaker · 01-30-2006, 05:20 PM

I have a CD with a 45 minute speech on it. Since it's all voice and no music, is there a way to rip it, and strip the non-audible range to shrink the file size???

My goal is to reduce the filesize as much as possible.

Thanks for any suggestion.

kodon · 01-30-2006, 06:12 PM

i suppose you can do some trials with lame or oggenc
lowering the bitrate and resampling frequency...check
the mans for other options such as lowpass, highpass, etc

you could also try a codec designed specifically for voice(eg speex)

shilo · 01-30-2006, 06:44 PM

I agree with Kodon. I found this website informative: http://jthz.com/mp3/

WindowBreaker · 01-31-2006, 03:13 PM

Okay, I followed the site's instructions, but the filesize is a whopping 60MB mp3. It's a 45min speech.

Since it's just voice, should I expect to be able to somehow reduce the filesize dramatically to like <10MB without losing a whole log of voice quality?

I'm not too handy with audio manipulation commands (one of my weaknesses), so any suggestions would be very appreciated.

Thanks

agreenwood · 01-31-2006, 03:33 PM

What did you use as the lowpass setting? By dropping that number, you're effectively filtering off the top end of the audio frequency spectrum. If it is a male voice (deeper) then you may be able to drop that number below 10. this could dramatically reduce the file size. Drop it too far, though, and it could get nasty pretty quick.

Fluxx · 01-31-2006, 03:38 PM

I have a speech with a length of 378 minutes, on 6 cd-roms in wav-format. I ripped the speech with ogg-vorbis in a good quality (a lower quality is possible, may be there is no difference to hear it) to 190 MB.

This should be a file with about 10 MB in your case (length of the speech is 45 minutes) ...

Fluxx.

shilo · 01-31-2006, 06:13 PM

I agree with what agreenwood. You say you followed that site, but there are several different recommnedations. If you used the high quality ones, you are gonna get big files. Try the settings recommneded for netcasts.

davidsrsb · 02-01-2006, 10:43 AM

Have a look at the Speex codec, which is designed for speech

Phathead · 02-03-2006, 09:21 PM

I get an hour long radio talk show down to about 7.4 MB with this:

Code:

lame -r -x -mj -s44.1 -V9 --vbr-new -q2 -b8 --lowpass 15 --cwlimit 10 -a --resample 16

check the lame man page for the details of each option. This is an FM broadcast, BTW, so it's relatively noise free. Noise may confuse the encoder and cause the variable bit rate to encode at a higher bitrate. Playing with the --lowpass number may cut out some or all of the noise as long as the noise is of a different frequency than the speech.

It can be made smaller than 7.4 MB, but the quality is too low for me. YMMV, but play with the options.

WindowBreaker · 02-04-2006, 09:09 AM

Phathead:
Thanks for the cmd, worked like a charm. It reduced the file from 60Mb to 6.5Mb!
Although my lame didn't recognize the --cwlimit option. That option is mentioned in the help, but not in the output of 'lame --morehelp'.

Thanks again buddy.