Help - Audio Conversion

Dear Audacity Team Members,
I seek your help in respect of a specific requirement-to extract audio from VOB files in mp3 format at 16 kbps, preferably in mono output. The files in question are on approx 80 DVDs and will amount to approx 120 hours of audio. The low bitrate (16 kbps) is intentional - to keep the size of files as small as possible with acceptable audio quality. I had stumbled onto Cleanspeech (based on Audacity V 1.3 ?) and would have stuck to the same but for one problem - it does not permit ripping straight from VOB files on DVDs. The biggest plus point of Cleanspeech for me was the one click process for conversion after importing of files - conversion from stereo to mono, noise removal, removal of clicks, truncating silences, normalisation and exporting to mp3 at 16 kbps all takes place automatically, requires no user intervention and makes batch processing of files very simple. The processed files have acceptable audio quality since I am only interested in making sense out of the narrations. The Cleanspeech program would have met my requirements perfectly had ripping from VOB files on DVDs been possible. I have tried Audacity V 2 but have to perform each of the steps (noise/silence/click removal, normalization and exporting to mp3) manually. Considering the large number of DVDs and the fact that each of those would have a minimum of four and sometimes up to ten VOB files, the process would be very cumbersome. Could you please suggest a solution so that I could somehow use Cleanspeech for my requirement. Alternately, can Audacity V 2 be configured to function like Cleanspeech ? By the way, I am a noob in this field. Thanks a ton.

Extracting audio from VOB files requires importing using FFMpeg.

To install FFmpeg see here:

Batch processing is achieved using the Audacity “Chains” feature. Chains may be customised to suit your needs (though there are some limits to which effects and processes are available). See these links for more details:

Dear Mr Steve,
I’m grateful for your prompt reply. While posting my query, I forgot to mention that I had already installed the FFmpeg and am familiar with the “chains” feature courtesy my trials of the “Cleanspeech” edition of Audacity.I understand that the “Chains” feature can also be made use of in Version 2 of Audacity with some modifications. My queries are as follows:-
(a) How do I modify the parameters of the in built Chains of Version 2 of Audacity - “Cleanspeech” and “Mp3 Conversion” so that mp3 files are encoded @16 kbps (and not the default value if 128kbps).
(b) How to edit the settings for saving the output (exported mp3) file (changing the destination folder).
(c) While trying out the “Cleanspeech” and Version 2 editions of Audacity, I have encountered a very strange phenomenon - some of the imported files have long periods of silence (sometimes upto 10 minutes) appended before the actual audio clip. In one instance, a one minute audio sample once imported into Audacity showed the length of the sample as nine minutes due to an eight minutes’ silence mysteriously added on to the start of the actual audio sample.
(d) Is it possible to merge multiple audio files as the last step of a Chain?
Your advice would be highly appreciated. Thanks.

If you use the MP3 export option in a Chain, then the encoding settings will be whatever MP3 encoding settings were last used.
If you generate (or record) a few seconds as a test file, then export as MP3 (File > Export) and export at 16kbps MP3, then those setting will be used until such time as you change them.

Move (or copy) all of the files that you want to process into the same folder. The exported files will be in a sub-folder called “cleaned”.

Sounds strange. No obvious reason comes to mind. Check the files that you are processing.

No. Chains process only one file at a time.

Dear Mr Steve,
1.Thanks for your reply once again. I tried various options based on the advice rendered and am stuck on the following aspects:-
(a) Can I import VOB files directly form DVDs, chain process them and save the exported files to my hard disk or do I perforce have to first copy the VOB files to the hard disk before processing them?
(b) If I import multiple VOB files from a single source and apply the “Cleanspeech” chain to the project, why does the chain terminate after the first VOB file has been exported as an mp3 file? Why is the second VOB file not automatically subjected to the actions of the previously run “Chain”?
2. Please enlighten!


I’m not sure exactly what you are doing, which options you are selecting.
When you select “Apply Chain” are you then clicking on “Apply to Files”?

Dear Mr Steve,

  1. Actions taken are as under:
    (a) Copied five VOB files from DVD to hard disk. (I would ideally like to avoid this step if possible, import the files directly from the DVD, process them using Audacity and store the converted mp3 files on the hard disk. However, by default the destination for converted files is the same as the folder which contains the source files. Is there a way to change the destination folder ?)
    (b) Opened Audacity.
    (b) File-Import audio (files to import the five VOB files into Audacity).
    (b) File-Apply Chain-Cleanspeech (or MP3 Conversion)-Apply to current project.
  2. The execution of various steps involved in the Cleanspeech/MP3 Conversion commence. Process ceases after the first of the five VOB files is converted and exported as an MP3 file.

Even if that could be done (which it can’t) it would still be better to copy the VOB files to the hard drive first so that any possible read errors can be dealt with separately and not in the middle of a batch processing run.

That’s where you’re going wrong.
Don’t import the files - that needs to be handled by the Chain.

While Audacity is open and there is not audio in it, use “File > Apply Chain”, then select the Chain that you want, the click “Apply to Files”.
Navigate to where the VOB files are, select them, then click “Open”.

If you get any pop-up dialogue window occurring, make a note of what they say and we can tell you how to disable them so that the entire batch runs automatically.

Dear Mr Steve,

  1. Sincere thanks for your patience and efforts towards answering my repeated queries. Your comments on copying of VOB files to the hard disk are well appreciated and clearly understood.

  2. Execution of chains was tried as advised by you. Actions were as follows:-
    (a) Opened Audacity.
    (b) Edit - preferences - quality - sampling - set default sample rate to 22050 Hz from the drop down menu - OK.
    (c) File - apply chain - Cleanspeech - apply to files - selected and imported the VOB files.
    (d) Observed that the Project Rate (Hz) in bottom left corner of Audacity GUI was reading 44000 Hz and not the desired value (22050 Hz). Could not reset it to a lower value since execution of the “Chain” had commenced automatically.
    (e) The first of the VOB files was subjected to various steps of the “Chain” till a window popped up informing the incompatibility of the sample rate (44 k Hz) with the export bitrate (16 kbps).
    (f) Re-set the sample rate to 22050 Hz from the drop down menu.
    (g) First VOB file exported as MP3 at 16 kbps.
    (h) Processing of next VOB file begins and proceeds smoothly till the “incompatibility” window pops up again and processing comes to a halt. Processing re-commences once the sampling rate is lowered to a compatible value.

  3. I think my problems will be adequately addressed if a way is found to set the “sample rate” to a default value of 22050 Hz.

  4. Further advise awaited. Please reply at your convenience.

When I follow your instructions, after 2 b) I see that the Project Rate in the lower left of the Audacity window has changed to 22050. How did you open Audacity? I simply clicked on the Audacity icon on my desktop. Did you, by any chance, open an existing sound file into Audacity? If so, that will have set the Project Rate to 44100 and may have thus over-ridden your Preferences setting.

I should have seen that coming.
It is quite normal that on importing a file into a new (empty) project, Audacity will default to the higher of (a) the current project rate or (b) the sample rate of the imported file. This is so that sound quality is not lost. Unfortunately in your case you need to deliberately cause sound quality loss.

I have an idea for a workaround - let me test it and I’ll get back to you.

I’ve checked but unfortunately it is not possible to (automatically) convert the sample rate using Chains without user input.

Do your really need the quality to go as low as 16 kbps? If you do then the only workaround that I can think of is to use a dedicated format converter.
SUPER by erightsoft is free software that should be able to do the job in one step, but it is a bit quirky and downloading it is a link jungle.

Alternatively, use Chains to do most of the process, but export as WAV, then use a free MP3 batch encoder (such as “LamedropXPd” to batch convert from WAV to MP3.

Dear PGA,
Is this a reply to my post? If so, I haven’t been able to understand much. Would you care to rephrase/elucidate? Thanks

DEAR Mr Steve,
Thanks for all the trouble taken.I had tried the “SUPER” program with unsatisfactory results before Audacity.You’re right - quirky and unpredictable is probably the best way to describe it. Anyway, I will manage somehow (the 16kbps is actually non negotiable)! Regards and best wishes.