VLC HowTo/Extract audio

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Revision as of 19:58, 23 May 2015 by Isotera (talk | contribs) (→‎Extracting audio in WAV format: Clarified the explanation.)
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VLC can extract audio from any of the many input sources it supports, and write this audio to an audio-file in a variety of formats. In other words, it discards any video content from the input source, and it converts the audio content to the desired format.

You can invoke audio extraction from the VLC graphical user interface, or from the VLC command line. When using the VLC command line, you can select options that let you monitor the audio (and/or video, actually) as the extraction happens. Or, you can select options to hide VLC's visual interfaces, leaving it to extract and convert the audio data as fast as the computer allows -- which might take a fraction of the time. You can also script the VLC command line invocations, letting you do many extraction tasks without manual effort.

Planning

Identify the source from which you want to extract the audio signal. You will open this source from VLC using the same GUI operations or command-line options as you would for any other VLC usage.

Is the source an audio-only file? If so, then this operation is a simple transcoding of audio content from one format to another. Be aware that, while VLC has certain facility for this task, other tools may be even more powerful, faster, or more reliable for the task. For instance, the FLAC tools include a command-line utility which can convert WAV files into FLAC files with excellent speed and reliability. Where VLC really shines is for sources which combine video and audio content.

Is the source a DVD, or other container with internal structure, such as multiple "Titles", and multiple "Chapters" in each Title? If so, then you need to identify which Title and Chapters include the audio content you want, and which are irrelevant. For instance, a DVD may have a menu in Title 1, an advertisement in Title 2, the main content in Title 3, and a trailer in Title 3. The main content in Title 3 may be divided into dozens of chapters, like the tracks in a CD. In a case like this, you probably want only the audio content from Title 3, not from the other Titles. You may want to extract a single audio file with the content of all of Title 3, or you may want a separate audio output file for each Chapter.

The VLC GUI provides a somewhat clumsy but workable way to explore the structure of a DVD or corresponding video file. Here is how (as of Windows version 1.1.11):

  1. Run the VLC app.
  2. Put the DVD into the computer's DVD reader.
  3. From Media menu, select Open Disc... (Ctl-D). The Open Media dialog appears.
  4. Select the Disc tab. In the Disc tab's "Disk Selection" section, select the "DVD" radio button . From the "Disc device" menu, select the menu entry corresponding to the computer's DVD reader. For example, it might be "F:\ - Wedding Movie". Click the Play button at the bottom of the dialog. The Open Media dialog disappears. The DVD now appears as an entry in the playlist, e.g. "DVD://F".
  5. Double-click on the DVD entry in the playlist. The DVD starts playing. If necessary, select entries in the DVD's menu to start the DVD playing the content from which you want to extract audio.
  6. From the Playback menu, hover over Title >. A second menu appears, with entries like "DVD Menu", "Title 1", "Title 2", "Title 3". These are the Title choices you have to pull from. A check mark will be next to one of the entries. This is the Title with your content.
  7. On the Playback menu, move down to hover over Chapter >. A second menu appears, with entries like "Chapter 1", "Chapter 2", etc. A check mark will be next to one of the entries. This is the Chapter with your content.
  8. Note the last entry in the Chapter > submenu. This tells how many chapters there are in total in that title.
  9. Note the Title and Chapter number of the start of the content from which you want to extract audio. Also note the final Title and Chapter number of the content.

Using the VLC graphical user interface (GUI)

See How to Rip DVD Audio to MP3 Using VLC Media Player, Edited by AudioDude and 2 others, WikiHow.com

Note that VLC's GUI lets you specify the Title and Chapter from which it will start, but VLC will continue extracting until the end of the Title. It doesn't let you extract a single Chapter at a time. To do that, you will need to use the VLC command line.

Using the VLC command line

This section gives examples of how to extract audio using VLC's command line invocation.

The VLC command invocation

The start of the command line is the VLC invocation. On Windows this looks like: 

 "c:\Program Files\VideoLAN\VLC\vlc.exe"

On Mac OS X it looks like: 

 /Applications/VLC.app/Contents/MacOS/VLC

On Linux, if the vlc executable is on your path, it looks like: 

 vlc

General options

The command line will have a sequence of general options. These are the same for all platforms. 

  -I dummy --no-sout-video --sout-audio --no-sout-rtp-sap --no-sout-standard-sap --ttl=1 --sout-keep

Here's what those options mean:

-I dummy
VLC should run with no GUI, typing error messages and asking for input in the command line window. This is better for scripting and for faster completion. Leave this option off if you want the GUI to appear.
--no-sout-video
VLC will not pass on a video component to the streaming output
--sout-audio
VLC will, however, pass on an audio component to the streaming output
--no-sout-rtp-sap --no-sout-standard-sap
VLC will not deliver streaming output in RTP-SAP or Standard SAP forms.
--ttl=1
A parameter for RTP and SAP; innocuous here.
--sout-keep
Keep a copy of the streaming output; innocuous here.

The sout string

An option string, marked by --sout, tells VLC how to transcode the content and in what format to write it. See below for fully detailed examples. However, here is one sout string, specifying to transcode to a WAV audio format. 

 --sout "#transcode{acodec=s16l,channels=2}:std{access=file,mux=wav,dst=C:\User\Admin\Desktop\yourAudio.wav}"

The source MRL

The Media Resource Locator (MRL) is a string which tells VLC where to find the source content, e.g. the DVD or source file. For more on the MRL syntax, see VLC command-line help.

The MRL for a DVD, selecting only Title 3, Chapter 38, in Windows looks like: 

 dvdsimple:///F:\#3:38-3:38

A similar MRL for Mac OS X looks like: 

 dvdsimple:///dev/rdisk2/@3:38-3:38

An MRL could also be a filename, directory name, or a path to a file or directory name. 

 Video.TS///C:\Users\Admin\Desktop\yourVideo.mp4\#1:33-16:38

At the every end of the command line, put this special second MRL. It tells VLC to end its run without looking for another MRL to transcode. 

  vlc://quit

Specifying output format

Extracting audio in original format

If you want the extracted audio in the same format as it is stored in the input, then VLC can provide it to you with no loss of quality, because there is no re-encoding of the content.

The way to do this for AC3 format audio from a DVD video is (on Linux): 

vlc --no-sout-video dvdsimple:///dev/scd0@1:1 :sout='#std{access=file,mux=raw,dst=./file.ac3}'

Note: :sout means that the option sout applies only to the preceding stream, not to the whole command line. See VLC command-line help.

Extracting audio in FLAC format

This is an example of a Windows command which extracts in FLAC format. 

"c:\Program Files\VideoLAN\VLC\vlc.exe" -I dummy --no-sout-video --sout-audio
--no-sout-rtp-sap --no-sout-standard-sap --ttl=1 --sout-keep 
--sout "#transcode{acodec=flac}:std{mux=raw,dst=C:\User\Admin\Desktop\yourAudio.flac}" 
Video.TS:///C:\User\Admin\Desktop\yourVideo.mp4\#0:01-3:38 vlc://quit

Notice the changes:

acodec=flac
tells VLC to convert audio content using the FLAC codec
mux=raw
uses a raw file structure instead of the WAV file structure
File extension .flac
The file extension is FLAC for FLAC-format content.

Extracting audio in MP3 format

TODO!

Extracting audio in WAV format

This is an example of a Windows command line which extracts the audio content of an arbitrary file, to a WAV audio file. "C:\User\Admin\Desktop\yourAudio.wav" is the destination of your file, and "C:\User\Admin\Desktop\yourVideo.mp4\#0:01-3:38" is the location of your original video, followed by arbitrary starting and ending times.

The example has line breaks for clarity, but your command should all be on one line: 

"c:\Program Files\VideoLAN\VLC\vlc.exe" -I dummy --no-sout-video --sout-audio
--no-sout-rtp-sap --no-sout-standard-sap --ttl=1 --sout-keep 
--sout "#transcode{acodec=s16l,channels=2}:std{access=file,mux=wav,dst=C:\User\Admin\Desktop\yourAudio.wav}" 
Video.TS:///C:\User\Admin\Desktop\yourVideo.mp4\#0:01-3:38 vlc://quit

The parameter acodec=s16l tells VLC to use convert the audio content using the s16l codec, which is the codec for WAV format audio. Parameter mux=wav tells VLC to write the s16l audio data into a file with the WAV structure. The file path starts with "\\\\", because each pair "\\" is converted to a single "\" by the command line environment, giving a server path of \\Server\Qmultimedia. The file extension is ".wav" for WAV format files.

Scripting extraction of multiple chapters using a batch file

The above example command lines caused VLC to extract audio for a single Chapter of a single Title into a single audio file. It is possible on Windows, Mac OS X, and Linux command lines to write a script that loops through the Chapters of a Title and calls VLC for each one. Such a script can run unnattended for the tens of minutes it might take to extract a couple of hours of audio content, in dozens of tracks.

Here is a windows batch file which scripts VLC to extract all Chapters from a Title to a set of files in a directory on a Windows server. The first five lines, each beginning set, define parameters. The final line, beginning for /L, performs the loop and invokes VLC. The Windows batch file processor replaces parameter names surrounded by percent characters, e.g. %DestPrefix%, by their values. 

set DVDDrive=F:
set DestPrefix=\\\\Server\Qmultimedia\Music\wav_files\audio
set Title=3
set FirstChapter=1
set LastChapter=38

rem the following has line breaks for legibility. Remove them so it's all on one line.
for /L %%i in (%FirstChapter%,1,%LastChapter%) do "c:\Program Files\VideoLAN\VLC\vlc.exe" 
  -I dummy --no-sout-video --sout-audio --no-sout-rtp-sap --no-sout-standard-sap --ttl=1 
  --sout-keep --sout "#transcode{acodec=s16l,channels=2}:std{access=file,mux=wav,dst=%DestPrefix%_c%%i.wav}"
   dvdsimple:///%DVDDrive%\#%Title%:%%i-%Title%:%%i vlc://quit

To use this script, copy its contents into a file, say with a name riploop.bat'. Be sure the final line, beginning with for /L and ending with vlc://quit, is all on a single line; remove the line breaks which were inserted for legibility on this page. Then type in a Windows command line window, connect to the directory with the script file, and type riploop.bat to run it. VLC will pop up a new command line window for each invocation of VLC.

See Also

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