Computer Audio Hints and Instructions
This collection of hints and tips for using computers to record
and process audio, mainly derived from the audacity-help mailing
list, archived here.
Most of it was written by me, but draws on the contributions of
many of the audacity developers, and the users who first asked the
questions.
or
How Do I Hear the other Tracks whilst I Record a New one?
Under File > Preferences, on the Audio I/O tab, check the box
"Play other tracks whilst Recording". This will play the current
project tracks whilst the new track is being recorded.
In order for audacity to use the LAME encoder, it needs to know
what the path to it is.
- In the dialogue where it says the file is
not found, there should also be a button to click to locate the
library, so that audacity can open it. This only needs to be done
once, and then will work each time you use the mp3 export.
- Alternatively, go to File > Preferences > File Formats and
click on the 'Find Library' button in the bottom right hand corner,
and browse to the location where the LAME file is located.
MP3 exporting will then be available.
We do not host or develop the LAME library. It's home
page for development is at lame.sourceforge.net but does
not host runnable programs, only source code. This is for patent reasons.
There are numerous
places hosting compiled binaries (programs) including the
lame_enc.dll or LameLib you need:
- A listing for windows is here.
- Mac users can find the .sit file here
- Linux users may well find LAME is available through their distribution's
package management system (Portage, Apt-get, RPM). If not, get the source from
here
and compile it. This should be straightforward.
Any of these means should produce the shared encoder library,
which you can extract and then use with audacity.
Windows
- Download the the archive file from the site above, and open it in a utility like
winzip, 7-zip,
or some versions of Windows Explorer
- Take the lameenc.dll file and extract (uncompress) it to a
directory on you hard drive.
The directory where you installed Audacity would be a good idea.
This is probably C:\Program Files\Audacity or similar if you used the installer
- Open Audacity and go to File > Preferences.
- Go to the 'File Formats' tab.
- In the bottom of the window there is a section tabled 'MP3
Export Setup'.
- Click on the link tabled 'Find Library'
- This will ask you if you want to locate the lame encoder. Click
'yes'.
- In the dialogue box, go to the folder where you put the
lame-enc.dll file earlier, and select it.
- Click OK.
- You should now be able to export files to the mp3
format.
Mac (OS X and OS 9)
- Download the the .sit file from the site above, and open it in
Stuffit Expander
- Take the LibLame.so file and extract (uncompress) it to a
directory on you hard drive.
The directory in Applications where you installed Audacity would
be a good idea.
- Open Audacity and go to File > Preferences.
- Go to the 'File Formats' tab.
- In the bottom of the window there is a section tabled 'MP3
Export Setup'.
- Click on the link tabled 'Find Library'
- This will ask you if you want to locate the lame encoder. Click
'yes'.
- In the dialogue box, go to the folder where you put the
LibLame.so file earlier, and select it.
- Click OK.
- You should now be able to export files to the mp3
format.
The Sockets on most PCs are as follows:
- The headphone sockets on the front of CD or DVD drives are
only usable to play audio CDs in
those drives, so are not avalible to any programs running on the
computer. Ignore them whilst using audacity.
- The Green (officially 'lime') colored socket is line output, to
feed to an amplifier, Hi-Fi or powered speakers.
- The Blue socket is Line input, to take signals from Hi-Fi or other
audio equipment and feed it in to the PC.
- The Red socket is Microphone In, or Mic In, which is normally used
to record sounds using a microphone. The output from a microphone
is much weaker than a line signal, hence a separate input circuit
and socket are needed.
Trying to feed a signal from the headphone or line output of some other
piece of equipment into the microphone input is unlikely to work, as the
level is too high and will cause distortion.
or
Input selector is greyed out
If you are running Audacity version 1.2, and don't have a drop-down
list on your tool bar to choose which input to use, then your sound
card doesn't let you select the input source from within a
program. In these cases Audacity doesn't display the control, or
shows it greyed out.
In this case you may need to select the correct input source using
your system volume control (Windows Volume Control etc).
This is very common with built in sound on Apple iBooks and the
like. In these cases the single input is automatically selected and
no list is displayed.
If you have multiple sound devices (e.g. built in sound and an
external USB adaptor) then to switch between them you will need to
either go to File > Preferences and select it on the Devices
tab, or set the device as the default recording device in the
computer settings (Windows control panel, OS X Sound and Midi
Preferences).
If you experience dropouts or other problems whilst recording,
try the following steps:
- Close all other programs while
recording. Be aware of background virus scanners and other system
tray programs. Norton, Sophos and other anti-virus products scan each file as it is opened
and closed by default. On a slow computer this scanning can affect recording as it takes too
long.
- Reduce the recording bit depth to 16 bit from 32 bit (the default). This is set under File >
Preferences on the Quality tab. Reducing the bit depth halves the amount of data stored and
the time taken to write it to the disk.
- Turn off "Auto-scroll while playing".
This stops the display re-drawing as the recording is made. Stoping this reduces the amount of
processing the display uses, freeing power for recording.
This is set under File > Preferences on the Interface tab.
- Upgrade to version 1.2 (especially on OSX / linux) as this has a better recording interface
than 1.0.0
- Defragment your hard drive (only affects Windows (and Mac?) users). This increases the speed
your computer can read and write information at by ensuring that files are kept close together in a
logical manner.
- Make sure DMA mode is enabled for your hard drive.
- Update your hardware drivers to avoid conflicts and get better hardware performance.
Key targets are:
- Sound Card. This is also a common cause of crashes, especially during
recording
- Video (Display) Card
- Hard Drive controller - This is especially important for RAID and other
high performance controllers.
DMA mode is a method of increasing the rate of data reading and
writing from the hard drive, and reducing the amount of processing
power needed to do so. On a modern system it can increase speed by 10-fold or more.
Windows
DMA should be on on almost all modern Windows systems by
default, and will cause problems if not. Some Windows NT and 98
systems may not work with DMA on, particularly for CD drives.
Consult your hardware driver documentation.See Here for
instructions on enabling it.Mac
Should not need intervention on this front. Hardware is very closely
supported by the OS.Linux
Linux supports DMA but it is off be default in many distributions.
You may need to use hdparm (as root) to enable it. It can then
be added to your initialisation scripts to be done at boot up.
- Go to Control Panel > System > Hardware > Device Manager >
IDE ATA/ATAPI controllers.
- Look under Advanced Settings on each channel, and make sure that all disk drives are
set to DMA mode, not PIO mode (unused slots and some old CD-roms may show as PIO).
- For the controller with the offending disk on it:
- Right click, then go to driver.
- Click Uninstall
- Reboot your system
- If the add new hardware wizard does not run, click Add Hardware in the
control pannel
- Install the driver Windows prompts you to
- PIO mode is now replaced with Ultra DMA mode
A lot of linux systems with generic (non-tuned) kernels run without DMA,
and suffer a big performance hit.
- Running (as root)
# hdparm /dev/hda
will give you a list of what mode your hard disk / controller is
in. If you have multiple drives, you will need to use the appropriate
last letter (hdb for 2nd drive, etc).
- My system gives me:
/dev/hda:
multcount = 32 (on)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 4095/16/63, sectors = 4127760, start = 0
- The key line is
using_dma = 1 (on)
which tells me I'm using dma mode on this drive. If you get
using_dma = 0 (off)
then you aren't using DMA.
- On any vaguly modern system, with the exception of a few bugged systems, you will
get faster I/O with it enabled.
- To try and enable dma, do
# hdparm -d1 /dev/hda
to turn on dma mode.
If this gives a "not permitted" error, then you may have to go further into IDE
controller support, (probably in the kernel) but this is a first starting point.
For more information see some of the many articles on the web, e.g.
this one.
- You will get distortion if the output level tries to exceed the maximum value the program
can handle (displayed as the top of the track waveform by default). This corresponds to the top of
the output (left hand) VU meters in Audacity 1.2.2 and newer.
- If you have several tracks then what matters is the sum of all the amplitudes, so you will
need to turn individual tracks down (with the volume fader on the left hand end of each
track) so the sum does not execeed the avaliable range.
- Most effects will raise the recorded level, at least in places, so if the recording is at
maximum already you will get distortion. Try lowering the record level when recording, or use
amplify with a negative amplification to reduce the level before processing.
- Don't amplifiy tracks too much early in processing as you may cause clipping later
In theory it should not be necessary to use the system volume mixer when working with
Audacity as audacity has recording and playback controls built in. However if you are having
difficulties or need to do something more complicated, these instructions may be of use.
- Click on Start > All Programs > Accessories > Entertainment >
Volume Control. This will launch the windows volume control panel
(possibly labeled 'Master Volume').
- To be able to hear what you are recording, turn up the fader for the input you are
recording, and turn others down. If you want to play back previous tracks during recording,
make sure the "wave out" or "PCM" fader is also up.
- On the 'Options' menu click on properties.
- In the box which appears, click on the entry marked 'Recording'.
- This tells the software we are setting up to record audio, rather than
play it back.
- Click 'OK' to accept the setting.
- The window title will change to read 'Recording Control'.
- Look for the column marked for the input you are trying to record.
- Click on the 'select' box at the bottom of that column to set it as
the source for recording from.
- The next step is to record. Simply press the Record button in Audacity.
Press Stop when you are done.
- To save the results as a sound file use the Export commands on the
File Menu. To save the audacity project, use File > Save Project As.
