source: trunk/third/esound/TIPS @ 15363

Playing back "other" sound formats:
-----------------------------------

The esdplay utility can be used to play a variety of audio files.
However, it can't play everything.  The sox utility understands
many more types of audio files.

The sound utility, sox, can be used with esd in primarily two ways.

Method 1:  use sox to convert the file format ahead of time.
Method 2:  use sox to generate output on stdout, and pipe into esdcat

For accurate playback using either method, be sure to match the 
audio format (size/signedness of data, number of channels, and 
sample rate) between sox and esd.  Converting mono to stereo, or
changing the sampling rate with sox is probably not necessary for
live playback, as it will have little effect on sound quality, 
and merely chew up additional CPU.  For example to play back a sample
that was recorded in Sun audio format (.au), mono, at 8000 Hz, using
esdcat, type the following:

sox sample.au -c 1 -r 8000 -t ub - | esdcat -b -m -r 8000

sox arguments:  -t ub   = data type unsigned byte
                -c 1    = mono
                -r 8000 = sample rate 8000 Hz
                -       = output file

esdcat arguments: -b    = data type unsigned byte
                -m      = mono
                -r 8000 = sample rate 8000 Hz

Currently, esd only supports unsigned byte, and signed word data types.


Playing back mp3 files:
-----------------------
From Wayne Johnson,
mpg123 -s sample.mp3 | esdcat

NOTE: recent versions of mpg123 support esd directly.
Type "make" to see possible executable varieties.


Checking recording capabilities:
--------------------------------

To make sure the recoding works, try this WITHOUT esd running:

dd bs=8k count=4 </dev/audio > sample.au


Cthugha - An Oscilloscope on Acid
---------------------------------

version 1.2:

    esd
    xcthugha --listen
    esdmon > /tmp/cthugha.com

NOTE: xcthugha may complain about:
Can't open `/dev/dsp' for writing. (16 - Device or resource busy)
No problem, keep on truckin'. esd gets the sound device, and 
cthugha gets the data it needs.

version 1.3:

    mkfifo /tmp/cthugha.esd 
    xcthugha --play /tmp/cthugha.esd --silent &
    esdmon > /tmp/cthugha.esd

ESD auto spawning:
------------------

libesd will automaticall spawn esd if it's not available when an esd using
application opens a connection to esd. By default the command issued is:
esd -terminate -nobeeps -as 2
BUT
if you wish to use different options, you can set the 
ESD_SPAWN_OPTIONS
environment variable that will contain the options passed to esd.
for example - if I:
export ESD_SPAWN_OPTIONS="-terminate -nobeeps"
esd is run with:
esd -terminate -nobeeps

if you set the environment variable (contents are irrelevant) called
ESD_NO_SPAWN
libesd will not attempt to spawn esd. and simply fail to connect.

You can also put these settings in $(sysconfdir)/esd.conf, or ~/.esd.conf.
See $(sysconfdir)/esd.conf for an example of how to make the config file.