AUDIO(1) AUDIO(1)
NAME
mp3dec, mp3enc, oggdec, oggenc, flacdec, flacenc, sundec,
wavdec, pcmconv, mixfs - decode and encode audio files
SYNOPSIS
audio/mp3dec [ -s seconds ] [ -d ]
audio/oggdec [ -s seconds ]
audio/flacdec [ -s seconds ]
audio/wavdec [ -s seconds ]
audio/sundec
audio/oggenc
audio/mp3enc [ -hprv ] [ -b bitrate ] [ -B bitrate ] [ -m
mode ] [ -q q ] [ -s sfreq ] [ -V q ] [ long or silly
options ]
audio/flacenc [ -i fmt ] [ -l compresslevel ] [ -P padding ]
[ -T field=value ]
audio/pcmconv [ -i fmt ] [ -o fmt ] [ -l length ]
audio/mixfs [ -D ] [ -s srvname ] [ -m mtpt ] [ /dev/audio ]
DESCRIPTION
These programs decode and encode various audio formats from
and to 16-bit stereo PCM (little endian). The decoders read
the compressed audio data from standard input and produce
PCM on standard output at a sampling frequency of 44.1KHz.
Mp3dec decodes MPEG audio (layer 1, 2 and 3). The -d option
enables debug output to standard error. Oggdec, flacdec,
sunwdec and wavdec are like mp3dec but decode OGG Vorbis,
FLAC lossless audio, Sun audio and RIFF wave.
Decoding options
-s seconds seek to a specific position in seconds before
decoding.
The encoders read PCM on standard input and produce
compressed audio on standard output.
Flacenc, oggenc and mp3enc produce FLAC, OGG Vorbis and MP3
audio. For mp3enc, the MP3 file will use `constant bit-rate'
(CBR) encoding by default, but that can be changed via --abr
(average bitrate desired, ABR) or -v (variable bitrate,
VBR).
Oggenc accept raw PCM in the same byte order as /dev/audio
(little-endian), while mp3enc -r expects big-endian.
Flacenc by default expects raw PCM in the same format as
/dev/audio, but also supports signed integer samples of bit
widths 4 to 32, either little- or big-endian, one to eight
channels and arbitrary samplerates, see -i option of
pcmconv.
Encoding options
-b set minimum allowed bitrate in Kb/s for VBR, default
32Kb/s. For CBR, set the exact bitrate in Kb/s, which
defaults to 128Kb/s.
-B set maximum allowed bitrate in Kb/s for VBR, default
256Kb/s.
-h same as `-q 2'.
-m mode may be (s)tereo, (j)oint, (f)orce or (m)ono
(default j). force forces mid/side stereo on all
frames.
-p add CRC error protection (adds an additional 16 bits
per frame to the stream). This seems to break play-
back.
-q sets output quality to q (see -V).
-r input is raw pcm
-s set sampling frequency of input file (in KHz) to sfreq,
default is 44.1.
-v use variable bitrate (VBR) encoding
-V set quality setting for VBR to q. Default q is 4; 0
produces highest-quality and largest files, and 9 pro-
duces lowest-quality and smallest files.
Long options
--abr bitrate sets average bitrate desired in Kb/s,
instead of setting quality, and generates
ABR encoding.
--resample sfreq set sampling frequency of output file (in
KHz) to sfreq, default is input sfreq.
--mp3input input is an MP3 file
Silly options
-f same as `-q 7'. Such a deal.
-o mark as non-original (i.e. do not set the original
bit)
-c mark as copyright
-k disable sfb=21 cutoff
-e emp de-emphasis n/5/c (default n)
-d allow channels to have different blocktypes
-t disable Xing VBR informational tag
-a autoconvert from stereo to mono file for mono
encoding
-x force byte-swapping of input (see dd(1) instead)
-S don't print progress report, VBR histograms
--athonly only use the ATH for masking
--nohist disable VBR histogram display
--voice experimental voice mode
Pcmconv is a helper program used to convert various PCM sam-
ple formats. The -i and -o options specify the input and
output format fmt of the conversion. Fmt is a concatenated
string of the following parts:
s# sample format is little-endian signed integer where #
specifies the number of bits
u# unsigned little-endian integer format
S# signed big-endian integer format
U# unsigned big-endian integer format
f# floating point format where # has to be 32 or 64 for
single- or double-precision
a8 8-bit a-law format
µ8 8-bit µ-law format
c# specifies the number of channels
r# gives the samplerate in Hz
The program reads samples from standard input converting the
data and writes the result to standard output until it
reached end of file or, if -l was given, a number of length
bytes have been consumed from input.
Mixfs is a fileserver serving a single audio file which
allows simultaneous playback of audio streams. When run, it
binds over /dev/audio and mixes the audio samples that are
written to it. A service name srvname can be given with the
-s option which gets posted to /srv. By default, mixfs
mounts itself on /mnt/mix and then binds /mnt/mix/audio and
/mnt/mix/volume over /dev. /dev/volume from the parent
namespace is proxied with an additional control "mix" which
is used to set the output volume of the mixer. Another
additional control "dev" can be used to switch between audio
devices. Mixfs will resample incoming audio to the format
of the audio device output if it does not match the default
(s16c2r44100). An alternative mountpoint mtpt can be speci-
fied with the -m option. The -D option causes 9p debug mes-
sages to be written to file-descriptor 2.
EXAMPLE
Play back an `.mp3'
audio/mp3dec <foo.mp3 >/dev/audio
Encode a `.wav' file as highest-quality MP3.
audio/mp3enc -q 0 -b 320 <foo.wav >foo.mp3
Create a fixed 128Kb/s MP3 file from a `.wav' file.
audio/mp3enc -h <foo.wav >foo.mp3
Streaming from stereo 44.1KHz raw PCM data, encoding mono at
16KHz (you may not need dd):
dd -conv swab | audio/mp3enc -a -r -m m --resample 16 -b 24
SOURCE
/sys/src/cmd/audio
SEE ALSO
play(1), zuke(1)
http://www.underbit.com/products/mad/
http://xiph.org/doc/
http://flac.sourceforge.net/documentation.html
HISTORY
Pcmconv first appeared in 9front (December, 2012). Mixfs
first appeared in 9front (December, 2013). Flacenc first
appeared in 9front (January, 2021).
REFORM(1) REFORM(1)
NAME
audio, pm, shortcuts - MNT Reform 2 support utilities
SYNOPSIS
reform/audio [ -1 ] [ -D ] [ -m mountpoint ] [ -s service ]
reform/pm [ -D ] [ -m mountpoint ] [ -s service ]
reform/shortcuts [ -l light_step ] [ -v vol_step ]
DESCRIPTION
These programs provide support for certain functions of MNT
Reform 2 computing device. Some of them also make control-
ling file systems available under /dev.
Audio
audio initializes the DAC (Digital-to-Analog Converter) on
the platform and provides a standard audio(3) interface to
control volume and other parameters. With -1 only the ini-
tialization is performed and the program exits immediately.
The following files are provided by the program:
audioctl
Shows the current status (on or off ) of the three
"outputs" - master, hp and spk. Each can be enabled,
disabled or toggled, by writing a single line to the
same file, consisting of the output name and the
desired action - on , off or toggle , accordingly.
DAC can be reinitialized by writing a single reset.
volume
Provides an interface for volume control (see
audio(3)). For ease of use, volume supports relative
adjustments by prefixing a number with a sign. master
+1, for example, will increase the volume on master by
1%, which is 0.5dB for this particular output. For hp
and spk one percent is 1dB.
Enhanced stereo separation can be enabled by writing
3d, followed by desired percentage of the effect.
Power and monitoring
pm presents a file system consisting of the following files:
battery
Returns attached battery array statistics in the same
manner as acpi(8).
cputemp
Exposes the current temperature reading of the CPU.
kbdoled
An uncompressed Plan 9 image can be written to the file
to display on the keyboard OLED. Zero-length write
clears the display.
light
Provides a way to control the backlight of the built-in
LCD by writing lcd [-+]N, kbd [-+]N, or tb N N N N N,
where N is expressed in percentage, either as an abso-
lute value (0-100) or relative to the current bright-
ness - by prefixing with a sign. For the trackball (tb)
only 0 and 1 are valid values. Reading light returns
the current brightness.
pmctl
Reading pmctl gives the System Controller firmware ver-
sion string, voltage (mV) of each cell and current(mA)
of the battery array.
Writing power off to pmctl will turn off all power
rails, which is what fshalt(8) does after halting the
file systems.
Shortcuts
shortcuts enables LCD brightness and audio volume adjustment
via keyboard shortcuts.
The program uses Rio's kbdtap to function:
reform/shortcuts </dev/kbdtap >/dev/kbdtap
Hyper+F1/F2 decreases/increases LCD brightness,
Hyper+F7/F8/F9 skips to the previous track, (un)pauses or
skips to the next track in zuke(1), Hyper+F10 (un)mutes the
audio, Hyper+F11/F12 decreases/increases "mix" volume, or
"master" if former isn't available. Optionally, a single
step amount can be set with -l for LCD light level (default
is 5) and -v for volume (default is 3). Values can be nega-
tive to essentially swap the decrement and increment keys.
SOURCE
/sys/src/cmd/reform
SEE ALSO
audio(3)
HISTORY
MNT Reform 2 support first appeared in 9front (August,
2022).
BUGS
Only 44100Hz (default) and 48000Hz sample rates are sup-
ported with audio, recording is not implemented.
Light was chosen as a shorter alternative to brightness.
Current keyboard light level reading is only an indication,
there is no way to get the actual value from the keyboard.
Values displayed in the battery file are not precise, cell
capacities are hardcoded in the System Controller firmware.
/plan9/man/1/