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.\" groff -man -Tascii opusenc.1
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.TH opusenc 1 2012-08-31 "Xiph.Org Foundation" "opus-tools"

.SH NAME
opusenc \- encode audio into the Opus format

.SH SYNOPSIS
.B opusenc
[
.B -h
] [
.B -V
] [
.B --help-picture
] [
.B --quiet
] [
.B --bitrate
.I kbit/s
] [
.B --vbr
] [
.B --cvbr
] [
.B --hard-cbr
] [
.B --music
] [
.B --speech
] [
.B --comp
.I complexity
] [
.B --framesize
.I 2.5, 5, 10, 20, 40, 60
] [
.B --expect-loss
.I pct
] [
.B --downmix-mono
] [
.B --downmix-stereo
] [
.B --no-phase-inv
] [
.B --max-delay
.I ms
] [
.B --title
.I 'track title'
] [
.B --artist
.I author
] [
.B --album
.I 'album title'
] [
.B --tracknumber
.I 'track number'
] [
.B --genre
.I genre
] [
.B --date
.I YYYY-MM-DD
] [
.B --comment
.I tag=value
] [
.B --picture
.IB filename | specification
] [
.B --padding
.I n
] [
.B --discard-comments
] [
.B --discard-pictures
] [
.B --raw
] [
.B --raw-bits
.I bits/sample
] [
.B --raw-rate
.I Hz
] [
.B --raw-chan
.I N
] [
.B --raw-endianness
.I flag
] [
.B --ignorelength
] [
.B --serial
.I serial number
] [
.B --save-range
.I file
] [
.B --set-ctl-int
.I ctl=value
]
.I input.wav
.I output.opus

.SH DESCRIPTION
.B opusenc
reads audio data in Wave, AIFF, FLAC, Ogg/FLAC,
or raw PCM format and encodes it into an Ogg
Opus stream. If the input file is "-" audio data is read from stdin.
Likewise, if the output file is "-" the Ogg Opus stream is written to stdout.

Unless quieted
.B opusenc
displays fancy statistics about the encoding progress.

.SH OPTIONS
.SS "General options"
.IP "-h, --help"
Show command help
.IP "-V, --version"
Show the version number
.IP "--help-picture"
Show help on attaching album art
.IP "--quiet"
Enable quiet mode. No messages are displayed.

.SS "Encoding options"
.IP "--bitrate N.nnn"
Set target bitrate in kbit/s (6-256 per channel)

In VBR mode this specifies the average rate for a large and diverse
collection of audio. In CVBR and Hard-CBR mode it specifies the specific
output bitrate.

The default for input with a sample rate of 44.1 kHz or higher is
64 kbit/s per mono stream and 96 kbit/s per coupled pair.
.IP "--vbr"
Use variable bitrate encoding (default)

In VBR mode the bitrate may go up and down freely depending on the content
to achieve more consistent quality.
.IP "--cvbr"
Use constrained variable bitrate encoding.

Outputs to a specific bitrate. This mode is analogous to CBR in AAC/MP3
encoders and managed mode in Vorbis coders. This delivers less consistent
quality than VBR mode but consistent bitrate.
.IP "--hard-cbr"
Use hard constant bitrate encoding.

With hard-cbr every frame will be exactly the same size, similar to how
speech codecs work. This delivers lower overall quality but is useful
where bitrate changes might leak data in encrypted channels or on
synchronous transports.
.IP "--music"
Override automatic detection and tune low bitrate encoding for music.
By default, music is detected automatically and the classification
may vary over time.

Tuning impacts lower bitrates that involve tradeoffs between speech
clarity and musical accuracy, and has no impact at bitrates typically
used for high quality music encoding.
.IP "--speech"
Override automatic detection and tune low bitrate encoding for speech.
By default, speech is detected automatically and the classification
may vary over time.

Tuning impacts lower bitrates that involve tradeoffs between speech
clarity and musical accuracy, and has no impact at bitrates typically
used for high quality music encoding.
.IP "--comp N"
Set encoding computational complexity (0-10, default: 10). Zero gives the
fastest encodes but lower quality, while 10 gives the highest quality
but slower encoding.
.IP "--framesize N"
Set maximum frame size in milliseconds (2.5, 5, 10, 20, 40, 60, default: 20)
.br
Smaller framesizes achieve lower latency but less quality at a given
bitrate.
.br
Sizes greater than 20ms are only interesting at fairly low
bitrates.
.IP "--expect-loss N"
Set expected packet loss in percent (default: 0)
.IP "--downmix-mono"
Downmix to mono
.IP "--downmix-stereo"
Downmix to stereo (if >2 channels input)
.IP "--no-phase-inv"
Disable use of phase inversion for intensity stereo. This trades some
stereo quality for a higher quality mono downmix, and is useful when
encoding stereo audio that is likely to be downmixed to mono after decoding.
.IP "--max-delay N"
Set maximum container delay in milliseconds (0-1000, default: 1000)

.SS "Metadata options"
.IP "--title title"
Set the track title comment field to
.I title
.IP "--artist artist"
Set the artist comment field to
.I artist.
This may be used multiple times to list contributing artists individually.
Note that some playback software does not display multiple artists gracefully.
.IP "--album album"
Set the album or collection title field to
.I album
.IP "--tracknumber N"
Set the track number comment field to
.I N
.IP "--date YYYY-MM-DD"
Set the date comment field to
.I YYYY-MM-DD.
This may be shortened to YYYY-MM or YYYY.
.IP "--genre genre"
Set the genre comment field to
.I genre.
This option may be specified multiple times to tag a track with
multiple overlapping genres.
.IP "--comment tag=value"
Add an extra comment.  This may be used multiple times.  The argument
should be in the form "tag=value".
See the vorbis-comment specification for well known tag names:
https://www.xiph.org/vorbis/doc/v-comment.html
.IP "--picture filename|specification"
Attach album art for the track.

Either a
.I filename
for the artwork or a more complete
.I specification
form can be used.
The picture is added to a
.B METADATA_BLOCK_PICTURE
comment field similar to what is used in
.SM FLAC.
The
.I specification
is a string whose parts are separated by | (pipe) characters.
Some parts may be left empty to invoke default values.
Passing a plain filename is just shorthand for the "||||filename"
specification.

The format of
.I specification
is [\fBtype\fR]|[\fBmedia-type\fR]|[\fBdescription\fR]|[\fBwidth\fRx\fBheight\fRx\fBdepth\fR[/\fBcolors\fR]]|\fBfilename\fR

.I type
is an optional number describing the nature of the picture.
Defined values are from one of:

  0: Other
.br
  1: 32x32 pixel 'file icon' (PNG only)
.br
  2: Other file icon
.br
  3: Cover (front)
.br
  4: Cover (back)
.br
  5: Leaflet page
.br
  6: Media (e.g., label side of a CD)
.br
  7: Lead artist/lead performer/soloist
.br
  8: Artist/performer
.br
  9: Conductor
.br
 10: Band/Orchestra
.br
 11: Composer
.br
 12: Lyricist/text writer
.br
 13: Recording location
.br
 14: During recording
.br
 15: During performance
.br
 16: Movie/video screen capture
.br
 17: A bright colored fish
.br
 18: Illustration
.br
 19: Band/artist logotype
.br
 20: Publisher/studio logotype

The default is 3 (front cover).
More than one --picture option can be specified to attach multiple pictures.
There may only be one picture each of type 1 and 2 in a file.

.I media-type
is optional and is now ignored.

.I description
is optional. The default is an empty string.

The next part specifies the resolution and color information, but
is now ignored.

.I filename
is the path to the picture file to be imported.

.IP "--padding n"
Reserve
.I n
extra bytes for metadata tags. This can make later tag editing more
efficient. Defaults to 512.
.IP "--discard-comments"
Don't propagate metadata tags from the input file.
.IP "--discard-pictures"
Don't propagate pictures or art from the input file.

.SS "Input options"
.IP "--raw"
Interpret input as raw PCM data without headers
.IP "--raw-bits N"
Set bits/sample for raw input (default: 16)
.IP "--raw-rate N"
Set sampling rate for raw input (default: 48000)
.IP "--raw-chan N"
Set number of channels for raw input (default: 2)
.IP "--raw-endianness [0/1]"
Set the endianness for raw input: 1 for big endian, 0 for little (default: 0)
.IP "--ignorelength"
Ignore the data length in Wave headers. Opusenc automatically ignores
the length when its implausible (very small or very large) but some STDIN
usage may still need this option to avoid truncation.

.SS "Diagnostic options"
.IP "--serial n"
Force use of a specific stream serial number, rather than one that is randomly generated.
This is used to make the encoder deterministic for testing and is not generally recommended.
.IP "--save-range file"
Save check values for every frame to a file
.IP "--set-ctl-int x=y"
Pass the encoder control x with value y (advanced).
Preface with s: to direct the ctl to multistream s
.br
This may be used multiple times

.SH EXAMPLES

Simplest usage. Take input as input.wav and produce output as output.opus:
.RS
opusenc input.wav output.opus
.RE
.PP

Produce a very high quality encode with a target rate of 160 kbit/s:
.RS
opusenc --bitrate 160 input.wav output.opus
.RE
.PP

Record and send a live stream to an Icecast HTTP streaming server using oggfwd:
.RS
arecord -c 2 -r 48000 -twav - | opusenc --bitrate 96 -  - | oggfwd icecast.somewhere.org 8000 password /stream.opus
.RE
.PP

.SH NOTES

While it is possible to use opusenc for low latency streaming (e.g. with --max-delay set to 0
and netcat instead of Icecast) it's not really designed for this, and the Ogg container
and TCP transport aren't the best tools for that application. Shell
pipelines themselves will often have high buffering. The ability to set
framesizes as low as 2.5 ms in opusenc mostly exists to try out the quality
of the format with low latency settings, but not really for actual low
latency usage.
.br
Interactive usage should use UDP/RTP directly.

.SH AUTHORS
.br
Gregory Maxwell <greg@xiph.org>

.SH SEE ALSO
.BR opusdec (1),
.BR opusinfo (1),
.BR oggfwd (1)