opusenc

Section: opus-tools (1)
Updated: 2012-08-31
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NAME

opusenc - encode audio into the Opus format

SYNOPSIS

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

DESCRIPTION

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 opusenc displays fancy statistics about the encoding progress.

OPTIONS

General options

-h, --help: Show command help
-V, --version: Show the version number
--help-picture: Show help on attaching album art
--quiet: Enable quiet mode. No messages are displayed.

Encoding options

--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.

--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.

--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.

--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.

--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.

--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.

--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.

--framesize N

Set maximum frame size in milliseconds (2.5, 5, 10, 20, 40, 60, default: 20)
Smaller framesizes achieve lower latency but less quality at a given bitrate.
Sizes greater than 20ms are only interesting at fairly low bitrates.

--expect-loss N

Set expected packet loss in percent (default: 0)

--downmix-mono

Downmix to mono

--downmix-stereo

Downmix to stereo (if >2 channels input)

--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.

--max-delay N

Set maximum container delay in milliseconds (0-1000, default: 1000)

Metadata options

--title title

Set the track title comment field to title

--artist artist

Set the artist comment field to artist. This may be used multiple times to list contributing artists individually. Note that some playback software does not display multiple artists gracefully.

--album album

Set the album or collection title field to album

--tracknumber N

Set the track number comment field to N

--date YYYY-MM-DD

Set the date comment field to YYYY-MM-DD. This may be shortened to YYYY-MM or YYYY.

--genre genre

Set the genre comment field to genre. This option may be specified multiple times to tag a track with multiple overlapping genres.

--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

--picture filename|specification

Attach album art for the track.

Either a filename for the artwork or a more complete specification form can be used. The picture is added to a METADATA_BLOCK_PICTURE comment field similar to what is used in FLAC. The 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 specification is [type]|[media-type]|[description]|[widthxheightxdepth[/colors]]|filename

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

  0: Other

  1: 32x32 pixel 'file icon' (PNG only)

  2: Other file icon

  3: Cover (front)

  4: Cover (back)

  5: Leaflet page

  6: Media (e.g., label side of a CD)

  7: Lead artist/lead performer/soloist

  8: Artist/performer

  9: Conductor

10: Band/Orchestra

11: Composer

12: Lyricist/text writer

13: Recording location

14: During recording

15: During performance

16: Movie/video screen capture

17: A bright colored fish

18: Illustration

19: Band/artist logotype

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.

media-type is optional and is now ignored.

description is optional. The default is an empty string.

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

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

--padding n

Reserve n extra bytes for metadata tags. This can make later tag editing more efficient. Defaults to 512.

--discard-comments

Don't propagate metadata tags from the input file.

--discard-pictures

Don't propagate pictures or art from the input file.

Input options

--raw: Interpret input as raw PCM data without headers
--raw-bits N: Set bits/sample for raw input (default: 16)
--raw-rate N: Set sampling rate for raw input (default: 48000)
--raw-chan N: Set number of channels for raw input (default: 2)
--raw-endianness [0/1]: Set the endianness for raw input: 1 for big endian, 0 for little (default: 0)
--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.

Diagnostic options

--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.
--save-range file: Save check values for every frame to a file
--set-ctl-int x=y: Pass the encoder control x with value y (advanced). Preface with s: to direct the ctl to multistream s
This may be used multiple times

EXAMPLES

Simplest usage. Take input as input.wav and produce output as output.opus:

: opusenc input.wav output.opus

Produce a very high quality encode with a target rate of 160 kbit/s:

: opusenc --bitrate 160 input.wav output.opus

Record and send a live stream to an Icecast HTTP streaming server using oggfwd:

: arecord -c 2 -r 48000 -twav - | opusenc --bitrate 96 - - | oggfwd icecast.somewhere.org 8000 password /stream.opus

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.
Interactive usage should use UDP/RTP directly.

AUTHORS

Gregory Maxwell <greg@xiph.org>