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The Opus audio codec looks like the best thing ever for compressing audio. It has recently become supported in the latest ffmpeg and VLC players. However, there is no documentation I can find on how to actually encode media with it. Can someone please direct me to said docs, preferably with specifics to ffmpeg flags and usage? I have a lot of audiobooks that are taking up far too much space and Opus looks like the perfect format to keep them in.

ffmpeg -i input -acodec libopus -b:a bitrate -vbr on -compression_level 10 output

The ffmpeg documentation has a list of options and descriptions for libopus.

Make sure you compiled ffmpeg with --enable-libopus!

1. Download Opus-tools




2. Encode:
   opusenc --bitrate 64 What_A_Feeling.wav What_A_Feeling_64.opus




3. Decode: (to play in any media player, useful if your media player does not support opus yet):
   opusdec What_A_Feeling_64.opus What_A_Feeling_opus64.wav

(What_A_Feeling is a song name)

Detailed options displayed when running opusenc by itself:

Usage: opusenc [options] input_file output_file.opus



Encodes input_file using Opus.

It can read the WAV, AIFF, FLAC, Ogg/FLAC, or raw files.



General options:

 -h, --help         This help

 -V, --version      Version information

 --quiet            Quiet mode



input_file can be:

  filename.wav      file

  -                 stdin



output_file can be:

  filename.opus     compressed file

  -                 stdout



Encoding options:

 --bitrate n.nnn    Target bitrate in kbit/sec (6-256/channel)

 --vbr              Use variable bitrate encoding (default)

 --cvbr             Use constrained variable bitrate encoding

 --hard-cbr         Use hard constant bitrate encoding

 --comp n           Encoding complexity (0-10, default: 10 (slowest))

 --framesize n      Maximum frame size in milliseconds

                      (2.5, 5, 10, 20, 40, 60, default: 20)

 --expect-loss      Percentage packet loss to expect (default: 0)

 --downmix-mono     Downmix to mono

 --downmix-stereo   Downmix to stereo (if >2 channels)

 --max-delay n      Maximum container delay in milliseconds

                      (0-1000, default: 1000)



Diagnostic options:

 --serial n         Forces a specific stream serial number

 --save-range file  Saves 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



Metadata options:

 --comment          Add the given string as an extra comment

                      This may be used multiple times

 --artist           Author of this track

 --title            Title for this track

 --album            Album or collection this track belongs to

 --date             Date for this track

 --genre            Genre for this track

 --picture          Album art for this track

                      More than one --picture option can be specified.

                      Either a FILENAME for the picture file or a more

                      complete SPECIFICATION form can be used. The

                      SPECIFICATION is a string whose parts are

                      separated by | (pipe) characters. Some parts may

                      be left empty to invoke default values. A

                      FILENAME is just shorthand for "||||FILENAME".

                      The format of SPECIFICATION is



                      [TYPE]|[MIME-TYPE]|[DESCRIPTION]|[WIDTHxHEIGHT

                      xDEPTH[/COLORS]]|FILENAME



                      TYPE is an optional number 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). There may only be

                      one picture each of type 1 and 2 in a file.



                      MIME-TYPE is optional. If left blank, it will be

                      detected from the file. For best compatibility

                      with players, use pictures with a MIME-TYPE of

                      image/jpeg or image/png. The MIME-TYPE can also

                      be --> to mean that FILENAME is actually a URL to

                      an image, though this use is discouraged. The

                      file at the URL will not be fetched. The URL

                      itself is stored in the metadata.



                      DESCRIPTION is optional. The default is an empty

                      string.



                      The next part specifies the resolution and color

                      information. If the MIME-TYPE is image/jpeg,

                      image/png, or image/gif, you can usually leave

                      this empty and they can be detected from the

                      file. Otherwise, you must specify the width in

                      pixels, height in pixels, and color depth in

                      bits-per-pixel. If the image has indexed colors

                      you should also specify the number of colors

                      used. If possible, these are checked against the

                      file for accuracy.



                      FILENAME is the path to the picture file to be

                      imported, or the URL if the MIME-TYPE is -->.

 --padding n        Extra bytes to reserve for metadata (default: 512)

 --discard-comments Don't keep metadata when transcoding

 --discard-pictures Don't keep pictures when transcoding



Input options:

 --raw              Raw input

 --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 n 1 for bigendian, 0 for little (defaults to 0)

 --ignorelength     Always ignore the datalength in Wave headers

The best Opus Codec commands in DOS/Windows Command would be:

For lib 1.3, smallest filesize (tape quality):

Opusenc a.wav a.opus --bitrate 24 --framesize 40 --discard-comments --discard-pictures

You will:

a- at 24kbits still have a 16kHz (32kHz stereo) sonic output, on a super small size. Any smaller, and Sonic output will drop to 11kHz

b- Increase framesize (save a few bits of data (about 6%), without perceivable loss in quality)

c- Discard unnecessary TAG info, and cover pictures that will only enlarge file size.

For lib 1.3, streaming (near CD quality) use '--bitrate 52' instead of '24'.

The default in 1.2 is 48kbits, but using 52 in 1.3, with 'framesize' set to 40, your file size is equal, but there are much less artifacts audible.

52 kbits with framesize 40, is arguably equal in quality to 160kbits MP3, at less than 1/3rd the size; while 48kbits on 1.2 equals 128kbits MP3, or only 2.5x smaller in size.

For near identical quality, you'll need between 80 to 96kbits. I hardly ever use this, as I want my audio as small as possible.

Over 96kbits, is only good for editing, and one can't audibly hear the difference between the original and the Opus encoded file.

That being said, I don't yet know how it all works in Linux.