The Opus audio codec looks like the best codec so far 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 to be the perfect format to keep them in.
ffmpeg -i <input> -c:a libopus -b:a bitrate <output>
The bitrate can be given like
-b:a 96K for 96 kBit/s.
The ffmpeg documentation has a list of options and descriptions for libopus. Here you can set
-vbr options or a different
Make sure you compiled ffmpeg with
opusenc --bitrate 64 What_A_Feeling.wav What_A_Feeling_64.opus
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
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.