README
1== Opus audio codec ==
2
3Opus is a codec for interactive speech and audio transmission over the Internet.
4
5 Opus can handle a wide range of interactive audio applications, including
6Voice over IP, videoconferencing, in-game chat, and even remote live music
7performances. It can scale from low bit-rate narrowband speech to very high
8quality stereo music.
9
10 Opus, when coupled with an appropriate container format, is also suitable
11for non-realtime stored-file applications such as music distribution, game
12soundtracks, portable music players, jukeboxes, and other applications that
13have historically used high latency formats such as MP3, AAC, or Vorbis.
14
15 Opus is specified by IETF RFC 6716:
16 http://tools.ietf.org/html/rfc6716
17
18 The Opus format and this implementation of it are subject to the royalty-
19free patent and copyright licenses specified in the file COPYING.
20
21This package implements a shared library for encoding and decoding raw Opus
22bitstreams. Raw Opus bitstreams should be used over RTP according to
23 http://tools.ietf.org/html/draft-spittka-payload-rtp-opus
24
25The package also includes a number of test tools used for testing the
26correct operation of the library. The bitstreams read/written by these
27tools should not be used for Opus file distribution: They include
28additional debugging data and cannot support seeking.
29
30Opus stored in files should use the Ogg encapsulation for Opus which is
31described at:
32 http://wiki.xiph.org/OggOpus
33
34An opus-tools package is available which provides encoding and decoding of
35Ogg encapsulated Opus files and includes a number of useful features.
36
37Opus-tools can be found at:
38 https://git.xiph.org/?p=opus-tools.git
39or on the main Opus website:
40 http://opus-codec.org/
41
42== Compiling libopus ==
43
44To build from a distribution tarball, you only need to do the following:
45
46% ./configure
47% make
48
49To build from the git repository, the following steps are necessary:
50
511) Clone the repository:
52
53% git clone git://git.opus-codec.org/opus.git
54% cd opus
55
562) Compiling the source
57
58% ./autogen.sh
59% ./configure
60% make
61
623) Install the codec libraries (optional)
63
64% sudo make install
65
66Once you have compiled the codec, there will be a opus_demo executable
67in the top directory.
68
69Usage: opus_demo [-e] <application> <sampling rate (Hz)> <channels (1/2)>
70 <bits per second> [options] <input> <output>
71 opus_demo -d <sampling rate (Hz)> <channels (1/2)> [options]
72 <input> <output>
73
74mode: voip | audio | restricted-lowdelay
75options:
76 -e : only runs the encoder (output the bit-stream)
77 -d : only runs the decoder (reads the bit-stream as input)
78 -cbr : enable constant bitrate; default: variable bitrate
79 -cvbr : enable constrained variable bitrate; default:
80 unconstrained
81 -bandwidth <NB|MB|WB|SWB|FB>
82 : audio bandwidth (from narrowband to fullband);
83 default: sampling rate
84 -framesize <2.5|5|10|20|40|60>
85 : frame size in ms; default: 20
86 -max_payload <bytes>
87 : maximum payload size in bytes, default: 1024
88 -complexity <comp>
89 : complexity, 0 (lowest) ... 10 (highest); default: 10
90 -inbandfec : enable SILK inband FEC
91 -forcemono : force mono encoding, even for stereo input
92 -dtx : enable SILK DTX
93 -loss <perc> : simulate packet loss, in percent (0-100); default: 0
94
95input and output are little-endian signed 16-bit PCM files or opus
96bitstreams with simple opus_demo proprietary framing.
97
98== Testing ==
99
100This package includes a collection of automated unit and system tests
101which SHOULD be run after compiling the package especially the first
102time it is run on a new platform.
103
104To run the integrated tests:
105% make check
106
107There is also collection of standard test vectors which are not
108included in this package for size reasons but can be obtained from:
109http://opus-codec.org/testvectors/opus_testvectors.tar.gz
110
111To run compare the code to these test vectors:
112
113% curl -O http://opus-codec.org/testvectors/opus_testvectors.tar.gz
114% tar -zxf opus_testvectors.tar.gz
115% ./tests/run_vectors.sh ./ opus_testvectors 48000
116
117== Portability notes ==
118
119This implementation uses floating-point by default but can be compiled to
120use only fixed-point arithmetic by setting --enable-fixed-point (if using
121autoconf) or by defining the FIXED_POINT macro (if building manually).
122The fixed point implementation has somewhat lower audio quality and is
123slower on platforms with fast FPUs, it is normally only used in embedded
124environments.
125
126The implementation can be compiled with either a C89 or a C99 compiler.
127While it does not rely on any _undefined behavior_ as defined by C89 or
128C99, it relies on common _implementation-defined behavior_ for two's
129complement architectures:
130
131o Right shifts of negative values are consistent with two's
132 complement arithmetic, so that a>>b is equivalent to
133 floor(a/(2^b)),
134
135o For conversion to a signed integer of N bits, the value is reduced
136 modulo 2^N to be within range of the type,
137
138o The result of integer division of a negative value is truncated
139 towards zero, and
140
141o The compiler provides a 64-bit integer type (a C99 requirement
142 which is supported by most C89 compilers).
143
README.draft
1To build this source code, simply type:
2
3% make
4
5If this does not work, or if you want to change the default configuration
6(e.g., to compile for a fixed-point architecture), simply edit the options
7in the Makefile.
8
9An up-to-date implementation conforming to this standard is available in a
10Git repository at git://git.xiph.org/opus.git or on a website at:
11http://opus-codec.org/
12However, although that implementation is expected to remain conformant
13with the standard, it is the code in this RFC that shall remain normative.
14To build from the git repository instead of using this RFC, follow these
15steps:
16
171) Clone the repository (latest implementation of this standard at the time
18of publication)
19
20% git clone git://git.opus-codec.org/opus.git
21% cd opus
22
232) Compile
24
25% ./autogen.sh
26% ./configure
27% make
28
29Once you have compiled the codec, there will be a opus_demo executable in
30the top directory.
31
32Usage: opus_demo [-e] <application> <sampling rate (Hz)> <channels (1/2)>
33 <bits per second> [options] <input> <output>
34 opus_demo -d <sampling rate (Hz)> <channels (1/2)> [options]
35 <input> <output>
36
37mode: voip | audio | restricted-lowdelay
38options:
39-e : only runs the encoder (output the bit-stream)
40-d : only runs the decoder (reads the bit-stream as input)
41-cbr : enable constant bitrate; default: variable bitrate
42-cvbr : enable constrained variable bitrate; default: unconstrained
43-bandwidth <NB|MB|WB|SWB|FB> : audio bandwidth (from narrowband to fullband);
44 default: sampling rate
45-framesize <2.5|5|10|20|40|60> : frame size in ms; default: 20
46-max_payload <bytes> : maximum payload size in bytes, default: 1024
47-complexity <comp> : complexity, 0 (lowest) ... 10 (highest); default: 10
48-inbandfec : enable SILK inband FEC
49-forcemono : force mono encoding, even for stereo input
50-dtx : enable SILK DTX
51-loss <perc> : simulate packet loss, in percent (0-100); default: 0
52
53input and output are little endian signed 16-bit PCM files or opus bitstreams
54with simple opus_demo proprietary framing.
55