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Contents
What Is It?
Licensing
Audio Quality
Features
Development
Current Affairs
Meta-FAQ
What Is It?
- What is Ogg Vorbis?
- Ogg Vorbis is a new audio compression format. It is roughly
comparable to other formats used to store and play digital
music, such as MP3, VQF, AAC, and other digital audio formats.
It is different from these other formats because it is
completely free, open, and unpatented.
- What do all the names mean?
- Vorbis is the name for the specific audio compression scheme
used to create Ogg Vorbis files. It is part of the Ogg project,
which is a blanket project designed to create a fully open
multimedia system. Right now, Ogg Vorbis is the only functional
part of the Ogg project which is anywhere near completion.
- Where do the names come from? What
does the logo mean?
- Xiph.org has
a page
explaining the sources and meanings of the names and logos.
- What is the file extension for Ogg
Vorbis?
- Since it is part of the Ogg project, Vorbis files have the
extension .ogg.
- What is the MIME content
type for an Ogg Vorbis stream?
- application/x-ogg
- Does Vorbis completely
replace MP3, or is it just a complementary codec?
- Ogg Vorbis has been designed to completely replace all
proprietary, patented audio formats. That means that you can
encode all your music or audio content in Vorbis and never look
back.
- When will Ogg Vorbis be done?
- There are stable reference implementations available now,
and the file format has been finished for some time. A Vorbis
file created today will still be compatible with future decoders
for years to come. The format has been designed to be flexible,
so that the developers can continue to improve file size and
sound quality without "breaking" older encoders and players.
- I'm an artist. Why should I be
interested?
- There are a couple of reasons:
Although not all artists
realize it, MP3 is what is known as a "lossy" format. Thus, much
of the sound data is removed when MP3 files are created. This
results in a file with inferior sound quality to a CD. Vorbis is
also a "lossy" format, but uses superior acoustic models to
reduce the damage. Thus, music released in Vorbis will sound
better than a comparably sized MP3 file.
Also, artists should be concerned about licensing terms for
formats. If you decide to sell your music in MP3 format, you are
responsible for paying Fraunhofer a percentage of each sale
because you are using their patents. Vorbis is patent and
license-free, so you will never need to pay anyone in order to
sell, give away, or stream your own music.
- I'm a music fan. Why should I be
interested?
- For one, Vorbis provides a high-quality format for you to
listen to your music. For a given file size, Vorbis sounds
better than MP3, and is getting better as development continues.
Vorbis already enjoys widespread player support and should be
compatible with several major hardware players soon. With
Vorbis, you can listen to your music with higher quality in less
space. Also, using Vorbis means your player and encoder choices
aren't bound by licensing terms. Right now, you can only choose
from a few encoders to create your MP3 files, because most
companies won't or can't pay the licensing terms for encoders.
Using Vorbis lets you choose from a wide variety of encoders.
- I'm a developer. Why should I be
interested?
- If you develop hardware or software audio players, you
cannot distribute your work without being affected by
proprietary audio patent licensing terms. With Vorbis, you can
create hardware or software products to encode or decode music
files without restrictions, royalty payments, or limits on
distribution. Vorbis also provides a flexible, high-quality
format that is of great interest to all the audio geeks out
there. For more developer information, please refer to our
developer
site.
- I run a music company. Why
should I be interested?
- Music companies should be very interested in the Ogg Vorbis
format. Other technologies require large financial investments
to get started, but Vorbis offers a unique platform that is
easily reachable for growing companies and a money saver for
established businesses. Because of its wide player support and
its open nature, your customers and clients will not be plagued
by incompatibilities and they will appreciate the higher sound
quality as well.
Back to Top
Licensing
- What licensing applies to the Ogg
Vorbis format?
- The Ogg Vorbis specification is in the public domain. It is
completely free for commercial or noncommercial use. That means
that commercial developers may independently write Ogg Vorbis
software which is compatible with the specification for no
charge and without restrictions of any kind. However, developers
that wish to use the open source software we have written must
adhere to certain rules.
- What licensing applies to the
included Ogg Vorbis software?
- The bundled Ogg Vorbis utility software is released under
the terms of the GNU GPL, or GNU General Public License. The
details can be found at
www.gnu.org.
The libraries and SDKs are released under the
more business-friendly BSD license. Please note that developers
are still free to use the specification to independently write
closed-source implementations of Ogg Vorbis which are not bound
by these licenses.
- We make commercial, closed source
software. Can I use Ogg Vorbis at all? What licensing do I need
to pay?
- Again, there are no licensing fees for ANY use of the Ogg
Vorbis specification. As a commercial developer, you are free to
create and sell (or give away) open or closed source
implementations of Vorbis encoders, decoders, or other tools.
However, if you use our software rather than writing an
independent implementation, you must respect the terms of the
license. Our libraries (available under the BSD license) can be
used whole or in part by closed source applications.
- Are there licensing fees for
distributing, selling, or streaming media in the Ogg Vorbis
format like there are in other formats, such as MP3?
- No.
- If there aren't any licensing
fees, how are you going to make money off the format? Will you
charge fees later, after Vorbis becomes popular?
- The benefits of a patent-free, license-free format outweigh
the concerns of making money directly from the format. The
Vorbis format will always be free and in the public domain.
Xiph.org is investigating a variety of models for funding
development, some of which may include licensing non-free
Vorbis-related programs and libraries to commercial projects.
One example of this is Tremor, the fixed-point decoder for
embedded systems. Nevertheless, the reference encoder and
decoder will always be open source and third parties will always
be free to modify or reimplement them.
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Audio Quality
- I've heard that Vorbis is a "lossy"
codec. What does this mean?
- There are two broad classes of compression algorithms:
lossless and lossy. Lossless compression algorithms produce
compressed data that can be decoded to output that is identical
to the original. Zip is a very common example of a lossless
compression format. FLAC
is a lossless compression format that is specifically designed
for audio.
The other type of compression algorithm is called lossy.
This form of compression is very popular with multimedia data,
like pictures, movies, and sound. Since these types of
information are perceived by humans with imperfect senses, the
original data does not have to be reproduced exactly. Some of
the information in the original file can actually be discarded
because we wouldn't notice it even if it was there. Lossy codecs
can achieve much higher compression than lossless codecs by
intelligently discarding unneeded information. In most cases,
some loss of quality can be tolerated, so even more data can be
discarded, further increasing compression. MP3, RealAudio, and
Vorbis all use lossy audio compression. This means that a Vorbis
file, for example, will decode to a WAV file that is different
than the original. The differences may or may not be noticable,
depending upon the quality selected during compression.
- Does Ogg Vorbis sound better
than MP3?
- Yes, definitely. Naturally, we invite you to judge this for
yourself.
- Will Ogg Vorbis audio
quality improve?
- Yes. Vorbis has a flexible format which allows significant
tuning of sound quality and training of the algorithms even
after the file format is frozen. Vorbis sounds very good today,
and will continue to sound better every day.
- Why is Ogg Vorbis better than
the other "New MP3" codecs that are available?
- Vorbis sounds better. Vorbis is open, so you're free to use
it on your favorite platform. Vorbis doesn't have intellectual
property restrictions to get in the way. And Vorbis doesn't just
try to sound better, it tries to do things fundamentally better
in all the ways that it can.
- Can I convert my MP3
collection to the Ogg Vorbis format?
- You can convert any audio format to Ogg Vorbis. However,
converting from one lossy format, like MP3, to another lossy
format, like Vorbis, is generally a bad idea. Both MP3 and
Vorbis encoders achieve high compression ratios by throwing away
parts of the audio waveform that you probably won't hear.
However, the MP3 and Vorbis codecs are very different, so they
each will throw away different parts of the audio, although
there certainly is some overlap. Converting a MP3 to Vorbis
involves decoding the MP3 file back to an uncompressed format,
like WAV, and recompressing it using the Ogg Vorbis encoder. The
decoded MP3 will be missing the parts of the original audio that
the MP3 encoder chose to discard. The Ogg Vorbis encoder will
then discard other audio components when it compresses the data.
At best, the result will be an Ogg file that sounds the same as
your original MP3, but it is most likely that the resulting file
will sound worse than your original MP3. In no case will you get
a file that sounds better than the original MP3.
Since many
music players can play both MP3 and Ogg files, there is
no reason that you should have to switch all of your files to
one format or the other. If you like Ogg Vorbis, then we would
encourage you to use it when you encode from original, lossless
audio sources (like CDs). When encoding from originals, you will
find that you can make Ogg files that are both smaller and
better quality than MP3.
(If you must absolutely must convert from MP3 to Ogg, there
are several conversion scripts available on
Freshmeat.)
- You're claiming that Vorbis has
great audio quality. Have you done any listening tests to back
this up?
- Over the last few public beta and prereleases, we've fixed
many of the outstanding bugs that affected audio quality. After
the 1.0 release, we're hoping to conduct double blind listening
tests with a variety of test samples to fairly compare Vorbis
with competing audio formats. Based on informal listening tests
by the developers and other interested parties, we are confident
that Vorbis will fare well in these tests. These tests will be
used to further tune the format as development continues.
- I've heard some test samples that
had audible artifacts. Why did this happen?
- While the Vorbis file format is standardized, the Vorbis
encoder has undergone several beta and prerelease testing
cycles. If the files you heard were encoded using an earlier
version encoder, they might contain serious audio quality bugs
that have already been fixed. Try re-encoding from the source
audio using the latest encoder. If you still think you've got a
bug that produces unreasonable artifacts, please e-mail the
vorbis-dev list with the details.
- What does the "Quality"
setting mean?
- Beginning with libvorbis 1.0rc3, audio quality is no longer
measured in kilobits per second, but on an arbitrary scale of 0
to 10, called "quality." This change in terminology was brought
about by a tuning of the variable-bitrate algorithm that
produces better sound quality for a given average bitrate, but
which does not adhere as strictly to that average as a target.
This new scale of measurement is not tied to a quantifiable
characteristic of the stream, like bitrate, so it's a fairly
subjective metric, but provides a more stable basis of
comparison to other codecs and is relatively future-proof. As
Segher Boessenkool <segher@xiph.org>
explained, "if you upgrade to a new vorbis encoder, and you keep
the same quality setting, you will get smaller files which sound
the same. If you keep the same nominal bitrate, you get about
the same size files, which sound somewhat better." The former
behavior is the aim of the quality metric, so encoding to a
target bitrate is now officially deprecated for all uses except
streaming over bandwidth-critical connections.
For now, quality 0 is roughly equivalent to 64kbps average, 5
is roughly 160kbps, and 10 gives about 400kbps. Most people
seeking very-near-CD-quality audio encode at a quality of 5 or,
for lossless stereo coupling, 6. The default setting is quality
3, which at approximately 110kbps gives a smaller filesize and
significantly better fidelity than .mp3 compression at 128kbps.
- How does Vorbis fare for
speech compression?
- It works well, but is generally not the optimal solution.
Vorbis is designed for the compression of music and general
purpose audio. Special purpose codecs can achieve much greater
compression of speech than Vorbis. Vorbis also tends to have a
latency that is too high for telephony, a common use of speech
codecs. Read the
Speech Coding and Compression FAQ for more details. Those
looking for an open-source, patent-free speech codec should take
a look at Speex.
Back to Top
Features
- How big are Ogg Vorbis files? How
do they compare to MP3 files at similar bitrates?
- Two files encoded at the same bitrate, will always be the
same size, if they are both encoded with CBR (Constant Bitrate).
The current Vorbis encoder can encode files in VBR (Variable
Bitrate) which can produce smaller files with better quality,
since it doesn't have to waste data for audio that is easy to
encode. Files produced by the Vorbis encoder at the default
quality will be similar in size to 110kbps MP3 files, but will
sound better.
- What is the maximum bitrate
at which Vorbis can be encoded?
- Theoretically, there isn't one. Vorbis is tuned for bitrates
of 16kbps to 128kbps PER CHANNEL. But there's nothing in the
spec that says you can't encode a file at 512kbps or 8kbps. The
current encoder supports the following bitrates: 64-500kbps
stereo and 32-256kbps mono (at 44.1kHz sampling rate). Lower
bitrates will be officially available in future versions.
-
- Yes, Vorbis includes a
flexible, complete comment field for song and artist info,
as well as other track data. The official encoder, oggenc,
allows you to enter comment info at encode-time. Other 3rd-party
encoding tools also let you enter or edit track data.
- How fast are the
encoders/decoders?
- Right now the encoder is about as fast as most commercial
audio encoders (and about twice as fast as beta 3), but not
nearly as fast as some others. Since we are using unoptimized
beta code, this is to be expected. As the vorbis tools mature
they will become faster. The decoding is roughly the same
complexity as MP3 decoding, and once the Vorbis decoding tools
are optimized, they should decode at similar speeds. Decoding
speed has increased 3-4x over the first beta already, after the
first stage of optimization.
- Where's video?
- If you're interested in our progress on a video codec, check
out Theora at http://www.theora.org. Theora's 1.0 release is
scheduled for Summer of 2003.
- What about streaming in Ogg
Vorbis format?
- Streaming is an important component of Vorbis. The format
has been designed from the ground-up to be easily streamable.
The designers of Vorbis are working alongside the creators of
Icecast streaming media software to make Icecast
Vorbis-compatible. We are also working on player support for
streaming Ogg files. Streaming Ogg files from the web will be
supported by the player plugins at the 1.0 Vorbis release.
- What software and hardware
support Ogg Vorbis?
- Ogg Vorbis encoding and/or playback is now native in a wide
variety of popular software. It's included in popular players
such as WinAmp, Sonique, FreeAmp for Windows, and Unsanity Echo
for MacOS. It's also supported in popular audio applications
such as CDex, Siren Jukebox, and GoldWave. For a more complete
list, refer to our
software page. Ogg Vorbis is not supported by any
publicly-available hardware yet, but portable playback is
possible for Sharp Zaurus owners by purchasing
tkcPlayer
software from TheKompany.
- Can I bundle Vorbis and
another media type (like text lyrics or pictures) in the same
file?
- Yes. The Ogg container format was designed to allow
different media types to be multiplexed together. In the future,
Ogg movies will most likely consist of a Vorbis audio track and
a video track (using Tarkin, VP3 or some other video codec)
inside of a single Ogg file. Some preliminary work has been done
to put MNG and MIDI content into Ogg files as well. Experimental
code is available in the ogg-tools module in the
Xiph.org CVS repository.
Programmers working on such extensions can discuss issues and
questions on the
vorbis-dev mailing list.
- What other unique features
does Ogg Vorbis have?
- Vorbis has a well defined comment header that is easy to use
and extensible and obviates the need for clunky hacks like ID3
tags. Vorbis has bitrate scaling - a feature that lets you
adjust the bitrate of a Vorbis file or stream without reencoding;
just chop the packets up in the sizes you want them. Vorbis
files can be sliced and edited with sample granularity. Vorbis
has support for many channels, not just 1 or 2. Vorbis files can
be logically chained together.
Back to Top
Development
- How do I get started with
Ogg Vorbis development?
- It is important to first become familiar with current
development efforts. The best ways to do this are:
- Download and compile the latest development code from
the Xiph.org CVS
repository. The important modules for Ogg Vorbis
development are ogg, vorbis, ao, and vorbis-tools. If you are
interested in working on putting other media types into Ogg
files, the ogg-tools module also has example code.
- Subscribe to the
vorbis user and
vorbis developer mailing lists.
- Talk to developers in IRC. They usually are hanging around
in #vorbis on irc.openprojects.net. They can tell you more
about what projects would be interesting at the current
moment.
Once you have seen what others are doing, you will have a
better chance to find a project to work on.
- How do I contribute a bug-fix
or enhancement of the Xiph.org Ogg Vorbis libraries and tools?
- If you want to contribute bug fixes or enhancements to
vorbis-tools, the preferred method is to generate a patch
against the latest CVS
code. You can do this by running the command "cvs diff -u >
mybugfix.patch" from the source code directory you checked out
from CVS.
Once you have a patch, you need to file a
bug/enhancement report on the
Xiph.org Bugzilla server. You can attach your patch to the
bug entry. If you consider the enhancement to be of general
interest or want comments from the developer community, you are
encouraged to post a message to the
Vorbis development
mailing list describing the patch and linking to the bug
entry with your patch.
Please note that patches contributed under license terms not
compatible with the existing package license (BSD for libogg and
libvorbis, GPL for libao and vorbis-tools) will generally not be
accepted.
- Is it feasible to port
the Vorbis decoder/encoder to a platform without floating point
support (such as a StrongARM CPU)?
- The reference implementations of the Vorbis decoder and
encoder provided on the
vorbis.com download
page depend heavily on floating point hardware. While this
presents no problem for workstation-class CPUs (like x86 and
PowerPC), it means that embedded CPUs without floating point
support (as are often found in portable devices) are at a severe
disadvantage. There are two possible ways to work around this
problem:
- Emulate the floating point instructions -- Kernel
emulation of floating point instructions is too slow to use
for vorbis. There are userspace libraries which provide
floating point emulation that might be fast enough for your
hardware. Examples are
MathLib
for PalmOS and the -msoft-float support in GCC.
- Change the vorbis library to use integer-only instructions
-- This is the more efficient solution, but also requires more
specialized knowledge to implement. Several people seem to
have attempted it or are working on it now, but no free
integer-based Vorbis decoder exists at the moment. Xiph.org
has an integer-based decoder library available for licensing.
Contact Emmett Plant for
details.
- Why doesn't the
latest release version compile properly on Linux-From-Scratch
systems?
- It's a bug in gcc-2.95. One workaround is to compile with
-march=i586 instead of the default -march=i686; real fixes
already exist in newer versions of gcc.
"Linux-From-Scratch"
users encounter this bug most frequently, since that
distribution uses the lethal combination of gcc-2.95 and
-march=i686 by default, but it may also affect other
distributions like Gentoo or users who choose their own
compilers or optimizations.
- Why can't I
compile the latest CVS on Red Hat 7.3?
- Red Hat 7.3 comes with two versions of autoconf. 2.13 is the
default; CVS will only compile with 2.53.
Back to Top
Current Affairs
- Version 1.0 is out!
What does that mean?
- For several months, and through several beta and prerelease
versions, the reference Vorbis encoder and auxiliary software
have been undergoing extensive bug-fixing, audio quality tuning,
and listening tests in order to make it the best quality
possible. We are now ready to offer Ogg Vorbis to the public in
a complete, open, and free software suite as an alternative to
other more restrictive or lower-quality music formats.
You are
encouraged to download the software, encode your favorite music,
and compare its quality to other compression schemes, and
developers are encouraged to use the software and format in
their own projects.
Back to Top
Meta-FAQ
- I have a
question that isn't answered by this FAQ. Where can I turn for
help?
- There are archived mailing lists for advocacy, user
discussion, and development at
Xiph.org's mailing list
page, as well as an IRC channel #Vorbis on IRC network
OpenProjects.net.
- Where can
discussions about and contributions to this FAQ be made?
- Xiph.org's mailing list
page also has subscription info and archives of the
Vorbis-FAQ mailing list. Contributions and discussion are
welcome there.
- How current is this
FAQ?
- It was updated on 2002-07-15 0310GMT.
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