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Old 2nd June 2004, 15:07   #1  |  Link
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Ogg Theora Information

Ogg Theora is the video coding format of the Xiph multimedia format family

What is Xiph all about?

Under the "Ogg" name the Xiph.Org Foundation, founded by Christopher Montgomery, aims at providing the public, developer and business markets a 100% license free and open multimedia framework, as free and opensource alternative to licensing requiring solutions, including closed formats (as WM9 or RV9/10), but also of course open formats, as the MPEG technologies!
read more about Xiph's philosophy here

Ogg multimedia formats

all coding formats from Xiph are 100% free for usage and no licensing payments have to be payed to Xiph, nor to any patent holder of the used technologies (in the case that patents exist), no matter in what way you use the codecs (commercial, non-commerical, private...)

the Xiph family includes
- Vorbis: lossy audio,
- Theora: lossy video,
- Flac: lossless audio,
- Speex: speech audio,
- Writ: subtitle/text streaming format,
- OggScrit: enabling interactivity (dvd-like menus aso) similar to MPEG-4 Systems (planning stage),
- Tarkin: wavelet-based video coding (planning stage),
- Ogg Container Format: the container format specified by Xiph for storing their formats (uses the .ogg extension)

Ogg Vorbis

The maybe most popular format of the Xiph family is the Ogg Vorbis lossy audio coding format.
I think it can be said that Ogg Vorbis is one of the best audio coding formats existing and as the following graph shows does in no way need to hide itself compared to other popular formats, like AAC or WMA9 for example, more the contrary is the case

quality comparison of Ogg Vorbis with other good formats @ 128kbps (thanks to rjamorim):

note that lame is the best MP3 codec available, and iTunes the best AAC codec at 128kbps
i especially want to point out that WMA9 (as used in some music stores/supported on some portable players) more than clearly provided less quality than even the old MP3 format!
also note that the Vorbis codec used here was aoTuV tuning b2 (which later became part of the Vorbis 1.1 reference encoder). read more about the different available Vorbis implementations here

also check out the Vorbis FAQ in the Audio encoding forum

Ogg Theora

Ogg Theora has been finalized on the 1st June 2004 and is therefore still a very young format

The final bitstream is the same as used by and starting with the alpha3 reference encoder (provided by Xiph), which means all streams encoded with alpha3 and later are compliant to the final theora format and all theora compliant decoders will be able to handle them!

Ogg Theora was derived from On2's VP3 codec, which On2 practically gives away for free, and can be called a superset of the VP3 video codec (VP3 Specs).

small list of the features available in the Theora Format (and a comparison to VP3 and MPEG-4 ASP):
- Theora is a lossy video coding format and supports
- a block-based motion compensation
- a 8x8 Type-II Discrete Cosine Transform
- free-form variable bit rates (VBR)
- adaptive in-loop deblocking applied to the edges of the coded blocks (not existing in MPEG-4 ASP)
- block sizes down to 8x8 (MPEG-4 ASP supports 8x8 only with 4MV)
- 384 8x8 custom quantization matrices: intra/inter, luma/chroma and even each quant (more than VP3 and MPEG-4 ASP/AVC)
- flexible entropy encoding (Theora supports 80 VLC tables selectable per-frame, MPEG-4 ASP has just one)
- 4:2:0, 4:2:2, and 4:4:4 chroma subsampling formats (VP3 and MPEG-4 ASP only support 4:2:0)
- multiple reference frames (not possible in MPEG-4 ASP)
- pixel aspect ratio (eg for anamorphic signalling/playback)
- non-multiple of 16 picture sizes (as possible in ASP, but not in VP3)
- non-linear scaling of quants values (as done in MPEG-4 AVC)
- adaptive quantisation down to the block level (as possible in MPEG-4 ASP/AVC, but not in VP3)
- intra frames (I-Frames in MPEG), inter frames (P-Frames), but no B-Frames (as supported in MPEG-4 ASP/AVC)
- HalfPixel Motion Search Precision (MPEG-4 ASP/AVC supports HalfPixel or QuarterPixel)
- technologies used already in Vorbis (decoder setup configuration, bitstream headers...) not available in VP3

available compliant Theora implementations:
- reference en/decoder: official packages | SVN | MMX | liboil | Java | C#, based on the original VP3 code
- experimental en/decoder, written from scratch by derf
- libavcodec/ffmpeg decoder, written from scratch by melanson and al3x
- FPGA encoder (Xilinx Spartan-3 1000K), written from scratch by elphel
- FPGA decoder, written from scratch

- reference encoder build (alpha3) - supports only .yuv input and outputs to .ogg - discussion
- ffmpeg2theora - supports a lot of formats as input (eg. dvd, avi, mpg), outputs vorbis/theora in .ogg - discussion
- Real HelixProducer plugin - usable for example with Sirber's RealAnime 2.25 GUI, outputs vorbis/theora in .ogg - discussion
- Illiminable DShow encoder filters - usable in GraphEdit, outputs theora/vorbis/flac/speex in .ogg - discussion
- VideoLAN - commandline, outputs vorbis/theora in .ogg
- ffdshow VFW encoder - usable in VirtualDub(Mod), outputs to .avi (like .ogm not defined by Xiph) and .ogg - discussion

- WMP10/DirectShow playback plugin by Illiminable - supports theora/vorbis/flac/speex in .ogg - discussion
- WMP10/DirectShow playback plugin by Radlight - supports theora/vorbis/speex in .ogg - discussion
- WMP10/DirectShow playback plugin by Fluendo - supports theora/vorbis in .ogg
- RealPlayer10 playback plugin - supports vorbis/theora in .ogg - discussion
- MPlayer - supports vorbis/theora in .ogg (via reference, experimental and libavcodec decoder)
- VideoLAN - supports vorbis/theora in .ogg
- Cortado by Fluendo - a java media player browser applet (no need to install), supports streamed vorbis/theora in .ogg (demos)
- ffdshow DShow/VFW decoder - usable in any DShow based player, supports playback of theora streams packed in .avi or .ogg

- Icecast Streaming Server by Xiph - opensource (GPL), able to stream vorbis/theora in .ogg (http)
- Flumotion Streaming Server by Fluendo - opensource (GPL), able to stream vorbis/theora in .ogg (http)
- VideoLAN - opensource (GPL), able to stream vorbis/theora in .ogg (http)
- Peercast - able to stream vorbis/theora in .ogg (http)

read more about Theora on the Theora Homepage, the Theora FAQ and of course the Theora Specifications

it deserves our support!
Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau)
I know, that I know nothing (Socrates)

MPEG-4 ASP FAQ | AVC/H.264 FAQ | AAC FAQ | MP4 FAQ | MP4Menu stores DVD Menus in MP4 (guide)
Ogg Theora | Ogg Vorbis
use WM9 today and get Micro$oft controlling the A/V market tomorrow for free

Last edited by bond; 4th February 2007 at 20:58.
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