This foils gives overview of open source Thoera video codec.

1. THEORA VIDEO
Mihir Mody

2. INTRODUCTION
 Owned by Xiph.org (http://xiph.org/)
 Free, Open source video codec, distributed without
licensing fees
 Initial software released in Oct 2002, the final / frozen
specification in Jun 2004
 Named after Theora Jones from Televison program “Max
Headroom”

3. HISTORY & RELATION TO ON2 VP3
 Derived from ON2”s TrueMotion VP3 Video codec
 Based on ON2’s VP3.2 release in Sep 2000
 ON2 later Donated to XIPH.org with BSD license in June
2002 to enable open source royalty free video codec
 Theora is a superset of VP3, and VP3 streams (with some
minor syntactic modifications in frame header) can be
converted into Theora streams without recompression (but
not vice versa).
 VP3 video compression can be decoded using Theora
implementations, but Theora video compression usually
cannot be decoded using old VP3 implementations.

4. RESOURCES
 Theora web site : http://www.theora.org/
 Specification: http://www.theora.org/doc/Theora.pdf
 Conformance suite:
http://wiki.xiph.org/TheoraTestsuite

5. THEORA : DECODER ALGORITHM
Deblocking
Filtering
Motion
Compensation
Residual
Decoding
Picture
Buffering
Picture
Buffering
IQ
& IT
+
Bitstream
Input
Video
Output
Post-
processing
Mode &
MVD
Picture
Buffering

6. DETAILS OF TOOL SET FOR THEORA VIDEO
No Topic Tool Overview Not supported in
Theora
1 Content type Progressive Interlaced
2 Frame type I and P frames B frame
3 Chroma format YUV 4:2:0, YUV 4:2:2, YUV 4:4:4 YUV 4:0:0
4 Bit-depth 8 bit 10,12,14 bits
5 Resolution Stamp size to HD -
6 Frame rate Fixed frame rate Variable frame rate
7 Bit-rate free-form variable bit rates (VBR)
from few Kbps to Mbps
CBR
8 Coding unit Block (8x8), Macro-block (16x16)
and Super Block (32x32)
-

7. DETAILS OF TOOL SET (CONTD)
No Topic Overview Not supported
9 Entropy coding VLC (Huffman) coding, 80 Table
selectable per frame
CABAC, CAVLC,…
10 Motion
compensation
Block based MC with Half pel
accuracy, 1 MV and 4 MV per MB
Qpel, > 4 MV
11 Reference
frame
2 Reference frame (Previous and
Golden frame)
> 2, Referance frame
selection per MB basis
12 Quantization Adaptive quantization down to the
block level , Upto 384 Qmatrix
based mode, Qp and
luma/chroma and support for
Scaling Matrix
13 Transform 8x8 Type-II Discrete Cosine
Transform
Fixed point, Second
transform
14 Loop filter adaptive in-loop deblocking
applied to the edges of the coded
blocks
Not sophisticated

8. AUDIO, CONTAINER AND RTP FORMAT
 Typically Theora video is used with Vorbis Audio in
Ogg Container format
 Ogg container is a free, open container format
maintained by the Xiph.Org Foundation
 Vorbis is a free software / open source audio codec
owned by Xiph.Org Foundation
 RTL payload format:
http://svn.xiph.org/trunk/theora/doc/draft-ietf-avt-rtp-
theora-00.txt

9. VIDEO QUALITY
 Comparable to MPEG part 2 (SP) based on specification
 As per MSU shoot-out (Video quality, encoding, decoding
speeds, options etc)
 http://compression.ru/video/codec_comparison/h264_2010/
 X264 beats Theora more than 50% in bit-rate to achieve
video quality.
 XVID (MP4) beats Theora than 10% in bit-rate to achieve
video quality

10. SW IMPLEMENTATION
 PC : Provides source code to generate “libtheora”, that
enables other players e.g. FFMPEG, Helix, VLC,…
 The SW API specification for “libtheorra”:
http://www.theora.org/doc/libtheora-1.2/
 ARM Optimized version
1. Theoarm project: http://wss.co.uk/pinknoise/theorarm/
2. FFMPEG release:
 DSP implementation
 Available for C64x from VINJAY SOFTWARE
(http://www.vinjey.com/)

11. HW IMPLEMENTATION
 Open source
 RTL Availability :
http://wiki.xiph.org/index.php/TheoraHardware
 Few Video IP and chip providers support it

12. KEY DRIVERS FOR THEORA
 Most important driver Adopted in HTML5 as a video format along with
WebM
 Video on Wikipedia project: http://www.videoonwikipedia.com/
 Open video alliance : http://openvideoconference.org/
 Mozilla support as default video codec in Firefox
 List of content provider for Theora:
http://wiki.xiph.org/List_of_Theora_videos

13. THEORA ADOPTION
 It remains low as MeFeedia on popularity of format
http://blog.mefeedia.com/html5-dec-2011
 The maximum Thoera content is centered around CIF and below
WVGA resolution.
 There is confusion to support Theora or move use directly WebM on
open source front for content creators.

14. THANKS