Bitrate peeling is a technique used in

Ogg Ogg is a free, open container format maintained by the Xiph.Org Foundation. The authors of the Ogg format state that it is unrestricted by software patents and is designed to provide for efficient streaming and manipulation of high-quality d ...

Vorbis Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression. Vorbis is most commonly used in conjun ...

streams A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...

, wherein a stream can be

encoded In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication ...

at one

bitrate In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction w ...

but can be served at that or any lower bitrate. The purpose is to provide access to the clip for people with slower

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

connections, and yet still allow people with faster connections to enjoy the higher quality content. The

server Server may refer to: Computing *Server (computing), a computer program or a device that provides functionality for other programs or devices, called clients Role * Waiting staff, those who work at a restaurant or a bar attending customers and su ...

automatically chooses which stream to deliver to the user, depending on user's connection speed. , Ogg Vorbis bitrate peeling existed only as a concept as there was not yet an encoder capable of producing peelable datastream
Bounties - XiphWiki

Difference from other technologies

The difference between SureStream and bitrate peeling is that SureStream is limited to only a handful of pre-defined bitrates, with significant difference between them, and SureStream encoded files are big because they contain all of the bitrates used, while bitrate peeling uses much smaller steps to change the available bitrate and quality, and only the highest bitrate is used to encode the file/stream, which results in smaller files on servers. A related technique to the SureStream approach is

hierarchical modulation Hierarchical modulation, also called layered modulation, is one of the signal processing techniques for multiplexing and modulating multiple data streams into one single symbol stream, where base-layer symbols and enhancement-layer symbols are s ...

, used in broadcast, where severally different streams at different qualities (and bitrates) are all broadcast, with the higher quality stream used if possible, with the lower quality streams fallen back on if not.

Lossy and correction

A similar technology is to feature a combination of a lossy format and a lossless correction; this allows stripping the correction to easily obtain a lossy file. Such formats include

MPEG-4 SLS MPEG-4 SLS, or MPEG-4 Scalable to Lossless as per ISO/IEC 14496-3:2005/Amd 3:2006 (Scalable Lossless Coding), is an extension to the MPEG-4 Part 3 (MPEG-4 Audio) standard to allow lossless audio compression scalable to lossy MPEG-4 General Audio ...

(scalable to lossless),

WavPack WavPack is a free and open-source lossless audio compression format and application implementing the format. It is unique in the way that it supports hybrid audio compression alongside normal compression which is similar to how FLAC works. I ...

DTS-HD Master Audio DTS-HD Master Audio (DTS-HD MA; known as DTS++ before 2004) is a multi-channel, lossless audio codec developed by DTS as an extension of the lossy DTS Coherent Acoustics codec (DTS CA; usually itself referred to as just DTS). Rather than being ...

and

OptimFROG DualStream OptimFROG is a proprietary lossless audio data compression codec developed by Florin Ghido. OptimFROG is optimized for very high compression (small file sizes) at the expense of encoding and decoding speed, and consistently measures among the hi ...

SureStream example

A SureStream encoded file is encoded at bitrates of 16 kbit/s, 32 kbit/s and 96 kbit/s. The file will be about the same in size as three separate files encoded at those bitrates and put together, or one file encoded at the sum of those bitrates, which is about 144 kbit/s (16 + 32 + 96). When a

dial-up Dial-up Internet access is a form of Internet access that uses the facilities of the public switched telephone network (PSTN) to establish a connection to an Internet service provider (ISP) by dialing a telephone number on a conventional telepho ...

user has only about 28 kbit/s of

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

available, the

Real Real may refer to: Currencies * Brazilian real (R$) * Central American Republic real * Mexican real * Portuguese real * Spanish real * Spanish colonial real Music Albums * ''Real'' (L'Arc-en-Ciel album) (2000) * ''Real'' (Bright album) (2010) ...

server will serve the 16 kbit/s stream. If the dial-up connection is of higher quality, and maybe about 42 kbit/s is available, the server will automatically switch to the 32 kbit/s stream. A

DSL Digital subscriber line (DSL; originally digital subscriber loop) is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric dig ...

cable Cable may refer to: Mechanical * Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof * Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...

Internet user will be served the 96 kbit/s stream. This looks good, but even though the user with 28 kbit/s can use a higher bitrate / higher quality stream (maybe 22–24 kbit/s), such thing can't be done with SureStream, unless the encoded file contains such a bitrate. This is where Bitrate Peeling comes into play.

Bitrate peeling example

Contrary to SureStream, bitrate peeling requires only the highest bitrate to be used when encoding a file/stream, which is 96 kbit/s in this case. The obvious benefit is much smaller space on a server required by such a file. An additional feature of bitrate peeling is a much finer tuning of available bitrate/quality. If a dial-up user with 28 kbit/s available bandwidth connects to an Ogg Vorbis file/stream, the server will "peel" the original 96 kbit/s file/stream down to just below available bandwidth (in this case it would be around 20–24 kbit/s). This so-called peeling process is different from

transcoding Transcoding is the direct digital-to-digital conversion of one encoding to another, such as for video data files, audio files (e.g., MP3, WAV), or character encoding (e.g., UTF-8, ISO/IEC 8859). This is usually done in cases where a target devic ...

because transcoding uncompresses the file and recompresses it (a computing-intensive process), whereas the peeling process removes excess bits from the stream without more processing. Aside from the obvious space-saving advantage bitrate peeling allows for smaller steps in the delivery bitrate (the end user will see the file in the highest quality possible for their bandwidth). These benefits are only theoretical, as the only Vorbis peeler available is still in experimental state and produces file qualities inferior to what

the higher bitrate file to a lower bitrate would.

Comparison with other progressive encodings

{{details, Lossy data compression#Downsampling / compressed representation scalability Bitrate peeling is theoretically possible, and is implemented in some other formats, notably

JPEG 2000 JPEG 2000 (JP2) is an image compression standard and coding system. It was developed from 1997 to 2000 by a Joint Photographic Experts Group committee chaired by Touradj Ebrahimi (later the JPEG president), with the intention of superseding the ...

JPEG JPEG ( ) is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and imag ...

progressive encoding, and

Scalable Video Coding Scalable Video Coding: (SVC) is the name for the Annex G extension of the H.264/MPEG-4 AVC video compression standard. SVC standardizes the encoding of a high-quality video bitstream that also contains one or more subset bitstreams (a form of la ...

. The reason that it is not available in Ogg Vorbis is that current encoders do not organize the code-stream to have progressive accuracy, thus peelers cannot tell which data is more or less important. See also the

Adam7 algorithm Adam7 is an interlacing algorithm for raster images, best known as the interlacing scheme optionally used in PNG images. An Adam7 interlaced image is broken into seven subimages, which are defined by replicating this 8×8 pattern across the f ...

used in PNG interlacing.

External links

Xiph.org Foundation

Xiph.org Bitrate Peeling Bounty

Ogg Vorbis site

Data compression Audio engineering