Rate–distortion optimization


Rate–distortion optimization

"Rate–distortion optimization" "(also RDO or RD)" is a method of improving video quality in video compression. The name refers to the optimization of the amount of "distortion" (loss of video quality) against the amount of data required to encode the video, the "rate". While it is primarily used by video encoders, rate-distortion optimization can be used to improve quality in any encoding situation (image, video, audio, or otherwise) where decisions have to be made that affect both file size and quality simultaneously.

Background

The classical method of making encoding decisions is for the video encoder to choose the result which yields the highest quality output image. However, this has the disadvantage that the choice it makes might require more bits while giving comparatively little quality benefit. One common example of this problem is that of the use of quarter pixel-precision motion estimation. Adding the extra precision to the motion of a block during motion estimation might increase quality, but in some cases that extra quality isn't worth the extra bits necessary to encode the motion vector to a higher precision.

How it works

Rate-distortion optimization solves the aforementioned problem by acting as a video quality metric, measuring both the deviation from the source material and the bit cost for each possible decision outcome. The bits are mathematically measured by multiplying the bit cost by the Lagrangian, a value representing the relationship between bit cost and quality for a particular quality level. The deviation from the source is usually measured as the mean squared error, in order to maximize the PSNR video quality metric.

Calculating the bit cost is made more difficult by the entropy encoders in modern video codecs, requiring the rate-distortion optimization algorithm to pass each block of video to be tested to the entropy coder to measure its actual bit cost. In MPEG codecs, the full process consists of a discrete cosine transform, followed by quantization and entropy encoding. Because of this, rate-distortion optimization is much slower than most other block-matching metrics, such as the simple sum of absolute differences (SAD) and sum of absolute transformed differences (SATD). As such it is usually used only for the final steps of the motion estimation process, such as deciding between different partition types in H.264/AVC.

List of encoders that support RDO

*Ateme H.264 encoder
*libavcodec
*Mainconcept H.264 encoder
*Microsoft VC-1 encoder
*x264 H.264 encoder
*Xvid MPEG-4 ASP encoder


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Rate-Distortion-Theorie — Die Rate Distortion Theorie (deutsch: Rate Verzerrungs Theorie) ist eine theoretische Grundlage für Berechnungen in der Informationstheorie. Mit ihrer Hilfe kann rechnerisch eine untere Grenze der Datenübertragungsrate für eine Nachrichtenquelle… …   Deutsch Wikipedia

  • JPEG 2000 — Infobox file format name = JPEG 2000 caption = Comparison of JPEG 2000 with the original JPEG format. extension = .jp2, .j2k mime = image/jp2 owner = Joint Photographic Experts Group creatorcode = jp2 genre = graphics file format containerfor =… …   Wikipedia

  • Sum of absolute differences — (SAD) is a widely used, extremely simple video quality metric used for block matching in motion estimation for video compression. It works by taking the absolute value of the difference between each pixel in the original block and the… …   Wikipedia

  • Optimisation débit-distorsion — L optimisation débit distorsion ou RDO pour (en) Rate distortion optimization est une méthode utilisée dans la compression vidéo afin d augmenter la qualité de la vidéo. Le nom se réfère à un calcul d optimisation entre le niveau de distorsion… …   Wikipédia en Français

  • X264 — Saltar a navegación, búsqueda x264 Desarrollador Equipo de x264 www.videolan.org …   Wikipedia Español

  • RDO — is a three letter initialism that stands for, among other things: *Raster Document Object (.rdo), a file format used in print on demand systems manufactured by Xerox *Remote Data Objects, a deprecated Microsoft technology *Rate distortion… …   Wikipedia

  • Qpel — Quarter pixel (also known as Q pel or Qpel) refers to a quarter of a standard pixel. It is used in many modern video encoding standards such as MPEG 4 ASP and H.264/AVC to refer to quarter pixel precision in motion estimation and motion… …   Wikipedia

  • Sum of absolute transformed differences — (SATD) is a widely used video quality metric used for block matching in motion estimation for video compression. It works by taking a frequency transform, usually a Hadamard transform, of the differences between the pixels in the original block… …   Wikipedia

  • Метод множителей Лагранжа — Метод множителей Лагранжа, метод нахождения условного экстремума функции , где , относительно ограничений , где меняется от единицы до . Содержание …   Википедия

  • Лагранжа множители — Метод множителей Лагранжа, метод нахождения условного экстремума функции f(x), где , относительно m ограничений , i меняется от единицы до m. Содержание 1 Описание метода …   Википедия


We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.