Harmonic and Individual Lines and Noise

Harmonic and Individual Lines and Noise

Harmonic and Individual Lines and Noise (HILN) is a parametric codec for audio. The basic premise of the encoder is that most audio, and particularly speech, can be synthesized from only sinusoids and noise. The encoder describes individual sinusoids with amplitude and frequency, harmonic tones by fundamental fequency, amplitude and the spectral envelope of the partials, and the noise by amplitude and spectral envelope. This type of encoder is capable of encoding audio to between 6 and 16 kilobits per second for a typical audio bandwidth of 8 kHz. The framelength of this encoder is 32 ms.

A typical codec extracts sinusoid information from the samples by applying a short-time Fourier transform to the samples and using that to find the important harmonic content of a single frame. By matching sinusoids across frames, the encoder is capable of grouping them into harmonic lines and individual sinusoids. The matching can take amplitude, frequency and phase into account when trying to match sinusoids across frames. Differences between amplitude and frequency within a track can be coded with fewer bits than each individual single sinusoid would require, thus the longer a track the encoder can find, the better it will be able to reduce the final bitrate.

The decoder uses an add-and-overlap strategy: each frame in the bitstream contains parameters for 32 ms, however, the next frame starts halfway the current frame. By filtering the synthesized segments with a Hanning filter adding two overlapping frames together will produce a smooth transition between the two. This also applies to the encoder because the short Fourier transform gives better results when the data is preprocessed with a Hanning filter.

Synthesizing only the sinusoids sounds artificial and metallic. To mask this, the encoder subtracts the synthesized sinusoids from the original audio signal. The residual is then matched to a linear filter that is excited with white noise. The extracted parameters can than be quantized, coded and multiplexed into a bitstream.

Further reading


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • Harmonic and Individual Lines and Noise — (HILN) ist ein parametrischer Audiocodec. Er zielt auf Bitraten von 6 bis 16 Kilobits pro Sekunde bei 4 bis 8 kHz Abtastrate und einer Framelänge von 32 ms. Jeder Frame des Bitstroms enthält Parameter für 32 ms und die Frames überlappen bis zur… …   Deutsch Wikipedia

  • Mathematics and Physical Sciences — ▪ 2003 Introduction Mathematics       Mathematics in 2002 was marked by two discoveries in number theory. The first may have practical implications; the second satisfied a 150 year old curiosity.       Computer scientist Manindra Agrawal of the… …   Universalium

  • Spider-Man's powers and equipment — The fateful spider bite that gave Peter Parker his powers. Amazing Fantasy #15, art by Steve Ditko. Spider Man s powers, abilities, and equipment are used by Marvel Comics superhero Spider Man in tandem to combat his many foes. He receives most… …   Wikipedia

  • HILN — Harmonic and Individual Lines and Noise (HILN) ist ein parametrischer Audiocodec. Er zielt auf Bitraten von 6 bis 16 Kilobits pro Sekunde bei 4 bis 8 kHz Abtastrate und einer Framelänge von 32 ms. Jeder Frame des Bitstroms enthält Parameter für… …   Deutsch Wikipedia

  • Electronic amplifier — A practical amplifier circuit An electronic amplifier is a device for increasing the power of a signal. It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude. In… …   Wikipedia

  • Music — For other uses, see Music (disambiguation). Music …   Wikipedia

  • Clavier-Übung III — Johann Sebastian Bach, 1746 The Clavier Übung III, sometimes referred to as the German Organ Mass, is a collection of compositions for organ by Johann Sebastian Bach, started in 1735–6 and published in 1739. It is considered to be Bach s most… …   Wikipedia

  • musical sound — Introduction       any tone with characteristics such as controlled pitch and timbre. The sounds are produced by instruments in which the periodic vibrations can be controlled by the performer.       That some sounds are intrinsically musical,… …   Universalium

  • Parametric Audio Coding — bezeichnet Audiokompressionsverfahren für ultraniedrige Bitraten. Technik Das Signal wird analysiert und in Objekte zerlegt, die mit Parametern beschrieben werden, aus denen auf Decoderseite wieder ein ähnlich klingendes Audiosignal synthetisiert …   Deutsch Wikipedia

  • Audioformat — Ein Audioformat ist ein Datenformat, das den Aufbau einer Audiodatei oder eines Audiodatenstromes beschreibt. Inhaltsverzeichnis 1 Allgemein 2 Datenreduktion oder Datenkompression 3 Liste gängiger Audioformate …   Deutsch Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”