Difference between revisions of "Apt-X"

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(add some information about apt-X and apt-X HD)
 
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* Website: http://www.aptx.com/content.asp?site=2&page=111&pt=apt-X+Audio+Compression
* Website: http://www.aptx.com/Technology-Portfolio.aspx
* Decoder: https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/aptxdec.c


apt-X is audio codec. There are Standard apt-X, Enhanced apt-X and apt-X Live.
apt-X is an established audio coding technology for high-performance applications in broadcast, pro audio, consumer electronics, and gaming. The technology is developed and licensed out by APTX, a privately-owned company which previously traded as Audio Processing Technology or APT.
 
There are several variants of apt-X, each optimised for key applications in audio-over-networks (eg, AoIP, Massively Multi-player On-line Gaming) and wireless audio (for microphones, speakers, Bluetooth headphones, cordless intercoms, etc): standard apt-X, Enhanced apt-X, apt-X Live, and apt-X Lossless.
 
For more up-to-date information, visit the apt-X entry on Wikipedia.
 
Apt-X and apt-X HD work by splitting audio signal into four sub-bands using QMF filter and applying ADPCM on each band and packing quantised result into 16-(for apt-X) or 24-bit word (for apt-X HD). Words for different samples are interleaved.
 
Packed word for apt-X HD (in MSB):
 
  2 bits - bits 1-2 of high band quantised sample
  1 bit  - parity bit
  2 bits - band 2 quantised sample
  4 bits - band 1 quantised sample
  7 bits - low band quantised sample
 
Packed word for apt-X HD (in MSB):
 
  4 bits - bits 1-4 of high band quantised sample
  1 bit  - parity bit
  4 bits - band 2 quantised sample
  6 bits - band 1 quantised sample
  9 bits - low band quantised sample
 
Each band has the same order-2 ADPCM applied to it. There are no differences between apt-X and apt-X HD beside the latter operating on 24-bit audio and outputting 24-bit words.


[[Category:Audio Codecs]]
[[Category:Audio Codecs]]
[[Category:Undiscovered Audio Codecs]]

Latest revision as of 03:49, 5 January 2021

apt-X is an established audio coding technology for high-performance applications in broadcast, pro audio, consumer electronics, and gaming. The technology is developed and licensed out by APTX, a privately-owned company which previously traded as Audio Processing Technology or APT.

There are several variants of apt-X, each optimised for key applications in audio-over-networks (eg, AoIP, Massively Multi-player On-line Gaming) and wireless audio (for microphones, speakers, Bluetooth headphones, cordless intercoms, etc): standard apt-X, Enhanced apt-X, apt-X Live, and apt-X Lossless.

For more up-to-date information, visit the apt-X entry on Wikipedia.

Apt-X and apt-X HD work by splitting audio signal into four sub-bands using QMF filter and applying ADPCM on each band and packing quantised result into 16-(for apt-X) or 24-bit word (for apt-X HD). Words for different samples are interleaved.

Packed word for apt-X HD (in MSB):

 2 bits - bits 1-2 of high band quantised sample
 1 bit  - parity bit
 2 bits - band 2 quantised sample
 4 bits - band 1 quantised sample
 7 bits - low band quantised sample

Packed word for apt-X HD (in MSB):

 4 bits - bits 1-4 of high band quantised sample
 1 bit  - parity bit
 4 bits - band 2 quantised sample
 6 bits - band 1 quantised sample
 9 bits - low band quantised sample

Each band has the same order-2 ADPCM applied to it. There are no differences between apt-X and apt-X HD beside the latter operating on 24-bit audio and outputting 24-bit words.