Codec Tieline Gateway, Руководство пользователя

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246 Gateway and Gateway 4 Manual v1.2
© Tieline Research Pty. Ltd. 2021
24.8
Selecting an Algorithm
The codec offers PCM uncompressed linear audio as well as aptX® Enhanced, LC-AAC, HE-AAC
v.1 and HE-AAC v.2, AAC-LD, AAC-ELD, AAC-ELDv2, MPEG Layer 2, G.711 and G.722, Tieline
Music and MusicPLUS algorithms. There is a range of pre-programmed connection profiles to
simplify codec configuration.
Overview of Tieline Algorithms
1. The Tieline Music algorithm is optimized for audio bit rates as low as 19.2kbps with only a 20
millisecond encode delay. It offers 15 kHz mono from 24kbps to 48kbps.
2. Tieline MusicPLUS delivers up to 20 kHz mono from 48kbps upwards. It can also deliver up to 20
kHz stereo from 96kbps upwards, offering huge savings on your IP data bills and outstanding
audio quality.
Overview of AAC Algorithms
AAC-LC
LC-AAC is optimized for audio bit rates of 64kbps per channel or higher using a sample rate of
48kHz. Tieline recommends using LC-AAC instead of HE-AAC if bandwidth of 64kbps or higher
per channel is available, to optimize audio quality. If lower bandwidth than 64kbps is available
consider using HE-AAC, Tieline Music or Tieline MusicPLUS.
AAC-HE
Codecs include both HE-AAC v.1 and HE-AAC v.2, which are optimized for low bit rate
connections. Selection of HE-AAC v.1 and v.2 is automatically managed within the codec, so
only
AAC-HE is displayed on the screen. When used for mono connections, HE-AAC v.1
performs best at bit rates of 24kbps per channel or higher. HE-AAC v.1 is also used for stereo
connections when audio connection bandwidth is 48kbps or higher.
HE-AAC v.2 is used for stereo connections when audio connection bandwidth is below 48kbps
and is capable of delivering 15kHz quality stereo audio at audio bit rates as low as 24kbps.
A sample rate of 32kHz is used in the codec's default profiles to achieve ultra-low bit-rate
connections, but this is adjustable to 44.1kHz or 48kHz if required.
AAC-LD
AAC-LD (Low Delay AAC), AAC-ELD (Enhanced Low Delay AAC) and AAC-ELDv 2 are
optimized for low latency real-time communication. AAC-LD is suited to bit rates of 96kbps or
higher for stereo audio.
AAC-ELD
AAC-ELD is optimized for high quality stereo connections from 48 - 96kbps and performs better
at these bit rates when compared with AAC-LD.
AAC-ELD v 2
For stereo connections below 48kbps AAC-ELD v2 will deliver better performance than AAC-
ELD down to 24kbps.