MAYAH Communications

Technology Highlights

6 ms audio latency via IP connections

Audio codec quality is measured quite often in terms of the delay time for the encoding and decoding process. Live applications, such as reporting and interviews are considered to be most critical. MAYAH's CENTAURI II sets a new standard in low delay offering 6ms for apt-X/Eapt-X and linear audio via IP.

The importance of low latency

A classification of broadcasting applications is made in consideration of their latency requirements. Table 1 „Applications classified by latency requirements” shows pros and cons of used algorithms and the essential need for a certain latency. Considered algorithms are all which are implemented in CENTAURI II, such as all MPEG 1, 2, 4 algorithms as well as G.711/722, J.41/57, apt-X, Eapt-X, ADPCM4SB and others.

Application

Requirements

Advantage/Disadvantage with MPEG

Alternative Algorithm

Monitoring

< 30ms

+ transmission cost

·	n-1-technique necessary
·	costs for n-1

Linear, J.41, J.57, apt-X

Interview

< 100ms

+ transmission cost
- delay sometimes still too high

Linear, J.41, J.57, apt-X
with G.722 quality with 7kHz too low

Reporting with backchanel

< 100ms

+ transmission cost
+ asymmetrical Codec

Linear, J.41, J.57, apt-X
G.722 quality 7kHz for way back adequate

Distribution

>> 100 ms

+ transmission cost
+ quality
- cascadability

Linear, J.57, Enhanced-apt-X

Contribution

>> 100 ms

+ transmission cost
+ quality
- cascadability

Linear, J.57, Enhanced-apt-X

Emission

>> 100 ms

+ bandwidth
+ quality

Table 1

It is possible: MPEG at 48ms, linear and Eapt-X at 6ms overall delay

MPEG is known to offer high efficiency encoding but at the same time introducing a delay which human sensation goes from noticeable to not acceptable. It is important to mention that this known delay obviously depends strongly on the MPEG implementation in hardware platforms. MAYAH was the first to offer a single-CPU implementation optimised for low latency and thus offering e.g. MPEG Layer 2 at only 48 ms setting a new standard in this domain (measured in loop and via IP connections at bit rates of 64, 128 and 256 kbps).

The optimum in low latency is achieved with linear and apt-X/Eapt-X encoding at 96kHz. In loop as well as via RTP/IP protocol, the MAYAH CENTAURI II achieves the optimum low latency of only 6ms in one direction, i.e. adding encoding and decoding process.

The latency requirements given by broadcasters need also to be considered from a historical point of view due to the transition of analog to digital technology. While in analog there was almost no latency noticed, digital techniques introduce different delay times depending on the applied algorithms. Some systems, such as DVB, DAB and others consider delay times of one second as state of the art. With a higher market penetration of such systems the need for very low latency in the distribution and contribution of signals may decrease to a certain extent.

Single CPU solution

MAYAH’s single CPU solution offers extremely low latency due to avoiding communication between more than one DSP and Control Processors.

This results in low delay times via all communication interfaces, such as IP, ISDN and X.21.