AEQ's Phoenix audio codecs, in London 2012

The Phoenix audiocodec, together with the new fully digital, automated and integrated AEQ commentary system, represents a qualitative leap in the quality and reliability of audio and communications for the broadcast of major sporting events.

In international sound broadcasting at major events, such as the Olympic Games, thousands of audio circuits must be transmitted from each source (whether a commentator's voice, public or ambient sound) to each radio/telecast operator.

When using a common infrastructure for this purpose, it is necessary to establish a complex “Commentator System” structure.

The audio is generated by the organization at the different headquarters through AEQ commentator positions, assigned to the various RHB radio/television operators or “rightholders”.

All the circuits of each headquarters are multiplexed and sent from each headquarters to the IBC (International Broadcasting Center), to the so-called CSC (Commentary Switching Center) through AEQ BC 2000D routers. This is what is called the Contribution part.

Once the circuits from all the headquarters (Concentration) have been collected, they are taken to a large main AEQ TITAN matrix of 5000x5000 circuits that switches the circuits according to a schedule that we have previously delivered to the organization, to be taken to their destinations. This switching can also be dynamic in the case of circuits shared by several operators at different times.

System redundancy

The system is redundant. In case of failure of the main path, the circuits automatically switch to the backup path. The hardware within each frame is also duplicated or at least has spare cards.

In addition to the individual operators, each with its DAP, represented above on the right, in the case of EBU (European Broadcasting Union), it works somewhat differently: the EBU switching within the IBC receives a direct high-capacity link from the main matrix of the CSC, and through another matrix AEQ TITAN will distribute to the different operators within the group. This audio will be sent through dedicated equipment to the destination countries using various link types, such as E1, IP or ISDN.

The transmission of E1 circuits is done directly with AEQ BC2000 frames and multiplexer cards, with other similar equipment existing in the client's studios. To transmit the circuits over IP and ISDN, however, it is necessary to use an audiocodec, with maximum audio quality, reliability and robustness against problems on the line, with automatic guaranteed recovery. Furthermore, optimal use of the channel is important. We have approved the AEQ Phoenix Studio audiocodec for this application.

Sending audio to international operators

At the London Olympic Games, IP and ISDN point-to-point links are used. Transmission can be performed with high quality, 15KHz with the AEQ-LD+ algorithm, or with traditional 7.5KHz G722 contribution circuits.

The digital transmission is maintained from the commentators' microphone inputs to the operators' mixing consoles or, where appropriate, the viewer's television.

Sending circuits over IP

Operators with greater resources use IP for the transmission of their circuits. This is a high-capacity WAN network with guaranteed Layer 2 quality of service. The equipment in London and in the destination countries, all Phoenix Studio, are configured within the same logical network, so they will all have an IP within the same range.

Phoenix Studio has two channels, it would be possible to transmit two different programs using a pair of equipment and a simple Ethernet link. Both channels will share the same IP address with RTP and RTCP (Real Time Control) Protocol.

The chosen signaling method is SIP (without using Proxy). Audio sending is done using RTP and RTCP (Real Time Control Protocol).

Each computer will have an identifier or “URI” of the form @. For example, Phoenix_233@172.26.33.55. These URIs can be stored in the Phoenix Studio address book
with a friendlier name (for example, “Audiocodec Paris 1”), to make calls with complete ease.

AEQ-LD+ encoding has dual modes that double the effective capacity of the device: we can send up to 4 independent bidirectional channels with a pair of devices.

Sending circuits via ISDN

The Phoenix Studio audiocodec is a multi-interface system, and also allows you to connect to ISDN networks, using the communications module integrated for this purpose. Some radio/television operators prefer to use ISDN lines to transmit their programs through Phoenix Studio.

Phoenix Studio allows the aggregation of both B channels into a single 128 Kbps channel that enables higher quality transmission. To transmit two 128 Kbps channels, two ISDN lines are necessary, but not two Phoenix Studio devices, since each device has two bays for communications modules.

Finally, in terms of fault protection, it is vital that the system is fault tolerant and provides automatic means of recovery. Phoenix Studio has several recovery methods: Backup, Auto-hangup due to lack of data (RTP Inactivity Mode) and Auto-redial.

Javier Polo

Head of EBU Sports Operations