Access - IP / Internet Digital Audio Codec
The industry-standard ACCESS from Comrex is a true revolution in audio codecs. Developed from the ground up for use over the public internet, it provides 2-way, stable, stereo, low-delay audio over pretty much any type of internet connection, including wireless systems such as wi-fi and 3G. A pair of rackmounts will provide a superb ISDN replacement whilst the portable unit effectively gives you a radiocar in the palm of your hand! It literally is as good as it sounds and is being used by a huge number of broadcasters worldwide.
ACCESS is the first codec to use BRIC (Broadcast Reliable Internet Codec) technology to deliver wideband audio over the public internet and other IP networks in real time. It includes three BRIC algorithms as standard, each tailored to different network conditions and broadcast requirements (see below). It is also possible to add AAC algorithms from Fraunhofer IIS - including the remarkable AAC-ELD - as an upgrade, which provide near-transparent audio transmission. There is also a built-in linear uncompressed mode and FLAC lossless audio coding, suitable for managed networks with a high Quality of Service. Because the ACCESS constantly adapts to changing network conditions, audio delay is kept to a minimum whilst maintaining audio stability.
If an internet connection is not available, Access is just as happy running 2-way 15KHz mono over a standard phone line (POTS) and is compatible in this mode with the Matrix and Vector. If connected to another Access unit, it is even possible to run 15KHz stereo over POTS!
The Access rackmount is a 1U unit with stereo audio inputs / outputs on analogue or digital AES XLRs. There are also serial and GPI ports which can be sent alongside the audio to the connected unit. A standard phoneline connection completes the rear panel.
The front panel contains only level indicators and a basic status LED. All setup and connection functions, as well as status information, audio levels and network statistics are accessed through the user-friendly web interface from any standard web browser. Operation is as simple as selecting a remote unit from the 'address book' and clicking Connect, while advanced configuration menus are available for power users who wish to configure all aspects of the audio coding process.
Apart from normal point-to-point connectivity, ACCESS also supports Multi-Streaming, Multi-Cast, Multi-Unicast and SHOUTcast™ connections. We can also provide an application for PC that provides "Live" switching between a number of remote codecs, all connected simultaneously to the studio codec and receiving return audio (such as talkback), to select "on-air" audio source.
The Access Portable is the perfect complement to the Rackmount and provides the same technology in a handheld, battery-powered unit not much bigger than a PDA. The Portable includes a CardBus card slot for use with WiFi or 3G cellular data cards, making it easy to get an IP connection from a wide range of locations. With current UK mobile data tariffs, you can use the ACCESS over 3G for just £1 per day!
The algorithm best suited to the network available can be selected from either the Rackmount web GUI or the built-in touch screen on the Portable. Audio meters are displayed on the Portable's screen and a web browser is included to allow easy connection to WiFi hotspots where a password or credit card number is required. An optional 5-channel mixer is also available, turning the Access Portable into a fully-integrated remote audio solution.
In addition to the ability to do linear uncompressed mono or stereo, the basic ACCESS codec includes three BRIC algorithms:
1- BRIC-HQ1 (High Quality 1) This algorithm keeps delay low (around 1/10 second) but allows for full fidelity (15 kHz) audio transmission. It delivers music or voice audio equally well and runs at a data rate of 28 kb/s. This mode also allows dual mono transmission, so that two independent audio signals (using twice the network bandwidth) can be sent to the same location. HQ1 settings offer choice of mono, dual mono or stereo.
2- BRIC-HQ2 (High Quality 2) This mode minimizes artifacts and encodes speech and music equally well, providing a 12 or 15 kHz fidelity signal over 24 kb/s of network bandwidth. BRIC-HQ2 also allows for stereo operation at the lowest data rate of 24-30 kb/s, making stereo over a single modem connection possible. BRIC-HQ2 has moderate delay of about 1/3 second, which is in the range of many ISDN codecs. HQ2 settings offer choice of mono 12K, mono 15K, stereo 12K or stereo 15K. Selecting 12K further reduces artifacts.
3- BRIC-ULB (Ultra Low Bitrate) This mode is designed for speech transfer only but has a remarkable compression ratio of around 25:1, allowing it to deliver 7 kHz at an astonishingly low bitrate (around 14 kb/s). The voice quality of BRIC-ULB is comparable to the old codec standard G.722 (7 kHz), but uses less than ¼ of the data rate.
MPEG-4 AAC algorithms, licensed by Fraunhofer IIS, are available as an optional upgrade and includes the remarkable AAC-ELD which makes effective use of some very aggressive, intelligent coding algorithms that are capable of allowing transmission of high quality audio over very constricted data channels at extremely low data rates.
The Comrex AAC package for the ACCESS codecs includes:
AAC - Which provides near transparent audio at a range of data rates. AAC has been extensively tested by critical listening studies and has been judged to be virtually indistinguishable from the original audio.
HE-AAC – Enhances the AAC standard by adding Spectral Band Replication. This is a way of delivering equivalent performance to AAC at lower rates. SBR is applied to high frequencies of audio, while normal AAC is applied to the lower frequencies. This is the standardized version of what has been known in the industry as AACPlus.
HE-AACv2 – Enhances the HE-AAC standard by adding a special form of parametric stereo coding to further reduce data rates.
AAC-LD – requires higher data rates but provides near transparent voice and music with low delay.
AAC-ELD - combines the best aspects of low-delay audio coding with Spectral Band Replication to reduce bitrate. This combination creates a coding algorithm that is uniquely suited to real-time IP transmission. Using AAC-ELD with ACCESS allows full-fidelity high quality audio transmission at a data rate that easily fits into satellite and 3G wireless upload channels. One way ACCESS transmission delay using AAC-ELD is an easily-managed 50 milliseconds.
Linear PCM – does not compress audio at all and uses 48KHz sampling to provide low-delay transparent audio but with large data throughput. Mono mode requires a network capacity of 804Kb/s whilst Stereo (Dual Mono) requires in excess of 1.5Mb/s.
FLAC – comresses the audio data using a low-delay loss-less algorithm that removes some 30-40% of the network data compared with PCM without introducing any coding artifacts. The actual data rate is variable based on the complexity of the coded audio.
G.711 – µ-law & a-law - are the coding algorithms used by standard digital POTS/PSTN calls and provides normal "telephone quality" 300Hz - 3.4KHz audio. These algorithms are included for compatibility with SIP-style VoIP 'phones and codecs.
G.722 - is the coding algorithms traditionally used by broadcasters used over ISDN for Sport and News commentaries and provide 7KHz low-delay speech and music. This algorithm is also included for compatibility with SIP-style VoIP 'phones and codecs.
For use in the most remote locations, the Access units will even work seamlessly with a satellite terminal to provide the same high-quality audio expected of the BRIC algorithms from almost anywhere in the world using the Inmarsat BGAN (Broadband Global Area Network) service. For more information please contact us.
Features
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Compatibility with a wide variety of wired and wireless circuits including:
- Domestic and business DSL, POTS and cable
- 802.11 WiFi networks (e.g. Public WiFi hotspots) and WiMAX
- 3G / UMTS / HSDPA mobile data networks
- Satellite services such as VSAT and BGAN
- Standard BRIC algorithms cater for all types of IP connection with low delay audio from 7kHz mono to 15kHz stereo or dual mono
- Optional AAC upgrade offers near-transparent MPEG-4 audio over reliable connections
- Linear PCM uncompressed and FLAC for lossless audio over managed networks
- N/ACIP SIP compatible connections are supported (Tech 3326 - except Layer-II) for interoperability between codecs from different manufacturers
- 'Set and forget' Rackmount unit for studio use; lightweight Portable unit for use on the road
- Easy to use web-based configuration and control of Rackmount unit and built-in touch-screen interface with web browser for Portable unit
- Optional 5-channel mixer available for the Access Portable
Access Algorithms
| Algorithm | Audio Bandwidth | Data Bitrate | Coding Delay |
|---|---|---|---|
| BRIC HQ1 | 15kHz mono | 28kbit/s | 80ms |
| 15kHz stereo | 42kbit/s | 80ms | |
| 15kHz dual mono | 56kbit/s | 80ms | |
| BRIC HQ2 | 15kHz mono | 24kbit/s | 320ms |
| 12kHz mono | 24kbit/s | 340ms | |
| 15kHz stereo | 30kbit/s | 320ms | |
| 12kHz stereo | 30kbit/s | 340ms | |
| BRIC ULB | 7kHz mono | 12kbit/s | 80ms |
| HE-AAC | 20kHz mono | 32kbit/s | 600ms |
| 20kHz stereo | 48kbit/s | 600ms | |
| 20kHz dual mono | 64kbit/s | 600ms | |
| HEv2-AAC | 20kHz | 18 - 48kbit/s | 300ms |
| AAC | 20kHz | 64 - 256kbit/s | 300ms |
| AAC-LD | 20kHz mono | 64kbit/s | 80ms |
| 20kHz stereo | 96kbit/s | 80ms | |
| 20kHz dual mono | 128kbit/s | 80ms | |
| AAC-ELD | 20kHz | 24 - 96kbit/s | 50ms |
| Linear uncompressed | 20kHz mono | 788kbit/s | 40ms |
| 20kHz stereo | 1536kbit/s | 40ms | |
| G.711 | 300Hz - 3.4kHz | 64kbit/s | 80ms |
| µ-law & a-law | Mono | ||
| G.722 | 7kHz Mono | 64kbit/s | 80ms |
| *44.1KHz and 32KHz modes are only supported via AES3 digital audio I/O on both ends of link. *FLAC bandwith is variable and based on audio input | |||
N/ACIP SIP / EBU-3326 Codec Compatibility
The N/ACIP international committee was set up by the European Broadcast Union to hammer out a common protocol to interconnect codec brands and resulted in EBU-3326, a technical document describing how best to achieve this goal. It defines several encoding algorithms plus the transport layer and incorporates the SIP protocol that determines the handshake that takes place at the start of an IP codec call. ACCESS and BRIC-Link codecs already include SIP compatibility which also has the advantage of making them compatible with with other non-broadcast products such as VoIP hardware, software and mobile phone apps such as the ARC (for Android phones). ACCESS and BRIC-Link do not fully comply with EBU3326 as they do not feature MPEG Layer-II but apart from this, they have been tested to be compatible with several other manufacturers' devices using encoders supported by both products. In general, when connecting between Comrex hardware, it is best to use one of the proprietarty modes which take advantage of other algorithms and special features such as BRUTE (UDP stability enhancement and congestion avoidance).
BRIC-TS - Traversal Server
The BRIC-TS Traversal Server is hard to describe but an extremely useful development it enables us to make make connections between BRIC-enabled devices, such as the ACCESS codec, fast and simple.
One of the issues that many users of our ACCESS codecs are faced with is having to deal with IP network firewalls or trying to access their codecs which are on a private Local Area Network or LAN. Just as when you are trying to make a telephone call, if you don't know the number, you can't make the call.
The BRIC-TS Traversal Server sits on the internet and is maintained by Comrex. You may have noticed when there is an incoming call, that the public IP address is reported by the ACCESS browser screen - even though the codec may be behind a firewall or NAT router - such as with 3G.
The Traversal Server takes advantage of this information and lets users call another codec by "name" rather than by "number" (or IP address) where the BRIC-TS routes the call to the correct IP connection. The audio does not pass through the BRIC-TS - only the IP addressing is handled by it. Imagine being able to call to a portable that is on a 3G network or to a codec that is connected to the internet at a WiFi Hotspot.
A codec connecting to BRIC TS "punches a hole" through the NAT or firewall which in turn allows for a return path back to the codec. Once a codec has reached out to another device on the BRIC TS, the two units handshake and exchange all of the "technical details" that they need to send audio back and forth.
These "details" include the specific route that data needs to travel to get to each device. This is really the tricky part since NATs and firewalls can make it difficult for data to get through. But, once the two devices have made contact via the BRIC TS, then a "Peer-to-Peer" connection is established and audio is bidirectionally transmitted until either one of the units disconnects or the circuit is terminated.
To take advantage of the BRIC-TS Traversal Server, you will need to buy a licence for each ACCESS Codec you wish to be registered on the BRIC-TS. This is a one-time cost. The licence code is entered into each codec via the normal user interface. You then get an account of your own on the BRIC-TS and you are prompted to enter the MAC address of each codec on the BRIC-TS and your name for the codec. Logging onto the BRIC-TS, you can see the status of each codec (idle, connected etc) - its software revision and other useful information.
On each codec's screen, you see a list of all your codecs by name and if they are available. The BRIC-TS makes using the ACCESS-IP easy and solves many of the firewall / network setup issues.
Optional Road / Flight Cases
AX-ROAD-EX – For Access Portable and Accessories
Olive Green waterproof Explorer case made from high impact poly-ethylene and rugged enough even for extremely severe and hazardous environments, fitted with high-density foam to take Access Portable, 1x Battery and 1 spare, mains power supply, 4x PC cards (2 long and 2 short), 1x Aerial (eg WiFi), ancillary cables and manual (in the lid held in behind velcro straps). Overall dimensions are 360 x 305 x 195mm approx (w x d x h) and the weight is 2.75Kg (empty) / approx 8.5Kg with equipment. There are two snap-shut catches to close the lid and the moulding incorporates provision for a padlock.
AX-ROAD-MX – FOR Access Portable With Its Mixer and Accessories
Silver-Grey Comrex high impact ridged plastic case with aluminium frame and sturdy fasteners, rugged enough for the cargo hold of an airplane. Custom foam for the Access (also available for the Vector/Envoy, Matrix or HotLine/Nexus) accommodates the Access Portable with battery, 1 spare battery, 2x PC cards, mains power supply, cables, headphones etc. A pre-cut area of foam can be easily removed to accommodate the AX-MIX add-on Mixer. With the cover closed, there is space for manual and other items between the foam. Outside dimensions: 495 x 395 x 215 mm approx (w x d x h) and the weight is 12.5Kg (empty) / Approx 18.5Kg with equipment. There are two wind-down catches to close the lid and provision for a padlock.
Data Packages – Unlocked 3G / UMTS Data Card and Paid-up data packages.
For the Access to connect via 3G / UMTS, a suitable plug-in data card (or USB dongle) needs to be used. We have a lot of experience with 3G / UMTS connectivity and are happy to share this information with customers.
In most situations, it is possible to choose a 3G / UMTS data network that will provide suitable coverage for a particular geographical area but it can be very useful to be able to choose a different network from time to time. This is particularly important when roaming where data charges can be extremely high and when visiting a different place where another network may provide better data coverage.
The Access runs under Linux and whilst most data cards will have Windows drivers available, Linux support may be less certain and we therefore stock unlocked data cards that we know work reliably with the Access and provide high quality connectivity.
We are also able to provide paid-up data packages – for example a year’s data connectivity on a specific network – and other data contracts in conjunction with the supply of our data cards (depending on network / geographical location) and have a good deal of experience in using various networks around the world. Please contact us if you have any specific requirements.
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| Front-panel indicators | Stereo input and output LED level meters Power LED |
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| Power Requirements | 12V DC supplied by Access Portable | ||||
