Audio Over CAT5: Proprietary alternatives and standardization efforts, Part II
Continued from 'Audio Over CAT5: Proprietary alternatives and standardization efforts'….
For an update on AES50, Grant deferred to Michael Page, engineering project leader for SuperMAC and HyperMAC at Sony's Pro Audio Lab in Oxford, UK. Here's what Page had to say in mid-May: “Oxford Technologies is the technology development and licensing business of Sony Pro-Audio Lab. Amongst other things, we develop core technology for high-performance audio-over-CAT5 interconnections. We sell components and hardware modules, and we also license technology. Our customers are pro-audio equipment manufacturers. Our focus is on developing interconnection technologies with the following characteristics:
- low, deterministic latency (for example, three samples at 44.1 or 48 kHz, approximately 66 µsec);
- high-quality clock frequency and phase synchronization;
- high-reliability, simple-to-implement redundant systems;
- support for a wide range of uncompressed audio formats, including high-resolution formats such as 192-kHz PCM and DSD (Direct Stream Digital);
- nonaudio interconnection (for example, control and status) is via general-purpose Ethernet bandwidth, running alongside the audio signal paths;
- alignment with existing AES standards (for example, AES3 2-channel interconnection, AES11 sample clock specification); and
- commitment to protocol standardization via AES.
“Our technologies are aimed at products including, but not limited to, digital mixing consoles, digital audio distribution and routing systems, signal processing systems, ADC/DAC units, and audio workstations. We have received especially strong interest from live sound and broadcast sectors, where our focus on low latency, reliability and standardization is particularly attractive.
“SuperMAC is the subject of a current AES standardization project. Project AES-X140 commenced in late 2003, under the auspices of AES Standards Working Group SC-02-02. The resulting draft standard was released on March 8, 2005, as a Public Call For Comment, named AES50-xxxx. This Call For Comment is scheduled to conclude on June 8, unless the CFC process results in further amendment. We intend to submit our HyperMAC technology for AES standardization in a similar manner, when the protocol is sufficiently mature.
“All current implementations of SuperMAC and Router technology are based on Xilinx FPGAs, preferably Spartan-3. The implementation IP is delivered to licensees in pre-compiled logic cores, as parts of a ‘kit’ of licensed materials and services. The same approach will be used for HyperMAC, once that is released later in 2005.
“A dedicated SuperMAC IC is under development, which may provide an alternative to the Xilinx FPGA in SuperMAC transceiver implementations, and will be license-free. It is hoped that this will considerably reduce the design effort required to implement SuperMAC, especially for simple and small-scale applications. For large applications, especially by companies with significant digital design expertise, we expect that the flexibility of the Logic Cores approach may remain more attractive.”
Gibson has chosen to work through the IEEE to drive its MaGIC technology towards industry standardization, under the name Residential Ethernet (formerly, Synchronous Ethernet). Michael Johas Teener from Broadcom is also on the IEEE's Residential Ethernet committee, and a recently published paper by him outlines the broad-stroke goals of the committee: “There are three primary differences between the proposed Residential Ethernet architecture and existing Ethernet:
- precise synchronization,
- scheduled priorities, and
- admission controls.
“Although these are significant changes, they can all be implemented using relatively small extensions to the standard Ethernet MAC (defined in IEEE 802.3) and bridges (defined in IEEE 802.1D).”
You can find Teener's paper at www.teener.com/ResidentialEthernet/Residential%20Ethernet.pdf. (His Web site is also an invaluable source of information on the history of FireWire). A more detailed tutorial, multipresentation set from various committee members is available at http://grouper.ieee.org/groups/802/3/tutorial/mar05/tutorial_1_0305.pdf.
