Multi Channel Audio Digital Interface
The Multichannel Audio Digital Interface ( MADI ) is a digital interface for multichannel, unidirectional audio transmission , which is mainly used in professional recording studio technology. It is standardized as AES10 by the Audio Engineering Society .
history
In the 1980s, the audio industry was looking for new and more modern transmission options and formats in order to be able to transmit many audio channels simultaneously over one cable and to develop an alternative to expensive and unwieldy multicores in live and recording studio operations. In order to bundle these efforts, the MADI-Group was formed, initially consisting of Sony , Mitsubishi , Neve and SSL . The aim was to develop a lossless and insensitive data transmission format, which was finally defined in 1989 at AES in the AES10 standard. It was the hour of birth of the “Multichannel Audio Digital Interface” (MADI).
The first official definition of this format was the AES10-1991. This was followed by updates in 2003, 2005 and 2008. AES10-1991 defined MADI with a resolution of 24 bits at 32 kHz up to a maximum of 48 kHz, with a tolerance of 12.5%. This enabled the clock frequency of 49.152, which was still in use at the time, to be achieved. This tolerance is known under the name "Varispeed" and was among other things. a. necessary for the earlier tape machines.
In AES10-1991, MADI was set to 56 channels. This changed with the revision of 2003. Since tape machines were being used less and less at that time, it was possible to do without “Varispeed” and to increase the possible number of channels. 64 channels with a resolution of up to 48 kHz were now available to the user
The possible maximum resolution was revised with the revision of 2003 and, similar to the ADAT procedure , the possible sampling rate was increased to 96 kHz, while foregoing the number of audio channels. With the AES10id-2005, resolutions of up to 192 kHz were finally possible.
technology
A MADI connection can consist of both optical ( FDDI ) and coaxial lines (75 Ohm) and contains 28 or 32 AES / EBU audio channels as well as additional synchronization signals. Since AES / EBU is its own format (for two mono channels with up to 48 kHz / 24 bit), MADI basically bundles the individual channels of another format. The different number of channels depends on whether you need the varispeed function with a speed change of ± 12.5%.
MADI can transmit up to 56 (with Varispeed) or 64 mono channels (without Varispeed) in one cable. This means that many more channels can be transmitted over significantly fewer lines than is possible with ADAT, TDIF , S / PDIF or AES / EBU, for example . Today MADI can even transmit with a sampling rate of up to 192 kHz. This is particularly interesting for studio cabling and enables the technical expansion of existing production environments, whereby the positive aspect of less cabling in LIVE applications stands out a lot more than in fixed installations. MADI is considered a very fault-tolerant and resource-saving protocol. It is particularly suitable for complex digital studio projects, since the individual channels can again be present as AES / EBU, for example on a signal matrix, which can then be distributed individually via cables.
specification
- Original resolution and quantization
- Sampling rate : 32 kHz to 48 kHz, ± 12.5%
- Sampling depth : 16 bit to 24 bit
- Synchronization over 48 kHz or 96 kHz
- Original data transfer
- up to 64 mono channels in one optical or coaxial cable
- Cable length max. 100 m (coaxial) or 2,000 m (optical)
- Transfer rate: 125 Mbit / s
- Data transfer rate: 100 Mbit / s
- Maximum data transfer rate: 96.768 Mbit / s = 56 channels at 48 kHz
- Minimum data transfer rate: 50.176 Mbit / s = 56 channels with 32 kHz
- The following forms of transmission are supported today:
- Standard (1991): 56 channels / 24 bit / 44.1 kHz - 48 kHz / varispeed ± 12.5%
- Standard (2003): 64 channels / 24 bit / 32 kHz - 48 kHz
- Double Wire 96 / 48k mode: 32 channels / 24 bit / 96 kHz
- Quad Wire 192 / 48k mode: 16 channels / 24 bit / 192 kHz
Individual evidence
- ↑ Audio Engineering Society [AES] (ed.): AES10-2003 AES Recommended Practice for Digital Audio Engineering - Serial Multichannel Audio Digital Interface (MADI) . 2003 ( ( Page no longer available , search in web archives: iis.ee.ethz.ch )).
- ↑ a b c Reaching your goal with light - What you should know about the MADI standard . In: 96 kHz, Pro Audio Magazin . November 22, 2011 ( ( Page no longer available , search in web archives )).
- ^ Robert A. Finger: AES Recommended Practice for Digital Audio Engineering - Serial Multichannel Audio Digital Interface (MADI). In: http://www.urbancom.us . Audio Engineering Society, Inc., 1991, accessed 2020 .
- ↑ Mary C. Gruszk: Serial Madi. October 15, 2008, accessed July 4, 2020 .
literature
- Andreas Friesecke: The Audio Encyclopedia - A reference work for sound engineers . Saur, Munich 2007, ISBN 978-3-598-11774-9 .
- Roland Enders: The home recording manual - the way to optimal recordings . 3rd, revised edition. Carstensen, Munich 2003, ISBN 3-910098-25-8 .
- Hubert Henle: The recording studio manual. Practical introduction to professional recording technology . 5th, completely revised edition. Carstensen, Munich 2001, ISBN 3-910098-19-3 .
