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An Overview to SPDIF Class I-7 by Prof. John McLaughlin 27.04.2012. SPDIF stands for Sony/Philips Digital Interconnect Format. This is an audio format used for carrying digital audio signals on DVD players, CD players, computer sound cards and car audio systems. The format is also known as IEC 958 type II, S/P-DIF and S/PDIF. Channel Data Two 192 bit blocks (right and left channel data) are used. These are segregated into a dozen 16 bit words. The control codes are the initial six bits. This audio format does not provide a specific resolution or data rate. The apparatus holding the connectors will establish the data rate hand shake. Bi-Phase Mark Code and Data Rates The audio format uses the Bi-phase mark code. This code can have one or two transitions per bit. This feature permits the first word clock to be pulled out of the base signal. 44.1 kHz and 48 kHz are the most common rates used by the format. 48 kHz is (DAT- Digital Audio Tape) data rate. 44.1 kHz is for CD audio. It should be noted that the SPDIF format can support 20 bit audio. However, standard transmissions are limited to 16 bit audio. The protocol can also support 24 bit audio. This is not natively supported however. If signals less than 20 bits are to be transmitted, the irrelevant bits will be trimmed off. Audio Data Format Information Data is relayed by 32-bit data word streams. A frame is made up of 384 words. 192 of the words are used for the stereo A channel. The other 192 words are for the stereo B channel. The specs of the program are set by the IEC standard 60958-3. The format is also part of the AES/EBU standards. This is also known as the IEC-60958 standards. Its designation is IEC-958 type II. The digital audio format is actually derivative of AES/EBU. At the protocol level, the two are very similar. The connectors were changed from the XLR (commercial and professional audio equipment) to TOSLINK or RCA. These were adapted because they have proven easier to work with. This modification meant changing the format’s cable as well. When used with RCA jacks, one is able to listen to high quality sound previously available in costly commercial equipment. Interface Applications The format has two major purposes. It is used mainly for sending out digital audio according to the IEC 61937 standard. The second is to relay the signal between the player or computer to the home theater. This is applicable in home theaters with DTS surround sound) or Dolby Digital. The SPDIF format is utilized for inter-connecting commercial audio apparatus. Aside from the technical features specified, the format can also reduce static and noise. This is possible because the format uses fiber optic cable. References:

An Overview To SPDIF