by John Bowen » Wed Feb 24, 2010 1:21 am
In what we could find (both myself and the engineers), S/PDIF is identified as the 'consumer' version of AES/EBU standard. While the data is (mostly) compatible, the consumer spec is only there for 48, 44.1, and 32 kHz. It's also the case, however, that the spec says the format has "no defined data rate". Note this quote from a Wikipedia post:
"S/PDIF is used to transmit digital signals of a number of formats, the most common being the 48 kHz sample rate format (used in DAT) and the 44.1 kHz format, used in CD audio. In order to support both systems, as well as others that might be needed, the format has no defined data rate. Instead, the data is sent using biphase mark code, which has either one or two transitions for every bit, allowing the original word clock to be extracted from the signal itself."
It is this lack of definition that has the engineer uncertain as to what is possible with the built-in S/PDIF processor of the SHARC chip.
As to bit depth, I am told the intention is to use 24-bits. Again, from Wiki:
"S/PDIF is meant to be used for transmitting 20-bit audio data streams plus other related information. To transmit sources with less than 20 bits of sample accuracy, the superfluous bits will be set to zero. S/PDIF can also transport 24-bit samples by way of four extra bits; however, not all equipment supports this, and these extra bits might be ignored."
Further testing next week should provide confirmation on this.
-john b.
In what we could find (both myself and the engineers), S/PDIF is identified as the 'consumer' version of AES/EBU standard. While the data is (mostly) compatible, the consumer spec is only there for 48, 44.1, and 32 kHz. It's also the case, however, that the spec says the format has "no defined data rate". Note this quote from a Wikipedia post:
"S/PDIF is used to transmit digital signals of a number of formats, the most common being the 48 kHz sample rate format (used in DAT) and the 44.1 kHz format, used in CD audio. In order to support both systems, as well as others that might be needed, the format has no defined data rate. Instead, the data is sent using biphase mark code, which has either one or two transitions for every bit, allowing the original word clock to be extracted from the signal itself."
It is this lack of definition that has the engineer uncertain as to what is possible with the built-in S/PDIF processor of the SHARC chip.
As to bit depth, I am told the intention is to use 24-bits. Again, from Wiki:
"S/PDIF is meant to be used for transmitting 20-bit audio data streams plus other related information. To transmit sources with less than 20 bits of sample accuracy, the superfluous bits will be set to zero. S/PDIF can also transport 24-bit samples by way of four extra bits; however, not all equipment supports this, and these extra bits might be ignored."
Further testing next week should provide confirmation on this.
-john b.