14.04.2025 | 09:31
U međuvremenu, frend audiofil, našao mi je dobar tekst o tome kako to sve funkcionira "ispod haube", pa koga zanima:
"S/PDIF combines clock data with the audio data. The converters generate a clock signal.
The computer tells your USB converter the format it will use e.g. 48kHz 24bit PCM data. The USB endpoint replies it wants to receive the data isochronously timed to its own 24.567MHz clock.
It takes this data splits it into blocks, which are split into frames, and then split into 192 sub-frames. Each subframe has a preamble attached at the front, 24bits of data, a validity bit, a user bit, a channel bit, and a parity bit attached to it. These subframes are then bi-phase mark encoded with the clock source which looks like this
markdingst.blogspot.com/2015/12/manchest...phase-mark-code.html and then whisked away down the wire.
The receiving device then decodes the bi-phase mark code to extract both the clock and the data. It goes through the data looking for the "B" Preamble indicating the start of the block and then starts decoding each of the subframes. Every 192 subframes it combines all the user bits, channel bits, validity bits, and parity bits, and then uses that data to figure out what to do with the data it just received since that data tells the receiver what format, sample rate, bit detph, etc the data has.
But ultimately, the data itself under all this protocol nonsense is still just PCM data, chopped up, rearranged, reassembled, sent with additional bits of information, but critically should never be converted into anything else, still completely original when it gets spat out the other end."