In cases where HDMI and-or SPDIF are using a HDA bus (released 2004), maximum available audio bitrate is ~37 Mbit/s due to the bus its self (not HDMI or SPDIF).
Now that USB audio has become a standard, I believe the USB 2.0 audio bitrate is 480 Mbit/s, allowing for full rate, high speed TOSLink.
I am not 100% sure how much transmission bitrate 37 Mbit/s is for HDMI, due to
data island periods (it will be more than 37 Mbit/s overall).
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RTN (raw, uncompressed), 32 channel consumer (based on HDMI):
32 (C) x 24 (B) = 768, + 31 (nil) = 799, + 20 packet bits = 819, x 48000 (S) =
39.312 Mbit/s.
32 (C) x 24 (B) = 768, + 31 (nil) = 799, + 20 packet bits = 819, x 96000 (S) =
78.624 Mbit/s.
32 (C) x 24 (B) = 768, + 31 (nil) = 799, + 20 packet bits = 819, x 192000 (S) = 157.248 Mbit/s.
32 (C) x 32 (B) = 1024, + 31 (nil) = 1055, + 20 packet bits = 1075, x 48000 (S) =
51.600 Mbit/s.
32 (C) x 32 (B) = 1024, + 31 (nil) = 1055, + 20 packet bits = 1075, x 96000 (S) =
103.200 Mbit/s.
32 (C) x 32 (B) = 1024, + 31 (nil) = 1055, + 20 packet bits = 1075, x 192000 (S) = 206.400 Mbit/s.
32 (C) x 48 (B) = 1536, + 31 (nil) = 1567, + 20 packet bits = 1587, x 48000 (S) =
76.176 Mbit/s.
32 (C) x 48 (B) = 1536, + 31 (nil) = 1567, + 20 packet bits = 1587, x 96000 (S) = 152.352 Mbit/s.
32 (C) x 48 (B) = 1536, + 31 (nil) = 1567, + 20 packet bits = 1587, x 192000 (S) = 304.704 Mbit/s.
The ones coloured with orange can be used with high speed TOSLink (125 Mbit/s, NRZ).
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25 (C) x 24 (B) = 600, + 24 (nil) = 624, + 20 packet bits = 644, x 192000 (S) =
123.648 Mbit/s.
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48 bits compressed to 24 bits would require the same bitrate as 24 bit (1st example).
Format: PCM
Sample rate: 48K
Bit depth: 48B
Channels: 32
Compressed: Yes
Compression: 24
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Also note, due to the metadata packet, all formats can be transmitted (bitstream) via RTN.
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48 Fixed vs 32 Float (sonicstudio.com)