USB C DSC Max Compression Capability

Per previous info, Spectrum will have DSC 1.2 for DisplayPort connections. It is currently supposed to support the choice of 4k 60hz with USB 3 or 4k 144hz with USB 2 bandwidth.
DP 1.4 can support 4k 97hz HDR uncompressed. 4k 144hz would therefore require a compression ratio of about ~1.5. As verified by VESA, USB C can do 4k 60hz SDR uncompressed with USB 3, by splitting the USB C lanes between USB data and DisplayPort. DSC can support a compression ratio of up to 3:1.
If using a 3:1 compression ratio with half DP 1.4’s bandwidth, 4k 144hz HDR would be very close to the maximum capability, while 4k 120hz HDR and 4k 144hz SDR would definitely be achievable.
It would be great it we could use a higher DSC ratio on USB C on the Spectrum so that we could take full advantage of its features. I am however not sure whether the DSC hardware in the Spectrum is capable of doing compression ratios above ~1.5. Could Eve look into that, and if so, whether it would be possible to improve through a firmware update?


The DSC specification is freely available and I downloaded a copy to take a look.

There are very few choices that can be made as part of the algorithm, with the main one looking to be the prediction algorithm. The encoder (i.e. video card) makes the choice, and it’s encoded into the bitstream. The decoder (i.e. monitor) uses this information to select the right prediction algorithm to reconstruct the signal.

I can’t see anything that would prevent the Spectrum from being able to decode and DSC 1.2 compressed video, no matter what compression ratio was used.


@Lore_Wonder @ReignDespair @nawthor @nkyadav
Could one of you or someone else pass this request on to the firmware team or whoever else at Eve would be appropriate?

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Hey @Daniel_Herr,
I’ll pass your queries onto the team, and get back to you when relevant data becomes available to better answer your queries.


Have you heard anything back on this from the team?