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DSC was arguably the hallmark change of DisplayPort 1.4[1]. To say something is "only capable of achieving" its performance by utilizing the very tech it is bui

DSC was arguably the hallmark change of DisplayPort 1.4[1]. To say something is "only capable of achieving" its performance by utilizing the very tech it is built on feels like there has been a misunderstanding somewhere. To be clear, Display Stream Compression is different from Chroma Subsampling[2], which the parent referenced. 1. https://en.wikipedia.org/wiki/DisplayPort#1.4 https://en.wikipedia.org/wiki/DisplayPort#1.4 2. https://en.wikipedia.org/wiki/Chroma_subsampling https://en.wikipedia.org/wiki/Chroma_subsampling

KolenCh 5y ago
“Only capable of achieving” is likely referring to it being lossy. It is reasonable for some consumers or manufacturers to not settled with lossy.
- lsaferite 5y ago
  FWIW, DSC is claimed to be lossless. https://www.cablematters.com/blog/DisplayPort/what-is-display-stream-compression https://www.cablematters.com/blog/DisplayPort/what-is-displa...
  - wtallis 5y ago
    "Visually lossless" isn't really lossless. What it actually means is "we're pretty sure you won't notice", which is probably correct but isn't a claim that should be accepted at face value.
    - lsaferite 5y ago
      Which is precisely why I included the "claimed" part in my statement. I don't know enough about how the compression works to know one way or the other definitively.
    - account42 5y ago
      To put it another way, there is no such thing as general lossless compression - to make some data smaller without losing any information your new representation has to make other data larger. You can limit that "larger" to 1 bit but you will still have some cases where the compressed data is definitly not smaller than the source so it will not help you with cases like this where there is a hard upper limit on how much data you can transport.
    - fomine3 5y ago
      VESA/display manufacturers should provide various DSC examples for consumer, rather than just saying "virtually lossless".
  - KolenCh 5y ago
    They claim it to be visually lossless. There's also a term for audio, but I forgot the exact terminology. Things like this is applying lossy compression carefully with lab test on real humans to claim that under an A/B test an average human would not discern the difference. But it still doesn't mean it should not be taken with a grain of salt. In any case, it is objectively inferior (and subjectively might not matters.) On top of my head one thing I'd question is generation loss (but if I am serious in the market of this kind of display I should study more carefully what their claim really is.) But this is enough a technical detail for anyone to say "they only achieve XxY resolution at Z FPS with DSC" because the theoretical bandwidth isn't there and make do with lossy compression.
    - foo_barrio 5y ago
      I believe "transparent" is the term used when claiming a lossy audio codec is indistinguishable to a lossless one by a human for some definition of an average human. For example I believe aac was considered transparent for most pop music at 160kbps for stereo, 16-bit @ 44.1khz (CD quality). So iTunes selling 192-256kbps was considered more than enough.

KolenCh 5y ago

“Only capable of achieving” is likely referring to it being lossy. It is reasonable for some consumers or manufacturers to not settled with lossy.

lsaferite 5y ago
FWIW, DSC is claimed to be lossless. https://www.cablematters.com/blog/DisplayPort/what-is-display-stream-compression https://www.cablematters.com/blog/DisplayPort/what-is-displa...
- wtallis 5y ago
  "Visually lossless" isn't really lossless. What it actually means is "we're pretty sure you won't notice", which is probably correct but isn't a claim that should be accepted at face value.
  - lsaferite 5y ago
    Which is precisely why I included the "claimed" part in my statement. I don't know enough about how the compression works to know one way or the other definitively.
  - account42 5y ago
    To put it another way, there is no such thing as general lossless compression - to make some data smaller without losing any information your new representation has to make other data larger. You can limit that "larger" to 1 bit but you will still have some cases where the compressed data is definitly not smaller than the source so it will not help you with cases like this where there is a hard upper limit on how much data you can transport.
  - fomine3 5y ago
    VESA/display manufacturers should provide various DSC examples for consumer, rather than just saying "virtually lossless".
- KolenCh 5y ago
  They claim it to be visually lossless. There's also a term for audio, but I forgot the exact terminology. Things like this is applying lossy compression carefully with lab test on real humans to claim that under an A/B test an average human would not discern the difference. But it still doesn't mean it should not be taken with a grain of salt. In any case, it is objectively inferior (and subjectively might not matters.) On top of my head one thing I'd question is generation loss (but if I am serious in the market of this kind of display I should study more carefully what their claim really is.) But this is enough a technical detail for anyone to say "they only achieve XxY resolution at Z FPS with DSC" because the theoretical bandwidth isn't there and make do with lossy compression.
  - foo_barrio 5y ago
    I believe "transparent" is the term used when claiming a lossy audio codec is indistinguishable to a lossless one by a human for some definition of an average human. For example I believe aac was considered transparent for most pop music at 160kbps for stereo, 16-bit @ 44.1khz (CD quality). So iTunes selling 192-256kbps was considered more than enough.