4 ms·

ARC and CEC come to mind. ARC probably isn't too important, but CEC is nice being able to control various boxes with the same remote. Or being able to control t

ARC and CEC come to mind. ARC probably isn't too important, but CEC is nice being able to control various boxes with the same remote. Or being able to control the TV's volume with another remote.

babypuncher 3y ago
ARC is actually pretty important, especially now that eARC is a thing. It finally decouples your receiver's HDMI capability requirements from your TV.
- simoncion 3y ago
  I see no __technical__ reason why you couldn't do CEC over the AUX channel... all that's required is for the software on either end to be updated to squirt and interpret the bits, and it's a low-speed protocol, so it'll fit just fine in the AUX channel. "ARC" seems to be "Audio over HDMI using CEC for discovery and control", which (if you've bothered to run CEC over the DisplayPort AUX channel) you get the rest automatically with DisplayPort. However, because both CEC and ARC are HDMI standards, you bet your biscuits that the HDMI Consortium will bar anyone who wants to use HDMI ports on their devices from shipping official firm/software that does the braindead-simple thing of running CEC over DP AUX, and having ARC-compatible firm/software. As is nearly always the case (and when it's not, it's not for long) DisplayPort is totally capable of everything HDMI is, but the HDMI Consortium stands in the way of having commercially-distributed DisplayPort "home theater" products that are compatible with the nice-to-have HDMI features.
  - babypuncher 3y ago
    When I say DisplayPort needs these features, I don't necessarily mean they need the HDMI Consortium's specific implementation of them. I see no reason VESA couldn't implement their own alternatives to CEC, ARC, Auto Lipsync, etc. These HDMI features solve a host of problems that are unique to home theater setups, so any HDMI alternative that wants to supplant it needs to also solve them as well. Like you point out, there's no technical reason DisplayPort cannot provide similar features. The issue is the lack of any standards for them built into the DisplayPort specification. Some of these features, like CEC, are 20 years old and could easily be improved upon in an ecosystem that doesn't have to worry about backwards compatibility.
    - simoncion 3y ago
      > When I say DisplayPort needs these features, I don't necessarily mean they need the HDMI Consortium's specific implementation of them. Ah, okay. Well, DisplayPort handles EDID, DDC/CI, E-DDC & friends... that's the CEC-equivalents handled. VESA does have standards for remote control of displays... it turns out that that's a thing that people want to be able to do. > The issue is the lack of any standards for them built into the DisplayPort specification. Nah. DisplayPort already supports everything (or just about everything) CEC can do. The reason you don't see this stuff often making its way into TVs is because the HDMI Consortium gets in the way of folks who want to add DP ports to their TVs. The reason you don't see explicit support for HDMI Consortium protocols such as CEC in VESA standards is -again- because the HDMI Consortium gets in the way of folks who want to add DP ports to their TVs... so why bother? (Especially when actually supporting the protocol is trivial... squirt exactly what you'd send over the HDMI cable over the DP AUX channel, instead.) If it was actually politically possible to have DP ports on TVs, then you'd see some of the more esoteric aspects of CEC (like manipulating a TV tuner) be quickly standardized into the VESA equivalents... assuming that VESA didn't just say "Oh yeah, y'all just go talk CEC to these new DP-equipped TVs. You already know how.".
  - jasomill 3y ago
    eARC is important not only because cable management and CEC, but because it's the only high bitrate digital audio output on most TVs: the only other commonly available digital audio output, TOSLINK, is limited to two-channel PCM[1], AC3, and DTS. [1] While the physical TOSLINK cable is able to support higher channel counts via ADAT[2], I'm not aware of any TVs with ADAT support. Similarly, while 192 kHz / 24-bit TOSLINK support is common in pro audio and audiophile gear, the standard only requires 48 kHz / 20-bit. I imagine most TVs output 48 kHz / 20-bit, if only for the sake of configuration simplicity: TOSLINK is strictly unidirectional, so automatically negotiating format support beyond mandatory minima is impossible. [2] https://en.wikipedia.org/wiki/ADAT_Lightpipe https://en.wikipedia.org/wiki/ADAT_Lightpipe
    - simoncion 3y ago
      > ...[eARC is] the only high bitrate digital audio output on most TVs... Great news! DisplayPort supports: > 1–8 channels, 16 or 24-bit linear PCM; 32–192 kHz sampling rate; maximum bitrate 36,864 kbit/s (4,608 kB/s)
      - babypuncher 3y ago
        But it doesn't support any of the common bitstreamed audio formats like Dolby Atmos or DTS. eARC lets your TV pass those along to your compatible receiver even if the TV itself can't make heads or tails of the format.
        simoncion 3y ago
        > But it doesn't support ... Dolby Atmos or DTS. No, I think you're wrong about that. > DisplayPort v1.2 also adds new audio enhancements including the following: — Audio Copy Protection and category codes — High definition audio formats such as Dolby MAT, DTS HD, all Blu-Ray formats, and the DRA standard from China — Synchronization assist between audio and video, multiple audio channels, and multiple audio sink devices using Global Time Code (GTC) MAT claims to require an Atmos-capable decoder, so that sure seems like Atmos to me. I dunno what DTS HD, but that sounds like a souped-up DTS. Also take note of the "High definition audio formats such as" statement... that list of formats is incomplete. The quote comes from: <https://vesa.org/press/vesa%C2%AE-introduces-displayporttm-v1-2-the-most-comprehensive-and-innovative-display-interface-available/ https://vesa.org/press/vesa%C2%AE-introduces-displayporttm-v...>

ARC and CEC come to mind. ARC probably isn't too important, but CEC is nice being able to control various boxes with the same remote. Or being able to control the TV's volume with another remote.

babypuncher 3y ago

ARC is actually pretty important, especially now that eARC is a thing. It finally decouples your receiver's HDMI capability requirements from your TV.

simoncion 3y ago
I see no __technical__ reason why you couldn't do CEC over the AUX channel... all that's required is for the software on either end to be updated to squirt and interpret the bits, and it's a low-speed protocol, so it'll fit just fine in the AUX channel. "ARC" seems to be "Audio over HDMI using CEC for discovery and control", which (if you've bothered to run CEC over the DisplayPort AUX channel) you get the rest automatically with DisplayPort. However, because both CEC and ARC are HDMI standards, you bet your biscuits that the HDMI Consortium will bar anyone who wants to use HDMI ports on their devices from shipping official firm/software that does the braindead-simple thing of running CEC over DP AUX, and having ARC-compatible firm/software. As is nearly always the case (and when it's not, it's not for long) DisplayPort is totally capable of everything HDMI is, but the HDMI Consortium stands in the way of having commercially-distributed DisplayPort "home theater" products that are compatible with the nice-to-have HDMI features.
- babypuncher 3y ago
  When I say DisplayPort needs these features, I don't necessarily mean they need the HDMI Consortium's specific implementation of them. I see no reason VESA couldn't implement their own alternatives to CEC, ARC, Auto Lipsync, etc. These HDMI features solve a host of problems that are unique to home theater setups, so any HDMI alternative that wants to supplant it needs to also solve them as well. Like you point out, there's no technical reason DisplayPort cannot provide similar features. The issue is the lack of any standards for them built into the DisplayPort specification. Some of these features, like CEC, are 20 years old and could easily be improved upon in an ecosystem that doesn't have to worry about backwards compatibility.
  - simoncion 3y ago
    > When I say DisplayPort needs these features, I don't necessarily mean they need the HDMI Consortium's specific implementation of them. Ah, okay. Well, DisplayPort handles EDID, DDC/CI, E-DDC & friends... that's the CEC-equivalents handled. VESA does have standards for remote control of displays... it turns out that that's a thing that people want to be able to do. > The issue is the lack of any standards for them built into the DisplayPort specification. Nah. DisplayPort already supports everything (or just about everything) CEC can do. The reason you don't see this stuff often making its way into TVs is because the HDMI Consortium gets in the way of folks who want to add DP ports to their TVs. The reason you don't see explicit support for HDMI Consortium protocols such as CEC in VESA standards is -again- because the HDMI Consortium gets in the way of folks who want to add DP ports to their TVs... so why bother? (Especially when actually supporting the protocol is trivial... squirt exactly what you'd send over the HDMI cable over the DP AUX channel, instead.) If it was actually politically possible to have DP ports on TVs, then you'd see some of the more esoteric aspects of CEC (like manipulating a TV tuner) be quickly standardized into the VESA equivalents... assuming that VESA didn't just say "Oh yeah, y'all just go talk CEC to these new DP-equipped TVs. You already know how.".
- jasomill 3y ago
  eARC is important not only because cable management and CEC, but because it's the only high bitrate digital audio output on most TVs: the only other commonly available digital audio output, TOSLINK, is limited to two-channel PCM[1], AC3, and DTS. [1] While the physical TOSLINK cable is able to support higher channel counts via ADAT[2], I'm not aware of any TVs with ADAT support. Similarly, while 192 kHz / 24-bit TOSLINK support is common in pro audio and audiophile gear, the standard only requires 48 kHz / 20-bit. I imagine most TVs output 48 kHz / 20-bit, if only for the sake of configuration simplicity: TOSLINK is strictly unidirectional, so automatically negotiating format support beyond mandatory minima is impossible. [2] https://en.wikipedia.org/wiki/ADAT_Lightpipe https://en.wikipedia.org/wiki/ADAT_Lightpipe
  - simoncion 3y ago
    > ...[eARC is] the only high bitrate digital audio output on most TVs... Great news! DisplayPort supports: > 1–8 channels, 16 or 24-bit linear PCM; 32–192 kHz sampling rate; maximum bitrate 36,864 kbit/s (4,608 kB/s)
    - babypuncher 3y ago
      But it doesn't support any of the common bitstreamed audio formats like Dolby Atmos or DTS. eARC lets your TV pass those along to your compatible receiver even if the TV itself can't make heads or tails of the format.
      - simoncion 3y ago
        > But it doesn't support ... Dolby Atmos or DTS. No, I think you're wrong about that. > DisplayPort v1.2 also adds new audio enhancements including the following: — Audio Copy Protection and category codes — High definition audio formats such as Dolby MAT, DTS HD, all Blu-Ray formats, and the DRA standard from China — Synchronization assist between audio and video, multiple audio channels, and multiple audio sink devices using Global Time Code (GTC) MAT claims to require an Atmos-capable decoder, so that sure seems like Atmos to me. I dunno what DTS HD, but that sounds like a souped-up DTS. Also take note of the "High definition audio formats such as" statement... that list of formats is incomplete. The quote comes from: <https://vesa.org/press/vesa%C2%AE-introduces-displayporttm-v1-2-the-most-comprehensive-and-innovative-display-interface-available/ https://vesa.org/press/vesa%C2%AE-introduces-displayporttm-v...>