Compression in VR.

Baldbloke

Baldbloke

Baldbloke

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I read a lot of folk talking about compression in VR headset images. I get that it's something undesirable in graphics. Seems that some folk see a poor image and blame it on compression. May be it is. Can anyone explain how to identify the effects of compression? Point me in the direction of any video examples showing clearly what the difference is between high/low/lots/little/no compression? Is compression Codec dependant?

Thank you
 
Very hard to see outside of the headset itself. Even inside it can be game/motion dependant.

Half life alyx for example looks very different to racing in car at 100mph.

Pcvr headsets just look and feel much better imho. They have their own issues though.
 
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TheOracle said:
Very hard to see outside of the headset itself. Even inside it can be game/motion dependant.

Half life alyx for example looks very different to racing in car at 100mph.

Pcvr headsets just look and feel much better imho. They have their own issues though.
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Thank you.
Yes. From what I've learned from googling I can't find any difinitive simple answers. (Other than the in depth technical explanations which are beyond me anyway) I think yours is a fair and practical answer. Reason I asked was I just got a Quest 3 for iracing on pcvr to replace my existing HP G2 headset.

I've had a good fiddle with the Oculus debug tool and settings on the Q3 in order to try and get it to be at least as good as the G2. I can't. It comes close but not quite there. I wondered if this compression thingy might be a contributing factor (I'm using an oculus link cable if that makes any diff? Dunno). Just not getting the Q3 to display any better than the G2. The G2 is a dedicated pcvr device I believe. Your answer seems to ring true.

Ah well, I think the Q3 will be going back. Sorry Meta. I tried :). No new toy for me then. ;)
 
Baldbloke said:
I read a lot of folk talking about compression in VR headset images. I get that it's something undesirable in graphics. Seems that some folk see a poor image and blame it on compression. May be it is. Can anyone explain how to identify the effects of compression? Point me in the direction of any video examples showing clearly what the difference is between high/low/lots/little/no compression? Is compression Codec dependant?

Thank you
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In Oculus Debug Tool, set the bitrate to 10. You'll see what compression is clearly then.

Then as you increment it up a bit at a time, you'll see that compression artifacting diminish. For me, it's difficult to notice any improvement above 200-300.

But there was a video recently suggesting trying 940, which I'm going to try myself soon. I've never taken it that high.
 
You can use your GPU to up the bitrate more and more so that compression artefacts become less and less evident. I personally find my GPU (4090) has more than enough work just keeping frame rate >= 90 some games. I’ll be getting a Quest 3 but will most likely keep my G2 still for PCVR games such as sims.
 
danlightbulb said:
In Oculus Debug Tool, set the bitrate to 10. You'll see what compression is clearly then.

Then as you increment it up a bit at a time, you'll see that compression artifacting diminish. For me, it's difficult to notice any improvement above 200-300.

But there was a video recently suggesting trying 940, which I'm going to try myself soon. I've never taken it that high.
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That's a good idea to drop the bitrate very low just to see what it does. Saw those vids on youtube about bumping it up. I tried 700 then 800. Didn't go any higher. I think my 3080 ti might be a bit underpowered to cope with that.
Oh, to heck with it. I'm going to give it a go. One last chance Mr Zuckerberg. I'm warning ya. This is yer last chance :)
Andy D said:
You can use your GPU to up the bitrate more and more so that compression artefacts become less and less evident. I personally find my GPU (4090) has more than enough work just keeping frame rate >= 90 some games. I’ll be getting a Quest 3 but will most likely keep my G2 still for PCVR games such as sims.
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I only do sim racing in VR. I'm sure the Q3 is great for other stuff the G2 can not do though. I'll only be keeping the Q3 if it can outdo or at least equal the G2 in pcvr. I'm really sceptical at the moment though.


Edit: I just tried bitrate at 940. Not great. No contest for iracing with my 3080 ti. between the Q3 and the G2. Concluded the G2 wins for my purposes. Having said that folks with better gpu and cpu may get nicer results.
 
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I think the g2 and even the Pico 3 link are better than quest 3 for racing sims. Even though quest has much better lenses and sweetspot, you can't beat that compression free / latency free image.
 
Have you tried via USB cable?
I felt that I could see compression noise with the Pico 4 that I tried.
With my Quest Pro, there’s nothing apparent, which I assume is due to the higher bandwidth available to the Pro.
 
Mr_Sukebe said:
Have you tried via USB cable?
I felt that I could see compression noise with the Pico 4 that I tried.
With my Quest Pro, there’s nothing apparent, which I assume is due to the higher bandwidth available to the Pro.
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Not yet, I'm waiting for a new cable. I couldn't get link working with the one I had. Hopefully it will arrive today.
 
With my quest 2 I could see compression especially with driving games but with the quest 3 I haven't noticed any. Not sure if it's the faster processor is just better at decoding. This is wired btw.
 
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It also depends on the game. Skyrim VR can look really badly compressed due to the muddy colours and lots of vegetation.

That said, if you have a link cable and up the bitrate to 500 or more then compression is less of an issue.

Also different panels will show up compression more, due to the way they handle colour. The LCD panel on the Q2 was pretty bad, but the Pro and Q3 panels are much better.

Also if you have 6E router you can run wireless at higher bitrates and get almost wired quality.
 
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Baldbloke said:
Thank you.
Yes. From what I've learned from googling I can't find any difinitive simple answers. (Other than the in depth technical explanations which are beyond me anyway) I think yours is a fair and practical answer. Reason I asked was I just got a Quest 3 for iracing on pcvr to replace my existing HP G2 headset.

I've had a good fiddle with the Oculus debug tool and settings on the Q3 in order to try and get it to be at least as good as the G2. I can't. It comes close but not quite there. I wondered if this compression thingy might be a contributing factor (I'm using an oculus link cable if that makes any diff? Dunno). Just not getting the Q3 to display any better than the G2. The G2 is a dedicated pcvr device I believe. Your answer seems to ring true.

Ah well, I think the Q3 will be going back. Sorry Meta. I tried :). No new toy for me then. ;)
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Have you sent it back yet? If not, would you be willing to try some other things?

The 3080Ti should be plenty powerful to get good results.

Would you mind telling me what resolution you are using in the Oculus App? And exactly what settings you have changed in the Debug tool and what you have changed them to?
 
melmac said:
Have you sent it back yet? If not, would you be willing to try some other things?

The 3080Ti should be plenty powerful to get good results.

Would you mind telling me what resolution you are using in the Oculus App? And exactly what settings you have changed in the Debug tool and what you have changed them to?
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No I haven't sent back yet. I'd really like to keep it if I thought id get better visuals. . I'd be delighted to try other things. I'm all ears . Tried it at 1.0 and full resolution (1.3?) In the oculus app.
At work right now but when I get home this evening I'm up for a twiddle. Thank-you.
 
Baldbloke said:
I read a lot of folk talking about compression in VR headset images. I get that it's something undesirable in graphics. Seems that some folk see a poor image and blame it on compression. May be it is. Can anyone explain how to identify the effects of compression? Point me in the direction of any video examples showing clearly what the difference is between high/low/lots/little/no compression? Is compression Codec dependant?

Thank you
Click to expand...
The classic place to see compression is in dark scenes with 8-bit encoding. You get blocky edges between one intensity of black/grey and the next one up. This happens because there are only 255 discrete levels of your 3 colours, and the encoder is playing tricks to try and make 8-bit colour space look really good in "nominal conditions",.

You can also get blocky textures, where the texture resolution looks to be lower in places. This is simply because the full texture cannot be encoded into the datastream with the selected bitrate, so you get something that looks like a texture where regions have been averaged in blocks. There are a bunch of other impacts, but for me the textures stand out.

Both issues are greatly improved with Quest 3 and recent Virtual Desktop updates: 10-bit HEVC encoding gives you 1024 discrete levels for your colours, and so makes those dark scenes less blocky. The quest 3 also has ~25% higher decoding capability, meaning you can push higher bit-rates without the latency running wild.

One final note is that the Quest 3 also includes AV1 (10-bit) decoding capability. AV1 has higher quality for the same bitrate as HEVC, so you can further reduce the aforementioned texture quality issues if you have a GPU that supports: NV 4000 series, and potentially AMD 7000 but that's TBC.

AV1 isn't always a golden bullet. Each format has strengths and weaknesses, and people subjectively prefer the quirks of some formats over others. Anecdotally at the limits of the quest 3 hardware, H264 @~400Mbps is better for racing & fast shooters than AV1/HEVC @ 200Mbps. For 99% of people though, newer codecs like AV1 and HEVC should be used always.

EDIT: One annoying thing about the Meta Air Link is the lack of configurability. I gather there are applications to get into the back-end and play with the selected encoder and bitrates. Honestly though, if you're doing wireless streaming Virtual Desktop is worth £15. It sucks, you shouldn't have to buy it, but it is objectively better in all ways, e.g. it actually allows you to use AV1.
 
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0h_no_not_again said:
The classic place to see compression is in dark scenes with 8-bit encoding. You get blocky edges between one intensity of black/grey and the next one up. This happens because there are only 255 discrete levels of your 3 colours, and the encoder is playing tricks to try and make 8-bit colour space look really good in "nominal conditions",.

You can also get blocky textures, where the texture resolution looks to be lower in places. This is simply because the full texture cannot be encoded into the datastream with the selected bitrate, so you get something that looks like a texture where regions have been averaged in blocks. There are a bunch of other impacts, but for me the textures stand out.

Both issues are greatly improved with Quest 3 and recent Virtual Desktop updates: 10-bit HEVC encoding gives you 1024 discrete levels for your colours, and so makes those dark scenes less blocky. The quest 3 also has ~25% higher decoding capability, meaning you can push higher bit-rates without the latency running wild.

One final note is that the Quest 3 also includes AV1 (10-bit) decoding capability. AV1 has higher quality for the same bitrate as HEVC, so you can further reduce the aforementioned texture quality issues if you have a GPU that supports: NV 4000 series, and potentially AMD 7000 but that's TBC.

AV1 isn't always a golden bullet. Each format has strengths and weaknesses, and people subjectively prefer the quirks of some formats over others. Anecdotally at the limits of the quest 3 hardware, H264 @~400Mbps is better for racing & fast shooters than AV1/HEVC @ 200Mbps. For 99% of people though, newer codecs like AV1 and HEVC should be used always.

EDIT: One annoying thing about the Meta Air Link is the lack of configurability. I gather there are applications to get into the back-end and play with the selected encoder and bitrates. Honestly though, if you're doing wireless streaming Virtual Desktop is worth £15. It sucks, you shouldn't have to buy it, but it is objectively better in all ways, e.g. it actually allows you to use AV1.
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Thank you for that explanation oh_no_not_again.

That was very helpful. Nicely written and described. Thank you for taking the time to do that. I'm going to have a twiddle with the settings later tonight. I'm using the hard wired Oculus link usb cable. VD sounds very good but presumably the USB lead I'm using is better than wireless?

I will be interested and hoping to see if melmac (if he has time) might come up with some helpful suggestions to see if the visuals can be improved over my amateur tinkering attempts.
@melmac, am I right in thinking you might offer some suggestions?

Difficult to describe what I am seeing. In iracing (that's the only thing I use VR for) the edges of the track, walls and objects shimmer noticably compared to the G2 when I'm racing around the track. Could be "blockiness"/compression over usb?. But the effect I see is "shimmer". The G2 I have been using also shows this effect but to a far, far smaller extent. As said above by TheOracle, perhaps the Q3 is not best suited to racing games. Horses for courses and all that.

But to listento one or two of the youtube guys describing it..... well, to listen to one or two these guys the picture on their Q3 is almost perfect. Sliced bread and all that. Tried those settings they suggested. Didn't work for me.

Only got myself the Q3 to see if it might be better than the G2. I wouldn't have bothered with the Q3 if I had't got that 20% discount from the site mentioned in the Quest 3 owners thread here.
Isn't the end of the world if the Q3 doesn't tank the G2. It's a toy and I'm a 63 year old kid :). I'm not going to throw my teddy out the pram :)
But it's £380 I could use elswhere if I can't make the Q3 pull its socks up.
 
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Baldbloke said:
I will be interested and hoping to see if melmac (if he has time) might come up with some helpful suggestions to see if the visuals can be improved over my amateur tinkering attempts.
@melmac, am I right in thinking you might offer some suggestions?
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Yeah. that's the plan. As long as it's not too late. I will have to leave at about 8:30pm.

Hope, the things I suggest aren't things you have tried before but will see.
 
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