The question of latency difference between sunshine streaming and scrcpy

[NiceGuy256]

I found latency of sunshine streaming + moonlight is low. I even hardly find latency when playing games.
It uses my GPU to encode and decode. I think it is a factor that it has lower latency.
When I use Scrcpy on my PC to control my smartphone by USB or wifi, it does not use my GPU to decode. The reason for this thing might be my GPU is too old. My gpu is r7 260x.Moreover, I do not know whether Scrcpy uses my GPU in my smartphone to encode or not.I am also curious about whether there might be another reason that Scrcpy has higher latency.

Thanks for answering my question.

[yume-chan]

The reason for this thing might be my GPU is too old.

See #3800, it's hard to implement hardware accelerated video decoding on SDL (the GUI library Scrcpy is using)

I do not know whether Scrcpy uses my GPU in my smartphone to encode or not.

Usually. It depends on the encoder, the default one is usually hardware accelerated by the SoC.

[rom1v]

In addition to what @yume-chan said, Android device hardware encoders usually have a higher latency than nvenc (or others) on a computer, especially at high resolutions.

How is the latency if you limit the resolution (scrcpy -m1024 for example). Also try different encoders. And over USB if you were using it over wifi.

[NiceGuy256]

@yume-chan Does it mean we are not able to use GPU in PC to decode no matter which GPU we use?

[NiceGuy256]

@rom1v Do you know how to check gpu encoder usage on Android devices like Windows PC?

[NiceGuy256]

@rom1v OK, I will try limit the resolution different encoder and use USB, but how to test latency accuratly?

[rom1v]

how to test latency accuratly?

To test glass-to-glass latency, you should capture both your device screen and computer screen with an external camera with a high framerate (tip: run https://www.vsynctester.com/ on your device with the option "frame indicator" in the website settings).

[NiceGuy256]

@rom1v OK, thanks.

[NiceGuy256]

@rom1v If I use online stopwatch like this instead of https://www.vsynctester.com/ to test latency, it will be more accurate? Thanks.

[rom1v]

As soon as you are able to count the number of frames of difference… but it's easier with squares moving than with a counter, because with a counter you might get several numbers blurred together when you record.

[NiceGuy256]

@rom1v I tested sunshine streaming, it is about 80ms latency. I used scrcpy to control my smartphone with usb2.0 wire,it is about 45-55ms latency.I also used scrcpy to control my smartphone with 5GHZ wif, it is about 55-65ms latency.The latency difference between two softwares is not very obvious. But the fluency between two softwares is obvious. I think the reason might be unstable refresh rate resulting from some frame be skipped. I am also curious about whether there are other reasons. Thanks for answering my question.

[NiceGuy256]

@rom1v I also tried other encoders and I think origin H264 is best for my devices.Lower resolution(like 480P)is benefit to decrease latency.

[rom1v]

But the fluency between two softwares is obvious. I think the reason might be unstable refresh rate resulting from some frame be skipped.

What is the refresh rate of your device and that of your computer screen? Does --max-fps=30 or --max-fps=60 improves the result?

But the fluency between two softwares is obvious. I think the reason might be unstable refresh rate resulting from some frame be skipped.

Indeed, scrcpy prioritizes lower latency over preserving frames regularity. Try with --display-buffer=50, is it better? (see #2464 for details)

[NiceGuy256]

My phone is 120hz, my pc is 60hz, my laptop is 120hz
OK，I will try limit refresh rate and use display buffer.

[rom1v]

If it works, try without display buffer, which adds latency.

[NiceGuy256]

--max-fps=60 and --display-buffer=50 increase fluency slightly.