ddagrab stuttering and cursor issues

[Sean-Zeo]

Hi, it seems ddagrab is currently broken in the latest builds.
The cursor causes a tail effect and the frame rate skips/jumbles.

[BtbN]

Works fine for me on latest win64 build.
Make sure your graphics driver is in working condition.

[Sean-Zeo]

Hi, same issue. Latest drivers for intel XE graphics.
It also has the same issue on a cloud A4000 nvidia GPU PC.

output.mp4

[BtbN]

I have just tested it, and it works perfectly for me. So I'm not sure what to tell you or what I should do about it.

[Sean-Zeo]

Hi, even this sample command causes such an issue;

ffmpeg -filter_complex ddagrab=output_idx=0:framerate=60,hwdownload,format=bgra -c:v libx264 -crf 18 output.mp4

[BtbN]

Your command also works perfectly fine for me, and produces clean and intact output.
This looks much more like some weird driver side issue than anything related to FFmpeg, let alone these specific builds of it.

[Sean-Zeo]

Hi, even software encoding, it does not work (no drivers required), same issue.
I've tested on several machines with latest Windows 10, same issue.

[BtbN]

ddagrab is quite low level and directly interfaces with the graphics driver.
It works perfectly for me on both Nvidia and Intel Iris Xe, so my suspicion is that it's some bug in older Intel GPU drivers or something.

It's probably fallout from FFmpeg/FFmpeg@21c6d12 but without that patch capturing is completely broken in different ways.
The patch still looks correct to me, and it's likely a driver bug where it does not honor the correct order of operations for some reason.

[Sean-Zeo]

Hi, as I said before, this issue is occurring on both an Intel Iris XE machine as well as a separate RTX 4000 machine. The issue also occurs when using software encoding.
So I don't think this is driver related at all.

[BtbN]

The encoder is not involved in this, so not sure why you keep bringing it up.
ddagrab always interfaces with the graphics driver.

And like I said before, I am completely unable to reproduce this on both an Nvidia and an Intel machine.

[BtbN]

Can you run a debugger on this? Since I can't reproduce this, I have no chance of fixing it otherwise.

Run ffmpeg like this:
./ffmpeg.exe -v debug -init_hw_device d3d11va=dbgdev:-1,debug=1 -filter_hw_device dbgdev -filter_complex ddagrab=0:framerate=60 -c:v hevc_nvenc -preset slow -cq:v 20 -y out.mp4

The output side doesn't matter, feel free to replace nvenc with x264 or whatever.

Run https://learn.microsoft.com/en-us/sysinternals/downloads/debugview before and while invoking ffmpeg like that. It should capture any D3D11 debug messages from ffmpeg, hopefully giving an explanation for this.
For me it comes up completely empty outside of a bit of noise on shutdown.

For this to work, you need to have the d3d11 debug layers installed.
You can check by running where.exe d3d11_1sdklayers.dll. It it's missing, you might have to install the "Graphical Tools" Optional Feature, or the full on D3D SDK.

[BtbN]

After quite a wild chase for this, we finally found the root cause and fixed it in FFmpeg/FFmpeg@b47abd5
I still don't fully understand why these flags are different per system or screen. But they are. And depending on what they are, it can break in multiple ways.