CODEWITHSUNDEEP
c++directx-11
junfanbl
junfanbl

Reputation: 461

Efficiently Capture Frames in DirectX 11

I'm trying to capture every frame of a game I am playing. There are plenty of good screen capturing softwares out there, One of which is built right into Windows 10.

However I need a custom approach for different reasons. I'm currently using the DirectX Tool Kits SaveWICTextureToFile() method to save every frame produced by Present().

https://github.com/microsoft/DirectXTK

For every frame that is captured, I'd like to tag the end of the file name with it's applicable number. ScreenShot_0 through ScreenShot_n.

The method SaveWICTextureToFile() saves the screenshot for you like so:

DirectX::SaveWICTextureToFile(context, backbufferTex, GUID_ContainerFormatJpeg, L"C:/Users/User Name/Desktop/Images/ScreenShot.JPG");

This doesn't allow you to capture frames sequentially. It simply writes over the same file for each frame. The performance however is very smooth. No lagging whatsoever during gameplay.

To try and write a file for each frame I did the following:

#include <sstream>
int Frame_Number;

//For each Call to Present() do the following:

//Get Device
ID3D11Device* device;
HRESULT gd = pSwapChain->GetDevice(__uuidof(ID3D11Device), (void**)&device);
assert(gd == S_OK);

//Get context
ID3D11DeviceContext* context;
device->GetImmediateContext(&context);

//get back buffer
ID3D11Texture2D* backbufferTex;
HRESULT gb = pSwapChain->GetBuffer(0, __uuidof(ID3D11Texture2d), (LPVOID*)&backbufferTex);
assert(gb == S_OK);

//Set-up Directory
std::wstringstream Image_Directory;
Image_Directory << L"C:/Users/User Name/Desktop/Images/ScreenShot_" << Frame_Number << L".JPG";

//Capture Frame
REFGUID GUID_ContainerFormatJpeg{ 0x19e4a5aa, 0x5662, 0x4fc5, 0xa0, 0xc0, 0x17, 0x58, 0x2, 0x8e, 0x10, 0x57 };
HRESULT hr = DirectX::SaveWICTextureToFile(context, backbufferTex, GUID_ContainerFormatJpeg, Image_Directory.str().c_str());
assert(hr == S_OK);
Frame_Number = Frame_Number + 1;

This worked, however the performance is choppy. As compared to the previous method, I don't get smooth gameplay anymore. Would somebody be able to recommend a more efficient way to do this?

Upvotes: 0

Views: 1749

Answers (2)

Acorn
Acorn

Reputation: 26066

It simply writes over the same file for each frame. The performance however is very smooth.

If everything else is equal, there are several possibilities for the slowdown:

  • The file is being written only on memory and never committed to disk, since it keeps being overwritten.

  • Opening many files per second is never a good idea, specially on Windows which is particularly slow at this compared to eg. Linux.

  • Writing many files into the same folder is another bad idea, since many filesystems do not handle that case well.

Find out which one of those three is the culprit, and iterate from there.

And let us know! It is always interesting to hear how fast IO is nowadays for different use cases :-)

Upvotes: 1

SoronelHaetir
SoronelHaetir

Reputation: 15164

If this is being done in a debug build I suspect that the stringstream has logic that is causing the problems, I suggest using character arrays instead and swprintf. Even better if you keep track of where the directory ends and so only need to write out the file name part (you could go even further and make it so you only need to format the number and extension).

Upvotes: 1

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