• Advertisement
Sign in to follow this  

OpenGL Need sugestion to optimize realtime bitblt->StretchBlt (scaling takes to much CPU)

This topic is 1297 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Here's my problem. I need to copy and scale the screen, ~30 times a second (live screen drawing).
I do this by first getting a handle to the screen DC:

GetDC(NULL)
Then, I create a compatible DC using CreateCompatibleDC, create a DIB using CreateDIBSection, and select the DIB into the new DC. Now I StretchBlt from the screen DC to my own DC  (blit and scale the image) .

So we have

while(1)
{
StretchBlt ... (get the screen and resize from 1440*900 to 1200*700)

}

As you probable know the scaling takes most of the CPU and time.
If i do only

while(1){bitblt()} i get ~400 fps - i.e 400 call of bitblt per second.

if i use the while(1){StretchBlt} i get only ~25 fps - i.e 25 call of StretchBlt per second.

(I need 30). also since i am doing other things as well, CPU will not be idle so this code need to be ran at least at 34 FPS.

As said, the bottleneck is not the Blitting from the screen. the bottleneck  is the scaling (i use SetStretchBltMode(hCompatible, HALFTONE)).
with COLORONCOLOR i get 60FPS but quality is not good (if there only something in the middle of HALFTONE to COLORONCOLOR  ...).

For now i do not want to use directx or open GL.

Any idea how to make it faster (i only need ~10 more FPS :))
I have an idea how to make it faster  but i do know how to do that and if it is possible.
Idea is to:
Bitblt to get the screen into buffer A.
StretchBlt to scale the image into buffer B.
Now on the next bitblt's to use SRCINVERT (XOR) to blt only the differences between the new capture and the old and to use the differences to update the scaled buffer B so no need to do more scaling.

Again just an idea but i do not think it is possible.

I would love to hear your suggestions.

I tries to use bitblt with some custom scaling functions (instead of StretchBlt) i found on the Internet or with image libs like FreeImage but results were dramatically worst than StretchBlt  (even using BOX filtering)

Again, i know that using DirectX/opengl may be faster but currently i do not have the time to learn that or deal with that - so currently i would like to use GDI/GDI+ only.

Thanks!

 

Share this post


Link to post
Share on other sites
Advertisement

Hi. are you running this bitblt in a loop like here.

 

while(1)
{
StretchBlt ... (get the screen and resize from 1440*900 to 1200*700)

}

 

may be you need to just update it on a wm_paint or what ever the message is.

Share this post


Link to post
Share on other sites

I do not think that there is an option to catch when wm_paint is sent to the screen itself, i.e tocatch some event that is thrown when what you see on the computer screen is changed.

Share this post


Link to post
Share on other sites

It seems that halftone blitter is really slow, couldn belive it to be so slow and i did quick testing - it shows the same result youre talking here about

abput 40 ms - what system do you have, it may depend on the system 

 

i dont know some say that in win7 it may run even worse than xp ;/ ?

(found something on this

http://vjforums.info/threads/stretchblt-can-hang-windows-by-hogging-gdi-lock.38179/ )

 

anyway normal mode blitter working ok and you could rescale this by hand code or ev trying to do some "opengl/dx blitter" with fast hardware resizin onboard - which i was not testing yet

Share this post


Link to post
Share on other sites

Hi Fir.

I tried to use custom scalling - some even with ASM byut could not get even near strechblt - with the custom scaling fucntion i got ~10 FPS ....

And as say i do not want to use opengl/dx.

 

Am am using win7.

Share this post


Link to post
Share on other sites

Hi Fir.

I tried to use custom scalling - some even with ASM byut could not get even near strechblt - with the custom scaling fucntion i got ~10 FPS ....

And as say i do not want to use opengl/dx.

 

Am am using win7.

you may show the code, we can taka a lok here and maybe come advices or conclusions will appear -i could do the test of some down of upscalling in bitmap arrays im not sure but i think it could work at 50 (100?) hz or more - not 100% sure though

 

PS i did some simle test of down and up scaling frame bitmap into some buffer then copying this to framebuffer array again -and even with this double copying i got no trouble

 

for screens size like 500p it was 4 ms (scaling forth somewhere and copying back) for screens like 1000p it was 12 ms (for such two way: scaling+copying back), so not a problem here -

 

got no idea what this halftone is doing to be so slow but this linear scaling works ok

 

Edited by fir

Share this post


Link to post
Share on other sites

First i tried this:

http://www.geisswerks.com/ryan/FAQS/resize.html

Gave me around 10 FPS only.

I then tried FreeImage lib (FreeImage_Rescale) got around 7 FPS.

None came even close to StretchBlt preformace.

 

I think the answer should be

1) To find fastest rescal (with good quality) scaling funtion/

OR AND

2)to somehow use the scaling histroy.

I.E to try to scal only the parts that changed from the last scale - but not sure how to do that ...

Maybe with SRCINVERT (XOR) - somehow.

Share this post


Link to post
Share on other sites

 

 

got no idea what this halftone is doing to be so slow but this linear scaling works ok

 

 

 

Well without halftone the image quality is not good.

Text does not look good and somehting is unreadable.

The halftone smoth the image by avraging pixels before it scall or something like that.

 

Share this post


Link to post
Share on other sites

Scaling is expensive. This is why, for instance, Fraps only offers fullscreen or halfscreen resolution when it captures the screen, so that scaling is either unnecessary or very easy. It's just too costly to handle cases where you're not scaling down to a power of two of the original size, because you have to handle filtering of multiple overlapping pixels, which also blows your cache because the resulting memory access patterns are.. suboptimal to say the least. There is one thing you can try, which drastically helped me back when I was on my old laptop and trying to capture stuff, which is to set your screen resolution to 16-bit colors.

 

Otherwise, what I would try is instead get a copy of the screen in a GPU-bound texture, using your favorite graphics API, scale it using the pixel shader (which ought to be fast enough, even with bilinear filtering) and read it back on the CPU. But this might incur significant capture latency, and might not be feasible, and you said you don't want to do this anyway, so...

 

I'm not sure what your specific needs are, but have you considered simply getting one of those screen recording devices? They don't have any system overhead and you might be able to get one to feed back into the computer to deliver the screen contents in realtime.

Share this post


Link to post
Share on other sites

Hi Bacterius

Yes i know scaling is expensive. that is why using the scaling history might help.

I just do not know how to do that. I.E to scale only the parts from the image that changed from the last scale - that way i scale one time and on next scales i only scale

the parts that were changed - but not sure if that can be done and how.

 

P.S

Just tried CxImgLib and got only 20 FPS still lower than  StretchBlt ...

 

P.S2 lowering to 16 bit did not help and in anyway it should run on all systems without making changes - that is why recording device is not a solution.

Edited by Jimkm

Share this post


Link to post
Share on other sites

Could you try comparing each pixel to the previous pixel to determine a difference, and then divvy the screen up into 32x32 sized chunks and only StretchBlt the chunks that contained at least one differing pixel?

Share this post


Link to post
Share on other sites

Hi Samith.

I am not sure this will work since the scaling also does some smoting and i think that doing this in your way will make the borders of the 32*32 squares to be seen ...

I can try that but i am not sure how to do that.

Share this post


Link to post
Share on other sites
The simplest solution would be to perform the resizing of the images in parallel in multiple threads. You could put the captured images into a queue, and have the threads grab the images from said queue and resize them.

It doesn't change the fact, that 40ms is awefully slow for a resize, but if you have the CPU cores to spare, why not use them.

Share this post


Link to post
Share on other sites

Hi Samith.
I am not sure this will work since the scaling also does some smoting and i think that doing this in your way will make the borders of the 32*32 squares to be seen ...
I can try that but i am not sure how to do that.

 

You might be able to work around that by having the grid squares "overlap" with a border that is as wide as the kernel of the filter.

It would mean processing some pixels twice, but it would still be less then doing every pixel.

 

Apart from that, and using multiple cores to update squares in paralell, I don't think its much you can do unless using graphics hardware. (which is a massively parallell processor designed for image processing, seems pretty ideal for the task)

 

Why not using graphics hardware? It would be a lot less complex to get to work.

 

MAybe a bit off-topic, but why exactly do you need to scale anyway? (I'm not sure what you mean by "live screen drawing" and why this implies scaling?)

Edited by Olof Hedman

Share this post


Link to post
Share on other sites

Olof Hi

I grab screenshot, scall it to the destination device resolution and trasmit it to that device.

The device that the screens are sent to can not do the scalling.

I already use the extra CPU to encode the images so it will not help to scall using the extra cpu.

I am more looking for a way to decrease cpu time than to have more fps (if i will be able to decrease cpu time then the extra fps will come by themself).

Share this post


Link to post
Share on other sites
Hi. I don't know why you have that while(1) in your render
What breaks it.
Can you show your render code.

Share this post


Link to post
Share on other sites

Whats break the while(1) is the user that press the stop button in the gui to stop.

It is

while(user did not press the stop button)

{

capture screenshot and scale it (Streachblt)

}

Share this post


Link to post
Share on other sites
I say the slowness is comming from your code set up.

Share this post


Link to post
Share on other sites

I say the slowness is comming from your code set up.

ankhd hi.

I do not think so since i think this is the most FPS my CPU can give me with StretchBlt which is done on the cpu (i use gpu monitor and i see that it does not do that on gpu).

But if you have more details why it is coming from my code then i would love to hear.

Share this post


Link to post
Share on other sites
What exactly are your requirements on the quality?

You wrote that "color on color", which is nearest downsampling, is not good enough. What about downsizing the image to exactly half it's original size with a box filter, compressing and sending that to the target device, and linearly upsampling there?
You can simulate that in GIMP/Photoshop to see, what it looks like.

Share this post


Link to post
Share on other sites

take ma advice and do it such way

 

1) wrote your own resizing code (inbeetween the raw scaling and halftone), this shouldnt be hard - you will not get as fast as simple resizing blitter  when doing something more complex than raw scalling but you also should get not as slow as halftone when writting something simpler than halftone

 

2) find some library - this should be the same, if you use something in between than raw sacling and halftone that should be both slower than raw scalling and faster than halftone 

 

thats all

Share this post


Link to post
Share on other sites

take ma advice and do it such way

 

1) wrote your own resizing code (inbeetween the raw scaling and halftone), this shouldnt be hard - you will not get as fast as simple resizing blitter  when doing something more complex than raw scalling but you also should get not as slow as halftone when writting something simpler than halftone

 

2) find some library - this should be the same, if you use something in between than raw sacling and halftone that should be both slower than raw scalling and faster than halftone 

 

thats all

I already tried few pro image library - all gave me worst FPS than strachblt

Share this post


Link to post
Share on other sites

I don't know how much time per day you've been spending on this, but in the time since you started this thread you could have already written a GPU solution. I know you say it's not what you want to do, but seriously, it wouldn't be that hard and you'll have excellent performance.

Share this post


Link to post
Share on other sites
what cpu are you using for benchmarking?

some possible solutions:
1. scale to half and then upscale to the resolution you wanted, e.g.
1440*900 -> 720*450 -> 1200*700

2. write a custom scaler for the solution you need.

3. maybe your source is in some YCbCr format or something? you could scale the source

4. interlace scaling (scale just every 2nd line per frame -> double fps)

5. scale to half and use a letterbox

6. don't interpolate, just fetch the closest pixel to show.

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
  • Advertisement
  • Popular Now

  • Advertisement
  • Similar Content

    • By reenigne
      For those that don't know me. I am the individual who's two videos are listed here under setup for https://wiki.libsdl.org/Tutorials
      I also run grhmedia.com where I host the projects and code for the tutorials I have online.
      Recently, I received a notice from youtube they will be implementing their new policy in protecting video content as of which I won't be monetized till I meat there required number of viewers and views each month.

      Frankly, I'm pretty sick of youtube. I put up a video and someone else learns from it and puts up another video and because of the way youtube does their placement they end up with more views.
      Even guys that clearly post false information such as one individual who said GLEW 2.0 was broken because he didn't know how to compile it. He in short didn't know how to modify the script he used because he didn't understand make files and how the requirements of the compiler and library changes needed some different flags.

      At the end of the month when they implement this I will take down the content and host on my own server purely and it will be a paid system and or patreon. 

      I get my videos may be a bit dry, I generally figure people are there to learn how to do something and I rather not waste their time. 
      I used to also help people for free even those coming from the other videos. That won't be the case any more. I used to just take anyone emails and work with them my email is posted on the site.

      I don't expect to get the required number of subscribers in that time or increased views. Even if I did well it wouldn't take care of each reoccurring month.
      I figure this is simpler and I don't plan on putting some sort of exorbitant fee for a monthly subscription or the like.
      I was thinking on the lines of a few dollars 1,2, and 3 and the larger subscription gets you assistance with the content in the tutorials if needed that month.
      Maybe another fee if it is related but not directly in the content. 
      The fees would serve to cut down on the number of people who ask for help and maybe encourage some of the people to actually pay attention to what is said rather than do their own thing. That actually turns out to be 90% of the issues. I spent 6 hours helping one individual last week I must have asked him 20 times did you do exactly like I said in the video even pointed directly to the section. When he finally sent me a copy of the what he entered I knew then and there he had not. I circled it and I pointed out that wasn't what I said to do in the video. I didn't tell him what was wrong and how I knew that way he would go back and actually follow what it said to do. He then reported it worked. Yea, no kidding following directions works. But hey isn't alone and well its part of the learning process.

      So the point of this isn't to be a gripe session. I'm just looking for a bit of feed back. Do you think the fees are unreasonable?
      Should I keep the youtube channel and do just the fees with patreon or do you think locking the content to my site and require a subscription is an idea.

      I'm just looking at the fact it is unrealistic to think youtube/google will actually get stuff right or that youtube viewers will actually bother to start looking for more accurate videos. 
    • By Balma Alparisi
      i got error 1282 in my code.
      sf::ContextSettings settings; settings.majorVersion = 4; settings.minorVersion = 5; settings.attributeFlags = settings.Core; sf::Window window; window.create(sf::VideoMode(1600, 900), "Texture Unit Rectangle", sf::Style::Close, settings); window.setActive(true); window.setVerticalSyncEnabled(true); glewInit(); GLuint shaderProgram = createShaderProgram("FX/Rectangle.vss", "FX/Rectangle.fss"); float vertex[] = { -0.5f,0.5f,0.0f, 0.0f,0.0f, -0.5f,-0.5f,0.0f, 0.0f,1.0f, 0.5f,0.5f,0.0f, 1.0f,0.0f, 0.5,-0.5f,0.0f, 1.0f,1.0f, }; GLuint indices[] = { 0,1,2, 1,2,3, }; GLuint vao; glGenVertexArrays(1, &vao); glBindVertexArray(vao); GLuint vbo; glGenBuffers(1, &vbo); glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW); GLuint ebo; glGenBuffers(1, &ebo); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, false, sizeof(float) * 5, (void*)0); glEnableVertexAttribArray(0); glVertexAttribPointer(1, 2, GL_FLOAT, false, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glEnableVertexAttribArray(1); GLuint texture[2]; glGenTextures(2, texture); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageOne = new sf::Image; bool isImageOneLoaded = imageOne->loadFromFile("Texture/container.jpg"); if (isImageOneLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageOne->getSize().x, imageOne->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageOne->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageOne; glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageTwo = new sf::Image; bool isImageTwoLoaded = imageTwo->loadFromFile("Texture/awesomeface.png"); if (isImageTwoLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageTwo->getSize().x, imageTwo->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageTwo->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageTwo; glUniform1i(glGetUniformLocation(shaderProgram, "inTextureOne"), 0); glUniform1i(glGetUniformLocation(shaderProgram, "inTextureTwo"), 1); GLenum error = glGetError(); std::cout << error << std::endl; sf::Event event; bool isRunning = true; while (isRunning) { while (window.pollEvent(event)) { if (event.type == event.Closed) { isRunning = false; } } glClear(GL_COLOR_BUFFER_BIT); if (isImageOneLoaded && isImageTwoLoaded) { glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glUseProgram(shaderProgram); } glBindVertexArray(vao); glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr); glBindVertexArray(0); window.display(); } glDeleteVertexArrays(1, &vao); glDeleteBuffers(1, &vbo); glDeleteBuffers(1, &ebo); glDeleteProgram(shaderProgram); glDeleteTextures(2,texture); return 0; } and this is the vertex shader
      #version 450 core layout(location=0) in vec3 inPos; layout(location=1) in vec2 inTexCoord; out vec2 TexCoord; void main() { gl_Position=vec4(inPos,1.0); TexCoord=inTexCoord; } and the fragment shader
      #version 450 core in vec2 TexCoord; uniform sampler2D inTextureOne; uniform sampler2D inTextureTwo; out vec4 FragmentColor; void main() { FragmentColor=mix(texture(inTextureOne,TexCoord),texture(inTextureTwo,TexCoord),0.2); } I was expecting awesomeface.png on top of container.jpg

    • By khawk
      We've just released all of the source code for the NeHe OpenGL lessons on our Github page at https://github.com/gamedev-net/nehe-opengl. code - 43 total platforms, configurations, and languages are included.
      Now operated by GameDev.net, NeHe is located at http://nehe.gamedev.net where it has been a valuable resource for developers wanting to learn OpenGL and graphics programming.

      View full story
    • By TheChubu
      The Khronos™ Group, an open consortium of leading hardware and software companies, announces from the SIGGRAPH 2017 Conference the immediate public availability of the OpenGL® 4.6 specification. OpenGL 4.6 integrates the functionality of numerous ARB and EXT extensions created by Khronos members AMD, Intel, and NVIDIA into core, including the capability to ingest SPIR-V™ shaders.
      SPIR-V is a Khronos-defined standard intermediate language for parallel compute and graphics, which enables content creators to simplify their shader authoring and management pipelines while providing significant source shading language flexibility. OpenGL 4.6 adds support for ingesting SPIR-V shaders to the core specification, guaranteeing that SPIR-V shaders will be widely supported by OpenGL implementations.
      OpenGL 4.6 adds the functionality of these ARB extensions to OpenGL’s core specification:
      GL_ARB_gl_spirv and GL_ARB_spirv_extensions to standardize SPIR-V support for OpenGL GL_ARB_indirect_parameters and GL_ARB_shader_draw_parameters for reducing the CPU overhead associated with rendering batches of geometry GL_ARB_pipeline_statistics_query and GL_ARB_transform_feedback_overflow_querystandardize OpenGL support for features available in Direct3D GL_ARB_texture_filter_anisotropic (based on GL_EXT_texture_filter_anisotropic) brings previously IP encumbered functionality into OpenGL to improve the visual quality of textured scenes GL_ARB_polygon_offset_clamp (based on GL_EXT_polygon_offset_clamp) suppresses a common visual artifact known as a “light leak” associated with rendering shadows GL_ARB_shader_atomic_counter_ops and GL_ARB_shader_group_vote add shader intrinsics supported by all desktop vendors to improve functionality and performance GL_KHR_no_error reduces driver overhead by allowing the application to indicate that it expects error-free operation so errors need not be generated In addition to the above features being added to OpenGL 4.6, the following are being released as extensions:
      GL_KHR_parallel_shader_compile allows applications to launch multiple shader compile threads to improve shader compile throughput WGL_ARB_create_context_no_error and GXL_ARB_create_context_no_error allow no error contexts to be created with WGL or GLX that support the GL_KHR_no_error extension “I’m proud to announce OpenGL 4.6 as the most feature-rich version of OpenGL yet. We've brought together the most popular, widely-supported extensions into a new core specification to give OpenGL developers and end users an improved baseline feature set. This includes resolving previous intellectual property roadblocks to bringing anisotropic texture filtering and polygon offset clamping into the core specification to enable widespread implementation and usage,” said Piers Daniell, chair of the OpenGL Working Group at Khronos. “The OpenGL working group will continue to respond to market needs and work with GPU vendors to ensure OpenGL remains a viable and evolving graphics API for all its customers and users across many vital industries.“
      The OpenGL 4.6 specification can be found at https://khronos.org/registry/OpenGL/index_gl.php. The GLSL to SPIR-V compiler glslang has been updated with GLSL 4.60 support, and can be found at https://github.com/KhronosGroup/glslang.
      Sophisticated graphics applications will also benefit from a set of newly released extensions for both OpenGL and OpenGL ES to enable interoperability with Vulkan and Direct3D. These extensions are named:
      GL_EXT_memory_object GL_EXT_memory_object_fd GL_EXT_memory_object_win32 GL_EXT_semaphore GL_EXT_semaphore_fd GL_EXT_semaphore_win32 GL_EXT_win32_keyed_mutex They can be found at: https://khronos.org/registry/OpenGL/index_gl.php
      Industry Support for OpenGL 4.6
      “With OpenGL 4.6 our customers have an improved set of core features available on our full range of OpenGL 4.x capable GPUs. These features provide improved rendering quality, performance and functionality. As the graphics industry’s most popular API, we fully support OpenGL and will continue to work closely with the Khronos Group on the development of new OpenGL specifications and extensions for our customers. NVIDIA has released beta OpenGL 4.6 drivers today at https://developer.nvidia.com/opengl-driver so developers can use these new features right away,” said Bob Pette, vice president, Professional Graphics at NVIDIA.
      "OpenGL 4.6 will be the first OpenGL release where conformant open source implementations based on the Mesa project will be deliverable in a reasonable timeframe after release. The open sourcing of the OpenGL conformance test suite and ongoing work between Khronos and X.org will also allow for non-vendor led open source implementations to achieve conformance in the near future," said David Airlie, senior principal engineer at Red Hat, and developer on Mesa/X.org projects.

      View full story
    • By _OskaR
      Hi,
      I have an OpenGL application but without possibility to wite own shaders.
      I need to perform small VS modification - is possible to do it in an alternative way? Do we have apps or driver modifictions which will catch the shader sent to GPU and override it?
  • Advertisement