Re: Can XCB return an image with an NVIDIA GPU memory address?

If you want to do this specifically on NVIDIA cards with NVENC, you'll 
more than likely want to be using this:

   https://developer.nvidia.com/capture-sdk

This will be much faster and lower latency than grabbing desktop content 
using shared memory via XCB commands.

Thanks,
-James

On 8/5/19 9:49 AM, Suhail Doshi wrote:
> Thanks so much Peter. I'll look at this stuff today.
> 
> Question: Do you have any guidance on how to extract/use the OBS library 
> that's cross-platform? I wouldn't want to include everything that OBS 
> has to offer to keep the footprint of our application low. Any docs on 
> their API as well?
> 
> Suhail
> 
> --
> 
> Founder
> 
> 
> On Mon, Aug 5, 2019 at 9:20 AM Peter Harris <[email protected] 
> <mailto:[email protected]>> wrote:
> 
>     On 2019-08-05 11:07 a.m., Suhail Doshi wrote:
>      > My question is: Is there a way to get an image of the desktop that
>      > returns a pointer that's GPU memory? For example, in Windows 10,
>     there's
>      > an API called the Desktop Duplication API which will allows you to do
>      > this. Then, it lets you copy the data in that GPU memory block to
>      > another one such that you can encode the frame with H264, for
>     example. I
>      > am using NVIDIA GPUs and utilizing their NVENC SDK.
>      >
>      > I am looking for an equivalent.
> 
>     XCB is very low-level. For most things, you probably want to use a
>     higher level library (such as, for example, OBS:
>     https://github.com/obsproject/obs-studio , which includes a
>     cross-platform library with an API that is probably closer to the
>     Desktop Duplication API than anything in XCB).
> 
>     With that said, if you want to implement the details yourself, you can
>     take a peek inside OBS and see that the capture method that copies
>     uncompressed pixels back to main memory uses xcb_shm_get_image (and
>     xcb_xfixes_get_cursor_image, and xcb_xinerama_query_screens, among other
>     things).
>     https://github.com/obsproject/obs-studio/blob/master/plugins/linux-capture/xshm-input.c
> 
>     Peter Harris
> 
> 
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