Re: Fast way to grab the screen
Re: Fast way to grab the screen
- Subject: Re: Fast way to grab the screen
- From: Ken Thomases <email@hidden>
- Date: Thu, 24 Feb 2011 09:53:07 -0600
On Feb 23, 2011, at 5:39 PM, Kyle Sluder wrote:
> On Wed, Feb 23, 2011 at 3:21 PM, Ken Thomases <email@hidden> wrote:
>> On Feb 23, 2011, at 4:40 PM, Kyle Sluder wrote:
>>
>>> On Wed, Feb 23, 2011 at 2:17 PM, eveningnick eveningnick
>>> <email@hidden> wrote:
>>>> i am trying to write a video grabber, CGWindow API seems pretty convenient
>>>> (because it allows to select which window to "grab"), but i am worried about
>>>> the speed, because i need to record the grabbed frames to the video file.
>>>
>>> http://developer.apple.com/library/mac/#samplecode/OpenGLScreenCapture/Introduction/Intro.html#//apple_ref/doc/uid/DTS10004445-Intro-DontLinkElementID_2
>>
>> Actually, I don't think that's an improvement over the CGWindow API that eveningnick was already using (CGWindowListCreateImage, I assume). In general, if a high-level (more abstract) API achieves the desired result, it will be at least as efficient as the low-level API -- because, if the low-level approach is faster, the high-level API would just use it.
>
> Except the high-level APIs are geared around taking a static
> screenshot. Remember, the OP is trying to capture a video.
>
> The method in the sample project creates multiple pixel buffers and
> asynchronously swaps the framebuffer contents into them. By design,
> the synchronous screen capture APIs cannot be as fast as working at
> this level.
My apologies. The URL has the name OpenGLScreenCapture in it, even though the sample project is actually called OpenGLCaptureToMovie. I only looked at the URL and thought it was for the sample code to capture a single screenshot using OpenGL -- there is such a sample that I've looked at previously. I guess I must have been thinking of <http://developer.apple.com/library/mac/#samplecode/OpenGLScreenSnapshot/>, which has a confusingly similar URL, if not title.
Regards,
Ken
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