Re: OpenGL-based framebuffer concepts

On Friday 26 May 2006 04:57, Alexander E. Patrakov wrote:
Jon Smirl wrote:
Most video hardware (99%) has enough memory to support double
buffering. You save it to the other buffer, display the error, and
copy it back on enter.

This is possible only if the video memory management is in the kernel.
Reason: userspace may also want to use double buffering, and we definitely
want to allocate the "other (maybe third) buffer" somewhere in the free
video memory. And allocating a lot of system RAM on oops seems to be a very
bad idea (cascade of oopses may follow).

Also, did anyone measure the video RAM usage during a typical Xgl session
(i.e.: is there really enough free video RAM, not occupied by various
caches)?

Although, a Microsoft-ish "lost context, please redraw" solution has been
already proposed.

In the case of an oops or a panic the system might not be stable enough to
continue operation. In fact, I have never had a system experience either and
still be able to run - even at the console.

In such a case, I think it'd be preferable to overwrite any graphics mode
currently in use to display the data. However, there must be some control on
this, to prevent people from arbitrarily killing the video mode to display
data. In any event, seeing the huge ideological split and the inability of
the people involved with this discussion to agree on a single, clear path for
the graphics system to take...

Let me put it this way: I may write code for free, but I don't write code
unless theres a design to it. I joined this conversation to toss a few ideas
off the top of my head out there and see if any were useful. This has become
something of a very genial flame war...

Over the next couple of days I'll work on a few design ideas for a replacement
to the current, somewhat poorly done graphics core in Linux and post them for
comments. These will hopefully cover all sides of the currently seen
ideological split as well as one or two that hopefully span the split.

All of them will be open for comment and revision, and if one of them is
ultimately agreed on, I'll start work on it. If not, then I'll go back to
just watching the traffic and hoping someone will finally start fixing the
problems in the graphics systems.

DRH
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Relevant Pages

  • Re: Why is everything on E4 always out if lipsync ?
    ... After playing a video there was always a lip sync ... i.e. why is it necessary to code audio & video separately. ... or shortage of memory for buffering to cause loss of sync. ...
    (uk.tech.digital-tv)
  • 2003 Server video playback issues
    ... on the same switch can connect and view demand content ... >norton firewall activated and can see the video, ... >>HTTP) and see if they see buffering? ... >>Windows media Player 9 or greater? ...
    (microsoft.public.windowsmedia.server)
  • Re: How to reduce startup latency while playing .wmv file - from Javas
    ... We are using html object tag to embed and play the video filesby ... No and there will never be - buffering is integral to streaming. ... but not with that embedding code. ...
    (microsoft.public.windowsmedia.sdk)
  • Re: double buffering
    ... >the middle of drawing a frame. ... If you're learning about double buffering, you might also want to look ... Once upon a time, not so long ago, we did not have frame ... whole and to display that whole. ...
    (comp.graphics.algorithms)
  • Re: Video Capture Performance with directshow
    ... I suspect you're using the WMV encoder? ... The memory usage spike you're seeing is the buffering filter storing up as ... filter on the low priority thread which the video encoding happens on. ... I'm writing a directshow based solution for capturing window (target ...
    (microsoft.public.pocketpc.developer)