"Xlib: unexpected async reply" with Mplayer embedded?

SDL Development
1

Hi Everyone,I have an SDL application which has a Mplayer embedded. I often get the error: “Xlib: unexpected async reply”. I found in mail-list there are a lot of discussions about “Xlib: unexpected async reply” problem. Based on these discussions, I guess, this problem is because Xlib functions are called in two threads(one is my main thread, i think there is another one in Mplayer). For my case, I can’t combine two threads into one, what should I do to avoid this problem? Any suggestion would be very appreciated.Thanks_________________________________________________________________
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2

This happens because the Xlib seem to be not thread-safe.

You would need to only ensure that the display updates happens only from the main thread only, you would not face this issue.

From the thread receiving asynchronous message, you need to signal the thread waiting under the context of main thread as and when asych message arrives and the main thread should do the job of display updates.

Hope this helps.

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From: sdl-bounces@lists.libsdl.org [mailto:sdl-bounces at lists.libsdl.org] On Behalf Of Miles Qi
Sent: Friday, April 04, 2008 1:59 AM
To: sdl at lists.libsdl.org
Subject: [SDL] “Xlib: unexpected async reply” with Mplayer embedded?

Hi Everyone,

I have an SDL application which has a Mplayer embedded. I often get the error: “Xlib: unexpected async reply”. I found in mail-list there are a lot of discussions about “Xlib: unexpected async reply” problem. Based on these discussions, I guess, this problem is because Xlib functions are called in two threads(one is my main thread, i think there is another one in Mplayer). For my case, I can’t combine two threads into one, what should I do to avoid this problem? Any suggestion would be very appreciated.

Thanks

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3

Is the SDL event subsystem thread-safe ? Can you for example post an expose
event (or a user one) from the secondary thread to signal some redraw has to
be done ?

This happens because the Xlib seem to be not thread-safe.

You would need to only ensure that the display updates happens only from
the main thread only, you would not face this issue.

From the thread receiving asynchronous message, you need to signal the
thread waiting under the context of main thread as and when asych message
arrives and the main thread should do the job of display updates.

4

Hi,

Do you, by any chance, have an ATI card?

FYI, yes, virtually everything in SDL is thread-safe, unless:

  1. The documentation states that it is not.
  2. You have found a bug.

Eddy

Miles Qi wrote:> Hi Everyone,

I have an SDL application which has a Mplayer embedded. I often get the
error: “Xlib: unexpected async reply”. I found in mail-list there are a
lot of discussions about “Xlib: unexpected async reply” problem. Based
on these discussions, I guess, this problem is because Xlib functions
are called in two threads(one is my main thread, i think there is
another one in Mplayer). For my case, I can’t combine two threads into
one, what should I do to avoid this problem? Any suggestion would be
very appreciated.

Thanks

Sign in to Windows Live Messenger, and enter for your chance to win
$1000 a day?today until May 12th. Visit SignInAndWIN.ca
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5

It’s not ATI-related. Really, graphics SDL are not thread safe, you
can only do graphics from the thread that created the graphics
context.

As for the original poster, there’s no other option than merging the
two pieces of code into the same codebase. Maybe you’ll want to use
smpeg instead of mplayer to help with that.

StephaneOn 5/9/08, Eddy Cullen wrote:

Hi,

Do you, by any chance, have an ATI card?

FYI, yes, virtually everything in SDL is thread-safe, unless:

6

Okay,

That was a brain-fart… perhaps what I mean was reentrant-safe…

There is no reason why one couldn’t have multiple threads accessing a
surface - as long as you make each access thread-safe, using a mutex or
some other locking mechanism.

Of course, that makes life 100x more difficult than it need be. so
you’re right, you’re probably better off just having one thread doing
drawing if you can…

Jitsu Love,

Eddy

Stephane Marchesin wrote:> On 5/9/08, Eddy Cullen wrote:

Hi,

Do you, by any chance, have an ATI card?

FYI, yes, virtually everything in SDL is thread-safe, unless:

It’s not ATI-related. Really, graphics SDL are not thread safe, you
can only do graphics from the thread that created the graphics
context.

As for the original poster, there’s no other option than merging the
two pieces of code into the same codebase. Maybe you’ll want to use
smpeg instead of mplayer to help with that.

Stephane

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