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Fixed bug #292 I might be on crack here. It looks like SDL_ConvertMono() in src/audio/SDL_audiocvt.c adds the left and right channels of a stereo stream together, and clamps the new mono channel if it would overflow. Shouldn't it be dividing by 2 to average the two sample points instead of clamping? Otherwise the mono sample point's volume doubles in the conversion. This would also make the conversion faster, as it replaces two branches per sample frame with a bitwise shift. --ryan.
author Sam Lantinga <slouken@libsdl.org>
date Sun, 24 Sep 2006 15:56:36 +0000
parents f12379c41042
children
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>Multi-threaded Programming</TITLE
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>Chapter 12. Multi-threaded Programming</H1
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><DL
><DT
><B
>Table of Contents</B
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><DT
><A
HREF="sdlcreatethread.html"
>SDL_CreateThread</A
>&nbsp;--&nbsp;Creates a new thread of execution that shares its parent's properties.</DT
><DT
><A
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>SDL_ThreadID</A
>&nbsp;--&nbsp;Get the 32-bit thread identifier for the current thread.</DT
><DT
><A
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>SDL_GetThreadID</A
>&nbsp;--&nbsp;Get the SDL thread ID of a SDL_Thread</DT
><DT
><A
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>SDL_WaitThread</A
>&nbsp;--&nbsp;Wait for a thread to finish.</DT
><DT
><A
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>SDL_KillThread</A
>&nbsp;--&nbsp;Gracelessly terminates the thread.</DT
><DT
><A
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>SDL_CreateMutex</A
>&nbsp;--&nbsp;Create a mutex</DT
><DT
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>SDL_DestroyMutex</A
>&nbsp;--&nbsp;Destroy a mutex</DT
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>&nbsp;--&nbsp;Lock a mutex</DT
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>SDL_mutexV</A
>&nbsp;--&nbsp;Unlock a mutex</DT
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>SDL_CreateSemaphore</A
>&nbsp;--&nbsp;Creates a new semaphore and assigns an initial value to it.</DT
><DT
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>SDL_DestroySemaphore</A
>&nbsp;--&nbsp;Destroys a semaphore that was created by <A
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>SDL_CreateSemaphore</A
>.</DT
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>SDL_SemWait</A
>&nbsp;--&nbsp;Lock a semaphore and suspend the thread if the semaphore value is zero.</DT
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>SDL_SemTryWait</A
>&nbsp;--&nbsp;Attempt to lock a semaphore but don't suspend the thread.</DT
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>SDL_SemWaitTimeout</A
>&nbsp;--&nbsp;Lock a semaphore, but only wait up to a specified maximum time.</DT
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>SDL_SemPost</A
>&nbsp;--&nbsp;Unlock a semaphore.</DT
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>SDL_SemValue</A
>&nbsp;--&nbsp;Return the current value of a semaphore.</DT
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>SDL_CreateCond</A
>&nbsp;--&nbsp;Create a condition variable</DT
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>SDL_DestroyCond</A
>&nbsp;--&nbsp;Destroy a condition variable</DT
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>SDL_CondSignal</A
>&nbsp;--&nbsp;Restart a thread wait on a condition variable</DT
><DT
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>SDL_CondBroadcast</A
>&nbsp;--&nbsp;Restart all threads waiting on a condition variable</DT
><DT
><A
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>SDL_CondWait</A
>&nbsp;--&nbsp;Wait on a condition variable</DT
><DT
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>SDL_CondWaitTimeout</A
>&nbsp;--&nbsp;Wait on a condition variable, with timeout</DT
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>SDL provides functions for creating threads, mutexes, semphores and condition variables.</P
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>In general, you must be very aware of concurrency and data integrity issues
when writing multi-threaded programs.  Some good guidelines include:
<P
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><UL
><LI
><P
>Don't call SDL video/event functions from separate threads</P
></LI
><LI
><P
>Don't use any library functions in separate threads</P
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><P
>Don't perform any memory management in separate threads</P
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><LI
><P
>Lock global variables which may be accessed by multiple threads</P
></LI
><LI
><P
>Never terminate threads, always set a flag and wait for them to quit</P
></LI
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>Think very carefully about all possible ways your code may interact</P
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></UL
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>Note: </B
>SDL's threading is not implemented on MacOS, due to that lack of preemptive thread support (Mac OS X dos nt suffer from this problem)</P
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