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Editors Note: The original patch was modified to use SDL_Delay() instead of
nanosleep because nanosleep may not be portable to all systems
using SDL with the ALSA backend. This may be a moot point with
the switch to blocking writes anyway...
Date: Sat, 27 Dec 2003 21:47:36 +0100
From: Michel Daenzer
To: Debian Bug Tracking System
Subject: [SDL] Bug#225252: [PATCH] ALSA fixes
Package: libsdl1.2debian-all
Version: 1.2.6-2
Severity: normal
Tags: patch
For SDL 1.2.6, the ALSA backend was changed to call snd_pcm_open() with
SND_PCM_NONBLOCK. That's a good idea per se, however, it causes high CPU
usage, interrupted sound and stuttering in some games here. Taking a nanosleep
whenever snd_pcm_writei() returns -EAGAIN fixes this, but I think it's more
efficient to use blocking mode for the actual sound playback. Feedback from the
SDL and ALSA lists appreciated.
The patch also fixes the default ALSA device to be used.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Sun, 04 Jan 2004 15:40:50 +0000 |
parents | e5bc29de3f0a |
children | 355632dca928 |
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<HTML ><HEAD ><TITLE >SDL_BuildAudioCVT</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.64 "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="Audio" HREF="audio.html"><LINK REL="PREVIOUS" TITLE="SDL_AudioCVT" HREF="sdlaudiocvt.html"><LINK REL="NEXT" TITLE="SDL_ConvertAudio" HREF="sdlconvertaudio.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >SDL Library Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="sdlaudiocvt.html" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdlconvertaudio.html" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLBUILDAUDIOCVT" >SDL_BuildAudioCVT</A ></H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN6614" ></A ><H2 >Name</H2 >SDL_BuildAudioCVT -- Initializes a SDL_AudioCVT structure for conversion</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN6617" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN6618" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >int <B CLASS="FSFUNC" >SDL_BuildAudioCVT</B ></CODE >(SDL_AudioCVT *cvt, Uint16 src_format, Uint8 src_channels, int src_rate, Uint16 dst_format, Uint8 dst_channels, int dst_rate);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6624" ></A ><H2 >Description</H2 ><P >Before an <A HREF="sdlaudiocvt.html" ><SPAN CLASS="STRUCTNAME" >SDL_AudioCVT</SPAN ></A > structure can be used to convert audio data it must be initialized with source and destination information. </P ><P ><TT CLASS="PARAMETER" ><I >src_format</I ></TT > and <TT CLASS="PARAMETER" ><I >dst_format</I ></TT > are the source and destination format of the conversion. (For information on audio formats see <A HREF="sdlaudiospec.html" ><SPAN CLASS="STRUCTNAME" > SDL_AudioSpec</SPAN ></A >). <TT CLASS="PARAMETER" ><I >src_channels</I ></TT > and <TT CLASS="PARAMETER" ><I >dst_channels</I ></TT > are the number of channels in the source and destination formats. Finally, <TT CLASS="PARAMETER" ><I >src_rate</I ></TT > and <TT CLASS="PARAMETER" ><I >dst_rate</I ></TT > are the frequency or samples-per-second of the source and destination formats. Once again, see <A HREF="sdlaudiospec.html" ><SPAN CLASS="STRUCTNAME" >SDL_AudioSpec</SPAN ></A >.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6640" ></A ><H2 >Return Values</H2 ><P >Returns <SPAN CLASS="RETURNVALUE" >-1</SPAN > if the filter could not be built or 1 if it could.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6644" ></A ><H2 >Examples</H2 ><P >See <A HREF="sdlconvertaudio.html" ><TT CLASS="FUNCTION" >SDL_ConvertAudio</TT ></A >.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6649" ></A ><H2 >See Also</H2 ><P ><A HREF="sdlconvertaudio.html" ><TT CLASS="FUNCTION" >SDL_ConvertAudio</TT ></A >, <A HREF="sdlaudiocvt.html" ><TT CLASS="FUNCTION" >SDL_AudioCVT</TT ></A ></P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdlaudiocvt.html" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sdlconvertaudio.html" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_AudioCVT</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="audio.html" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_ConvertAudio</TD ></TR ></TABLE ></DIV ></BODY ></HTML >