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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 355632dca928
children
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<HTML
><HEAD
><TITLE
>SDL_Overlay</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
"><LINK
REL="HOME"
TITLE="SDL Library Documentation"
HREF="index.html"><LINK
REL="UP"
TITLE="Video"
HREF="video.html"><LINK
REL="PREVIOUS"
TITLE="SDL_VideoInfo"
HREF="sdlvideoinfo.html"><LINK
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><BODY
CLASS="REFENTRY"
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>SDL Library Documentation</TH
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><HR
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WIDTH="100%"></DIV
><H1
><A
NAME="SDLOVERLAY"
></A
>SDL_Overlay</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN3464"
></A
><H2
>Name</H2
>SDL_Overlay&nbsp;--&nbsp;YUV video overlay</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3467"
></A
><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct{
  Uint32 format;
  int w, h;
  int planes;
  Uint16 *pitches;
  Uint8 **pixels;
  Uint32 hw_overlay:1;
} SDL_Overlay;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3470"
></A
><H2
>Structure Data</H2
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN3472"
></A
><P
></P
><TABLE
BORDER="0"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>format</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Overlay format (see below)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>w, h</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Width and height of overlay</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>planes</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Number of planes in the overlay. Usually either 1 or 3</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>pitches</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>An array of pitches, one for each plane. Pitch is the length of a row in bytes.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>pixels</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>An array of pointers to teh data of each plane. The overlay should be locked before these pointers are used.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>hw_overlay</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>This will be set to 1 if the overlay is hardware accelerated.</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3499"
></A
><H2
>Description</H2
><P
>A <SPAN
CLASS="STRUCTNAME"
>SDL_Overlay</SPAN
> is similar to a <A
HREF="sdlsurface.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
></A
> except it stores a YUV overlay. All the fields are read only, except for <TT
CLASS="STRUCTFIELD"
><I
>pixels</I
></TT
> which should be <A
HREF="sdllockyuvoverlay.html"
>locked</A
> before use. The <TT
CLASS="STRUCTFIELD"
><I
>format</I
></TT
> field stores the format of the overlay which is one of the following:
<PRE
CLASS="PROGRAMLISTING"
>#define SDL_YV12_OVERLAY  0x32315659  /* Planar mode: Y + V + U */
#define SDL_IYUV_OVERLAY  0x56555949  /* Planar mode: Y + U + V */
#define SDL_YUY2_OVERLAY  0x32595559  /* Packed mode: Y0+U0+Y1+V0 */
#define SDL_UYVY_OVERLAY  0x59565955  /* Packed mode: U0+Y0+V0+Y1 */
#define SDL_YVYU_OVERLAY  0x55595659  /* Packed mode: Y0+V0+Y1+U0 */</PRE
>
More information on YUV formats can be found at <A
HREF="http://www.webartz.com/fourcc/indexyuv.htm"
TARGET="_top"
>http://www.webartz.com/fourcc/indexyuv.htm</A
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3510"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlcreateyuvoverlay.html"
><TT
CLASS="FUNCTION"
>SDL_CreateYUVOverlay</TT
></A
>,
<A
HREF="sdllockyuvoverlay.html"
><TT
CLASS="FUNCTION"
>SDL_LockYUVOverlay</TT
></A
>,
<A
HREF="sdlunlockyuvoverlay.html"
><TT
CLASS="FUNCTION"
>SDL_UnlockYUVOverlay</TT
></A
>,
<A
HREF="sdlfreeyuvoverlay.html"
><TT
CLASS="FUNCTION"
>SDL_FreeYUVOverlay</TT
></A
></P
></DIV
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