From Bug #36: There are a couple of issues with the selection of Altivec alpha-blitting routines in CalculateAlphaBlit() in src/video/SDL_Blit_A.c. 1) There's no check for the presence of Altivec when checking if the Blit32to565PixelAlphaAltivec() routine can be selected. 2) Altivec cannot be used in video memory, and there's no check if the destination surface is a hardware surface. (Alpha-blitting to a hardware surface with GPU support is a bad idea, but somebody's bound to do it anyway.) Patch to fix these attached.

#if defined(USE_ASM_MIXER_VC)
// headers for MMX assembler version of SDL_MixAudio
// Copyright 2002 Stephane Marchesin (stephane.marchesin@wanadoo.fr)
// Converted to Intel ASM notation by Cth
// This code is licensed under the LGPL (see COPYING for details)
// 
// Assumes buffer size in bytes is a multiple of 16
// Assumes SDL_MIX_MAXVOLUME = 128

void SDL_MixAudio_MMX_S16_VC(char* ,char* ,unsigned int ,int );
void SDL_MixAudio_MMX_S8_VC(char* ,char* ,unsigned int ,int );
#endif