SDL无法打开音频设备的问题：Couldn‘t open audio/video device: No available audio/video device

解决中标麒麟下SDL无法打开音频设备的问题：

root登录

首先就是一定要用root登录，这个可能是权限问题，否则后面实验不能成功

安装ALSA库

首先下载alsa-lib：https://www.alsa-project.org/main/index.php/Main_Page


tar -jxvf alsa-lib-1.1.2.tar.bz2
cd alsa-lib-1.1.2
./configure
make && make install
这样alsa-lib库就安装好了，不需要去管安装到哪里，系统自动安装了，测试时发现使用此版本库在播放音频时会出现：ALSA lib pcm.c:8251:(snd_pcm_recover) underrun occurred
此时音频播放会断断续续，怀疑是安装alsa-lib的版本太低了，于是换到了alsa-lib-1.2.2，就可以正常播放了

测试

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "SDL2/SDL.h"
static unsigned char *pAudio_chunk;
static unsigned int audio_len;
static unsigned char *pAudio_pos;
void fill_audio_buffer(void *userdata, Uint8 * stream, int len)
{
    SDL_memset(stream, 0, len);
    // 判断是否有读到数据
    if (audio_len == 0)
        return;
    len = (len > audio_len ? audio_len : len);
    SDL_MixAudio(stream, pAudio_pos, len, SDL_MIX_MAXVOLUME);
    pAudio_pos += len;
    audio_len -= len;
}
int main(int argc, char *argv[])
{
	if (SDL_Init(SDL_INIT_AUDIO | SDL_INIT_TIMER))
    {
        printf("Initialize SDL failed: %s\n", SDL_GetError());
        return -1;
    }
    /*** 初始化初始化SDL_AudioSpec结构体 ***/
    SDL_AudioSpec audioSpec;
    audioSpec.freq = 44100;                     // 音频数据的采样率。常用的有48000，44100等
    audioSpec.format = AUDIO_S16SYS;            // 音频数据的格式
    audioSpec.channels = 2;                     // 声道数。例如单声道取值为1，立体声取值为2
    audioSpec.silence = 0;                      // 设置静音的值
    audioSpec.samples = 1024;                   // 音频缓冲区中的采样个数，要求必须是2的n次方
    audioSpec.callback = fill_audio_buffer;     // 填充音频缓冲区的回调函数
    // 打开音频设备
    if (SDL_OpenAudio(&audioSpec, NULL) < 0)
    {
        printf("Can not open audio!");
        return -1;
    }
    printf("Open audio success!\n");
	return 0;
}

MakeFile

############################################################
# main makefile
############################################################

############################################################
# Target setting
############################################################

TARGET_DEMO = sdl_test

TOP_DIR = .
BIN_DIR = $(TOP_DIR)/.bin
OBJ_DIR = $(TOP_DIR)/.obj
SRC_DIR = $(TOP_DIR)
TPARTY_DIR = $(TOP_DIR)/../install/x86/SDL2/lib
INC_DIR = $(TOP_DIR)/../install/x86/SDL2/include

############################################################
# Project options
############################################################

INCLUDES += \
	-I$(INC_DIR)
	
LIBINCLUDES += \
	-L$(TPARTY_DIR)

LINK_LIBRARIES += \
	-lSDL2 -lm -ldl -lpthread -lrt

VPATH := \
		./
	
SRCS_CPP := 
		
SRCS_C := 

SRCS_DEMO_CPP := \
		$(SRCS_CPP)

SRCS_DEMO_C := \
		$(SRCS_C) \
		main.c
		
############################################################
# Compiler
############################################################

CXX = g++
CC = gcc
LINKXX = g++
LINK = gcc
AR = $(CROSS_PREFIX)ar -r
AS = $(CROSS_PREFIX)as
LD = $(CROSS_PREFIX)ld
MAKE = make 
SUBMAKE = $(MAKE) --no-print-directory -f
PY = python
SED = sed
MKDIR = mkdir -p
CP = cp
RM = rm -f
MV = mv
ECHO = echo

CXXFLAGS += -O3 -Wall -std=c++11
CFLAGS   += -O3 -Wall

############################################################
# build rules
############################################################

CC_TITLE   = @$(ECHO) "==> Compiling $@ "
LINK_TITLE = @$(ECHO) "==> Linking $(BIN_DIR)/$@ "

CXXFLAGS += $(INCLUDES)
CFLAGS   += $(INCLUDES)

define MK_OBJ_DIR
	if test ! -d $(OBJ_DIR); then $(MKDIR) $(OBJ_DIR); fi
endef

define MK_BIN_DIR
	if test ! -d $(BIN_DIR); then $(MKDIR) $(BIN_DIR); fi
endef

$(OBJ_DIR)/%.o: %.cpp
	$(CC_TITLE)
	@$(MK_OBJ_DIR)
	@$(CXX) -o $@ -c $(CXXFLAGS) $<
	
$(OBJ_DIR)/%.o: %.c
	$(CC_TITLE)
	@$(MK_OBJ_DIR)
	@$(CC) -o $@ -c $(CFLAGS) $<
	
OBJS_C = $(patsubst %.c, $(OBJ_DIR)/%.o, $(SRCS_C))
OBJS_CPP = $(patsubst %.cpp, $(OBJ_DIR)/%.o, $(SRCS_CPP))
OBJS_DEMO_C = $(patsubst %.c, $(OBJ_DIR)/%.o, $(SRCS_DEMO_C))
OBJS_DEMO_CPP = $(patsubst %.cpp, $(OBJ_DIR)/%.o, $(SRCS_DEMO_CPP))

############################################################
# make target
############################################################

all: $(TARGET_DEMO)
$(TARGET_DEMO):$(OBJS_DEMO_CPP) $(OBJS_DEMO_C)
	@$(LINK_TITLE)
	@$(MK_BIN_DIR)
	@$(LINK) $^ -o $(BIN_DIR)/$(TARGET_DEMO) $(LIBINCLUDES) $(LINK_LIBRARIES)

.PHONY:install clean distclean
install:
	@$(MKDIR) install/$(CROSS_NAME)/include
	@$(CP) -rf include/* install/$(CROSS_NAME)/include 
	@$(MKDIR) install/$(CROSS_NAME)/lib
	@if [ -e $(BIN_DIR)/$(TARGET_SO) ];   then $(CP) -f $(BIN_DIR)/$(TARGET_SO) install/$(CROSS_NAME)/lib;fi
	@if [ -e $(BIN_DIR)/$(TARGET_A) ];    then $(CP) -f $(BIN_DIR)/$(TARGET_A) install/$(CROSS_NAME)/lib;fi
	@if [ -e $(BIN_DIR)/$(TARGET_DEMO) ]; then $(MKDIR) install/$(CROSS_NAME)/sbin; $(CP) -f $(BIN_DIR)/$(TARGET_DEMO) install/$(CROSS_NAME)/sbin; fi
	
clean:
	@$(RM) -r $(OBJ_DIR) $(BIN_DIR)
	
distclean:
	@$(RM) -r $(OBJ_DIR) $(BIN_DIR)

运行的时候一定要在前面加上SDL_AUDIODRIVER=alsa

SDL_AUDIODRIVER=alsa ./sdl_test