我使用ALSA API与linux中的USB音频编解码器连接。我的代码检查-r
或-p
标志,并分别录制或播放音频:
int main(int argc, char** argv){
if(argc > 1){
if(strcmp("-p", argv[1]) == 0){
// Create data buffer, choose sampling rate
char* playback_data;
unsigned int sampling_rate = 44100;
// Declare handle and params structure
snd_pcm_t* handle;
snd_pcm_hw_params_t* params;
// Initiate and configure sound device
init_playback_device(&handle, ¶ms);
config_playback_device(handle, params, sampling_rate);
// Playback
printf("playing...\n");
playback(handle, params, playback_data, "test.raw", 3);
// Close
snd_pcm_hw_params_free(params);
snd_pcm_close(handle);
free(playback_data);
} else if(strcmp("-r", argv[1]) == 0){
// Create data buffer, choose sampling rate
char* record_data;
unsigned int sampling_rate = 44100;
// Declare handle and params structure
snd_pcm_t* handle;
snd_pcm_hw_params_t* params;
// Initiate and configure sound device
init_recording_device(&handle, ¶ms);
config_recording_device(handle, params, sampling_rate);
// Record
printf("recording...\n");
record(handle, params, record_data, "test.raw", 3);
// Close
snd_pcm_hw_params_free(params);
snd_pcm_close(handle);
free(record_data);
}
}
return 0;
}
每当我运行./audio -r
时,我都会遇到分段错误。奇怪的是,当我在第一个if语句(-p
标志)中注释掉代码时,我没有得到分段错误。我不明白为什么评论未首先运行的代码(由于错误的条件)会产生段错误。使用valgrind会显示以下问题:
==22959== Conditional jump or move depends on uninitialised value(s)
==22959== at 0x4848BAC: free (vg_replace_malloc.c:530)
==22959== by 0x10DA7: main (audio.c:59)
==22959== Uninitialised value was created by a stack allocation
==22959== at 0x10C5C: main (audio.c:14)
==22959==
==22959== Invalid free() / delete / delete[] / realloc()
==22959== at 0x4848BFC: free (vg_replace_malloc.c:530)
==22959== by 0x10DA7: main (audio.c:59)
==22959== Address 0x10b2c is in the Text segment of /home/pi/audio/audio
==22959== at 0x10B2C: ??? (in /home/pi/audio/audio)
它不喜欢free(record_data)
行,因为它认为record_data
未初始化,但在我的record
函数中,我会处理此问题:
void record(snd_pcm_t* handle, snd_pcm_hw_params_t* params, char* data_buffer, char file[], int duration){
// Open file
FILE* audio_file;
audio_file = fopen(file, "w+");
data_buffer = (char*) malloc(NUM_FRAMES * 4);
int i;
for(i = 0; i < (duration*10); i++){
snd_pcm_readi(handle, data_buffer, NUM_FRAMES);
fwrite(data_buffer, sizeof(char), NUM_FRAMES * 4 , audio_file);
}
fclose(audio_file);
}
将指向record_data
的指针作为参数data_buffer
传递。任何人都知道出了什么问题?
编辑:
解决方案是传递record_data
的指针,因为playback
函数正在发出指向局部变量的指针:
void record(snd_pcm_t* handle, snd_pcm_hw_params_t* params, char** data_buffer, char file[], int duration){
// Open file
FILE* audio_file;
audio_file = fopen(file, "w+");
*data_buffer = (char*) malloc(NUM_FRAMES * 4);
int i;
for(i = 0; i < (duration*10); i++){
snd_pcm_readi(handle, *data_buffer, NUM_FRAMES);
fwrite(*data_buffer, sizeof(char), NUM_FRAMES * 4 , audio_file);
}
fclose(audio_file);
}
我仍然很好奇为什么注释掉第一个条件块中的代码会删除错误。仍然不确定为什么会这样。
答案 0 :(得分:1)
首先,Valgrind是对的。您正在使用单位指针。在写入该位置之前,您需要先分配内存。虽然您在函数内部分配内存,但只覆盖指针的 local 值,但不要将新指针返回给周围的代码。
比较record_data
指向函数调用之前,之内和之后的位置。
考虑在记录函数内移动free
调用,或返回更新的数据指针,或通过引用传递。这些问题中的任何一个都应解决大部分(如果不是全部)问题。