将音频流写入循环缓冲区但分段错误读取值
Posted
技术标签:
【中文标题】将音频流写入循环缓冲区但分段错误读取值【英文标题】：Writing audio stream to circular buffer but Segmentation error reading value 【发布时间】：2021-06-05 11:03:04 【问题描述】：我非常新的音频处理概念和 C++ 的基本知识，我的最终目标是创建一种方法来测量线路输入音频的谐波失真；我的想法是将音频输入流写入循环缓冲区，然后从循环缓冲区读取到 FFT 函数；从 FFT 数据中我可以锻炼音频失真。
到目前为止，我正在使用 Portaudio 将流式音频从其流式输入回调写入循环缓冲区；我创建了一个 Thread 来检查循环缓冲区中是否有任何数据，如果有数据，则将其读入临时缓冲区。作为一种简单测试的方法，我只是在回显要从循环缓冲区中读取的元素数量，这是可行的，但是大约一秒钟后，会为“可用的读取元素”(18446744073709542400) 产生不正确的值接着是分段错误；示例输出和我的代码如下：
+Read available 0
Stream started
+Read available 8192
>>dataIndex: 8192
+Read available 2048
>>dataIndex: 10240
+Read available 0
+Read available 9216
>>dataIndex: 19456
+Read available 18446744073709542400
Segmentation fault: 11
在理解上述非常大的读取值 (18446744073709542400) 和分段错误的原因方面提供任何帮助；我的想法是可能是因为循环缓冲区读取是在单独的线程中完成的；但是使用的循环缓冲区确实声明其线程安全。
ringbuffer.hpp
main.cpp：
#include <array>
#include <stdio.h>
#include <thread>
#include "ringbuffer.hpp"
#include "portaudio.h"
/* #define SAMPLE_RATE (17932) // Test failure to open with this value. */
#define SAMPLE_RATE (44100)
#define FRAMES_PER_BUFFER (512)
#define NUM_SECONDS (1)
#define NUM_CHANNELS (2)
#define NUM_WRITES_PER_BUFFER (4)
#define DITHER_FLAG (paDitherOff)
//#define DITHER_FLAG (0)
/* Select sample format. */
#if 1
#define PA_SAMPLE_TYPE paFloat32
typedef float SAMPLE;
#define SAMPLE_SILENCE (0.0f)
#define PRINTF_S_FORMAT "%.8f"
#elif 1
#define PA_SAMPLE_TYPE paInt16
typedef short SAMPLE;
#define SAMPLE_SILENCE (0)
#define PRINTF_S_FORMAT "%d"
#elif 0
#define PA_SAMPLE_TYPE paInt8
typedef char SAMPLE;
#define SAMPLE_SILENCE (0)
#define PRINTF_S_FORMAT "%d"
#else
#define PA_SAMPLE_TYPE paUInt8
typedef unsigned char SAMPLE;
#define SAMPLE_SILENCE (128)
#define PRINTF_S_FORMAT "%d"
#endif
static unsigned long int rbs_min(unsigned long int a, unsigned long int b)
return (a < b) ? a : b;
typedef struct
unsigned long int frameIndex;
unsigned long int dataIndex;
unsigned long int maxFrameIndex;
int threadSyncFlag;
SAMPLE *sampleData;
const SAMPLE* buff;
Ringbuffer<const SAMPLE*, 65536> ringBuffer;
void *threadHandle;
paTestData;
static int cons(void* ptr)
unsigned long int ra_i;
paTestData* pData = (paTestData*)ptr;
/* Mark thread started */
pData->threadSyncFlag = 0;
while(1)
ra_i = pData->ringBuffer.readAvailable();
printf("+Read available %lu\n",ra_i);
if ( (pData->dataIndex <= 65536) )
if (! pData->ringBuffer.isEmpty())
pData->dataIndex += pData->ringBuffer.readBuff(&pData->buff,ra_i);
printf(">>dataIndex: %lu\n",pData->dataIndex);
else
break;
Pa_Sleep(100);
pData->threadSyncFlag = 0;
return 0;
static unsigned NextPowerOf2(unsigned val)
val--;
val = (val >> 1) | val;
val = (val >> 2) | val;
val = (val >> 4) | val;
val = (val >> 8) | val;
val = (val >> 16) | val;
return ++val;
/* This routine will be called by the PortAudio engine when audio is needed.
** It may be called at interrupt level on some machines so don't do anything
** that could mess up the system like calling malloc() or free().
*/
static int recordCallback( const void *inputBuffer, void *outputBuffer,
unsigned long framesPerBuffer,
const PaStreamCallbackTimeInfo* timeInfo,
PaStreamCallbackFlags statusFlags,
void *userData )
paTestData *data = (paTestData*)userData;
unsigned long int elementsWriteable = data->ringBuffer.writeAvailable();
unsigned long int elementsToWrite = rbs_min( elementsWriteable, (unsigned long int)(framesPerBuffer * NUM_CHANNELS) );
SAMPLE *rptr = (SAMPLE*)inputBuffer;
(void) outputBuffer; /* Prevent unused variable warnings. */
(void) timeInfo;
(void) statusFlags;
(void) userData;
data->frameIndex += data->ringBuffer.writeBuff( &rptr, elementsToWrite);
return paContinue;
PaError pa_term(PaError err)
Pa_Terminate();
if( err != paNoError )
fprintf( stderr, "An error occured while using the portaudio stream\n" );
fprintf( stderr, "Error number: %d\n", err );
fprintf( stderr, "Error message: %s\n", Pa_GetErrorText( err ) );
err = 1; // Always return 0 or 1, but no other return codes.
return err;
int main(void);
int main(void)
PaStreamParameters inputParameters,
outputParameters;
PaStream* stream;
PaError err = paNoError;
paTestData data = 0;
unsigned delayCntr;
unsigned long int totalFrames;
unsigned numSamples;
unsigned numBytes;
data.dataIndex = 0;
err = Pa_Initialize();
if( err != paNoError )
pa_term(err);
inputParameters.device = Pa_GetDefaultInputDevice(); /* default input device */
if (inputParameters.device == paNoDevice)
printf("Error: No default input device.\n");
pa_term(paDeviceUnavailable);
inputParameters.channelCount = 2; /* stereo input */
inputParameters.sampleFormat = PA_SAMPLE_TYPE;
inputParameters.suggestedLatency = Pa_GetDeviceInfo( inputParameters.device )->defaultLowInputLatency;
inputParameters.hostApiSpecificStreamInfo = NULL;
/* Record some audio. -------------------------------------------- */
err = Pa_OpenStream(
&stream,
&inputParameters,
NULL, /* &outputParameters, */
SAMPLE_RATE,
FRAMES_PER_BUFFER,
paClipOff, /* we won't output out of range samples so don't bother clipping them */
recordCallback,
&data );
if( err != paNoError )
pa_term(err);
// Start stream logging thread
std::thread first (cons, &data);
err = Pa_StartStream( stream );
if( err != paNoError )
pa_term(err);
printf("Stream started\n");
while(!paNoError)
Pa_Sleep(1);
err = Pa_CloseStream( stream );
if( err != paNoError )
pa_term(err);
【问题讨论】：
【参考方案1】：RingBuffer::readAvailable() 返回一个小的负数作为size_t。因为size_t 是一个无符号类型并且因为您在printf 中使用%lu，所以它被显示为好像它是一个巨大的unsigned long。 （不知何故，你的输出有多余的数字。）
RingBuffer 可能有错误。似乎假设尾部索引将始终小于或等于头部索引。我不是无锁代码中使用的内存排序约束方面的专家，但在我看来，当它读取头部和尾部以计算可用数量时，它可能是一个同步问题。
【讨论】：
以上是关于将音频流写入循环缓冲区但分段错误读取值的主要内容，如果未能解决你的问题，请参考以下文章