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[英]Different Number of Character in Java Android InputStream and C++ ifstream
[英]Alternative for ifstream (c++) whilst trying to read a .wav file in android
我正在嘗試從存儲在SD卡上的wav文件計算MFCC系數。 我正在使用該庫: https : //github.com/dspavankumar/compute-mfcc
輸入是使用ifstream的wav文件路徑。 我需要能夠根據時間段訪問從單個wav文件分割的不同pcm文件,並為每個段計算MFCC。 我在尋找一種方法來從java類將數據(原始pcm數據)獲取到下面方法所示的緩沖區中時遇到麻煩。 (使用JNI)
int process (std::ifstream &wavFp, std::ofstream &mfcFp) {
// Read the wav header
wavHeader hdr;
int headerSize = sizeof(wavHeader);
wavFp.read((char *) &hdr, headerSize);
// Check audio format
if (hdr.AudioFormat != 1 || hdr.bitsPerSample != 16) {
std::cerr << "Unsupported audio format, use 16 bit PCM Wave" <<
std::endl;
return 1;
}
// Check sampling rate
if (hdr.SamplesPerSec != fs) {
std::cerr << "Sampling rate mismatch: Found " << hdr.SamplesPerSec << " instead of " << fs <<std::endl;
return 1;
}
// Initialise buffer
uint16_t bufferLength = winLengthSamples-frameShiftSamples;
int16_t* buffer = new int16_t[bufferLength];
int bufferBPS = (sizeof buffer[0]);
// Read and set the initial samples
wavFp.read((char *) buffer, bufferLength*bufferBPS);
for (int i=0; i<bufferLength; i++)
prevsamples[i] = buffer[i];
delete [] buffer;
// Recalculate buffer size
bufferLength = frameShiftSamples;
buffer = new int16_t[bufferLength];
// Read data and process each frame
wavFp.read((char *) buffer, bufferLength*bufferBPS);
while (wavFp.gcount() == bufferLength*bufferBPS && !wavFp.eof()) {
mfcFp << processFrame(buffer, bufferLength);
wavFp.read((char *) buffer, bufferLength*bufferBPS);
}
delete [] buffer;
buffer = nullptr;
return 0;
}
`
看來我無法直接從c ++庫訪問sd卡上的wav文件。 所以我嘗試傳遞一個jbytearray並將其轉換為char *使用:
extern "C"
JNIEXPORT void JNICALL
Java_com_example_nikhar_mst04v10_RecordActivity_doMFCC(JNIEnv *env, jobject
instance,
jbyteArray wavBytes_) {
int len = env ->GetArrayLength(wavBytes_);
char* buf = new char[len];
env->GetByteArrayRegion(wavBytes_,0,len, reinterpret_cast<jbyte *>(buf));
// TODO
/* env->ReleaseStringUTFChars(wavPath_, wavPath);
env->ReleaseStringUTFChars(mfccPath_, mfccPath);*/
// Assign variables
int numCepstra = 12;
int numFilters = 40;
int samplingRate = 16000;
int winLength = 25;
int frameShift = 10;
int lowFreq = 50;
int highFreq = samplingRate/2;
// Initialise MFCC class instance
MFCC mfccComputer (samplingRate, numCepstra, winLength, frameShift,
numFilters, lowFreq, highFreq);
mfccComputer.process(buf);
}
但這是不成功的。 任何建議,我如何才能做到這一點?
在這里看看:
http://jnicookbook.owsiak.org/recipe-No-012/
熟悉在Java和C之間傳遞數組。
至於jbyte-這種類型取決於機器。 通常,它將是“ signed char”。 我建議將您的數據傳遞給C,然后將數組轉換為char *。 它應該工作。
但! 確保仔細檢查目標系統中如何聲明jbyte。 您可以在這里找到它:$ YOUR_PLATFORM_NAME / jni_md.h
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