I do have a very particular problem, I wish I could find the answer to.
I'm trying to read an AAC stream from an URL (online streaming radio e.g. live.noroc.tv:8000/radionoroc.aacp) with NAudio library and get IEEE 32 bit floating samples.
Besides that I would like to resample the stream to a particular sample rate and channel count (rate 5512, mono).
Below is the code which accomplishes that:
int tenSecondsOfDownloadedAudio = 5512 * 10;
float[] buffer = new float[tenSecondsOfDownloadedAudio];
using (var reader = new MediaFoundationReader(pathToUrl))
{
var ieeeFloatWaveFormat = WaveFormat.CreateIeeeFloatWaveFormat(5512, 1); // mono
using (var resampler = new MediaFoundationResampler(reader, ieeeFloatWaveFormat))
{
var waveToSampleProvider = new WaveToSampleProvider(resampler);
int readSamples = 0;
int tempBuffer = new float[5512]; // 1 second buffer
while(readSamples <= tenSecondsOfDownloadedAudio)
{
int read = waveToSampleProvider.Read(tempBuffer, 0, tempBuffer.Length);
if(read == 0)
{
Thread.Sleep(500); // allow streaming buffer to get loaded
continue;
}
Array.Copy(tempBuffer, 0, buffer, readSamples, tempBuffer.Length);
readSamples += read;
}
}
}
These particular samples are then written to a Wave audio file using the following simple method:
using (var writer = new WaveFileWriter("path-to-audio-file.wav", WaveFormat.CreateIeeeFloatWaveFormat(5512, 1)))
{
writer.WriteSamples(samples, 0, samples.Length);
}
What I've encountered is that NAudio does not read 10 seconds of audio (as it was requested) but only 5, though the buffer array gets fully loaded with samples (which at this rate and channel count should contain 10 seconds of audio samples).
Thus the final audio file plays the stream 2 times as slower as it should (5 second stream is played as 10).
Is this somewhat related to different bit depths (should I record at 64 bits per sample as opposite to 32).
I do my testing at Windows Server 2008 R2 x64, with MFT codecs installed.
Would really appreciate any suggestions.
The problem seems to be with MediaFoundationReader failing to handle HE-AACv2 in ADTS container with is a standard online radio stream format and most likely the one you are dealing with.
Adobe products have the same problem mistreating this format exactly the same way^ stretching the first half of the audio to the whole duration and : Corrupted AAC files recorded from online stream
Supposedly, it has something to do with HE-AACv2 stereo stream being actually a mono stream with additional info channel for Parametric Stereo.
Related
I am new to signal processing and I don't really understand the basics (and more). Sorry in advance for any mistake into my understanding so far.
I am writing C code to detect a basic signal (18Hz simple sinusoid 2 sec duration, generating it using Audacity is pretty simple) into a much bigger mp3 file. I read the mp3 file and copy it until I match the sound signal.
The signal to match is { 1st channel: 18Hz sin. signal , 2nd channel: nothing/doesn't matter).
To match the sound, I am calculating the frequency of the mp3 until I find a good percentage of 18Hz freq. during ~ 2 sec. As this frequency is not very common, I don't have to match it very precisely.
I used mpg123 to convert my file, I fill the buffers with what it returns. I initialised it to convert the mp3 to Mono RAW audio:
init:
int ret;
const long *rates;
size_t rate_count, i;
mpg123_rates(&rates, &rate_count);
mpg123_handle *m = mpg123_new(NULL, &ret);
mpg123_format_none(m);
for(i=0; i<rate_count; ++i)
mpg123_format(m, rates[i], MPG123_MONO, MPG123_ENC_SIGNED_32);
if(m == NULL)
{
//err
} else {
mpg123_open_feed(m);
}
(...)
unsigned char out[8*MAX_MP3_BUF_SIZE];
ret = mpg123_decode(m, buf->data, buf->size, out, 8*MAX_MP3_BUF_SIZE, &size);
`(...)
unsigned char out[8*MAX_MP3_BUF_SIZE];
ret = mpg123_decode(m, buf->data, buf->size, out, 8*MAX_MP3_BUF_SIZE, &size);
(...) `
But I have to idea how to get the resulting buffer to calculate the FFT to get the frequency.
//FREQ Calculation with libfftw3
int transform_size = MAX_MP3_BUF_SIZE * 2;
fftw_complex *fftout = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * transform_size);
fftw_complex *fftin = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * transform_size);
fftw_plan p = fftw_plan_dft_r2c_1d(transform_size, fftin, fftout, FFTW_ESTIMATE);
I can get a good RAW Audio (PCM ?) into a buffer (if I write it, it can be read and converted into wave with sox:
sox --magic -r 44100 -e signed -b 32 -c 1 rps.raw rps.wav
Any help is appreciated. My knowledge of signal processing is poor, I am not even sure of what to do with the FFT to get the frequency of the signal. Code is just fyi, it is contained into a much bigger project (for which a simple grep is not an option)
Don't use MP3 for this. There's a good chance your 18 Hz will disappear or at least become distorted. 18 Hz is will below audible. MP3 and other lossy algorithms use a variety of techniques to remove sounds that we're not going to hear.
Assuming PCM, since you only need one frequency band, consider using the Goertzel algorithm. This is more efficient than FFT/DFT for your use case.
Hi Core Audio/Au community,
I have hit a roadbloc during development. My current AUGraph is set up as 2 Mono streams->Mixer unit->remoteIO unit on an iOS platform. I am using the mixer to mix two mono stream into stereo interleaved. However, the need is that mono streams neednt be mixed at all times while being played out in stereo i.e the interleaved stereo output should be composed of: the 1st mono stream in the left ear and the 2nd mono stream in the right ear. I am able to accomplish this using the kAudioUnitProperty_MatrixLevels property on the Multichannel mixer.
//Left out //right out
matrixVolumes[0][0]=1; matrixVolumes[0][1]=0.001;
matrixVolumes[1][0]=0.001; matrixVolumes[1][1]=0.001;
result = AudioUnitSetProperty(mAumixer, kAudioUnitProperty_MatrixLevels, kAudioUnitScope_Input, 0,matrixVolumes , matrixPropSize);
if (result) {
printf("Error while setting kAudioUnitProperty_MatrixLevels from mixer on bus 0 %ld %08X %4.4s\n", result, (unsigned int)result, (char*)&result);
return -1;
}
printf("setting matrix levels kAudioUnitProperty_MatrixLevels on bus 1 \n");
//Left out //right out
matrixVolumes[0][0]=0.001; matrixVolumes[0][1]=1;
matrixVolumes[1][0]=0.001; matrixVolumes[1][1]=0.001;
result = AudioUnitSetProperty(mAumixer, kAudioUnitProperty_MatrixLevels, kAudioUnitScope_Input, 1,matrixVolumes , matrixPropSize);
if (result) {
printf("Error while setting kAudioUnitProperty_MatrixLevels from mixer on bus 1 %ld %08X %4.4s\n", result, (unsigned int)result, (char*)&result);
return -1;
}
As shown above I am using the volume controls to control the streams playing as unmixed stereo interleaved separately. This works fine when I am using a wired headset to play the audio; the 1st mono stream plays on the left ear and the second mono stream plays on the right ear. But when I am switching to a bluetooth headset the audio output is a mix of both the mono streams playing on both the left and right channel. So, the matrix levels do not seem to work there. The formats used for the i/p and o/p of the mixer are as follows:
printf("create Input ASBD\n");
// client format audio goes into the mixer
obj->mInputFormat.mFormatID = kAudioFormatLinearPCM;
int sampleSize = ((UInt32)sizeof(AudioSampleType));
obj->mInputFormat.mFormatFlags = kAudioFormatFlagsCanonical;
obj->mInputFormat.mBitsPerChannel = 8 * sampleSize;
obj->mInputFormat.mChannelsPerFrame = 1; //mono
obj->mInputFormat.mFramesPerPacket = 1;
obj->mInputFormat.mBytesPerPacket = obj->mInputFormat.mBytesPerFrame = sampleSize;
obj->mInputFormat.mFormatFlags |= kAudioFormatFlagIsNonInterleaved;
// obj->mInputFormat.mSampleRate = obj->mGlobalSampleRate;(// set later while initializing audioStreamer or from the client app)
printf("create output ASBD\n");
// output format for the mixer unit output bus
obj->mOutputFormat.mFormatID = kAudioFormatLinearPCM;
obj->mOutputFormat.mFormatFlags = kAudioFormatFlagsCanonical | (kAudioUnitSampleFractionBits << kLinearPCMFormatFlagsSampleFractionShift);
obj->mOutputFormat.mChannelsPerFrame = 2;//stereo
obj->mOutputFormat.mFramesPerPacket = 1;
obj->mOutputFormat.mBitsPerChannel = 8 * ((UInt32)sizeof(AudioUnitSampleType));
obj->mOutputFormat.mBytesPerPacket = obj->mOutputFormat.mBytesPerFrame = 2 * ((UInt32)sizeof(AudioUnitSampleType));
// obj->mOutputFormat.mSampleRate = obj->mGlobalSampleRate; (// set later while initializing)
N.B : I am setting the sample rates separately from the application.The i/p and o/p sample rate of the mixer is same as sample rate of the mono audio files.
Thanks in advance for taking a look at the issue...:)
Suppose I've got a 16-bit PCM audio file. I wanna pan all of it completely to the left. How would I do this, purely through byte manipulation? Do I just mix the samples of the right channel with those of the left channel?
I'd also like to ask (since it seems related), how would I go about turning stereo samples into mono samples?
I'm doing this with Haxe, but code in something like C (or just an explanation of the method) should be sufficient. Thanks!
You'll first need to convert the raw bytes into int arrays. Your output for the left channel will be the sum divided by 2.
for (int i = 0 ; i < numFrames ; ++i)
{
*pOutputL++ = (*pInputL++ + *pInputR++) >> 1;
*pOutputR++ = 0;
}
I am trying to generate a tone to the sound card (Frequency: 1950 hz, duration: 40 ms, level: -30 db, right-channel, on steam 1). Any recommendations on how to accomplish this using C++ or C#. Are there any libraries (C++ or C#) for generating such precise tone?
David, playing audio to the speakers was built right into .NET (i think in the .NET 2.0 Framework). Using the System.Media.SoundPlayer you can play a sound from a memory stream that you build (in WAV format). Here is a function i coded that plays a simple frequency for a certain duration. Regarding the decibels and sending it to the sound card, i don't really understand what specifics you are referring to. For instance i fail to understand how audio as measured in decibels is sent to the sound card. My understanding is that decibels are simply a measure of how loud a sound is, thus after it's been reproduced by the speakers. Thus the volume control on the speakers affects what decibel your sounds will produce, and sending a certain decibel to the sound card thus makes no sense to me. Maybe you need something more detailed and maybe this doesn't work for you. But maybe you can run with this and get it to work for what you need. And maybe it is almost exactly what you are asking.
The process i use in this code allows one to build any audio you want, and plays it. So you can create 2 sine waves or many, many more, or triangle waves, or even speech synthesis with this method if you want. This method takes sound samples which are calculated and then plays those, so you need to code what each audio sample needs to be at the given moment in time. WAV allows stereo sound too, but this code sample only uses non-stereo sound. If you want stereo sound then it just needs modified to generate the bytes for a stereo WAV format instead. I expect it would not be too difficult.
Happy coding!
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Windows.Forms;
public static void PlayBeep(UInt16 frequency, int msDuration, UInt16 volume = 16383)
{
var mStrm = new MemoryStream();
BinaryWriter writer = new BinaryWriter(mStrm);
const double TAU = 2 * Math.PI;
int formatChunkSize = 16;
int headerSize = 8;
short formatType = 1;
short tracks = 1;
int samplesPerSecond = 44100;
short bitsPerSample = 16;
short frameSize = (short)(tracks * ((bitsPerSample + 7) / 8));
int bytesPerSecond = samplesPerSecond * frameSize;
int waveSize = 4;
int samples = (int)((decimal)samplesPerSecond * msDuration / 1000);
int dataChunkSize = samples * frameSize;
int fileSize = waveSize + headerSize + formatChunkSize + headerSize + dataChunkSize;
// var encoding = new System.Text.UTF8Encoding();
writer.Write(0x46464952); // = encoding.GetBytes("RIFF")
writer.Write(fileSize);
writer.Write(0x45564157); // = encoding.GetBytes("WAVE")
writer.Write(0x20746D66); // = encoding.GetBytes("fmt ")
writer.Write(formatChunkSize);
writer.Write(formatType);
writer.Write(tracks);
writer.Write(samplesPerSecond);
writer.Write(bytesPerSecond);
writer.Write(frameSize);
writer.Write(bitsPerSample);
writer.Write(0x61746164); // = encoding.GetBytes("data")
writer.Write(dataChunkSize);
{
double theta = frequency * TAU / (double)samplesPerSecond;
// 'volume' is UInt16 with range 0 thru Uint16.MaxValue ( = 65 535)
// we need 'amp' to have the range of 0 thru Int16.MaxValue ( = 32 767)
double amp = volume >> 2; // so we simply set amp = volume / 2
for (int step = 0; step < samples; step++)
{
short s = (short)(amp * Math.Sin(theta * (double)step));
writer.Write(s);
}
}
mStrm.Seek(0, SeekOrigin.Begin);
new System.Media.SoundPlayer(mStrm).Play();
writer.Close();
mStrm.Close();
} // public static void PlayBeep(UInt16 frequency, int msDuration, UInt16 volume = 16383)
NAudio provides a robust audio library for .NET.
NAudio is an open source .NET audio and MIDI library, containing dozens of useful audio related classes intended to speed development of audio related utilities in .NET. It has been in development since 2002 and has grown to include a wide variety of features. While some parts of the library are relatively new and incomplete, the more mature features have undergone extensive testing and can be quickly used to add audio capabilities to an existing .NET application. NAudio can be quickly added to your .NET application using NuGet.
Here's an article that walks step-by-step through using NAudio to create a sine wave. You can create the sine wave with any desired frequency, for any desired duration:
http://msdn.microsoft.com/en-us/magazine/ee309883.aspx
I'm using libav to encode raw RGB24 frames to h264 and muxing it to flv. This works
all fine and I've streamed for more then 48 hours w/o any problems! My next step
is to add audio to the stream. I'll be capturing live audio and I want to encode it
in real time using speex, mp3 or nelly moser.
Background info
I'm new to digital audio and therefore I might be doing things wrong. But basically my application gets a "float" buffer with interleaved audio. This "audioIn" function gets called by the application framework I'm using. The buffer contains 256 samples per channel,
and I have 2 channels. Because I might be mixing terminology, this is how I use the
data:
// input = array with audio samples
// bufferSize = 256
// nChannels = 2
void audioIn(float * input, int bufferSize, int nChannels) {
// convert from float to S16
short* buf = new signed short[bufferSize * 2];
for(int i = 0; i < bufferSize; ++i) { // loop over all samples
int dx = i * 2;
buf[dx + 0] = (float)input[dx + 0] * numeric_limits<short>::max(); // convert frame of the first channel
buf[dx + 1] = (float)input[dx + 1] * numeric_limits<short>::max(); // convert frame of the second channel
}
// add this to the libav wrapper.
av.addAudioFrame((unsigned char*)buf, bufferSize, nChannels);
delete[] buf;
}
Now that I have a buffer, where each sample is 16 bits, I pass this short* buffer, to my
wrapper av.addAudioFrame() function. In this function I create a buffer, before I encode
the audio. From what I read, the AVCodecContext of the audio encoder sets the frame_size. This frame_size must match the number of samples in the buffer when calling avcodec_encode_audio2(). Why I think this, is because of what is documented here.
Then, especially the line:
If it is not set, frame->nb_samples must be equal to avctx->frame_size for all frames except the last.*(Please correct me here if I'm wrong about this).
After encoding I call av_interleaved_write_frame() to actually write the frame.
When I use mp3 as codec my application runs for about 1-2 minutes and then my server, which is receiving the video/audio stream (flv, tcp), disconnects with a message "Frame too large: 14485504". This message is generated because the rtmp-server is getting a frame which is way to big. And this is probably due to the fact I'm not interleaving correctly with libav.
Questions:
There quite some bits I'm not sure of, even when going through the source code of libav and therefore I hope if someone has an working example of encoding audio which comes from a buffer which which comes from "outside" libav (i.e. your own application). i.e. how do you create a buffer which is large enough for the encoder? How do you make the "realtime" streaming work when you need to wait on this buffer to fill up?
As I wrote above I need to keep track of a buffer before I can encode. Does someone else has some code which does this? I'm using AVAudioFifo now. The functions which encodes the audio and fills/read the buffer is here too: https://gist.github.com/62f717bbaa69ac7196be
I compiled with --enable-debug=3 and disable optimizations, but I'm not seeing any
debug information. How can I make libav more verbose?
Thanks!