I'm using the web audio API to apply effects and export a file. It works great, but I would like to export the file at 32 bit instead of 16.
How could I alter the below settings to achieve this?
setUint32(0x46464952); // "RIFF"
setUint32(length - 8); // file length - 8
setUint32(0x45564157); // "WAVE"
setUint32(0x20746d66); // "fmt " chunk
setUint32(16); // length = 16
setUint16(1); // PCM (uncompressed)
setUint16(numOfChan);
setUint32(abuffer.sampleRate);
setUint32(abuffer.sampleRate * 2 * numOfChan); // avg. bytes/sec
setUint16(numOfChan * 2); // block-align
setUint16(16);
setUint32(0x61746164); // "data" - chunk
setUint32(length - pos - 4); // chunk length
// write interleaved data
for (i = 0; i < abuffer.numberOfChannels; i++)
channels.push(abuffer.getChannelData(i));
while (pos < length) {
for (i = 0; i < numOfChan; i++) {
// interleave channels
sample = Math.max(-1, Math.min(1, channels[i][offset])); // clamp
sample = (0.5 + sample < 0 ? sample * 32768: sample * 32767) | 0;
view.setInt16(pos, sample, true); // update data chunk
pos += 2;
}
offset++; // next source sample
}
The basic idea is simple. Convert the float to an Uint32 by using an array view. Then write out the uint32 values instead of int16 values. No clipping is needed. And be sure to output the correct wav header for the changed length and format type.
I know Chromium has some code to do this for WebAudio testing. But you'll have to abide by Chromium licenses to use it.
I receive raw image data from server. The server uses MS Dib() function which returns in BGR format. Now, what i want to do is to read this raw data and use glDrawPixels to draw it in Linux.
I was advised that GetClrTabAddress function in MS and alike shall be used to get me the RGB values for each index of 800 by 600 image sent to me.
I do not know how to get these values using indices. Could anyone give some tips.
void func(QByteArray)
{
window_width = 800;
window_height = 600;
size = window_width * window_height;
pixels = new float[size*3];
memcpy(pixels, bytes, bytes.size());
}
void GlWidget::paintGL()
{
//! [5]
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDrawPixels(window_width,window_height,GL_RGB,GL_FLOAT,pixels);
}
You can use GL_BGR in glDrawPixels, which will do the conversion for you and will probably be faster since AFAIK the GPU will do the work.
QByteArray sounds like you should be using unsigned bytes/chars instead of floats, which means GL_UNSIGNED_BYTE.
I'd assert(size*3*sizeof(float) == bytes.size());.
In this case make sure to set glPixelStorei(GL_UNPACK_ALIGNMENT, 1) if your width doesn't align to the default 4-byte boundry. With GL_BGR very pixel is 3 bytes and by default each row of your pixels is assumed to be padded to the next 4-byte boundary.
[EDIT]
OK, it looks like the image uses a palette. This means every value inthe QByteArray maps to an rgb value in another array. I'm not 100% sure where the palette is and maybe it can be computed implicitly, but you mentioned GetClrTabAddress which sounds promising.
The code will then look something like this
for(int i = 0; i < size; ++i)
{
unsigned char index = btmp[i];
//and something like..
memcpy(bytes + i * 3, GetClrTabAddress() + index * 3, 3);
//or
bytes[i*3+0] = someOtherPaletteData[index].red;
bytes[i*3+1] = someOtherPaletteData[index].green;
bytes[i*3+2] = someOtherPaletteData[index].blue;
}
I'm trying to create a program, using Qt (c++), which can record audio from my microphone using QAudioinput and QIODevice. I made a research and I came up with an example located on the this page. This example does what I need.
Now, I am trying to create an audio waveform of the recorded sound. I want to extract audio amplitudes and save them on a QList. To do that I use the following code:
//Check the number of samples in input buffer
qint64 len = m_audioInput->bytesReady();
//Limit sample size
if(len > 4096)
len = 4096;
//Read sound samples from input device to buffer
qint64 l = m_input->read(m_buffer.data(), len);
if(l > 0)
{
//Assign sound samples to short array
short* resultingData = (short*)m_buffer.data();
for ( i=0; i < len; i++ )
{
btlist.append( resultingData[ i ]);
}
}
m_audioInput is QAudioinput | m_buffer is QBytearray | m_input is QIODevice | btlist is QList
I use the following QAudioFormat:
m_format.setFrequency(44100); //set frequency to 44100
m_format.setSampleRate(44100); //set sample rate to 44100
m_format.setChannels(1); //set channels to mono
m_format.setSampleSize(16); //set sample sze to 16 bit
m_format.setSampleType(QAudioFormat::SignedInt ); //signed integer sample
m_format.setByteOrder(QAudioFormat::LittleEndian); //Byte order
m_format.setCodec("audio/pcm"); //set codec as simple audio/pcm
When I print my QList, using qWarning() << btlist.at(int), I get some positive and negative numbers which represents my audio amplitudes. I used Microsoft Excel to plot the data and compare it with the actual sound waveform.
(EDIT BASED ON THE OP COMMENT)
I am drawing the waveform using QPainter in Qt like this
for(int i = 1; i < btlist.size(); i++){
double x1 = (i-(i/1.25))-0.2;
double y1 = btlist.at(i-1);
double x2 = i-(i/1.25);
double y2 = btlist.at(i);
painter.drawLine(x1,y1,x2, y2);
}
The problem is that I also get lots of zeros (0) in my QList between the amplitude data like this, which if I draw as a waveform they are a straight line, which is not normal because it causes corruption to my waveform.
My question is why is that happening? What these zeros (0) represent? Am I doing something wrong? Also, is there a better way to extract audio amplitudes from QBytearray?
Thank you.
The drawline method you are using take integer values. Which means most of the time both of your x indexes will be the same. By simplifiyng your formula the x value at a given i is (i/5.0). By itself it is not an issue because the lines will be superposed, and it is a perfect way of drawing (just to make sure that's what you want to do).
The zero you see can be perfectly valid. They represent silence.
The real issue is that the range of your 16 bits PCM values is [-32767 , 32768]. I doubt that the paint device you are using cover this range. You need to normalize your y-axis. Moreover, it seems taht the qt coordinated system doesn't have negative values (edit: Nevermind the negatives, its says logical coordinates are converted).
For instance, convert your pcm values using :
((btlist.at(i) / MAX_AMPLITUDE + 1.0) / 2) * paintDevice.height();
Edit:
Btw, you are not using l, which is the real amount of data you read. If it is inferior to len, you will read invalid values at the end of your buffer, possibly read garbage\ read zeros\crash.
And your buffer is a byte buffer. And you iterate using a short pointer. So whether you use l or len the maximum size need to be divided by two. This is probably the cause of the ling line of zero in your picture.
for ( i=0; i < l/2; i++ )
{
btlist.append( resultingData[ i ]);
}
I need to extract frames from a video in my Qt based application. Using ffmpeg libraries I am able to fetch frames as AVFrames which I need to convert to QImage to use in other parts of my application. This conversion needs to be efficient. So far it seems sws_scale() is the right function to use but I am not sure what source and destination pixel formats are to be specified.
Came up with the following 2-step process that first converts a decoded AVFame to another AVFrame in RGB colorspace and then to QImage. It works and is reasonably fast.
src_frame = get_decoded_frame();
AVFrame *pFrameRGB = avcodec_alloc_frame(); // intermediate pframe
if(pFrameRGB==NULL) {
;// Handle error
}
int numBytes= avpicture_get_size(PIX_FMT_RGB24,
is->video_st->codec->width, is->video_st->codec->height);
uint8_t *buffer = (uint8_t*)malloc(numBytes);
avpicture_fill((AVPicture*)pFrameRGB, buffer, PIX_FMT_RGB24,
is->video_st->codec->width, is->video_st->codec->height);
int dst_fmt = PIX_FMT_RGB24;
int dst_w = is->video_st->codec->width;
int dst_h = is->video_st->codec->height;
// TODO: cache following conversion context for speedup,
// and recalculate only on dimension changes
SwsContext *img_convert_ctx_temp;
img_convert_ctx_temp = sws_getContext(
is->video_st->codec->width, is->video_st->codec->height,
is->video_st->codec->pix_fmt,
dst_w, dst_h, (PixelFormat)dst_fmt,
SWS_BICUBIC, NULL, NULL, NULL);
QImage *myImage = new QImage(dst_w, dst_h, QImage::Format_RGB32);
sws_scale(img_convert_ctx_temp,
src_frame->data, src_frame->linesize, 0, is->video_st->codec->height,
pFrameRGB->data,
pFrameRGB->linesize);
uint8_t *src = (uint8_t *)(pFrameRGB->data[0]);
for (int y = 0; y < dst_h; y++)
{
QRgb *scanLine = (QRgb *) myImage->scanLine(y);
for (int x = 0; x < dst_w; x=x+1)
{
scanLine[x] = qRgb(src[3*x], src[3*x+1], src[3*x+2]);
}
src += pFrameRGB->linesize[0];
}
If you find a more efficient approach, let me know in the comments
I know, it's too late, but maybe someone will find it useful. From here I got the clue of doing the same conversion, which looks a bit shorter.
So I created QImage which is reused for every decoded frame:
QImage img( width, height, QImage::Format_RGB888 );
Created frameRGB:
frameRGB = av_frame_alloc();
//Allocate memory for the pixels of a picture and setup the AVPicture fields for it.
avpicture_alloc( ( AVPicture *) frameRGB, AV_PIX_FMT_RGB24, width, height);
After the the first frame is decoded I create conversion context SwsContext this way (it will be used for all the next frames):
mImgConvertCtx = sws_getContext( codecContext->width, codecContext->height, codecContext->pix_fmt, width, height, AV_PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);
And finally for every decoded frame conversion is performed:
if( 1 == framesFinished && nullptr != imgConvertCtx )
{
//conversion frame to frameRGB
sws_scale(imgConvertCtx, frame->data, frame->linesize, 0, codecContext->height, frameRGB->data, frameRGB->linesize);
//setting QImage from frameRGB
for( int y = 0; y < height; ++y )
memcpy( img.scanLine(y), frameRGB->data[0]+y * frameRGB->linesize[0], mWidth * 3 );
}
See the link for the specifics.
A simpler approach, I think:
void takeSnapshot(AVCodecContext* dec_ctx, AVFrame* frame)
{
SwsContext* img_convert_ctx;
img_convert_ctx = sws_getContext(dec_ctx->width,
dec_ctx->height,
dec_ctx->pix_fmt,
dec_ctx->width,
dec_ctx->height,
AV_PIX_FMT_RGB24,
SWS_BICUBIC, NULL, NULL, NULL);
AVFrame* frameRGB = av_frame_alloc();
avpicture_alloc((AVPicture*)frameRGB,
AV_PIX_FMT_RGB24,
dec_ctx->width,
dec_ctx->height);
sws_scale(img_convert_ctx,
frame->data,
frame->linesize, 0,
dec_ctx->height,
frameRGB->data,
frameRGB->linesize);
QImage image(frameRGB->data[0],
dec_ctx->width,
dec_ctx->height,
frameRGB->linesize[0],
QImage::Format_RGB888);
image.save("capture.png");
}
Today, I have tested directly pass the image->bit() to swscale and finally it works, so it doesn't need to copy to memory. For example:
/* 1. Get frame and QImage to show */
struct my_frame *frame = get_frame(source);
QImage *myImage = new QImage(dst_w, dst_h, QImage::Format_RGBA8888);
/* 2. Convert and write into image buffer */
uint8_t *dst[] = {myImage->bits()};
int linesizes[4];
av_image_fill_linesizes(linesizes, AV_PIX_FMT_RGBA, frame->width);
sws_scale(myswscontext, frame->data, (const int*)frame->linesize,
0, frame->height, dst, linesizes);
I just discovered that scanLine is just seeking thru the buffer.. all you need is use AV_PIX_FMT_RGB32 for the AVFrame and QImage::FORMAT_RGB32 for the QImage.
Then after decoding just do a memcpy
memcpy(img.scanLine(0), pFrameRGB->data[0], pFrameRGB->linesize[0] * pFrameRGB->height());
I had problems with the other proposed solutions as :
They did not mention freeing either AVFrame, SwsContext or the allocated buffers, which caused massive memory leaks (I had thousands of frames to handle). These problems couldn't all be solved easily as QImage relies on the underlying data, and does not copy it. If freeing the buffer directly, the QImage points to freed data and breaks. This could be solved by using QImage's cleanupFunction to free the buffer once the image is no longer needed, but with other problems it wasn't good anyways.
In some cases one of the suggestions, of passing QImage.bits directly to sws_scale, would not work as QImage are minimum 32 bit aligned. Therefore for certain dimensions it would not match the expected width by sws_scale and output each line shifted a little bit.
A third problem is that they used deprecated AVPicture elements.
I listed the problem in another question Converting an AVFrame to QImage with conversion of pixel format and in the end found a solution using a temporary buffer, which could be copied to the QImage, and then safely freed.
So see my answer for a fully working, efficient, and with no deprecated function calls, implementation : https://stackoverflow.com/a/68212609/7360943
I'm trying to print a image from a Dicom file. I pass the raw data to a convertToFormat_RGB888 function. As far as I know, Qt can't handle monochrome 16 bits images.
Here's the original image (converted to jpg here):
http://imageshack.us/photo/my-images/839/16bitc.jpg/
bool convertToFormat_RGB888(gdcm::Image const & gimage, char *buffer, QImage* &imageQt)
Inside this function, I get inside this...
...
else if (gimage.GetPixelFormat() == gdcm::PixelFormat::UINT16)
{
short *buffer16 = (short*)buffer;
unsigned char *ubuffer = new unsigned char[dimX*dimY*3];
unsigned char *pubuffer = ubuffer;
for (unsigned int i = 0; i < dimX*dimY; i++)
{
*pubuffer++ = *buffer16;
*pubuffer++ = *buffer16;
*pubuffer++ = *buffer16;
buffer16++;
}
imageQt = new QImage(ubuffer, dimX, dimY, QImage::Format_RGB888);
...
This code is a little adaptation from here:
gdcm.sourceforge.net/2.0/html/ConvertToQImage_8cxx-example.html
But the original one I got a execution error. Using mine at least I get an image, but it's not the same.
Here is the new image (converted to jpg here):
http://imageshack.us/photo/my-images/204/8bitz.jpg/
What am I doing wrong?
Thanks.
Try to get values of pixels from buffer manually and pass it to QImage::setPixel. It can be simplier.
You are assigning 16-bit integer to 8-bit variables here:
*pubuffer++ = *buffer16;
The result is undefined and most compilers just move the lower 8 bits to the destination. You want the upper 8 bits
*pubuffer++ = (*buffer16) >> 8;
The other issue is endianness. Depending to the endianness of the source data, you may need to call one of the QtEndian functions.
Lastly, you don't really need to use any of the 32 or 24-bit Qt image formats. Use 8-bit QImage::Format_Indexed8 and set the color table to grays.