Is it possible to get sound data during playing in OpenAl? For example: I generate white noise and I want to present this in graphically in chart amplitude and frequency. So I want to get which part of sound actually is playing and use it with SDL for example.
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I've already loaded the .wav audio to the buffer with XAudio2 (Windows 8.1) and to play it I just have to use:
//start consuming audio in the source voice
/* IXAudio2SourceVoice* */ g_source->Start();
//play the sound
g_source->SubmitSourceBuffer(buffer.xaBuffer());
I wonder, how can I get the frequency value at given time with XAudio2?
The question does not make much sense, a .wav file contains a great many frequencies. It is the blend of them that makes it sound like music to your ears, instead of just an artificial generated tone. A blend that's constantly changing.
A signal processing step is required to convert the samples in the .wav file from the time domain to the frequency domain. Generally known as spectrum analysis, the Fast Fourier Transform (FFT) is the standard technique.
A random Google hit on "xaudio2 fft" produced this code sample. No idea how good it is, but something to play with to get the lay of the land. You'll find more about it in this gamedev question.
Given that FFmpeg is the leading multimedia framework and most of the video/audio players uses it, I'm wondering somethings about audio/video players using FFmpeg as intermediate.
I'm studying and I want to know how audio/video players works and I have some questions.
I was reading the ffplay source code and I saw that ffplay handles the subtitle stream. I tried to use a mkv file with a subtitle on it and doesn't work. I tried using arguments such as -sst but nothing happened. - I was reading about subtitles and how video files uses it (or may I say containers?). I saw that there's two ways putting a subtitle: hardsubs and softsubs - roughly speaking hardsubs mode is burned and becomes part of the video, and softsubs turns a stream of subtitles (I might be wrong - please, correct me).
The question is: How does they handle this? I mean, when the subtitle is part of the video there's nothing to do, the video stream itself shows the subtitle, but what about the softsubs? how are they handled? (I heard something about text subs as well). - How does the subtitle appears on the screen and can be configured changing fonts, size, colors, without encoding everything again?
I was studying some video players source codes and some or most of them uses OpenGL as renderer of the frame and others uses (such as Qt's QWidget) (kind of or for sure) canvas. - What is the most used and which one is fastest and better? OpenGL with shaders and stuffs? Handling YUV or RGB and so on? How does that work?
It might be a dump question but what is the format that AVFrame returns? For example, when we want to save frames as images first we need the frame and then we convert, from which format we are converting from? Does it change according with the video codec or it's always the same?
Most of the videos I've been trying to handle is using YUV720P, I tried to save the frames as png and I need to convert to RGB first. I did a test with the players and I put at the same frame and I took also screenshots and compared. The video players shows the frames more colorful. I tried the same with ffplay that uses SDL (OpenGL) and the colors (quality) of the frames seems to be really low. What might be? What they do? Is it shaders (or a kind of magic? haha).
Well, I think that is it for now. I hope you help me with that.
If this isn't the correct place, please let me know where. I haven't found another place in Stack Exchange communities.
There are a lot of question in one post:
How are 'soft subtitles' handled
The same way as any other stream :
read packets from a stream to the container
Give the packet to a decoder
Use the decoded frame as you wish. Here with most containers supporting subtitles the presentation time will be present. All you need at this time is get the text and burn it onto the image at the same presentation time. There are a lot of ways to print the text on the video, with ffmpeg or another library
What is the most used renderer and which one is fastest and better?
most used depend on the underlying system. For instance Qt only wrap native renderers, and even has a openGL version
You can only be as fast as the underlying system allows. Does it support ouble-buffering? Can it render in your decoded pixel format or do you have to perform color conversion before? This topic is too broad
Better only depend on the use case. this is too broad
what is the format that AVFrame returns?
It is a raw format (enum AVPixelFormat), and depends on the codec. There is a list of YUV and RGB FOURCCs which cover most formats in ffmpeg. Programmatically you can access the table AVCodec::pix_fmts to obtain the pixel format a specific codec support.
I am making a simple game for fun and learning using SFML for 2D stuff. The game is rather simple.. I loath to say it is a HoG (hidden object game) but I guess that would be a way to get my point across quickly. Basically I am using SFML to load and display 2D still art and capture mouse events.
Anyway... I would like to add video clips to my project. All the art is rendered and for example.. if my image is of a park with a fountain, I would like to have a looping video of the water running so the image has some life even though it is just a still.
All I need is the ability to play videos in the window, preferably compatible with sfml but I am in the planning projects I can swap to something else if needed. The project will have a set resolution (not scalable) and I just want to load the video and play them at a certain pixel location in x,y. So if I have a 1200x720 image I play a 100x100 pixel video on loop at a certain location to make the water of the fountain move.
Now then I am thinking I can just load 2D sprites onto of the video matching the background image to do simple masking. There are some formats like quicktime that can embed an alpha channel directly into the video and if that is supported awesome.. but some planning in the set design should mean that is not really needed. Though if that was supported more options open in set design.
I am pretty good with video as I am a 3D animator by profession, new to programming as a learning hobby. So the format and container of the video is not really an issue though I have been working with OGV a lot recently.
What I see as it needing is
Load multiple videos at once
Play with out any boarders or anything
Play at specific locations in a window.
loop seamlessly
Allow zdepth so I can place sprites onto of it
Dose anyone know were I would go to start looking into this? It seams like something that could possibly be a library I could use? Preferably an open source one as this is just a for fun project nothing commercial.
Thanks in advance for any ideas you may have.
I'm going to using openFrameworks to develop a music visualizer--music drive graphics.
I can use Opengl to do the graphics. But the problem is the audio processing part. I have no experience in this field. I once thought I could extract music features-such as pitch, beat, volume to control the graphics. But I now I don't know how to start. I learned fft in math, but I don't know what to do after I get the spectrum of a piece of music, how can I extract those music features after fft? Or how to do the music processing part?
I would begin by playing with ofxFFT and then learning intuitively. Do you have set music you will be using? What are the characteristics you are looking for? You should probably start by looking for specific frequencies - like high, low, mid. You will likely find that depending on the type of sound / music you are playing that you won't always get a connection between what you think it should detect and what it actually detects. The wave is a series of values which you can perform operations on. You could detect the rate at which it changes, how many times it dips above or a below a range, etc.
Right now, what I'm trying to do is to make a new GUI, essentially a software using directX (more exact, direct3D), that display streaming images from Axis IP cameras.
For the time being I figured that the flow for the entire program would be like this:
1. Get the Axis program to get streaming images
2. Pass the images to the Direct3D program.
3. Display the program, on the screen.
Currently I have made a somewhat basic Direct3D app that loads and display video frames from avi videos(for testing). I dunno how to load images directly from videos using DirectX, so I used OpenCV to save frames from the video and have DX upload them up. Very slow.
Right now I have some unclear things:
1. How to Get an Axis program that works in C++ (gonna look up examples later, prolly no big deal)
2. How to upload images directly from the Axis IP camera program.
So guys, do you have any recommendations or suggestions on how to make my program work more efficiently? Anything just let me know.
Well you may find it faster to use directshow and add a custom renderer at the far end that, directly, copies the decompressed video data directly to a Direct3D texture.
Its well worth double buffering that texture. ie have texture 0 displaying and texture 1 being uploaded too and then swap the 2 over when a new frame is available (ie display texture 1 while uploading to texture 0).
This way you can de-couple the video frame rate from the rendering frame rate which makes dropped frames a little easier to handle.
I use in-place update of Direct3D textures (using IDirect3DTexture9::LockRect) and it works very fast. What part of your program works slow?
For capture images from Axis cams you may use iPSi c++ library: http://sourceforge.net/projects/ipsi/
It can be used for capturing images and control camera zoom and rotation (if available).