I am studying coremidi and trying just few experiments
I am wondering how to make a transpose in semitones of a miditrack of a midifile.
Can someone show me how to do it?
thank so much
CoreMIDI does nothing with MIDI files.
You'll have to parse the MIDI file until the desired track chunk is encountered and apply a transposition offset to the note number of each Note On/Off message (including running status).
Related
For an app I'm working on a i need to be able to 'search' a sound file to find a particular frequency.
Basically, the iPhone mic records for 5 seconds writes to an a lossless music file. I then need to 'open' that file and search for a particular frequency. The frequency is very particular (eg not between 15hz and 300hz, its is a fixed number).
Also, as soon the the frequency is found the search can stop.
I've got the iPhone recording the sound and writing to the file, I am just unsure how to open that file and search for the frequency.
Any help would be greatly appreciated!
Thanks
Checkout PitchDetector and the related tutorial.
Can't get you any closer :)
If you're just looking for a specific, fixed, pure tone then the simplest method is probably Goertzel's algorithm - it's very simple to implement and is relatively lightweight computationally compared to using e.g. an FFT or autocorrelation method.
guys.
I'm working on some audio services on iOS.
I trying to search any examples or tutorials about
how audio service or stream can read a existing audio file than
process something like filter, than write another file.
Is there any body who can help me?
Dirac3LE (by Stephan M. Bernsee) is a great library for this job.
There are examples and manual included in the download.
It is particulary inteded for time and pitch manipulation
but in your case you'll be interested in its EAFRead and EAFWrite
classes.
If you want to get familiar with the lower level library that you can also use for microphone input/sound output, and that you can get raw samples into and out of, I would suggest taking a look at Audio Queue Services.
I used it in my side project to get audio from the microphone, and I also wrote some code you might find useful to do fast vectorized, FFT based FIR filtering on input audio. You can find the code here https://github.com/jamescarlson/FreeAPRS
I've been searching for some examples that show how to do ADSR in iOS using audio samples (preferably WAV files with loop points, but thats secondary). I guess most people who write a sampler/synth app use audio unit for this. Does any one know a good code example that shows ADSR in any iOS audio library?
In the new iOS SDK 5.0 there's now a Sampler Audio Unit! Which can do ADSR envelopes.
The presets demo shows how to use the sampler:
http://developer.apple.com/library/ios/#samplecode/LoadPresetDemo/Introduction/Intro.html#//apple_ref/doc/uid/DTS40011214
If you want to load different sound formats to play this article is helpful:
https://developer.apple.com/library/mac/#technotes/tn2283/_index.html
And here's the iOS documentation reference:
http://developer.apple.com/library/ios/#documentation/AudioUnit/Reference/AUComponentServicesReference/Reference/reference.html#//apple_ref/doc/uid/TP40007291
you can find (a very basic) one in the Apple's SinSynth sample. That is an AU, but it should demonstrate how one would apply a envelope to an audio buffer. i don't remember - it may simply be an ASR, but adding a fourth stage is simple once you have understood the existing program. The implementation is right in the note's render.
Envelope Generators are not platform specific.
musicdsp.org will be a better resource if you want more than a push in the right direction.
MusicDSP has source code for an example envelope follower with attack/release. If you understand this, then sustain/decay should be pretty logical. ;)
But an ADSR envelope is basically just a matter of applying gain to your output signal with a state machine. Each state has a starting value, and ending value, and a duration. Calculating the slope of that line and the value of each point along it was covered in your algebra class back in high school. ;) If you want to be really fancy, you can implement other types of curves, but the concept remains the same.
My aim is code a project which records human sound and changes it (with effects).
e.g : a person will record its sound over microphone (speak for a while) and than the program makes its like a baby sound.
This shall run effectively and fast (while recording the altering operation must run, too)
What is the optimum way to do it ?
Thanks
If you're looking for either XNA or DirectX to do this for you, I'm pretty sure you're going to be out of luck (I don't have much experience with DirectSound; maybe somebody can correct me). What it sounds like you want to do is realtime digital signal processing, which means that you're either going to need to write your own code to manipulate the raw waveform, or find somebody else who's already written the code for you.
If you don't have experience writing this sort of thing, it's probably best to use somebody else's signal processing library, because this sort of thing can quickly get complicated. Since you're developing for the PC, you're in luck; you can use any library you like using P/Invoke. You might try out some of the solutions suggested here and here.
MSDN has some info about the Audio namespace from XNA, and the audio recording introduced in version 4:
Working with Microphones
Recording Audio from a Microphone
Keep in mind that recorded data is returned in PCM format.
Is there a way to get the note data from a MIDI file? That is, I want to break down the MIDI file into its constituent parts so they are in the form of a unique word (or any other data type).
What I want to do in the end is take in a MIDI file and find patterns in the notes. Get in each note, find it's frequency (of being played) and note how likely other notes are to be played after it.
It would be nice to do this in C/C++, but any language would be fine.
Nik Reisman - sorry, but I don't agree with you...parsing midi in C#, C++ is something about 400 rows of code..It's nothing hard and it is nothing difficult.
I will advise you start with this link: https://web.archive.org/web/20141227205754/http://www.sonicspot.com:80/guide/midifiles.html
There is everything you need to know about midi and how to read it..
In the short description how the parser will work:
1)Open midi in byte mode
2)Read the header chunk where there is info about size, number of tracks and IMPORTANT file format!!
- There are 3 types of formats: 0,1,2 (type 2 is really "valuable", there are only few midi files with this type, so you don't need to read the midi if there is type 2)
- if there is not written: "MThd" (0x4D546864), end with error (it's a bad midi file)
3)Read track chunk
- if there is not written: "MTrk" (0x4D54726B) end with error (it's a bad midi file)
4)Read the midi events..
- There are very many events, you can read them all with if-else commands, or you can read only the events what you want to know, for example NOTE ON, NOTE OFF
- Sometimes in some midi files are not NOTE OFF..this event is changed with NOTE ON and velocity 0
On the websites everything is explained really nicely. If you open the midi file in byte mode you will have only a few methods and everything is then only about if-else commands and there you will catch what is stored right now.
It is important to understand VARIABLE LENGTH, but on the websites it is also explained. It's not hard. You can google many sites where VARIABLE LENGTH is explained too, with some images and examples. So I don't think that it is hard to explain it in here.
If you want a bit more advice, write me, I will try it. But parsing midi is not as hard as how it looks. If you have some problems, write me..
Parsing MIDI files by hand is no fun, take my word on this. ;) The format, although well documented, is difficult to deal with since you are always on the raw byte level. Since you are interested in extracting some meaningful information from MIDI files themselves, I'd recommend using a framework such as Juce, which is written in C++ and has support for reading MIDI files.
Juce is pretty large, but the API is good and well-documented. The class for parsing MIDI files, for instance, is pretty straightforward and easy to use.
There is a number of ready made solutions, taking input from MIDI file, generating musical visualization,
so in theory and practice, MIDI parser works fine
I am working on such musical visualizer in HTML5, generating vertical top > down notes timeline live to support handicapped piano players.
DLP projector is great but it seems, I need to install large LCD TV screen, just over the piano keyboard to get visualization to match the notes played
#Brendan Kavanagh is the leader
another key developer is called Stephen Malinowski
just follow my question to get the right web links
How to build MIDI file visualizer to get input from MIDI file and display MIDI timeline over the keyboard to match notes played by a real player