My real objective is to be able to use 1 audio file and create X amount of different pitches and then playing them in the app using some code to handle the timing.
TIA for any helpful insight
You can read Core Audio documentation.
See this answer, which recommends using the AVFoundation framework.
Core Audio is supposed to be fairly low level. Great if you need more flexibility/control, but AVFoundation may be more appropriate for your app.
Related
I'm very new to audio programming, but I know this must be possible. (This is an iOS/iPhone related question).
How would I go about changing the tempo of a loaded audio file without changing the pitch, and then playing it back?
I think I need to delve into the CoreAudio framework, but I'm not sure where to begin.
If anyone could let me know what classes I need to look at, or the general process involved, that would help me get started and I'd really appreciate it!
Cheers!
This question is highly related: it relates to pitch shifting, rather than time shifting, but I'd check out the comments and links.
Real-time Pitch Shifting on the iPhone
What you are looking for is a time-pitch modification library. Core Audio on iOS currently does not contain such, but there appear to be some 3rd party libraries available (commercially). There are also time pitch tutorials on the web, such as at dspdimention, which require a large amount of DSP development to get working.
On iOS, is it possible to get the user's audio stream in a decompressed format? For example, the MP3 is returned as a WAV that can be used for audio analysis? I'm relatively new to the iOS platform, and I remember seeing that this wasn't possible in older iOS versions. I read that iOS 4 brought in some advanced APIs but I'm not sure where I can find documentations/samples for these.
If you don't mind using API for iOS 4.1 and above, you could try using the AVAssetReader class and friends. In this similar question you have a full example on how to extract video frames. I would expect the same to work for audio, and the nice thing is that the reader deals with all the details of decompression. You can even do composition with AVComposition to merge several streams.
These classes are part of the AVFramework, which allows not only reading but also creating your own content.
Apple has an OpenAL example at http://developer.apple.com/library/mac/#samplecode/OpenALExample/Introduction/Intro.html where Scene.m should interest you.
The Apple documentation has this picture where the Core Audio framework clearly shows that it gives you MP3 out. It also states that you can access audio units in a more radical way if you so need.
The same Core Audio document gives also some information about using MIDI if it may help you.
Edit:
You're in luck today.
In this example an audio file is loaded and fed into an AudioUnit graph. You could fairly easily write an AudioUnit of your own to put into this graph and which analyzes the PCM stream as you see fit. You can even do it in the callback function, although that's probably not a good idea because callbacks are encouraged to be as simple as possible.
In my app,i need to generate video with audio. Now i am using Air Play Sample But its contains only generate video only and i need to generate video with audio.Any one help me to solve with problem.
Regards,
First of all, you need to increase your accept rate.
Secondly, this is quite a lot what you are asking for. I'm not familiar with Air Play, but my suggestion would be to start with the SpeakHere project. That will get you familiarised with core-audio and give you a template for accessing the audio input.
As for the visual aspect I highly recommend O'Reilly's 3D Programming book which provides a lot of example code.
It will take a bit of time to assimilate both materials, but you'll end up with a better application.
I need to play mp3 audio data in iPhone continuously. I am getting continuous mp3 data via server in iPhone. Now I need to play this data in iPhone. I cannot access url to play as it is of mms protocol. So, for playing this type of data which is the best method to use. Can anyone help me out with this thing.
Thanks in advance.
You have a few options sanctioned by or directly from Apple. You should look into:
Core Audio and the Audio Toolbox
The AVFoundation Framework
The OpenAL Framework
Also, you can try Matt Gallagher's AudioStreamer class. It should be able to do the job, or at least help you figure out how to do so, if you look at the code.
Between those four options, there should be something to help.
NOTE:
After writing this, I did a bit of Googling and I found this thread that discusses the possibility of streaming MMS media to iPhone. It appears that it is not possible, due to the cost of a license from Microsoft. In theory, the above-mentioned frameworks should do everything you need, but it seems that you cannot because of the licensing issue.
Good luck!
audioPlayer = [[AVAudioPlayer alloc]initWithData:<#(NSData )data#> error:<#(NSError *)outError#>];
try this else tell me more clear what you want to do
I want to change the pitch of my audio and I know that AV Foundation is not the place to look for that, but I don't want to learn Open AL because it is to low level, does anyone know what I would use as an alternative?
take a look at this link. Lately, I used csound API for creating MIDI sounds.
But OpenAL is cross-platform audio manipulation library that is supported on the iPhone. Hope this answer helps you. Take a look at this FAQ.
Take a look at Dirac 2 for iPhone:
http://www.dspdimension.com/technology-licensing/dirac2-iphone/
If you want to implement this yourself, you could also consider using Core Audio and the RemoteIO audio unit.
Core Audio is also a low level API, but if you want to do DSP, you will have to use this kind of APIs sooner or later.
To get started with the RemoteIO unit:
http://atastypixel.com/blog/2008/11/04/using-remoteio-audio-unit/