Well, I will try best not to make it as a 'I just want the code' question...
I'm recently working on a project which requires some audio signal processing from local music files (e.g. iTunes Library). The whole work includes:
Get the PCM data of an audio file (normally from iTunes library); <--AudioQueue (?)
Write the PCM data to a new file (it seems that Apple does not allow direct modification on music tracks); <--CoreAudio(?)
Do some processing and modification, like filters, manipulators, etc. <-- Will be developed in C++
Play the processed track. <--RemoteIO
The problem is, after going through some blogs and discussions:
http://lists.apple.com/archives/coreaudio-api/2009/Aug/msg00100.html, http://atastypixel.com/blog/using-remoteio-audio-unit/
http://osdir.com/ml/coreaudio-api/2009-08/msg00093.html
as well as the official sample codes, I got a feeling that the CoreAudio SDK allow us to apply audio processing only on voice demos recorded from Mic.
My question is that:
Can I get raw data from iTunes library tracks instead of Mic input?
If the first question is 'No', is there a way to 'fool' the SDK to let it think it is getting data from Mic input, not from iTunes? (I have done some similar 'hacking' stuff in C# before XD)
If the whole processing just doesn't work, can anyone provide some alternative ideas?
Any help will be appreciated. Thank you very much :-)
Thanks.
Just found something really cool yesterday.
From iPhone Media Library to PCM Samples in Dozens of Confounding, Potentially Lossy Steps
(http://www.subfurther.com/blog/?p=1103
And also a class library by MIT:
TSLibraryImport: Objective-C class + sample code for importing files from user's iPod Library in iOS4.
(http://bitbucket.org/artgillespie/tslibraryimport/changeset/a81838f8c78a
Hope they help!
Cheers,
Manca
1) No. Apple does not allow direct access to PCM data of songs. Otherwise you could create music-sharing apps, which is not in Apple's interests.
2) No. Hacking and getting approved is impossible due to Apple's code approval mechanism.
3) The only alternative I could think of is that you have to do the processing part on PC/Mac and then transfer it to the iPhone. Or you would have to store the files in your own applications folder - you should be able to load and process these via CoreAudio.
I know this thread is old but... did this work for you, Manca? And did this app get approved?
EDIT: just discovered the AVAssetReader class, introduced since iOS 4.1, should help
Related
I am working for Music app in that one of the feature is recording user voice and playback the same. So far all things are in control. Yesterday I got a thought and straight away I started Googling, the idea is adding artist names and album image to my recorded audio using AVAudioRecorder, But there is not much success in it.
I also seen AV Foundation Audio Settings Constants to set the AVAudioRecorder settings, failed in this also.
You probably can use an existing audio tagging library, so after creating the file, you can use it to add the required data. I did a quick search and found this libraries:
SonatinaTag: It was made for OSX but it may work for iOS (The project state that has very few external requirements). Not sure if support writing.
TagLib-ObjC: A wrapper for the popular TagLib. Seems to be in development.
TagLib: TagLib, I know is just pure C pain, but maybe is not that hard to use.
Good luck!
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.
I'm looking for a way (doesn't need to be app-store save!!) to get ahold of video-streaming-relevant debugging information.
What I'm trying to do, is to write an application that opens a video stream and displays information like:
framerate
bitrate audio / video
etc etc.
codec information
basically i want to display as much information for any given stream.
Thanks for any information in advance,
best regards
sam
Even though you tagged your question with MPMoviePlayerController, that class probably isn't going to help you out very much. First of all, there's a limited amount of information you can access from it at a high level, certainly nothing about codecs and audio bitrate. And even if the class does store this type of information somehow, your app would be disqualified from being in the iTunes App Store if you access non-public methods or properties.
Secondly, MPMoviePlayerController only supports a limited number of codecs itself, namely the ones that can be decoded in hardware on the iPhone/iPad (H.264 baseline and MPEG-4 videos).
Anyways, a good option could be FFMpeg for the iPhone. Getting the information you need seems to be much more straightforward this way; check out this blog post for a nice tutorial for using the libraries.
I'm not sure about the potential legal issues concerning distributing such a program in the App Store, but if you statically link it with your binary that would at least satisfy Apple... you'll have to check the FFMpeg Legal Site for their end.
Is it possible to edit music files stored on iphone in app and create ringtone from them?
Any help would be appreciated.
If I understand correctly, you want to extract the music from an existing iPhone app, and then turn that music from the app into a ring tone?
The short answer is no, not if you keep your iDevice up to date and within apple's licensed operating paradigm.
The longer answer is maybe. If you jailbreak the device, you may be able to hack access to the application and extract the desired data.
If I don't understand correctly, and you're just looking to change any old mp3 into an iPhone ringtone, try googling for iPhone ringtone hacks. Of course your mileage may vary but google is again your friend.
Sorry to not provide any code. This question didn't seem to warrant it.
No, for a number of reasons. The SDK doesn't give you access to the actual file data from the music library (just an object that will play music back for you), and while you can probably export an M4A file, with an "m4r" extension that iTunes will recognize as a ringtone, you'll have to get the user to take the file off their device and import it into iTunes manually for it to be usable as an actual ringtone on their phone.
I see that the IPhone core audio does not include audioDevice objects to render audio input directly into RAM. I hear people talking about using files to do this(like speak here) but I am thinking there must be a way to do this otherwise. Your thoughts would be appreciated.
Check out the aurioTouch sample in the iPhone Developer site.