Is it possible to play .mid files directly via some API, or one have to convert the midi file to e.g. AAC first?
(2 years later…) You can use MusicPlayer and MusicSequence APIs. Available in iOS 5.
There is no Apple API for this. You could write your own, which i think would depend on what you are hoping it is going sound like.
There is lots of available source code for reading midi files and there are a few open source synths for the iphone - or you could use openAl for triggering samples. It probably isn't going to sound like Garageband tho.
If you want it to sound as good as possible you will have to convert it first.
Related
I have a music file with a particular tone(music.mp4). I want to convert existing sound file (speech.mp4) into the tone which is specified in music.mp4. Its like converting a speech into some particular tone. I do not want to play both files simultaneously. I want to convert source file with help of some music file. So, output file will be converted file.
Is it possible? I searched for Audio Unit Hosting and Multimedia guide. But do not get any clue.
Thanks in advance.
The answer is: it sounds (no pun intended) like it would be possible with the iOS. You just need to find someone who knows how to program that specific functionality. I do not know why you would think to find the answer in the Apple Docs. I want to know if it's possible to program music that plays backwards. I want to know if I can program a sound that converts my words into something my dog understands. I can't imagine the documentation could possibly cover everything everyone ever wants to program an iPhone to do.
There are no iOS public APIs for frequency analysis of audio files. You would have to write your own DSP code for that. The AVFoundation and Accelerate frameworks have some audio file conversion and math functions that may help, but that is only a small portion of the code needed.
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 can create a basic MIDI file from scratch verified using TiMidity++, and I know enough OpenAL to play a streamed source from a file.
I'm just wondering if it's possible to create a program in C to play MIDI files by reading in a SF2 and MIDI file and using OpenAL to play the sound. Do I need to use another library? I want to know beforehand because the SF2 format looks pretty complicated.
Core audio is where it's at!
If you are doing this on a mac, DLSMusicDevice does what you want.
if you are on iOS, you will need to do much 'by hand' but it is manageable (tedious, as well). If you go this route, look at the sample code 'mixer host'.
You need to use an CoreAudio. Create an AUGraph with a Sampler connected to an IOUnit. Look at header files AUComponent.h in the AudioUnit framework. Once you've got your audio graph setup you can play a note using the following function:
MusicDeviceMIDIEvent(sampler, status, note, velocity, 0);
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
Can iphone mix two sound files or build custom equalizer?
I have studied for weeks about this problem,
and it seems unable to use iphone-sdk to mix two or more sound files or to build custom equalizer.
Is anyone have the experience to do this?
Yes you can. AVAudioPlayer can play multiple sounds and you can control the volume for each. Or you can use Audio Units and have more control over the audio data.
aurioTouch is a good sample app for what you are thinking of.
For simple playback of sound files you can use the AVAudioPlayer class introduced in the 2.2 SDK. It provides playback and volume controls for playing any audio file. As far as I am aware, there are no restrictions on the number of sound files you can play on the iPhone. The only restriction on playing sound files is that you may only play one AAC or MP3 compressed file at a time, the rest of the files must be either uncompressed or in the IMA4 format.
If your needs are more low-level (If you need to do DSP) you might want to look at AudioQueue Services or AudioUnits - two Mac OS X audio processing APIs that are also available on the iPhone.