I've got a couple of wav files and possibly a mp3 that I'd like to mix down to a single wav or mp3-file. I'm using C/C++/Obj-C (iPhone). I have really no experience with this sort of thing. If anyone could give me some pointers, I would be very grateful.
Basically what I want to do is similar things like for example Audacity can do, but programmatically. Isn't there a sound library where you can easily open audio files and "paste" them into a new one at defined positions? Where mixing is something you don't have to worry about?
Thanks.
Mixing two sound buffers of linear PCM is only a matter of adding each sample value in them together, and of course make sure you don't overflow. Normally you would use floating point values in the buffers though, so the issue is when you go back to the file. You should also have CoreAudio available on the iPhone, it has all the means to open/read/write sound files in different formats. I think there is also a more high level api available to the iPhone that isn't on the mac, look up the apple docs.
If you are specifically looking for the features of Audacity, it uses PortAudio under the hood (looks like an MIT license). Perhaps you can just try to use that?
Read Multimedia support as a starting point it contains alot info. Here is an extract:
There are 3 ways to mix the audio on iphone:
Audio Unit framework
Multichannel Mixer - "lets you mix multiple audio streams to a single stream"
3D Mixer unit - "lets you mix multiple audio streams, specify stereo output panning, manipulate sample rate"
OpenAl used in games development
Also check the following sample out: iPhoneMultichannelMixerTest:
Two input busses are created each with input volume controls. An overall mixer output volume control is also provided and each bus may be enabled or disabled
Related
I have a series of sounds that a user will play, rearrange, and edit etc. while using my app. When the user is finished, I want them to be able to save their work and record it to an mp3.
I don't want to play it through speakers and record it with the mic since that will result in low sound quality and interference. I cannot think of any ways of doing this that doesn't require extra hardware and/or a computer.
How can I do this using just their device?
Well, I would say it cant be done with AVFoundation.
My suggestion is to use Audio Units, and transform all your interactions to an audio graph. at some point you set a render notify on the RemoteIO so every time it renders sounds to the speakers you get a callback where you can write it down those frames/packets/data into a file.
I will probably suggest to use AAC(m4a) over MP3. I am not very fond of MP3, and to be honest as far as I know the sdk does not provide encoding to MP3, probably due to licensing issues. I could be wrong though. Check this sample code below, probably the best sample code you will ever find on Audio units on the web.
AudioGraph by Tom Zic
I am looking at creating an app for OS X and/or iOS that allows the user to arbitrarily embed markers into the audio at various intervals during the audio recording process. It would be nice to have a single file that could contain this information, but may or may not be efficient or feasible. I suppose it is similar to what YouTube annotations allows.
Requirements:
Ability to insert markers at certain time points of an audio recording
Ability to save a name for the marker as well as a brief description
This is for audio created by the app I'm working on, so is not for importing audio from other sources for markup.
-- snip --
EDIT: Maybe MP4 + XMP?
EDIT2: Has anyone tried using custom XMP fields with Audio or Video on the iOS platform? On the Mac platform? I have downloaded the XMP Toolkit from Adobe (which has an Xcode project) - but it is a touch out of my comfort zone. From a high level it appears pretty straightforward, but anyone with experience with the XMP Toolkit have any thoughts?
As is suggested in an answer below, does anyone have experience with alternative solutions such as QuickTime with chapter markers? Pros and Cons to various approaches?
After thinking about it, it would be nice to do something that supports both audio and video formats, even if initially the current requirement is audio only.
EDIT3 (cleanup):
So, just to close the loop here. I ended up digging into the iOS 4.0 APIs for AVAsset, AVMetadataItem, et al in the AV Foundation Framework. Still have not completed the project, but it appears these APIs will satisfy the requirement without the need for an external library.
have you read up on the CAF format?
basically, it functions as a wrapper for many audio formats, and allows you to embed all sorts of data (as well as user defined data). it may be an option since interchange is not an issue (in your case).
The CAF File Specification
You might consider MPEG-4 or QuickTime formats with a chapter track.
I have a children's iPhone application that I am writing and I need to be able to shift the pitch of a sound sample using Core Audio. Does anyone have any example code I could look at where this is done. There are many music and game apps in the app store that do this so I know I am not the first one. However, I cannot find any examples of it being done.
you can use dirac-2 from dsp dimension for pitch shifting on the iphone. quote: -
"DIRAC2 is available as both a commercial object library offering unlimited sample rates and phase locked multichannel support and as a free single channel, 44.1/48kHz LE version."
use the soundtouch open source project to change pitch
Here is the link : http://www.surina.net/soundtouch/
Once you add soundtouch to your project, you have to give the input sound file path, output sound file path and pitch change as the input.
Since it takes more time to process your sound its better to modify soundtouch so that when you record the voice, directly give the data for processing. It will make your application better.
I know it's too late for the person who asked but it is really a valuable link (As I found) for any one else who is looking for the solution of the same problem.
So Here we have latest DIRAC3 with it's own audio player classes which will take care of run time pitch and speed(explore for god knows what more) shifting. Run the sample and have huge round of applause for that.
Try Dirac - it's the best technology out there and it's available on Win, Linux, MacOS X and iOS. We're using it in all our products (and a couple of others do as well, search for "Capo" on the App Store). They're at version 3 now which has seen a huge increase in performance since previous versions. Hope this helps.
See: Related question
How much control over pitch do you need... could you precalculate all the different sounds?
If the answer is yes, then you can just pick the right sounds and play them.
You could also use Audio Converter Services in conjunction with AVAudioPlayer, which will allow you to resample the audio (which will effectively repitch them, though they'll change duration).
Alternatively, as the related question points out, you could use OpenAL and AL_PITCH
I'm looking to create an app that emulates a physical instrument. I've got audio samples but I want to be able to increase the pitch/frequency dynamically so I don't have to load from too many files.
Any idea which audio API will be able to do this? I reckon either OpenAL or Audio Queue Services but am not sure which is suitable. Any links to guides/sample code is also much appreciated.
Thanks in advance.
I went down this road in 2009, trying Audio Toolkit, Audio Queue Services, openAL, and finally settling on the RemoteIO AudioUnit.
Audio Toolbox is fine for basic triggered sound effects, but it wasn't able to change frequencies or loop samples.
Audio Queue Services can loop samples, but the only way I could find to adjust the playback frequency of a sample was to re-read the data from the file -- very painful. Plus, the framework is tremendously cumbersome - I'd only use it if I was trying to stream something off the Internet.
OpenAL was a godsend - was up and running with it in under an hour, after getting my hands on the no-longer-available-from-Apple "CrashLanding" iPhone sample app. I found OpenAL to be ideally suited to games or even a musical instrument -- samples could be pre-loaded, adjusting the frequency was easy, and looping was no problem. The deal-breaker for me was that starting and stopping a looped sample would result in a nasty "pop" almost every time. Also the builtin 3d positional audio mixer was a bit too CPU-intensive for my liking.
If your instrument does not use looped samples, I'd suggest trying the OpenAL route first - the learning curve is much less intimidating. Try to track down "SoundEngine.h", "CrashLanding" or "TouchFighter", or check out the following link:
http://benbritten.com/blog/2008/11/06/openal-sound-on-the-iphone/
Since looped samples was a requirement for me, I finally settled on AudioUnits (which, on the iPhone, is referred to as "RemoteIO" if you want to do input or output). It was tremendously difficult to implement - very similar to Audio Queue Services, in that the core of your implementation will be inside a "buffer callback", being called several times per second to fill a buffer of outbound audio with raw SInt16 values.
Ultimately, I got my instrument working beautifully with multi-note polyphony, looped samples, no popping, and minimal latency.
Unfortunately, RemoteIO is not well documented. Michael Tyson was one of the first in the field to write about RemoteIO at length, and his posts (and the comments) were very useful to me:
http://michael.tyson.id.au/2008/11/04/using-remoteio-audio-unit/
Good luck!
Edited years later: I've open-sourced the RemoteIO/AudioUnits code I alluded to above: https://github.com/glenn-barnett/hexaphone/blob/master/Classes/Instrument.m - apologies for the mess, I hope to get some time to clean up the code and comments.
Try creating an Audio Unit. I'm doing something similar an AU worked well for me.
Initially I used an audio queue as it was simpler (higher level?) and
synchronous, however it was lacking in responsiveness, so I dumped it for
the Audio Unit.
It sounds, a bit, like you're creating essentially the wavetable synthesis method of playing MIDI files. You might be able to find a MIDI synthesizer for the iPhone that you can use, and then use your audio samples to build a wavetable set. Anytime you'd want to play tones, you would simply send the MIDI event into the iPhone MIDI synth with your loaded wavetable set.
Another option now is AUSampler.
http://developer.apple.com/library/mac/#technotes/tn2283/_index.html
I have a number of static audio files that I want to be able to dynamically mix together and play on the iPhone (not all at once, most common case is to mix two or three audio streams into one stream).
What shall I use? I know there are OpenAL and Audio Units that could be useful, but which one?
To get a kick-start, is there a concrete code snippet for how to do this somewhere?
Thanks in advance,
/Steve
I recommend you take a look at the some of the Apple documentation and sample code relating to reading files and mixing.
e.g. Mixing sample code
and Audio Queue Services sample code
and playing audio
For a higher level API, use AudioQueueServices which does a lot of the buffering for you, but if you need to have maximum control and flexbility, then I suggest an AudioUnit along with AudioFileReadPackets which is part of AudioFileServices
Hope that helps,
Ben.