How does one record audio using iOS? Not the input recording from the microphone, but I want to be able to capture/record the current playing audio within my app?
So, e.g. I start a recording session, and any sound that plays within my app only, I want to record it to a file?
I have done research on this but I am confused with what to use as it looks like mixing audio frameworks can cause problems?
I just want to be able to capture and save the audio playing within my application.
Well if you're looking to just record the audio that YOUR app produces, then yes this is very much possible.
What isn't possible, is recording all audio that is output through the speaker.
(EDIT: I just want to clarify that there is no way to record audio output produced by other applications. You can only record the audio samples that YOU produce).
If you want to record your app's audio output, you must use the remote io audio unit (http://atastypixel.com/blog/using-remoteio-audio-unit/).
All you would really need to do is copy the playback buffer after you fill it.
ex)
memcpy(void *dest, ioData->mBuffers[0].mData, int amount_of_bytes);
This is possible by wrapping a Core Audio public utility file CAAudioUnitOutputCapturer
http://developer.apple.com/library/mac/#samplecode/CoreAudioUtilityClasses/Introduction/Intro.html
See my reply in this question for the wrapper classes.
Properly use Objective C++
There is no public API for capturing or recording all generic audio output from an iOS app.
Check out the MixerHostAudio sample application from Apple. Its a great way to start learning about Audio Units. Once you have an grasp of that, there are many tutorials online that talk about adding recording.
Related
My application uses Google WebRTC framework to make audio calls and that part work. However I would like to find a way to stream an audio file during a call.
Scenario :
A calls B
B answer and play a music
A hear this music
I've downloaded entire source code of WebRTC and trying to understand how it works. On the iOS part it seems that it is using Audio Unit. I can see a voice_processing_audio_unit file. I would (maybe wrongly) assume that I need to create a custom audio_unit that is reading its data from a file?
Does anyone has an idea in which direction to go?
After fighting an entire week with this issue. I finally manage to find a solution for this problem.
By editing WebRTC Code, I was able to get to the level of AudioUnits and in the AudioRenderingCallback, catch the io_data buffer.
This callback is called every 10ms to get the data from the mic. Therefor in this precise callback I was able to change this io_data buffer to put my own audio data.
I am trying to write a program for live streaming the audio to the server. Does AVAudioRecorder has the streaming functionality or should I use any other frameworks? Preferably I am trying to use apple builtin frameworks.
I have used AVCaptureSession for streaming audio coupled with AVCaptureDevice as Audio as input device and output device as AVCaptureAudioDataOutput which in turn calls AVCaptureAudioDataOutputSampleBufferDelegate and gives data as a buffered stream.
AVFoundation Cameras and Media Capture
According to this document, you have to initialize an AVAudioRecorder with a file path, which means: if you want to do the live streaming, you have to either wait for the current recording to finish, or initialize a new AVAudioRecorder with another path.
I would recommend you to create multiple AVAudioRecorder instances and run each instance based on the size of the audio chunk. (You can also divide them based on the time, but make sure your buffer is large to keep them all)
And, just upload previous chunks and then start a new instance to keep the recording going on.
I'm working on a mobile application that can perform basic analysis on audio input from the microphone in real time. However, the usual way to do it using the 'AVAudioRecorder` as shown in this guide and the API requires you to save it to a file first.
Since the app is meant to stay on for a long time and be used multiple times a day, I want to avoid clutter the phone with many audio files or audio files that are too big. However, I can't seem to find the way around it. Searching for solutions on the internet always lead to solutions of how to save an audio to a file, instead of avoiding saving to a file and work with some kind of buffer.
Any pointers would be super helpful!
Both the iOS Audio Unit and the Audio Queue APIs allow one to process short buffers of audio input in real-time without saving to a file.
You can also use a tap on the AVAudioEngine. See Apple's documentation: https://developer.apple.com/library/ios/samplecode/AVAEMixerSample/Introduction/Intro.html
You can use /dev/null as path in the AVAudioRecorder instance. This way it will not save to a file, but just discard the data.
var url = NSUrl.FromString("/dev/null");
var recorder = new AVAudioRecorder(url, settings, out error);
Is it possible to record output audio in an app using Swift? So, for example, say I'm listening to a podcast, and I want to, within a separate app, record a small segment of the podcast's audio. Is there any way to do that?
I've looked around but have only been able to find information on recording microphone recording and such.
It depends on how you are producing the audio. If the production of the audio is within your control, you can put a tap on the output and record to a file as it plays. The easiest way is with the new AVAudioEngine feature (there are other ways, but AVAudioEngine is basically an easy front end for them).
Of course, if the real problem is to take a copy of a podcast, then obviously all you have to do is download the podcast as opposed to listening to it. Similarly, you could buffer and save streaming audio to a file. There are many apps that do this. But this is not because the device's output is being hijacked; it is, again, because we have control of the sound data itself.
I believe you'll have to write a kernel extension to do that
https://developer.apple.com/library/mac/documentation/Darwin/Conceptual/KEXTConcept/KEXTConceptIOKit/iokit_tutorial.html
You'd have to make your own audio driver to record it
It appears as though
That is how softonic made soundflowerbed.
http://features.en.softonic.com/how-to-record-internal-sound-on-a-mac
What I want to do is to take the output samples of an AVAsset corresponding to an audio file (no video involved) and send them to an audio effect class that takes in a block of samples, and I want to be able to this in real time.
I am currently looking at the AVfoundation class reference and programming guide, but I can't see a way of redirect the output of a player item and send it to my effect class, and from there, send the transformed samples to an Audio output (using AVAssetReaderAudioMixOutput?) and hear it from there. I see that the AVAssetReader class gives me a way to get a block of samples using
[myAVAssetReader addOutput:myAVAssetReaderTrackOutput];
[myAVAssetReaderTrackOutput copyNextSampleBuffer];
but Apple documentation specifies that the AVAssetReader class is not made and should not be used for real-time situations. Does anybody have a suggestion on where to look, or if I am having the right approach?
The MTAudioProcessingTap is perfect for this. By leveraging an AVPlayer, you can avoid having to block the samples yourself with the AVAssetReaderOutput and then render them yourself in an Audio Queue or with an Audio Unit.
Instead, attach an MTAudioProcessingTap to the inputParameters of your AVAsset's audioMix, and you'll be given samples in blocks which are easy to then throw into an effect unit.
Another benefit from this is that it will work with AVAssets derived from URLs that can't always be opened by other Apple APIs (like Audio File Services), such as the user's iPod library. Additionally, you get all of the functionality like tolerance of audio interruptions that the AVPlayer provides for free, which you would otherwise have to implement by hand if you went with an AVAssetReader solution.
To set up a tap you have to set up some callbacks that the system invokes as appropriate during playback. Full code for such processing can be found at this tutorial here.
There's a new MTAudioProcessingTap object in iOS 6 and Mac OS 10.8 . Check out the Session 517 video from WWDC 2012 - they've demonstrated exactly what you want to do.
WWDC Link
AVAssetReader is not ideal for realtime usage because it handles the decoding for you, and in various cases copyNextSampleBuffer can block for random amounts of time.
That being said, AVAssetReader can be used wonderfully well in a producer thread feeding a circular buffer. It depends on your required usage, but I've had good success using this method to feed a RemoteIO output, and doing my effects/signal processing in the RemoteIO callback.