I am working on radio app in which i want to record live radio streaming on an record button click.It should record just the radio streaming sound. Currently i am recording from Mike but its not the way i want as it also captures the surrounding/background voice. I did read few post but all of them are regarding AVaudioRecorder. I have used wunderradio api for playing the radio from url. I haven't got any method/function in their api which will record that audio from url. I want to record the buffered audio only from that url,so that I can play that recorded file later.
Any help would be appreciated.
Recording audio playback by using the microphone is really not the right way to do it. If you're using AudioQueue services for audio playback you can use the AudioFileWritePackets function to write audio data to a file.
If you implement recording this way you can write audio files in the format they're streamed in. So an mp3 audio stream can be written as an mp3 file to disk since you're writing encoded audio packets with the AudioFileWritePackets function.
To get a better understanding of how this all should be implemented you can have a look at the SpeakHere sample code of Apple. The SpeakHere project records from the microphone but it's still a good example to see how the AudioFileWritePackets function works. In your case you need to use the AudioFileWritePackets function in the output callback of your AudioQueue. This is the callback that's called when a buffer is finished playing. So it's a good to place to write the already played audio buffers data to a file.
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I have an HLS live stream (from an external source, not one I created or can edit) with video and several audio options. I can successfully change the audio to one of the alternatives, but the alternative audio the stream provides doesn't match up perfectly with with video (it's about 1.5 seconds ahead of the video).
Is there a way to have the AVPlayer delay the audio portion of the stream by some specified amount to correct for this? Or is that not possible?
I am trying to record the sound from iPhone speaker. I am able to do that, but I am unable to avoid mic input in the recorded output. Tried with sample code available in different websites with no luck.
The sample which I used does the recording with audio units. I need to know if there is any property for audio unit to set the mic input volume to zero. Above that I came to from other posts that Audio Queue services can do the thing for me. Can any one redirect me with sample code for the audio queue services implementation. I need to know whether there is a way of writing the data to an separate audio file before sending it as input to speaker.
Thanks in advance
There is no public iOS API or property for recording generic audio sent to the iPhone speaker. Only mic input can be recorded.
But if you are playing audio in your app using only uncompressed samples with Audio Queues or the RemoteIO Audio Unit, you can just copy those samples to a file before you write them to the audio callback buffers. Those saved samples can be used to construct a recording.
I'm currently working on a project where it is necessary to record sound being played by the iPhone. By this, I mean recording sound being played in the background like a sound clip or whatever, NOT using the built-in microphone.
Can this be done? I am currently experimenting with the AVAudioRecorder but this only captures sound with the built-in microphone.
Any help would be appreciated!
This is possible only when using only the Audio Unit RemoteIO API or only the Audio Queue API with uncompressed raw audio, and with no background audio mixed in. Then you have full access to the audio samples, and can queue them up to be saved in a file.
It is not possible to record sound output of the device itself using any of the other public audio APIs.
Just to elaborate on hotpaw2's answer, if you are responsible for generating the sound then you can retrieve it. But if you are not, you cannot. You only have any control over sounds in your process. yes, you can choose to stifle sounds coming from different processes. but you can't actually get the data for these sounds or process them in any way.
Instead of playing something out the speaker and recording it through the mic, can I just record the system sound and not use the mic at all? How should I proceed for this? What should I use as framework?
If you are playing uncompressed sounds using the Audio Queue or Audio Unit Remote IO APIs, you can just write to a file the same sound samples which you use to fill the callback buffers, and you will have recorded what you played.
I want to record the sound of my iPhone-App. So like someone is playing something on a iPhone instrument and after that you can hear it.
Is it possible without the micro?
Do you mean an App you build yourself? If yes, you could just save the rendered waveform (maybe encoded/compressed to save space) for later playback. (see: Extended Audio File Services, it can write the same AudioBufferList to a file that you would render to the RemoteAudio Unit when playing audio in your Instrument-App)
[Edit: removed comments on recording third-party app audio output ...]
With the AVFoundation you are currently using, you're always working on the level of the sound files. Your code never sees the actual audio signal. Thus, you can't 'grab' the audio signal that your app generates when it is used. Also, AVAudioPlayer does not provide any means of getting to the final signal. If you're using multiple instances of AVAudio player to play multiple sounds at the same time you also wouldn't be able to get at the mixed signal.
Alas, you probably need to use CoreAudio which is a much more low level interface.
I'd like to suggest an alternative approach: Instead of recording the audio output, why not record the sequence of actions together with their time which lead to the audio being played? Write this sequence of events to a file and read it back in to reproduce the 'performance' - it's a bit like your own MIDI sequencer :)