As is demonstrated in this answer, I have recently learned how to play audio files using both AVAudioPlayer and AudioToolbox. I have successfully played a single audio test file using both methods. However, I want to ask about which one I should actually use in my app (or if it even matters).
Here are the relevant characteristics of my app:
There are about 800 audio clips.
Most of the clips last less than one second.
Any could be chosen to be played at random by the user, but only a small subset will be used on any particular run.
No special volume control or playback options are needed.
These are my questions:
Which method for playing a sound would be better? Why?
Should I preload the sounds or just load them when they are needed? I'm guessing that preloading 800 sounds every time is a bad idea. But if I wait to load them until they are needed, I am worried about performance (ie, a noticeable pause before the clip is played)
Do I need to play sounds on a background thread?
So my concerns in choosing which audio player to go with are memory and performance. I couldn't tell from any of the documentation that I saw which is better in this case.
Related
I need to have a series of sound samples (audio files) being played back at the touch of a button. The audio samples need to be played back simultaneously and precisely (think 4 voices in a piece of music).
I managed to do this with several instances of AVAudioPlayer but it will go out of sync.
Reading about it, due to lack of precision it seems to not be the right choice for I'm trying to do.
Audio queue (is this part of Core Audio?) seems to be able to do what I want but I can hardly find any code bits in Swift to setup what I’m trying to do, which is:
Load the audio file, prepare it to be played, then play it (I would trigger it with an NSTimer).
Is this straightforward to implement with audio queue or should I look elsewhere?
If you could point me into the right direction I would be very grateful.
Thanks a lot!
I'm looking for a way to create a audio bars visualizer similar to this in iOS.
Every white bar will move up and down depending of audio wave. I'm really lost because haven't much experience dealing with audio in Objective-c.
EDIT: What i'm seeking is what Overcast's app does on its visualizer (the group of vertical orange bars on the lower part of the podcast's image)
Anyone can help?
Thanks
EDIT: Thanks to Tomer's answer I finally made it. First I did this tutorial in order to make it all clear. Then I created my own VisualizerView for my project, you can find it in this gist. Maybe is not perfect but it does what I needed to do.
Generally, you have a few options if you want to get an idea of what something sounds like in iOS:
Use the simple AVAudioPlayer audio player, and then use the [audioPlayer averagePowerForChannel:] method to get the avarage audio level for the current moment. Check out this tutorial.
Use the Audio Queue API, which lets you send whatever audio you want to the speaker: You would read audio from your source and fill the buffers with it every time. (If you're reading from a file, use AVAssetReader) This way you always know exactly what waveform you're playing, so you can, for example, calculate its avarage power or process it in other ways like FFT. Then you'd update the bars accordingly.
EDIT: The standard way of doing such a thing is to use the Fast Fourier Transform (FFT) - it extracts frequency information from a sound. Here's a good example of using it on iOS (Apple's guide here). But, of course, to use it you have to know exactly what waveform you're playing every time, so you'd probably want to use a lower-level API such as Audio Queue.
I am recording videos and playing them back using AVFoundation. Everything is perfect except the hissing which is there in the whole video. You can hear this hissing in every video captured from any iPad. Even videos captured from Apple's inbuilt camera app has it.
To hear it clearly, you can record a video in a place as quiet as possible without speaking anything. It can be very easily detected through headphones and keeping volume to maximum.
After researching, I found out that this hissing is made by preamplifier of the device and cannot be avoided while recording.
Only possible solution is to remove it during post processing of audio. Low frequency noise can be removed by implementing low pass filter and noise gates. There are applications and software like Adobe Audition which can perform this operation. This video shows how it is achieved using Adobe Audition.
I have searched Apple docs and found nothing which can achieve this directly. So I want to know if there exists any library, api or open source project which can perform this operation. If not, then how can I start going in right direction because it does looks like a complex task.
I am interested in recording media using an AVCaptureSession in iOS while playing media back using an AVPlayer (specifically, I am playing back audio and recording video, but I'm not sure it matters).
The problem is, when I play the resulting media back together later, they are out of sync. Is it possible to synchronize them, either by ensuring that playback and recording start simultaneously, or by discovering what the offset is between them? I probably need the sync to be on the order of 10 ms. It is unreasonable to assume that I can always capture audio (since the user may use headphones), so syncing via analysis of original and recorded audio is not an option.
This question suggests that it's possible to end playback and recording simultaneously and determine the initial offset from the resulting lengths that way, but I'm unclear how to get them to end simultaneously. I have two cases: 1) the audio playback runs out, and 2), the user hits the "stop recording" button.
This question suggests priming and then applying a fixed, but possibly device-dependent delay, which is obviously a hack, but if it's good enough for audio it's obviously worth considering for video.
Is there another media layer I can use to perform the required synchronization?
Related: this question is unanswered.
If you are specifically using AVPlayer to playback Audio and i would suggest you to use AudioQueueServices for the same. Its seamless and fast as it reads buffer by buffer and play pause is faster than AVPLlayer
There can also be the possibility that you are missing the initial statement of [avPlayer prepareToPlay] which might be causing much overhead for it to sync before playing the Audio.
Hope it helps you.
I am creating an iphone application that use audio.
I want to play a beep sound that loop indefinitely.
I found an easy way to do that using the upper layer AVAudioPlayer and the numberOfLoops set to "-1". It works fine.
But now I want to play this audio and be able to change the rate / speed. It may works like the sound played by a car when approaching an obstacle. At the beginning the beep has a low frequency and this frequency accelerate till reaching a continuous sound biiiiiiiiiiiip ...
It seems this is not feasible using the high layer AVAudioPlayer, but even looking at AudioToolBox I found no solution.
Any help?
Take a look at Dave Dribin's A440 sample application, which plays a constant 440 Hz tone on the iPhone / iPad. It uses the lower-level Audio Queue Services, but it does what you're asking (short of the realtime tone adjustment, which would just require a tweak of the existing code).