Is there an easy way to control the playback speed/tempo of a sound file loop played using Audio Queue Services? For example, if a game is playing background music, I want to make the BGM speed up as time runs out, but without changing the pitch of the music. Thx!
There's no trivial way to do this that I know of. On the Mac, you'd presumably use Audio Units to do this, but I think the support for those is limited on the iPhone SDK.
You can do some processing during your AudioQueue playback callback, between AudioFileReadPackets() and AudioQueueEnqueueBuffer() but I think speed-shifting without changing the tone will require rather a lot of CPU time.
It'd probably be easier to have more than one recording of the music, and switch files during a silent passage of the music.
Related
We have a VOIP application, that records and plays audio. As such, we are using PlayAndRecord (kAudioSessionCategory_PlayAndRecord) audio session category.
So far, we have used it successfully with iPhone 4/4s/5 with both iOS 6 and iOS 7 where call audio and tones played clearly and were audible.
However, with iPhone 5s, we observed that both the call audio and tones sound robotic/garbled in speaker mode. When using earpiece/bluetooth/headset, sound is clear and audible.
iOS Version used with iPhone 5s: 7.0.4
We are using audiounits for recording/playing of call audio.
When setting audio properties like session category, audio route, session mode etc., we tried both the older (deprecated) AudioSessionSetProperty() and AVAudioSession APIs.
For playing tones, we are using AVAudioPlayer. Playing of tones during the VOIP call and also when pressing keypad controller within the app produces robotic sound.
When instantiating the audio component using AudioComponentInstanceNew, we set componentSubType to kAudioUnitSubType_VoiceProcessingIO.
When replacing kAudioUnitSubType_VoiceProcessingIO with kAudioUnitSubType_RemoteIO, we noticed that the sound of call audio and tones was no longer robotic, it was quite clear, but the volume level was very low when using speaker mode.
In summary, keeping all the other audio APIs the same:
kAudioUnitSubType_VoiceProcessingIO: Volume is high (desirable) but sound of tones and call audio was robotic in speaker mode.
kAudioUnitSubType_RemoteIO: Sound of tones and call audio was clear but it is not audible.
STEPS TO REPRODUCE
- Set audio session category to playAndRecord.
- Set audio route to speaker
- Set all the other audio properties like starting audio unit, activating the audio session, instantiating the audio components.
- Set the input and render callbacks
- Try both options
1. Play tones using AVAudioPlayer
2. Play call audio
Any suggestions on how to get over this issue. Raised as an issue with Apple but no response yet from them.
i have shared the code here github link
The only difference between kAudioUnitSubType_VoiceProcessingIO and kAudioUnitSubType_RemoteIO is that voiceProcessing includes code to tune out acoustic echo i.e. tunes out the noise from the speaker so the microphone doesn't pick it up. Its been a long time since I've played with the audio framework but I remember that to sound off there could be any number of things,
Are you doing any work in the audio callbacks that could be taking a long time?
The callbacks run on realtime threads. if your processing takes too long you can miss data. Would be helpful to track the data over a fixed period of time to see are you capturing it all. Use something like wireShark to sniff the network. Record the number of packets and see did the phone capture the same.
Are you modifying any of the audio?
Do you have a circular buffer that might be causing an issue?
I've had several issues doing this and one was using a third party circular buffer that was described as low latency and efficient ... it wasn't. I answered my own question here and included my circular buffer implementation that greatly improved my audio as the issue was I was skipping data.
Give this a go and let me know:
iOS UI are causing a glitch in my audio stream
Please be aware that some of this code is unique to the audio format ALaw, 0xD5 is a byte of silence in ALaw, if you are using linear PCM or any other that will probably be a noise of some kind.
I need to play sounds (~5 seconds each) throughout my iphone application. When they're triggered, they need to play immediately.
For the moment I'm using AudioServices and (as you probably know) the first time you play a sound it lags, then every time there after it's perfect. Is there some code available that's clever enough to preload an AudioServices sound (by playing it silently maybe?). I've read adjusting the system volume programmatically will get your app rejected, so that's not an option. Seems AudioServices isn't made for volume correction from what I can see.
I've looked into OpenAL and while feasible seems a little over kill. AVAudioPlayer seems like a little bit of a better option, I'm using that for background music at present. Extending my music player to handle a 'sound board' might be my last resort.
On the topic of OpenAL, does anyone know of a place with a decent (app store friendly) OpenAL wrapper for the iPhone?
Thanks in advance
Finch could be perfect for you. It’s a tiny wrapper around OpenAL with very low latency and simple API. See also all SO questions tagged ‘Finch’.
If you use an AVAudioPlayer, you can call prepareToPlay when you initialize the object to reduce the delay between calling play and having the audio start.
I am playing sounds in loop in my app. So it should continue playing through out the app. but sometimes it stops after playing sound for 3/4 times.I don't understand whats happening.
I am using audio-toolbox framework for playing sound. creating audio queue and then playing sounds in loop. I am also playing sound from ipod library using mediaplayer. Same thing happening with song from ipod.
I have set [musicPlayer setRepeatMode: MPMusicRepeatModeOne]; but still it stops after 3/4 times.
How exactly are you playing the sound? Show us the code. Do you use System Sound Services? They are not meant to play longer sounds, quote Audio Toolbox Reference:
You can use System Sound Services to
play short (30 seconds or less)
sounds.
This could be the source of your problem. But until you show us the code we can’t but guess.
I built an iPhone app using AudioServices to play short sounds. The first time a sound is played, there's a delay of half a second or so while the sound loads before it plays. This definitely makes for an awkward user experience.
Is there a way to preload sounds for AudioServices to play, or do I need to switch to audioQueues or some other method of playing sounds?
Thanks,
Maha
This is a well known problem. Everything in AudioServices is initialized lazily.
I think that your best choice is between Core Audio or OpenAL. OpenAL might be overkill, but it has a simple API. The oalTouch example is a good place to start.
Core Audio is a bit more raw, but it's well documented. The iPhone's OpenAL SDK is built on top of it.
So I have an app which plays many short sound clips. I need to know when the sounds are finished playing, and I need to use mp3s, so I'm using AVFoundation for the sound playback.
When a sound is actively playing, and the user uses the hardware volume buttons, the playback volume changes. Problem is, the app is NOT constantly playing sounds, and when it's not, and the hardware buttons are used, the RINGER volume gets adjusted instead.
How do I set it up so, as long as the app is running, the user can adjust the playback volume?
Thanks!
Turns out this can be accomplished by allocating an AVAudioPlayer with any valid sound file and calling the prepareToPlay method, without ever calling the play method.
Works perfectly.
Start an AudioSession and don't stop it when you're not playing sounds.
so you want to disable ringer playback volume as long as the app is running? therefore the hardware controls will only adjust the app playback sounds?
i dont think this is possible unless you are "always playing sound" for example, many games are always playing background music or what have you.
You might be able to accomplish this by constantly playing a 0 volume sound as long as your app is running. You could then play your sound clips over it.
How do I play multiple sounds simultaneously?