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• Unexpected behavior with AudioQueueServices callback while recording audio

  - by rcw3

  I'm recording a continuous stream of data using AudioQueueServices. It is my understanding that the callback will only be called when the buffer fills with data. In practice, the first callback has a full buffer, the 2nd callback is 3/4 full, the 3rd callback is full, the 4th is 3/4 full, and so on. These buffers are 8000 packets (recording 8khz audio) - so I should be getting back 1s of audio to the callback each time. I've confirmed that my audio queue buffer size is correct (and is somewhat confirmed by the behavior). What am I doing wrong? Should I be doing something in the AudioQueueNewInput with a different RunLoop? I tried but this didn't seem to make a difference... By the way, if I run in the debugger, each callback is full with 8000 samples - making me think this is a threading / timing thing.

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• Best way to learn iphone audio queue services, step by step tutorial

  - by optician

  Hi Everyone, I'm trying to learn how to handle audio at a fairly low level with audio queue services. I have been progrmaing in memory managed languages for quite a while, and have just completed the c programing tutorial by vtc (2007). This has left me comfortable with the understanding of pointers and memory allocation, but the apple documention still leaves me wanting for a simpler implenation and explaination. Maybe I need to learn objective c and cocoa better. I have heard that this book is good. Cocoa(R) Programming for Mac(R) OS X (3rd Edition) Could someone suggest a learning path that is going to help me get an better understanding of working with audio and an iphone. I want to be able to play mp3 files back and also alter the pitch of them as they are playing. I am prepared that I may have to temporarily convert the mp3 files into pcm files to do things like that to them. Thanks everyone.

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• Using Audio Queue Services to play PCM data over a socket connection

  - by Rohan

  I'm writing a remote desktop client for the iPhone and I'm trying to implement audio redirection. The client is connected to the server over a socket connection, and the server sends 32K chunks of PCM data at a time. I'm trying to use AQS to play the data and it plays the first two seconds (1 buffer worth). However, since the next chunk of data hasn't come in over the socket yet, the next AudioQueueBuffer is empty. When the data comes in, I fill the next available buffer with the data and enqueue it with AudioQueueEnqueueBuffer. However, it never plays these buffers. Does the queue stop playing if there are no buffers in the queue, even if you later add a buffer? Here's the relevant part of the code: void wave_out_write(STREAM s, uint16 tick, uint8 index) { if(items_in_queue == NUM_BUFFERS){ return; } if(!playState.busy){ OSStatus status; status = AudioQueueNewOutput(&playState.dataFormat, AudioOutputCallback, &playState, CFRunLoopGetCurrent(), NULL, 0, &playState.queue); if(status == 0){ for(int i=0; i<NUM_BUFFERS; i++){ AudioQueueAllocateBuffer(playState.queue, 40000, &playState.buffers[i]); } AudioQueueAddPropertyListener(playState.queue, kAudioQueueProperty_IsRunning, MyAudioQueuePropertyListenerProc, &playState); status = AudioQueueStart(playState.queue, NULL); if(status ==0){ playState.busy = True; } else{ return; } } else{ return; } } playState.buffers[queue_hi]->mAudioDataByteSize = s->size; memcpy(playState.buffers[queue_hi]->mAudioData, s->data, s->size); AudioQueueEnqueueBuffer(playState.queue, playState.buffers[queue_hi], 0, 0); queue_hi++; queue_hi = queue_hi % NUM_BUFFERS; items_in_queue++; } void AudioOutputCallback(void* inUserData, AudioQueueRef outAQ, AudioQueueBufferRef outBuffer) { PlayState *playState = (PlayState *)inUserData; items_in_queue--; } Thanks!

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• iPhone SDK: Audio Queue control

  - by codemercenary

  Hi all, I am new to the audio queue services so I have taken an example from a book called iPhone Cool Projects where it describes how to stream audio. I want to extend this to being able to play a continuous playlist of links to mp3 files like an internet radio. The problem with the example code it that it does not detect when a stream ends and does not call AudioQueueStop at any point, so I added a counter to number of buffers added to the queue, and then decrement this counter each time audioQueueOutputCallback is called by the queue. This works fine except if when the buffer count goes to 0, and then I add a call AudioQueueFlush(audioQueue) and then AudioQueueStop(audioQueue, false) I get an error. If I only call AudioQueueReset, it continues to load the buffers again, but plays them out faster then it loads them... getting stuck in a loop and then crashing. 2010-04-14 13:56:29.745 AudioPlayer[2269:207] init player with URL 2010-04-14 13:56:29.941 AudioPlayer[2269:207] did recieve data 2010-04-14 13:56:29.942 AudioPlayer[2269:207] audio request didReceiveData 2010-04-14 13:56:29.944 AudioPlayer[2269:207] >>> start audio queue 2010-04-14 13:56:29.960 AudioPlayer[2269:207] packetCallback count 2 2010-04-14 13:56:29.961 AudioPlayer[2269:207] add buffer: 1 2010-04-14 13:56:29.962 AudioPlayer[2269:207] did recieve data 2010-04-14 13:56:29.963 AudioPlayer[2269:207] audio request didReceiveData 2010-04-14 13:56:29.963 AudioPlayer[2269:207] packetCallback count 1 2010-04-14 13:56:29.964 AudioPlayer[2269:207] add buffer: 2 2010-04-14 13:56:29.965 AudioPlayer[2269:207] packetCallback count 13 2010-04-14 13:56:29.967 AudioPlayer[2269:207] add buffer: 3 2010-04-14 13:56:29.968 AudioPlayer[2269:207] done with buffer: 3 2010-04-14 13:56:29.969 AudioPlayer[2269:207] done with buffer: 2 2010-04-14 13:56:29.974 AudioPlayer[2269:207] done with buffer: 1 So this loop continues some 20 - 30 times and then it crashes. The first time it plays an audio file it queues up the buffers and then plays sound, but doesn't callback to delete them until some 100 or more have been played. Can anyone explain this behavior? I read that there was a limit of 1 audio queue for MP3 playback for the iPhone. Is that still true? If not then I suppose I should use another audio queue for the next mp3 stream. I've had a look through the apple docs but it doesn't explain this in any particular detail. A better insight into this would be great. TIA.

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• AudioQueue recording as float

  - by niklassaers

  Hi guys, I would like to have the result from my recording as a float in the range [0.0, 1.0], alternatively [-1.0, 1.0] because of a bit of math I want to do on it. When I set my recordingformat to be in float, like this: mRecordFormat.mFormatFlags = kLinearPCMFormatFlagIsFloat; I get: Error: AudioQueueNewInput failed ('fmt?') Does this mean the hardware doesn't support recording to floats? If not, how do I set it to record in floats? If so, are there any processor-friendly ways I can convert a signed integer array to a float array? Cheers Nik

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• 2 AudioQueue questions

  - by iter

  I am learning to use AudioQueue. I wish to generate an audio stream programmatically. I have 2 issues that I cannot account for. I am getting audio when I run in the simulator, but not on an iPhone. (Other apps do produce sound on the phone). I get about 20ms-long gaps of silence between buffers. In my testing, I generate an audio buffer on startup and repeatedly enqueue it without modification. I don't spend any processing on filling audio buffers at runtime, not even copying them. Ari.

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• AudioQueueOfflineRender returning empty data

  - by hyn

  I'm having problems using AudioQueueOfflineRender to decode AAC data. When I examine the buffer after the call, it is always filled with empty data. I made sure the input buffer is valid and packet descriptions are provided. I searched and found that a few others have had the same problem: http://lists.apple.com/archives/Coreaudio-api/2008/Jul/msg00119.html Also, the inTimestamp argument doesn't make sense to me. Why should the renderer care where in the audio the beginning of the buffer corresponds to? The function throws an error if I pass in NULL, so I pass in the timestamp anyway.

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• Core Audio on iPhone - any way to change the microphone gain (either for speakerphone mic or headpho

  - by Halle

  After much searching the answer seems to be no, but I thought I'd ask here before giving up. For a project I'm working on that includes recording sound, the input levels sound a little quiet both when the route is external mic + speaker and when it's headphone mic + headphones. Does anyone know definitively whether it is possible to programmatically change mic gain levels on the iPhone in any part of Core Audio? If not, is it possible that I'm not really in "speakerphone" mode (with the external mic at least) but only think I am? Here is my audio session init code: OSStatus error = AudioSessionInitialize(NULL, NULL, audioQueueHelperInterruptionListener, r); [...some error checking of the OSStatus...] UInt32 category = kAudioSessionCategory_PlayAndRecord; // need to play out the speaker at full volume too so it is necessary to change default route below error = AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(category), &category); if (error) printf("couldn't set audio category!"); UInt32 doChangeDefaultRoute = 1; error = AudioSessionSetProperty (kAudioSessionProperty_OverrideCategoryDefaultToSpeaker, sizeof (doChangeDefaultRoute), &doChangeDefaultRoute); if (error) printf("couldn't change default route!"); error = AudioSessionAddPropertyListener(kAudioSessionProperty_AudioRouteChange, audioQueueHelperPropListener, r); if (error) printf("ERROR ADDING AUDIO SESSION PROP LISTENER! %d\n", (int)error); UInt32 inputAvailable = 0; UInt32 size = sizeof(inputAvailable); error = AudioSessionGetProperty(kAudioSessionProperty_AudioInputAvailable, &size, &inputAvailable); if (error) printf("ERROR GETTING INPUT AVAILABILITY! %d\n", (int)error); error = AudioSessionAddPropertyListener(kAudioSessionProperty_AudioInputAvailable, audioQueueHelperPropListener, r); if (error) printf("ERROR ADDING AUDIO SESSION PROP LISTENER! %d\n", (int)error); error = AudioSessionSetActive(true); if (error) printf("AudioSessionSetActive (true) failed"); Thanks very much for any pointers.

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• How to play next file using Audio Queue Services

  - by Stanislav

  What is the right way to play next file using Audio Queue Services? When "play next" button is pressed should I first call AudioQueueStop and then AudioQueuePrime/AudioQueueStart or it is enough to just fill buffers with next file data? The problem is that the latter gives me sound glitches on iPhone.

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• Is there a FSRef in iPhone SDK or is there something that can be FSRef's alternative?

  - by unknownthreat

  The question may sound stupid, but the thing is this: I am learning how to use a Audio Queue, and the example I've taken (aqtest) has been a nice guide for me until I recently found out that aqtest is not for iPhone. (stupid me) I served around the Internet and found out that there is no FSRef for iPhone. If possible, I want to find a way to work around FSRef thinggie. So here comes the question: can I use something else instead of FSRef that exists on the iPhone SDK? Or am I missing something?

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• After interruption, delayed audio route change notifications when recording

  - by Frank Shearar

  My iPhone application requires that I know when a user has/has not plugged in her headphones. That's easy. AudioSessionAddPropertyListener with a callback listening to kAudioSessionProperty_AudioRouteChange. I write logs with NSLog as things happen. User plugs the headphones in? Get a notification, and a line in the gdb console. User unplugs the headphones? Ditto. At the same time I'm sensing the noise level of the environment by starting a recording audio queue. This, too, works great: I can get the mic noise level and listen for audio route changes just fine. What I find is that after an interruption, and I've reactivated the audio session and restored the audio category to kAudioSessionCategory_RecordAudio, the audio route notifications go a bit haywire. When I plug in the headphones, I see no notification. When I unplug the headphones I see BOTH the "plugged in" notification AND the "unplugged" notification, in rapid succession. It's like the "plugged in" notification's delayed and, when the "unplugged" notification arrives, the queue of pending notifications is flushed. What am I doing wrong? How do I correctly restore the audio session to get timeous notifications? EDIT: iPhone OS 3.1.2, running on an iPhone 3G. I'm running a program compiled with the 3.0 SDK (from within XCode 3.1.2).

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• How to start writing out an existing AudioQueue in response to an event?

  - by Halle

  Hello, I am writing a class that opens an AudioQueue and analyzes its characteristics, and then under certain conditions can begin or end writing out a file from that AudioQueue that is already instantiated. This is my code (entirely based on SpeakHere) that opens the AudioQueue without writing anything out to tmp: void AQRecorder::StartListen() { int i, bufferByteSize; UInt32 size; try { SetupAudioFormat(kAudioFormatLinearPCM); XThrowIfError(AudioQueueNewInput(&mRecordFormat, MyInputBufferHandler, this, NULL, NULL, 0, &mQueue), "AudioQueueNewInput failed"); mRecordPacket = 0; size = sizeof(mRecordFormat); XThrowIfError(AudioQueueGetProperty(mQueue, kAudioQueueProperty_StreamDescription, &mRecordFormat, &size), "couldn't get queue's format"); bufferByteSize = ComputeRecordBufferSize(&mRecordFormat, kBufferDurationSeconds); for (i = 0; i < kNumberRecordBuffers; ++i) { XThrowIfError(AudioQueueAllocateBuffer(mQueue, bufferByteSize, &mBuffers[i]), "AudioQueueAllocateBuffer failed"); XThrowIfError(AudioQueueEnqueueBuffer(mQueue, mBuffers[i], 0, NULL), "AudioQueueEnqueueBuffer failed"); } mIsRunning = true; XThrowIfError(AudioQueueStart(mQueue, NULL), "AudioQueueStart failed"); } catch (CAXException &e) { char buf[256]; fprintf(stderr, "Error: %s (%s)\n", e.mOperation, e.FormatError(buf)); } catch (...) { fprintf(stderr, "An unknown error occurred\n"); } } But I'm a little unclear on how to write a function that will tell this queue "from now until the stop signal, start writing out this queue to tmp as a file". I understand how to tell an AudioQueue to write out as a file at the time that it's created, how to set files format, etc, but not how to tell it to start and stop midstream. Much appreciative of any pointers, thanks.

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• How to deal with forward declaration / #import in Cocoa Touch (Objective-C cross C++) correctly?

  - by unknownthreat

  I am trying to write this header file: //@class AQPlayer; //#import "AQPlayer.h" @interface AQ_PWN_iPhoneViewController : UIViewController { AQPlayer* player; } @end AQPlayer is a .mm file written in C++. I tried to make a class forward declaration here, but it complains to me: error: cannot find interface declaration for 'AQPlayer' So I tried to "#import" the header file instead, but it complains something completely off and weird. Here's a slice of the error complained: In file included from /Users/akaraphan/Desktop/SpecialTopic1/AQ_PWN_iPhone/Classes/AQPlayer.h:51, from /Users/akaraphan/Desktop/SpecialTopic1/AQ_PWN_iPhone/Classes/AQ_PWN_iPhoneViewController.h:12, from /Users/akaraphan/Desktop/SpecialTopic1/AQ_PWN_iPhone/Classes/AQ_PWN_iPhoneAppDelegate.m:10: /Developer/Examples/CoreAudio/PublicUtility/CAStreamBasicDescription.h:78: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'CAStreamBasicDescription' /Developer/Examples/CoreAudio/PublicUtility/CAStreamBasicDescription.h:230: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token /Developer/Examples/CoreAudio/PublicUtility/CAStreamBasicDescription.h:231: error: expected '=', ',', ';', 'asm' or '__attribute__' before '==' token /Developer/Examples/CoreAudio/PublicUtility/CAStreamBasicDescription.h:233: error: expected '=', ',', ';', 'asm' or '__attribute__' before '!=' token /Developer/Examples/CoreAudio/PublicUtility/CAStreamBasicDescription.h:234: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<=' token /Developer/Examples/CoreAudio/PublicUtility/CAStreamBasicDescription.h:235: error: expected '=', ',', ';', 'asm' or '__attribute__' before '>=' token /Developer/Examples/CoreAudio/PublicUtility/CAStreamBasicDescription.h:236: error: expected '=', ',', ';', 'asm' or '__attribute__' before '>' token /Developer/Examples/CoreAudio/PublicUtility/CAStreamBasicDescription.h:239: error: expected ';', ',' or ')' before '&' token Am I missing something? Can't I do a forward declaration for this?

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• How to slow down or speed up the playback of audio when using Audio Queue Services?

  - by mystify

  Is that possible? How is this done in theory? Would I simply make a very small buffer packet size and then delay the playback artificially? I assume that's the low-brain way? How could I do it in such a way that the sound is smooth and doesn't suck?

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