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Audio glitches with aach on iPhone when locked

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Audio glitches with aach on iPhone when locked

Subject: Audio glitches with aach on iPhone when locked
From: Neil Mix <email@hidden>
Date: Wed, 11 Mar 2009 11:20:27 -0500

I've been noticing glitches (very short gaps or stutters) in AAC+ (aach) audio on the iPhone, only when the device is locked. Based on Bill's note from yesterday mentioning that I/O sizes change when the device is dimmed, I decided to peruse the docs once more and discovered the kAudioQueueProperty_DecodeBufferSizeFrames property of AudioQueue. I changed it from the default (66150) to 102400, and lo and behold it looks like the glitches have decreased dramatically in number or gone away.

I'm fine with this as a solution, but it feels a bit "magic" to me -- I don't *know* that the problem is fixed. I'm wondering if someone can fill in some knowledge gaps for me:

- is this expected behavior? If yes, why doesn't this happen with AAC or MP3 audio?

- is there any way to calculate the correct value for this property, or is it a judgement call?

- the docs say that "A larger buffer provides more reliability and better long-term performance" (yes!) "at the expense of memory" (understood) "and decreased responsiveness in some situations." Decreased responsiveness in what way -- latency before audio starts? Of the audioQueue to play/pause commands? Of the device in general? What's my downside risk if this buffer gets too big? _______________________________________________ Do not post admin requests to the list. They will be ignored. Coreaudio-api mailing list (email@hidden) Help/Unsubscribe/Update your Subscription: This email sent to email@hidden Follow-Ups: Re: Audio glitches with aach on iPhone when locked From: Doug Wyatt <email@hidden> Prev by Date: Re: Multiple ExtAudioFileRefs pointing to the same file Next by Date: Re: Slight audio glitch when pressing the sleep/wake button on iPhone Previous by thread: Use of AAC Next by thread: Re: Audio glitches with aach on iPhone when locked Index(es): Date Thread