Thanks. The trouble is, memcpy as a symbol does not show at all in the Time Profiler. (Nor any other symbol in its place.) If you stick a long hard loop on just memcpy() from whatever location to wherever else, it simply does not show up as a sample anywhere. Which then leaves wrapping it or signposts around every place I can conceive of as a potentially hot spot for copying.

@eskimo You said "If you're using NSXPCConnection ....." but isn't that the only way to send an endpoint anywhere? You can't simply archive an endpoint up (with NSKeyedArchiver for instance) and send it anywhere; It'll return an error saying it can only be encoded with NSXPCCoder, which there's no API to use in that way.

I've seen this error pop up for a handful of users in the past year, and I've looked and I see that the sample buffers I am handing to AVAssetWriter also have no duration. It's working well over 99% of the time, so there's some smaaaall edge case that must be occurring. As far as I understand, there's no requirement to ever specify the duration of a frame. @ Media Engineer can you shed some light on what the -17771 error means a bit more specifically?

Since I just spent far too long, once again stuck with this error, for posterity it's worth noting that: For non-interleaved pcm audio the mBytesPerFrame value should be the number of bytes for a single channel. The header comment for mBytesPerFrame itself is not very clear, but you can see this in FillOutASBDForLPCM() in CoreAudioBaseTypes.h for example. This ends up failing check #10 above.

You're not alone. :\ System Status suggests there was a problem yesterday, but not one today (at least yet). https://developer.apple.com/system-status/