问题
AAC is an audio codec which was "Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates." (AAC on Wikipedia).
However, similarly to MP3, parts of the AAC codec are patented, which means you can't simply use these codecs in all situations without making sure you are licensed to do so.
This is also true if you developed your own encoder or decoder. This is because writing an own encoder or decoder frees you only from copyright issues and software licenses (because you hold the copyright), but it doesn't free you from requirements imposed on you by patents.
Do I need to acquire a license for my iPhone app, which can encode and/or decode AAC files?
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回答1:
As long as you use the integrated encoders and/or decoders, you do not need to acquire your own license for using the AAC codec on the iPhone.
I've contacted vialicensing.com about this and they replied:
If your app uses the integrated decoder of the iPhone, no license is required. If however, you are providing a separate decoder as part of your product you will need to obtain a license for every unit shipped.
Moreover, also about encoders:
that also applies to recording using the integrated encoder of the iPhone. Providing an encoder and/or decoder is what requires the patent license. If a product relies on the integrated encoder/decoder in a device it is the device brand owner which is required to fulfill the license obligation.
Still, because this is a legal topic rather than a programming topic, you should contact via licensing if you have any uncertainties about your specific app.
来源：https://stackoverflow.com/questions/21912715/aac-license-required-for-iphone-app