What is the file format used to store the recordings?

Recordings are stored in a m4a or a wav file, depending on the "Auto compress" setting. This setting is enabled by default, which means m4a files are produced by default. Note that in the free version of Audio Memos you need to make an in app purchase to access this setting. The audio in m4a files is encoded using AAC, in wav files the PCM encoding is used. If the trash can is enabled (it is by default) and recording is done to a m4a file, a second audio file is saved in the trash can in the wav format.

The quality of the recording is determined by its sample rate, the higher the sample rate the higher the quality. The sample rate of memos created inside the app can be any of the following: 8000 Hz, 16000 Hz, 44100 Hz or 48000 Hz (to record at 48000 Hz, you will need an active "Audio Memos Pro+" subscription - the standard "Audio Memos Pro" subscription, or no subscription, will let you record at up to 44100 Hz). You can change the default sample rate in the settings. When you create a new memo using the "+" button, you can specify the sample rate for a single recording. When saving to a compressed format like m4a, Audio Memos will not let you specify a specific bit rate, but increasing the sample rate will increase the bit rate.

The "Audio Memos Pro+" subscription will let you record in stereo. Newer iPhone models have multiple internal microphones and you will be able to record in stereo using the internal microphones. It is also possible to connect an external stereo microphone using the Lightning or USB port.

Note that the hardware you use can limit the available options. The internal microphones are fine, but the best quality will be obtained by using an external microphone. When using a Bluetooth microphone, you are limited to a mono audio stream at 8000 Hz. When recording from an Apple Watch, memos will always be saved as m4a files and the quality is limited to 44100 Hz. Also, the watch does not allow stereo recording.

All the information about a memo, including its position markers and transcription, are stored in the file. Some third party apps can access some of this information. However, only Audio Memos can read it all. Audio Memos will let you export most information as text.

In addition to m4a and wav files, Audio Memos can also playback mp3 files and other common audio formats. However, it will not let you create such files. If you add position markers or a transcription to a memo based on such files, they will not be stored in the file. You can convert existing audio files to m4a or wav files inside Audio Memos if needed.