Importing and Exporting Audio and MIDI : Audio Conversion on Import : Supported Audio File Formats
 
Supported Audio File Formats
WAV or BWF (.WAV) (including support for WAV Extensible and RF64) audio files that are the same sample rate as the project can be imported into a Pro Tools | First project without conversion.
Audio files of the following types can be imported into Pro Tools projects, but are converted to 32-bit Float WAV on import:
AAC audio (including audio with AAC, Mp4, and M4a file extensions)
ACID files
AIFF
MP3
QuickTime (Mac only)
ReCycle (REX 1 and 2) files
Sound Resource (AIFL—Mac only)
*Pro Tools cannot import protected AAC or MP4 files with the .M4p file extension. These files are protected under the rules of digital rights management.