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NOTES.md

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Reverse-engineering recording meta-data

The meta-data for written notes is available as XML but the meta-data for recordings is stored in binary files using a proprietary format.

Recordings are stored in e.g:

  • userdata/AYE-AP7-BSH-66/Paper Replay/223/0/sessions/PRS-223277b7e/

The number after "PRS-" is the datetime of recording in hex.

The dir contains two or three files:

  • audio-0.aac
  • session.info
  • session.pages (only present if written notes were taken during recording)

Since session.info does not seem to contain any page information, recordings seem to only become associated with a page if written notes are taken during recording.

audio-0.aac

The .aac file appears to contain no meta-data.

session.info

  • Byte 0 to 7 is always "fa ce 03 00 00 00 00 00"
  • Byte 8 to 15 is the recording start datetime.
  • Byte 16 to 23 is the recording end datetime.
  • Byte 24 to 31 is not known but is also a datetime

session.pages

  • First 6 bytes: Unknown. Probably always "ca be 01 00 00 01".
  • Next 8 bytes: Page identifier
  • Next 8 bytes: Unknown (maybe page area?)
  • Next 8 bytes: Page identifier
  • and so on

Page identifier

An example page identifier looks like 2208.1.12.89

  • Bytes 0 to 2: The first part of the page identifier (e.g. 2208)
  • Bytes 9 to 10: The second part of the page identifier (e.g. 1)
  • Byte 11 and first half of 12: The third part.
  • Second half of 12 and 13: The fourth part.