4.19. Audio encryption
This frame indicates if the actual audio stream is encrypted, and by
whom. Since standardisation of such encryption scheme is beyond this
document, all "AENC" frames begin with a terminated string with a
URL containing an email address, or a link to a location where an
email address can be found, that belongs to the organisation
responsible for this specific encrypted audio file. Questions
regarding the encrypted audio should be sent to the email address
specified. If a $00 is found directly after the 'Frame size' and the
audio file indeed is encrypted, the whole file may be considered
useless.
After the 'Owner identifier', a pointer to an unencrypted part of the
audio can be specified. The 'Preview start' and 'Preview length' is
described in frames. If no part is unencrypted, these fields should
be left zeroed. After the 'preview length' field follows optionally a
data block required for decryption of the audio. There may be more
than one "AENC" frames in a tag, but only one with the same 'Owner
identifier'.
<Header for 'Audio encryption', ID: "AENC">
Owner identifier <text string> $00
Preview start $xx xx
Preview length $xx xx
Encryption info <binary data>
@author Eric Farng
@version $Revision: 1.4 $