4.24. Commercial frame
This frame enables several competing offers in the same tag by
bundling all needed information. That makes this frame rather complex
but it's an easier solution than if one tries to achieve the same
result with several frames. The frame begins, after the frame ID,
size and encoding fields, with a price string field. A price is
constructed by one three character currency code, encoded according
to ISO 4217 [ISO-4217] alphabetic currency code, followed by a
numerical value where "." is used as decimal separator. In the price
string several prices may be concatenated, separated by a "/"
character, but there may only be one currency of each type.
The price string is followed by an 8 character date string in the
format YYYYMMDD, describing for how long the price is valid. After
that is a contact URL, with which the user can contact the seller,
followed by a one byte 'received as' field. It describes how the
audio is delivered when bought according to the following list:
$00 Other
$01 Standard CD album with other songs
$02 Compressed audio on CD
$03 File over the Internet
$04 Stream over the Internet
$05 As note sheets
$06 As note sheets in a book with other sheets
$07 Music on other media
$08 Non-musical merchandise
Next follows a terminated string with the name of the seller followed
by a terminated string with a short description of the product. The
last thing is the ability to include a company logotype. The first of
them is the 'Picture MIME type' field containing information about
which picture format is used. In the event that the MIME media type
name is omitted, "image/" will be implied. Currently only "image/png"
and "image/jpeg" are allowed. This format string is followed by the
binary picture data. This two last fields may be omitted if no
picture is attached. There may be more than one 'commercial frame' in
a tag, but no two may be identical.
<Header for 'Commercial frame', ID: "COMR">
Text encoding $xx
Price string <text string> $00
Valid until <text string>
Contact URL
<text string> $00
Received as $xx
Name of seller <text string according to encoding> $00 (00)
Description <text string according to encoding> $00 (00)
Picture MIME type <string> $00
Seller logo <binary data>
@author Eric Farng
@version $Revision: 1.4 $