Re: OpenMG file formats part 2

Hi,

note that in general I am not at all interested too much in OMG.  What I am
interested in is how files are transfered to the player, and if that
includes an understanding of the OMG format, then I will have to care about
that, but otherwise I would like to stick with free formats like wav and
ogg.  Now, we suspect that files recorded in SP are transfered as raw audio
data + a bit of formatting, and only for LP2/LP4 ATRAC encoded data is
needed.  So eventually we want to have some way to load the proprietary
atrac encoder plugin to do the conversion for LP2/LP4 uploads.  It's not
clear to me if any of this actually includes OMG or not.

On Thu, Jan 16, 2003 at 09:36:53AM -0800, bla bla wrote:
> ---------------------------------
> USB LP2 Transfer to net MD device
> 
> The data bulk transfered via usb to the NetMD device 
> consists of :
> 
> 0-15 	16 bytes
> 
> 	** for LP2 encoding
> 		the first 8 bytes seem always to be
> 		00 00 00 00 00 00 3f 00

The 3f00 was proposed to be a block size.  Does this header only occur once
per file, or every 3f10 bytes?

> 		the second 8 bytes vary from track to 
>                 track but are the same for multiple 
>                 downloads of the same track. A hash or
>                 key of some kind perchance?

If it is only once, it might be the track ID.  You could check this by
sending the following command to the player:

00 18 00 08 00 46 f0 03 01 03 23 ff 10 01 00 $t

where $t is the track number.  If the returned bytes match the bytes in the
header, then it's the hash id, which is used to identify the file in the
database.  You can also see this command and the reply by sniffing the
check in/delete process over USB.

Another possibility is that this is a block key or MAC of some sort.
 
> 	** for Stereo encoding
> 
> 		thefirst 8 bytes appear related to size
>                 of track the second 8 bytes are always
>                  00 unlike for LP2 tracks

Mmh, this is interesting.  It kinda would defeat the hash id idea, although
I am not sure... can you check in stereo recordings back to Jukebox?

Thanks,
Marcus

-- 
`Rhubarb is no Egyptian god.' GNU      http://www.gnu.org    [email protected]
Marcus Brinkmann              The Hurd http://www.gnu.org/software/hurd/
[email protected]
http://www.marcus-brinkmann.de/