Re: set playback position?

On Thu, Jan 02, 2003 at 07:57:39PM +0000, Pete Bentley wrote:
> Ooof, I only really just sobred up really from a very long New Year's so
> I'm just replying to some of the easier messages tonight, I don't quite
> feel up to staring at big blocks of hex yet... :)

Sure, no problem :)
 
> On Thursday, Jan 2, 2003, at 03:35 Europe/London, Marcus Brinkmann 
> wrote:
> >when I tried out the omg jukebox program, I saw that you could move a
> >slider to set the current playback position in the current track.  I 
> >don't
> >remember having it actually tried out, but if it is possible on a netmd
> >device, has anybody sniffed out what happens in the background on the 
> >USB
> >protocol doing that?  This seems to me the only obvious gap in what 
> >openmg
> >jukebox has and we don't (apart from checking out music of course).
> 
> Yup, we can do this.
> 
> Check out the functions netmd_set_playback_position() and the slightly
> higher level omd_set_playback_position().
> 
> The slider in Xmd behaves exactly the same as the one in Open MG.

Yeah, I just realized that after generating debug output and tracing it :)

I got my incomplete information from netmd_cmd.c where you have:

int netmd_set_playback_track( omd_unit_t *unit, uint16 track )
{
    int rc = -1,
        p1 = 0x0000;

    netmd_cmd_buf_t *cmdbuf =
        netmd_simple_command( unit, 32, "001850 ff010000 WW",
                              p1, track );

But this is dangerous.  If I sent first
"001850 ff010000 0000 0001 00123400"

and then
"001850 ff010000 0000 0001"

the playback position will be at 12:34 in the second track, because the
internal buffer still has the 1234 around and the command does not honor the
too small request length.  I suggest that you always add the time position,
even if it is just 00000000.

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/