When playing back music from an iPod through the QNX Aviage
Multimedia Suite, there are occasions where the updates to the playback
time are absent for some noticeable period and at different times a
'jitter' in the values (up to around 500ms) can sometimes be observed.
This behavior is simply the result of the communication of
this 'playback time' information between the iPod and the iPod driver.
Specifically note the following about the operation of the software:
- The iPod driver tells the iPod to send notifications
asynchronously, which means that the iPod hardware sends these time
updates whenever it determines is best. In practice the iPod sends a
time update about every 500 msec.
- Each time our iPod driver gets such a notification, io-media
is woken up and it notices the time has changed and delivers this
information to the MME.
- During meta-data (album art) retrieval from the iPod,
notifications relaying playback time are not sent from the iPod
hardware.
- The timing interval set at the MME level (see the API function
mme_set_notification_interval) basically has no effect on the iPod at
all. These notifications will arrive at the user application at the
rate that the iPod sends them out, regardless of what notification
period is specified. This behavior is specific to iPods.
