Deciding whether to run mm-detect

You can choose whether or not to run mm-detect in your car system. The mm-detect service is a convenience feature for automating the delivery of media information to client applications but clients can also obtain this information manually.

By default, mm-detect is running on QNX CAR systems. The mm-detect process is started at boot time by the System Launch Monitor (SLM) service. You can modify the SLM configuration file (/etc/slm-config-all.xml) to prevent mm-detect from being started, as explained in the Preventing mm-detect from running section.

When to use mm-detect

You should use mm-detect if you want to:

simplify client applications so they don't have to constantly scan the device listings directory to detect new devices and then manually load and synchronize the databases for those devices
guarantee that devices have all their media information synchronized as soon as they're inserted
guarantee that the media information for different devices is synchronized in the same order in which those devices are inserted
limit the number of QDB databases kept in memory by automatically unloading device databases when the applications using them terminate

When not to use mm-detect

You should not use mm-detect and instead manage devices from client applications if you want to:

synchronize some but not all media information from an attached device; this can improve performance by avoiding potentially expensive synchronizations of unneeded media content
control the order in which media information for different devices is synchronized, to prioritize synchronizations in response to user actions
defer synchronizing media information from a device until the client application reaches a certain state (for example, its HMI has finished loading)
prevent synchronizing media information from certain types of devices to enforce an application policy or design

Detecting and synchronizing devices manually

To detect device insertions, a client application must constantly monitor the device listings directory (/pps/qnx/mount/). For any new PPS object written into this directory, the client must read the object's id and mount attributes to obtain the device's unique ID and mountpoint. The unique ID is used to construct the database device path and the name of the database configuration object.

Before it can synchronize any media metadata, the client must write the database configuration object to the appropriate PPS directory (/pps/qnx/qdb/config/) to load the database that stores media information for the newly inserted device. The client can then pass the database device path and the mountpoint to the mm-sync service to start synchronizing the device's media metadata.

For the full details on all the steps a client must perform to manually detect and synchronize devices, see the "Synchronizing multimedia content" section of the Multimedia Synchronizer Developer's Guide.

Note: To use Media Player when you're not running mm-detect, you must modify the application to manually detect devices and synchronize their media metadata.