![]() The following examples illustrate typical interactions between an MS and an MR.The default video player gets a big upgrade with iOS 16 and iPadOS 16. Invalid Command (0xA1): The command was improperly formatted.Ībsent Attribute (0xA2): The corresponding attribute is empty. it wrote to the Entity Update or Entity Attribute characteristic without subscribing to GATT notifications for the Entity Update characteristic. Invalid State (0xA0): The MR has not properly set up the AMS, e.g. When writing to any characteristic, or when reading the Entity Attribute, an MR may receive the following AMS-specific error codes: If the write is successful, the value of the corresponding entity/attribute pair is loaded as the Entity Attribute characteristic’s value, and can simply be read by the MR at its convenience. The format of an Entity Attribute command is shown below:Īn Entity Attribute command contains the following information:ĮntityID: The entity the subsequent attribute corresponds to.ĪttributeID: The attribute whose value is to be loaded as the characteristic’s value. To retrieve the full value of a specific entity/attribute pair, the MR must first send a command by writing to the Entity Attribute characteristic. This characteristic should ideally only be used if the value of an entity/attribute pair was marked as truncated in the corresponding Entity Update notification, and the MR wants to display more of the associated value. The Entity Attribute characteristic is the characteristic by which an MR can retrieve the extended value of an attribute. Value: A string which corresponds to the value associated with the given attribute. For example, an MR could be informed that the data had to be truncated in order to fit into the GATT notification. The format of a Remote Command request written by the MR is shown below:Ī GATT notification delivered through the Entity Update characteristic contains the following information:ĮntityID: The entity to which the subsequent attribute corresponds.ĪttributeID: The attribute whose value is being sent in the notification.ĮntityUpdateFlags: A bitmask whose set bits give the MR specific information about the notification. The complete list of possible commands is available in the Appendix. This characteristic is also used to report to the MR the list of commands supported by the MS. The Remote Command characteristic is the characteristic by which an MR can send remote commands to affect the playback state of an MS, such as Play, Next Track, Increase Volume, etc. Remote Command: UUID 9B3C81D8-57B1-4A8A-B8DF-0E56F7CA51C2 (writeable, notifiable)Įntity Update: UUID 2F7CABCE-808D-411F-9A0C-BB92BA96C102 (writeable with response, notifiable)Įntity Attribute: UUID C6B2F38C-23AB-46D8-A6AB-A3A870BBD5D7 (readable, writeable)Īny subset of these characteristics can be supported. In its basic form, the AMS exposes three characteristics: ![]() Figure 2-1 Typical operation of the Media Service Service Characteristics The MS will then notify the MR of the initial, current values of all registered entity/attribute pairs, and subsequently notify the MR whenever these values change. The MR may want to know only the value of a specific subset of entity/attribute pairs.įor each entity, the MR must indicate once to the MS which entity/attribute pairs, if any, it wants to monitor. The complete list of attributes for each of these entities is available in Appendix A, Reference. Attributes for this entity include values such as its artist, title, and duration. Attributes for this entity include values such as its size and its shuffle and repeat modes. Queue: The currently loaded playback queue. Attributes for this entity include values such as its name, playback state, and playback volume. ![]() The AMS defines 3 distinct entities, each with a different set of attributes: The MS exposes information about its state by the way of pre-defined entities, each of which exposes its state by the way of pre-defined attributes. As a result, the MR should look for and subscribe to the Service Changed characteristic of the GATT service in order to monitor the potential publishing and unpublishing of the AMS at any time. Due to the nature of iOS, the AMS is not guaranteed to always be present. Only one instance of the AMS may be present on an MS. The Apple Media Service is a primary Bluetooth 4.0 service whose service UUID is 89D3502B-0F36-433A-8EF4-C502AD55F8DC.
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