- What is the focus of the functionality that will be controlled by the HAVi specification?
- How does the device control model in HAVi differ from that of IEEE-1394?
- What are the merits of using DCM/FCM for controlling devices? (Doesn't it introduce overhead)?
- What is the advantage to users of HAVi's remote User Interface capability?
- How are applications installed on HAVi devices?
- Do IAV and FAV devices contain their own DCMs?
- Is a single IAV or FAV device capable of controlling multiple devices?
- How do Intermediate AV (IAV) devices or Full AV (FAV) devices get access to a particular device?
- Can an FAV device contain an embedded DCM or does it only upload DCMs?
- How does a DCM for a particular device get installed on an IAV or FAV?
- If there are multiple FAV devices, is it possible that the DCM of a BAV device could be loaded by more than one FAV device, creating a conflict?
- If a DCM/FCM in an FAV device disappears (due to damage of the device) can this DCM/FCM be moved to another FAV device on the network?
- Why is the DCM stored in a BAV device, instead of simply indicating a URL where it can be downloaded from?
- Since the FAV is the center for three types of processing [audio (AV center); video (TV); and data (PC)], won't these three processes require a large amount of processing capability and burden the FAV?
- Which input data formats are converted into meaningful data formats in a HAVi environment?
- What security measures are provided to protect the HAVi network from unauthorized access via outside connections (telephone lines, antenna wires, etc.)?
- In addition to the digital authentication certificate, what other protection is available?
- How does HAVi handle marking devices such as printers?
- What are the resolution requirements and limitations for the GUI display elements for buttons, widgets, etc?
1. What is the focus of the functionality that will be controlled by the HAVi specification?
HAVi specifically focuses on the transfer of digital audio/video (AV) content between HAVi devices, as well as the processing (rendering, record, play back) of this content by these devices.
2. How does the device control model in HAVi differ from that of IEEE-1394?
In IEEE-1394, an application on one 1394 device sends the AV/C command (or data) directly to another 1394 device via the 1394 device drivers (which are on both devices).
In HAVi, the HAVi application sends the command (or data) to the DCM (or FCM) that represents the target device (or functionality of the target device), and the DCM/FCM converts the command into a format that the target device can understand. It then sends this command to the target device.
3. What are the merits of using DCM/FCM for controlling devices? (Doesn't it introduce overhead)?
The merits of using DCM/FCM are as follows:
- The home-networking application only sends a HAVi-standardized command (such as "Play") to the DCM/FCM, and it does not need to know the internal hardware/software of the target device. This simplifies application development.
- Future Proofing: Compatibility with future devices/functionalities is guaranteed, since using new or upgraded devices or functionalities requires only that the new or upgraded DCM be uploaded, installed and run.
When using DCM/FCM, minor overhead is involved, however, this overhead is relatively insignificant, especially in view of ever faster and more affordable CPU's, memory, etc. This overhead is clearly outweighed by the ease of developing applications, which will reduce time-to-market of new products.
4. What is the advantage to users of HAVi's remote User Interface capability?
A remote User Interface enables a user to interact with an application via any HAVi device in the network that has a display. For example, a user could program the VCR in the living room from his TV in the bedroom; again, regardless of which manufacturer made either device.
Another important advantage for users is that display devices need not take part in the application themselves or even be aware of the functionality behind the User Interface shown by an application. The devices simply offer their display to other applications. This allows devices from different manufacturers to access functionality that is not standardized by HAVi. This greatly improves the flexibility of HAVi, since not every application- or device-specific feature has to be standardized. Therefore, device manufacturers or independent software vendors can develop these features and bring them to market quickly and efficiently.
5. How are applications installed on HAVi devices?
There are several possibilities, and HAVi does not require or mandate any specific procedure. Some options are:
- Applications can be embedded in the HAVi device at the time of manufacture.
- Applications can be distributed on a removable medium (diskettes, CD-ROM, etc.) enabling a user to install applications onto HAVi devices.
- Applications can be placed on a web site from where a HAVi device can download and install them. This requires that the HAVi device have either direct access to the Internet, or direct access to another HAVi device that has the web access APIs (as defined by HAVi).
The factor that determines if applications will run on a particular device depends on whether they are native applications or Java Applications, as well as the type of HAVi device accessed (FAV or IAV, as defined elsewhere in this FAQ).
6. Do IAV and FAV devices contain their own DCMs?
If the FAV or IAV device is designed to be controlled from other IAV and FAV devices, it can contain its own DCM/FCMs.
7. Is a single IAV or FAV device capable of controlling multiple devices?
Yes, one IAV or FAV device can control multiple devices via multiple DCMs (for each target device).
8. How do Intermediate AV (IAV) devices or Full AV (FAV) devices get access to a particular device?
DCMs (Device Control Modules) are installable Software Elements on an IAV or FAV that are intended to control specific devices (HAVi or non-HAVi devices). There are several methods to access a DCM . (HAVi does not require or mandate any specific procedure). Some of the possible approaches are:
- DCMs may be embedded in an IAV or FAV at the time of manufacture. This will most likely include a DCM for the device to make itself controllable by other HAVi devices. (For example, a set-top box could contain a DCM that implements the HAVi defined tuner APIs to enable other HAVi devices to select a TV program). However, a HAVi device may also contain DCMs for a variety of devices other than itself. The vendor would determine whether or not a HAVi device had this capability.
- DCMs may be distributed on removable media (diskettes, CD-ROM, etc.) allowing the consumer to install DCMs onto HAVi devices.
- HAVi devices may download and install DCMs from a web site. This requires that the HAVi device have either direct access to the Internet, or direct access to another HAVi device that has the web access APIs (as defined by HAVi).
For a BAV (Base AV) device, the DCM must either be uploaded from the BAV device itself, or the BAV device must contain a URL (Uniform Resource Locator) indicating where its DCM is located on the Internet.
9. Can an FAV device contain an embedded DCM or does it only upload DCMs?
For controlling other devices, a FAV device can contain embedded DCM(s) for target device(s), and it can also upload DCMs from BAV devices. In addition, an FAV device can contain its own DCM to be controlled from other devices.
10. How does a DCM for a particular device get installed on an IAV or FAV?
In principle there can be multiple DCMs for one particular device present in a HAVi network. When a device is inserted or powered up in the network, all IAVs and FAVs will check to determine if they have a DCM for that device, then negotiate with each other for which DCM will be installed for the device, and upon which IAV or FAV it will be installed.
Only one DCM can be installed at any time for each particular device. This selection and installation process is controlled by the DCM Managers on the IAVs and FAVs, however, HAVi offers several user definable preferences settings for this process.
11. If there are multiple FAV devices, is it possible that the DCM of a BAV device could be loaded by more than one FAV device, creating a conflict?
No, the HAVi specification provides for this by specifying that when BAVs are detected by FAV devices on the network, the DCM managers on the FAVs will negotiate among themselves as to which FAV device will load the DCM onto the BAV.
12. If a DCM/FCM in an FAV device disappears (due to damage of the device) can this DCM/FCM be moved to another FAV device on the network?
Yes, in the case of a BAV device which has an uploadable DCM written with Java bytecode. It is possible to move the DCM to another FAV device simply by uploading the BAV's DCM to the new FAV device. However, if this FAV device only contains the DCM in embedded form, for the LAV device, then the DCM cannot be moved to another FAV device.
13. Why is the DCM stored in a BAV device, instead of simply indicating a URL where it can be downloaded from?
While downloading the DCM from a URL does have some benefits (such as eliminating the need for a DCM to be embedded in a device and having the ability to download the latest DCM), there are some drawbacks to having the DCM only available from a URL:
- Each time the device is connected, its DCM would have to be downloaded from the URL and installed. This takes time due to the (usually slow) Internet connections, forcing the user to wait for the download.
- To run the downloaded DCM, an FAV device containing Java Virtual Machine is usually required, forcing the end-user to purchase a relatively costly FAV device.
- If the URL cannot be accessed for some reason (network connection problems, etc.) then the device's DCM cannot be downloaded and thus it cannot be controlled.
14. Since the FAV is the center for three types of processing [audio (AV center); video (TV); and data (PC)], won't these three processes require a large amount of processing capability and burden the FAV?
HAVi has been designed so that the HAVi software elements such as DCM Manager, Resource Manager, etc., in different devices cooperate to reduce load on a single device. For example, other than the presence of Java VM, IAV devices are also capable of being FAV devices.
15. Which input data formats are converted into meaningful data formats in a HAVi environment?
- Image-data (DV, MPEG2/1, etc.)
- Audio-data (PCM, MPEG, AC-3, ATRAC, etc.)
- Analog
16. What security measures are provided to protect the HAVi network from unauthorized access via outside connections (telephone lines, antenna wires, etc.)?
The basic security mechanism is a digital authentication certificate that will be attached to all downloadable DCMs. This digital certificate will be attached to all downloadable DCMs, and the provider of the DCM can only obtain the certificate if they assert that the DCM is HAVi compliant.
The confirmation of this digital certificate, combined with applications written to check for this certificate, will establish a "trusted" or "untrusted" test that the DCM must pass before being authorized for download onto a HAVi device.
While this reduces the risk of intentionally malicious DCMs, it may be that a DCM has unintentional errors. If this turns out to be the case, and the provider of a DCM wants to replace a DCM that is in the field they may:
- Provide a proprietary mechanism for patching/upgrading the BAV.
- Refer to the DCM via a URL in the BAV.
17. In addition to the digital authentication certificate, what other protection is available?
Java bytecode verifier is used.
18. How does HAVi handle marking devices such as printers?
Currently, HAVi does not handle marking devices such as printers. However, these can be handled by creating FCM APIs for printers and opening/licensing them to HAVi application writers.
19. What are the resolution requirements and limitations for the GUI display elements for buttons, widgets, etc?
HAVi does not demand high-resolution displays for a display GUI. HAVi has flexible output device models that allow devices to display text only, graphics and text, or rich graphics. If the target device has limited graphics, or text-only capability, then that is what will be displayed.
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