Analysis of dlna Technology

First, we recommend you to the dlna official website to learn more about the updated information. Http://www.dlna.org/

Dlna (digital living Network Alliance) was established by Sony, Intel, Microsoft, etc. The organization aims to solve the problems of personal PC and consumer appliances, the interconnection between wireless networks and wired networks, including mobile devices, allows unlimited sharing of digital media and content services.Dlna is an industrial standard for data sharing in a home network.

Dlna (Digital Life Network Alliance) is a solution and a standard that everyone can abide by. It is a standardized attempt. The various technologies and protocols it chooses are currently widely used technologies and protocols.

The dlna standard defines the following main product types:

Digital Media Server (DMS)-provides the ability to obtain, record, store, and act as the source of media files. Of course, if necessary, the multimedia file's copyright protection mechanism can also be included. DMS will provide multimedia file servo capabilities, such as the direct access to content and playback capabilities of multiple digital media playback devices. This type of device includes a host box, recording and releasing machine, a personal computer with multimedia server functions, a home theater containing a hard disk, a broadcast receiver, and an image capturing device.

Digital Media Player (DMP)-this device is generally capable of online searching and playing or outputting any media files provided by DMS. Some DMP devices include TVs, home theaters, printers, PDAs, multimedia mobile phones, wireless screens, and some game instrument terminals.

Digital media render (DMR)-This device is a consumer electronic device, either wired or wirelessHome NetworkReceives digital media streams from a computer. Some
DMR integrates display and speakers. Some DMR must be connected to external output devices, such as televisions, active speakers, or stereo systems.

Media Relay Device: transfers or receives media files from the server to another device as a generalization of multimedia formats. For later storage or upload and download.

Digital media controller (DMC)-used as a remote control device, you can find media files that can be played on DMS and specify the action that can be played by a terminal playing the content. This type of device is not only intended for remote control, but also can be used as a smart terminal device with basic operation interfaces.

Digital media printer, the output of printed images can be in the standard format. Basically, the dflat function is similar to that of a traditional USB printer.

Definition of the transport layer of dlna

The dlna standard is based on the middle border layer in a distant network architecture. It mainly enables devices that support the definition of this layer to communicate with each other without any other setting actions, based on the 1.0 dlna standard, Ethernet (ieee803.3u) and Wi-Fi (802.11 a/B/g) are supported. As a standard dlna device, network support is essential. The UPnP standard is used for mutual detection between devices. DMP devices use the UPnP mechanism to search for DMS devices that match each other on the network. After successful connection, they can perform subsequent playback or transmission operations. This action is fully automated, so the user does not need to interfere with it. In terms of media content discovery, the UPnP mechanism is also used. However, in transmission, it is still only supported by the HTTP standard protocol, and later versions will
Transfer protocol.

In terms of multimedia formats that can be transmitted, there are two types of support: required and optional. In terms of required support, the image file format is jpg and the sound format is lpcm, the film format is MPEG-2. In the aspect of selectable format, the graphic file is PNG, GIF and Tiff, the audio compression format is AAC, AC-3, atrac3plus, MP3, wma9 and so on, as to the video compression format, it contains the MPEG-1, MPEG-4, AVC and wmv9 and so on, because the current network transmission speed is still to be broken, so most manufacturers also prefer to support high compression ratio compression format.

Dlna defines its entire application as five functional components. From bottom to top: network interconnection, network protocol, media transmission, device discovery control and management, and media format. See figure 1 and table 1. The following sections describe each function component.

1. network interconnection. It specifies the type and protocol of the connected network. Currently, it mainly includes:
Wired Network: 802.3. I/u
Wireless: 802.11/a/B/g

2. network protocol. It specifies the network protocol used. Currently, it must support IPv4. However, considering the disadvantages of IPv4 such as address space, IPv6 will be supported in the near future. Of course, consider the existing IPv4 applications and devices. In the future, the dual protocol stack that supports both IPv4 and IPv6 at the same time and ensures the interconnection between IPv4 and IPv6 will be affected.

3. Media transmission. It specifies that all dlna devices must support media transmission over HTTP. This will make it a topic to improve the high-speed and secure transmission of large data volumes over the HTTP protocol for a long time in the future. Secure routing, TLS may be a good choice. In addition, IPSec has become a required option in the IPv6 protocol. This solves the security problem to some extent. However, it seems that the use of software for encryption and decryption is always not a correct choice. Because, in real applications, few customers do not mean your speed. Of course, you can also use
Other dedicated media stream transmission protocols of RTP. However, the premise is that you have supported transmission over HTTP.

4. device discovery, control, and media management. This function component is the most important layer. Maybe it is because intel is the initiator of UPnP, so when it initiates dlna again, all UPnP things will of course not be wasted. Is it because UPnP has been in the Protocol phase for a long time, and there are few applications. IDG is an exception, and Intel has initiated dlna again? I don't know. :) At present, it uses UPnP.
Device architecture 1.0 and UPnP AV 1.0 and UPnP printer: 1. This is just the tip of the iceberg in the UPnP forum. It seems that there are quite a lot of UPnP items. I will not detail them here. In short, it achieves device discovery and management through a series of steps and protocols, and also achieves media management through the AV and printer standards defined by the vendor. A lot of concepts and terms will be introduced later :)

5. Media format. This is the last component. It specifies the media format when digital media and content are shared and used. Which must support JPEG, lpcm, and MPEG2. For other optional media formats, see table 2.

In terms of technology alone, dlna is very close to us. However, there are still many commercial factors. Therefore, dlna is still a long way away from us.

The vision of dlna is quite promising, and the current methods used to solve device communication are also quite suitable, but there are still some shortcomings in the Standard Specification of dlna, for example, the digital copyright protection mechanism of multimedia archives is still quite lacking, and the dlna network also lacks security protection capabilities, which can easily cause hacker, virus, Trojan, and other intrusions, the entire dlna environment is worrying. In addition, the network architecture has yet to be enhanced in terms of instant audio and video playback capabilities. Even if the QoS mechanism is added, the overall bandwidth has not been broken through (for example, the new 802.11n standard is passed ), at the same time, it is still quite difficult to achieve multi-party high-definition audio and video playback.