Wireless HD-video and sound transmission over Wi-Fi, digest - spring'12
Dear reader, I welcome you to the open spaces of Habrahabr, this unique platform for the exchange of experience and opinions. In this post I want to return to the topic of wireless transmission of high-quality video and sound without the use of wires, using various technologies. In doing so, I will consider the aspect of wireless transmission more broadly than just the network “sharing” of movies and music. A necessary and sufficient condition for the mention of a particular technology will be the ability to transfer the desktop screen and the operation of any programs, with support for a resolution not lower than 1280x720 (HD-ready / 720p).
Since quite a long time has passed since my previous publications (relative to this industry, which is developing at an explosive pace), and the N-th number of innovations has appeared, I would like to share their descriptions.
No matter how strange this may seem, a lot of HD video and sound transfer technologies (hereinafter HD video and sound means not just music and movie files, but real-time and high-resolution programs) and they are all The current note will not fit. And since any technical mind, the majority on our resource, requires accuracy and categorical, then if the topic turns out to be interesting, at the end I will summarize all the notes with a general sign, which will bring all wireless standards and their numerous characteristics. As I noted earlier, the reader’s brain, though technical, but not rubber as the first capital, and in order to limit the phenomenon of many books (Lord, although the article turned out to be huge!), We will start with the most affordable technology of wireless video and audio transmission - Wi -Fi.
So, before starting the review of specific technologies for transmitting video and sound over Wi-Fi, we must understand the general advantages and disadvantages caused by such use of Wi-Fi.
')
On it not numerous, but significant advantages, come to an end.
Common words are said, now we went on specific technologies (sorted by accessibility):
This is the easiest way and, probably, the most widespread technology of transferring movies and music over LAN / Wi-Fi today. Many will be surprised: he himself said that the “shared” technologies with files are dismissed? - Easy, colleagues, I'll explain everything now.
The very principle of DLNA lies in the fact that a sever server is launched on a computer, in which a folder with movies and music opened for viewing is registered. The (smart) TV itself, or some “okolotvshny” intermediary, such as SetTop box or tuner or game console, connects (under your strict guidance) via Wi-Fi to the shared folder and outputs content from it to HDTV.
Now the question for sufferers: how to transfer the desktop on DLNA? Answer: capturing (capture) a real-time screen to a file (for example, VLC's), which is shared and opened by a DLNA TV / set-top box. Note: since compression and transmission will be configured in a “home-made” way, don’t expect anything good from it - a 12-second delay, no cursor is visible and there is no sound (checked personally and found in Google on request “DLNA desktop”).
And in general, in our rapidly changing IT world, having a server on your PC and forcing additional client devices to connect to it is not at all kosher. The wireless transmission should look like this: a button was pressed on the computer - “connect TV”, a picture appeared on the TV. Without dreary settings and file selection via the remote or joysticks or other bad ones.
So, the main, derived by me and supporting, paradigm for wireless video / audio transmission - the transmitter must be the client to the receiver, but not vice versa!
There is a violation of the paradigm derived above: to receive video and sound from your computer, the server of one of the remote desktop protocols must be running on it, and the client must be near the TV set (read, another fucking electricity box), which should initiate a connection to your computer is not without the help of muddy manipulations (even if it is the launch of a script with a wireless mouse / keyboard). Yes, and the performance here will be from low to very low because of the "handicraft" method.
On the other hand, this is an outlet for low-budget solutions, when the TV is enough to put only the old computer and optimally configure it.
An interesting class of glands, very little common, but existing. Imagine the following picture: in addition to the Internet, you can connect a TV or monitor with speakers to a Wi-Fi access point and use a small utility to display a picture and sound from a PC to these TV / monitor / speakers. This is the scheme of the wireless presentation server. Roughly speaking, this is an access point / wi-fi router, which in addition to the Internet provides your PC / smartphone with an image and sound output device.
In most cases, when you want to transfer through the presentation server no longer the desktop and programs, but the movie and music, the player is built into the transfer utility, opening which your media files are transferred to the access point already via the DLNA protocol, ie you don’t look at the full screen only. When the movie / music ends, the application automatically switches back to the desktop image transfer mode.
At different times, similar access points were released by Dlink, Planet, Edimax, ViewSonic, and other less famous authors. But Awind has achieved the best result in transmission quality and reduced latency with its McTivia product: it is a small 802.11n access point with an HDMI output (maximum resolution is 1280x720, stereo sound). There is also an ethernet input for providing general access to the network (by the way, the connection between the utility and the access point also works over the LAN); and there is also a USB input for the keyboard / mouse so that you can control the computer on which the utility is running remotely. Since the transfer protocol is noticeably optimized compared to its predecessors, we managed to remove the DLNA part and launch video and sound directly, through any player. At the same time, the utility has several quality modes: with the lowest quality, respectively, the lowest latency is for presentations and other interactivity; with the highest quality, the delay is almost a second, but this is for the movie, where they run it in good quality and don’t touch it, so the delay is not annoying.
The abundance of clients to McTivia for different platforms is surprising: there are clients for both MacOS and for different versions of Windows, and even clients (albeit without sound) for iOS and Android. Unfortunately, Linux, in my opinion - unfairly, cheated.
The most interesting thing is that Awind cooperates with the firm mirrorop, which writes software for smartphones and communicators. So mirrorop also writes software versions of presentation servers for different platforms: instead of McTivia, you can transfer a picture to a tablet and a smartphone, which can also be connected to a TV. But here, alas, there will no longer be such performance as that of iron.
Colleagues shot a Russian-language video about McTivia:
Itel (so far) is a key chip maker in the PC and laptop processor market, and, like any self-respecting industrial giant, has a number of its ups and downs slipped in by huge research centers and research laboratories it contains around the world. There is a goodadvertising article on the habre about WiDi , which, by the way, prompted me to break out this sim manifesto.
In short, Intel is increasingly connecting all the components of a modern computer, such as a CPU, GPU and Wi-Fi adapter, as part of its single platform, they can afford to produce software, strongly sharpened for this platform, because it is massive.
WiDi works only on second-generation Core processors and only with Intel's Wi-Fi chip. Compression of the stream for transmission is helped by the graphics adapter built into the processor's crystal.
To receive the signal on the TV, a special WiDi set-top box is used, the quality is FullHD 1080p, but so far only 30fps. The sound is multichannel. Delay - from 20ms and more (usually - more). To connect to the WiDi-receiver, a special technology from Intel is used, like multiple Wi-Fi p2p, ie your PC can be connected to the WiDi-adapter simultaneously with the Internet connection via an access point.
As an alternative to the receiver, Intel promises to embed technology in modern televisions (several prototypes, including those from Samsung, were already shown at the beginning of the year). Or, even more interesting: they offer to send / receive content via DLNA slyly (as proof, C32012 showed PS3 and Xbox360, which receive a signal from a laptop with WiDi). Only it is not clear whether it will be necessary to install any software from Intel on the console. Most likely - yes, but this is not very problematic.
The apple company started it all a long time ago from an access point to which you can connect speakers (AirPort Express) and play music from the monstrous iTunes iTunes nightly, while iTunes from Windows could also send. Then it was also expanded in the broadcast on AppleTV (all technology was based on DLNA in the apple wrapper, nothing complicated). Then i'gadgets and AirPlay technology appeared: now it became possible to send both video and music on AppleTV and only music on AirPort Express from the built-in i'adz. The keen eye will notice that while it still looks like the good old DLNA in apple skins (although there is software from rogueamoeba, it’s called airfoil, which can output the sound of any application to Apple receivers, and the computers themselves turn into AirPlay receivers).
But with the advent of dual-core iPhones and iPads, everything has changed. Now the power is enough and one processor core can be responsible for the main tasks, fully complying with the characteristics of the previous generation, and the second core can compress everything that happens on the screen and in the speakers, and send it to AppleTV. So, AirPlay has grown to a full-fledged transfer of the desktop of mobile devices to a TV (though only at a resolution of 1280x720, but still ahead).
And what about ordinary poppies? Did Apple abandon its computers to please smartphones and tablets? As it turned out - not at all, in the upcoming updated Mac OS - Mountain Lion, which is scheduled for release in summer'12, there appeared such a long-awaited AirPlay function, which is deeply integrated into the system and recognizes the TV connected to AppleTV, just like the second screen. With it, you can make any settings, as well as with a monitor connected via a wire, it is very convenient.
Rumor has it that an updated version of AppleTV should come out soon, most likely it will be possible to accept not only HD-Ready (720p), but FullHD (1080p) as well.
Since Apple's devices have now achieved an incredible rise in their popularity, a huge number of accessory manufacturers have begun to build AirPlay audio support into their speakers. Most likely something similar will start happening soon for the video.
Transmission of HD-video and sound via Wi-Fi is now in the stage of the most active development. And the constant news about Intel WiDi and Apple AirPlay is proof of that. Qualcomm (with Atheros’s daughter) and Cavium are working on a similar project: the first promises high power and speed from its mobile platform, and the second - its implementation of the wireless HD signal transmission protocol, and as you know, Qualcomm is not the last manufacturer on mobile platform market.
In summary, everyone is trying to make the solution integrated using an existing hardware platform and a Wi-Fi adapter, but as you can see, even the most recent implementations have not yet reached the absolute HD quality and very low latency. They will develop and improve as new, more powerful equipment becomes available.
If it will be interesting, then we will talk about specialized standards with individual transmitters that provide imitation of an HDMI cable in all respects.
PS: No matter how hard the guys tried to compress the material, but as they say, you can’t say otherwise. Write whether to write a sequel about other technologies. Also I will be glad to answer any questions in the comments.
Since quite a long time has passed since my previous publications (relative to this industry, which is developing at an explosive pace), and the N-th number of innovations has appeared, I would like to share their descriptions.
A few words before the start
No matter how strange this may seem, a lot of HD video and sound transfer technologies (hereinafter HD video and sound means not just music and movie files, but real-time and high-resolution programs) and they are all The current note will not fit. And since any technical mind, the majority on our resource, requires accuracy and categorical, then if the topic turns out to be interesting, at the end I will summarize all the notes with a general sign, which will bring all wireless standards and their numerous characteristics. As I noted earlier, the reader’s brain, though technical, but not rubber as the first capital, and in order to limit the phenomenon of many books (Lord, although the article turned out to be huge!), We will start with the most affordable technology of wireless video and audio transmission - Wi -Fi.
Wi-Fi transmission
So, before starting the review of specific technologies for transmitting video and sound over Wi-Fi, we must understand the general advantages and disadvantages caused by such use of Wi-Fi.
Virtues
- Most computers (and not only them) are already equipped with Wi-Fi - no separate transmitter is needed, everything that is needed for broadcasting is already available;
- It can be used not only for wireless transmission of video and sound, but also to gain access to the network;
- Because of the widespread occurrence, the attention of the largest participants in the IT industry, such as Intel, Apple, Qualcomm, Cavium Networks, is attracting attention.
')
On it not numerous, but significant advantages, come to an end.
disadvantages
- Wireless video and audio transmission clogs / takes away a portion of the air from the direct destination of the Wi-Fi access network;
- The work of your network can interfere with the surrounding Wi-Fi networks, which every year becomes more and more;
- In order for HD video and sound to fit into the Wi-Fi bandwidth, it is necessary to “pack” them with the appropriate codec (in most cases - h.264), which results in (generally speaking, insignificant) quality loss;
- The need for compression creates a need for software that can work on one, but not on another OS / platform;
- Because of the need for software, it will work only on a PC-shaped gland - the transmission from gaming (Xbox360, PS3) / satellite (NTV +) / television (BeelineTV, Akado) prefixes disappears (with some exceptions where the light came off the wedge and on the console there is the ability to run third-party software and the software itself is written for it, the probability of which is 0.01%, and independent of the computer transmitters are not in a hurry to release);
- The work of the content compression codec requires hardware resources, though considerable ones;
- Because of the work of the codec, the signal transmission is delayed by the time delta, which goes into compression (from 20 ms to 2 seconds, depending on the distance and power of the compression equipment).
Common words are said, now we went on specific technologies (sorted by accessibility):
DLNA
This is the easiest way and, probably, the most widespread technology of transferring movies and music over LAN / Wi-Fi today. Many will be surprised: he himself said that the “shared” technologies with files are dismissed? - Easy, colleagues, I'll explain everything now.
The very principle of DLNA lies in the fact that a sever server is launched on a computer, in which a folder with movies and music opened for viewing is registered. The (smart) TV itself, or some “okolotvshny” intermediary, such as SetTop box or tuner or game console, connects (under your strict guidance) via Wi-Fi to the shared folder and outputs content from it to HDTV.
Now the question for sufferers: how to transfer the desktop on DLNA? Answer: capturing (capture) a real-time screen to a file (for example, VLC's), which is shared and opened by a DLNA TV / set-top box. Note: since compression and transmission will be configured in a “home-made” way, don’t expect anything good from it - a 12-second delay, no cursor is visible and there is no sound (checked personally and found in Google on request “DLNA desktop”).
And in general, in our rapidly changing IT world, having a server on your PC and forcing additional client devices to connect to it is not at all kosher. The wireless transmission should look like this: a button was pressed on the computer - “connect TV”, a picture appeared on the TV. Without dreary settings and file selection via the remote or joysticks or other bad ones.
So, the main, derived by me and supporting, paradigm for wireless video / audio transmission - the transmitter must be the client to the receiver, but not vice versa!
Virtues
- Built into most modern TV technology.
disadvantages
- Poor performance when transferring desktop / programs;
- Difficulty in configuration due to the role exchange client <-> server.
Remote Desktop or remote desktop (Radmin, RDP, VNC, Citrix ICA, Teamviewer, X.org, etc.)
There is a violation of the paradigm derived above: to receive video and sound from your computer, the server of one of the remote desktop protocols must be running on it, and the client must be near the TV set (read, another fucking electricity box), which should initiate a connection to your computer is not without the help of muddy manipulations (even if it is the launch of a script with a wireless mouse / keyboard). Yes, and the performance here will be from low to very low because of the "handicraft" method.
On the other hand, this is an outlet for low-budget solutions, when the TV is enough to put only the old computer and optimally configure it.
Virtues
- Any old PC or even a smartphone with TV output is sufficient for operation.
disadvantages
- The same as in DLNA, although the performance of the desktop and higher.
Wireless presentation servers (wireless presentation gateway)
An interesting class of glands, very little common, but existing. Imagine the following picture: in addition to the Internet, you can connect a TV or monitor with speakers to a Wi-Fi access point and use a small utility to display a picture and sound from a PC to these TV / monitor / speakers. This is the scheme of the wireless presentation server. Roughly speaking, this is an access point / wi-fi router, which in addition to the Internet provides your PC / smartphone with an image and sound output device.
In most cases, when you want to transfer through the presentation server no longer the desktop and programs, but the movie and music, the player is built into the transfer utility, opening which your media files are transferred to the access point already via the DLNA protocol, ie you don’t look at the full screen only. When the movie / music ends, the application automatically switches back to the desktop image transfer mode.
At different times, similar access points were released by Dlink, Planet, Edimax, ViewSonic, and other less famous authors. But Awind has achieved the best result in transmission quality and reduced latency with its McTivia product: it is a small 802.11n access point with an HDMI output (maximum resolution is 1280x720, stereo sound). There is also an ethernet input for providing general access to the network (by the way, the connection between the utility and the access point also works over the LAN); and there is also a USB input for the keyboard / mouse so that you can control the computer on which the utility is running remotely. Since the transfer protocol is noticeably optimized compared to its predecessors, we managed to remove the DLNA part and launch video and sound directly, through any player. At the same time, the utility has several quality modes: with the lowest quality, respectively, the lowest latency is for presentations and other interactivity; with the highest quality, the delay is almost a second, but this is for the movie, where they run it in good quality and don’t touch it, so the delay is not annoying.
The abundance of clients to McTivia for different platforms is surprising: there are clients for both MacOS and for different versions of Windows, and even clients (albeit without sound) for iOS and Android. Unfortunately, Linux, in my opinion - unfairly, cheated.
The most interesting thing is that Awind cooperates with the firm mirrorop, which writes software for smartphones and communicators. So mirrorop also writes software versions of presentation servers for different platforms: instead of McTivia, you can transfer a picture to a tablet and a smartphone, which can also be connected to a TV. But here, alas, there will no longer be such performance as that of iron.
Colleagues shot a Russian-language video about McTivia:
Virtues
- It works on almost any platform, including mobile OS;
- Optimized quality, acceptable with an average computer;
- Software partially uses a GPU to speed up compression;
- It is possible to control a remote computer directly from the access point (USB keyboard / mouse);
- It can also be used simultaneously as an access point for network distribution.
disadvantages
- The weaker the computer, the worse the performance;
- The video is limited to 1280x720 resolution, there is no 3D speech, the sound is only stereo;
- Quite a big delay, there may be problems with games;
- You need to spend money on the purchase of WPG-equipment.
Intel WiDi
Itel (so far) is a key chip maker in the PC and laptop processor market, and, like any self-respecting industrial giant, has a number of its ups and downs slipped in by huge research centers and research laboratories it contains around the world. There is a good
In short, Intel is increasingly connecting all the components of a modern computer, such as a CPU, GPU and Wi-Fi adapter, as part of its single platform, they can afford to produce software, strongly sharpened for this platform, because it is massive.
WiDi works only on second-generation Core processors and only with Intel's Wi-Fi chip. Compression of the stream for transmission is helped by the graphics adapter built into the processor's crystal.
To receive the signal on the TV, a special WiDi set-top box is used, the quality is FullHD 1080p, but so far only 30fps. The sound is multichannel. Delay - from 20ms and more (usually - more). To connect to the WiDi-receiver, a special technology from Intel is used, like multiple Wi-Fi p2p, ie your PC can be connected to the WiDi-adapter simultaneously with the Internet connection via an access point.
As an alternative to the receiver, Intel promises to embed technology in modern televisions (several prototypes, including those from Samsung, were already shown at the beginning of the year). Or, even more interesting: they offer to send / receive content via DLNA slyly (as proof, C32012 showed PS3 and Xbox360, which receive a signal from a laptop with WiDi). Only it is not clear whether it will be necessary to install any software from Intel on the console. Most likely - yes, but this is not very problematic.
Virtues
- Works on all PCs with a modern Intel platform;
- The software is optimized for the platform, the power of the GPU is actively used;
- Constant updates, high signal quality (FullHD + 5.1), low latency;
- The emergence of receivers built into TV and Sat / IPTV set-top boxes and broadcast through the ubiquitous DLNA.
disadvantages
- Only hardware from Intel - CPU Core, runs on an integrated video card, you need an Intel Wi-Fi chip;
- Works only under Windows;
- On the mobile platform only in the prototype stage on the Intel platform (Cedar Trail), on the ARM is missing;
- There is still a noticeable delay in signal transmission;
- It is still required to buy a separate WiDi receiver.
Apple AirPlay
The apple company started it all a long time ago from an access point to which you can connect speakers (AirPort Express) and play music from the monstrous iTunes iTunes nightly, while iTunes from Windows could also send. Then it was also expanded in the broadcast on AppleTV (all technology was based on DLNA in the apple wrapper, nothing complicated). Then i'gadgets and AirPlay technology appeared: now it became possible to send both video and music on AppleTV and only music on AirPort Express from the built-in i'adz. The keen eye will notice that while it still looks like the good old DLNA in apple skins (although there is software from rogueamoeba, it’s called airfoil, which can output the sound of any application to Apple receivers, and the computers themselves turn into AirPlay receivers).
But with the advent of dual-core iPhones and iPads, everything has changed. Now the power is enough and one processor core can be responsible for the main tasks, fully complying with the characteristics of the previous generation, and the second core can compress everything that happens on the screen and in the speakers, and send it to AppleTV. So, AirPlay has grown to a full-fledged transfer of the desktop of mobile devices to a TV (though only at a resolution of 1280x720, but still ahead).
And what about ordinary poppies? Did Apple abandon its computers to please smartphones and tablets? As it turned out - not at all, in the upcoming updated Mac OS - Mountain Lion, which is scheduled for release in summer'12, there appeared such a long-awaited AirPlay function, which is deeply integrated into the system and recognizes the TV connected to AppleTV, just like the second screen. With it, you can make any settings, as well as with a monitor connected via a wire, it is very convenient.
Rumor has it that an updated version of AppleTV should come out soon, most likely it will be possible to accept not only HD-Ready (720p), but FullHD (1080p) as well.
Since Apple's devices have now achieved an incredible rise in their popularity, a huge number of accessory manufacturers have begun to build AirPlay audio support into their speakers. Most likely something similar will start happening soon for the video.
Virtues
- It works on almost all modern devices from Apple, including mobile, and through iTunes on Windows;
- The software is optimized for the platform; hardware features are widely used;
- The signal has guaranteed quality and lack of gradation: Apple guarantor;
- It will definitely develop further;
- AirPlay is built into a variety of accessories for Apple devices.
disadvantages
- Only hardware from Apple, Linux and Android are resting;
- Works only under MacOS / iOS, with the exception of DLNA functions via iTunes on Windows (or Airfoil)
- The quality is still only 720p and the delay is still there, albeit subtle;
- It is not known whether it will be possible to embed AirPlay HD video and audio receivers into a different technique besides the existing AppleTV.
Conclusion
Transmission of HD-video and sound via Wi-Fi is now in the stage of the most active development. And the constant news about Intel WiDi and Apple AirPlay is proof of that. Qualcomm (with Atheros’s daughter) and Cavium are working on a similar project: the first promises high power and speed from its mobile platform, and the second - its implementation of the wireless HD signal transmission protocol, and as you know, Qualcomm is not the last manufacturer on mobile platform market.
In summary, everyone is trying to make the solution integrated using an existing hardware platform and a Wi-Fi adapter, but as you can see, even the most recent implementations have not yet reached the absolute HD quality and very low latency. They will develop and improve as new, more powerful equipment becomes available.
If it will be interesting, then we will talk about specialized standards with individual transmitters that provide imitation of an HDMI cable in all respects.
PS: No matter how hard the guys tried to compress the material, but as they say, you can’t say otherwise. Write whether to write a sequel about other technologies. Also I will be glad to answer any questions in the comments.
Source: https://habr.com/ru/post/138670/
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