Thursday, August 1, 2013

How to watch digital TV on computers, mobile devices

It can be done: Digital TV on a laptop.

It can be done: Digital TV on a laptop. Photo: iStock

Want to be able to watch digital TV anywhere? You have a laptop or tablet with plenty of battery power, and a USB digital TV tuner, so what could stop you? If the answer is the lack of an antenna point or poor signal strength, there is a solution, which involves having a Wi-Fi signal available at the location.

The antenna provided with USB digital TV tuners might not have sufficient gain to guarantee a picture free from pixelation, or, more fatally, the dreaded digital TV ''cliff-edge'' effect that results in no picture at all. Depending on where you are, even a good set of ''rabbit ears'' might not do the job.

The solution is to install a digital TV tuner on a device (PC or laptop, for example) that has sufficient signal strength. The digital TV signal received by this tuner can then be streamed to remote locations via Wi-Fi. But how?

Illustration: Judy Green.

Illustration: Judy Green

You are probably already familiar with watching and listening to media files from various sources on your home network via Wi-Fi. If you can get your digital TV broadcast into a media file, you can watch it.


''Hang on,'' you say, ''digital TV is not a media file.''

Correct - digital TV is not a media file, but it can be, with the touch of a button: record.

Once record (or even time-shift) is selected in the digital TV tuner's software, a file is created to store the recording. The software also allows a location to be set to save the recording file. If that location is shared on the home network, the file can be accessed via Wi-Fi.

Let's say you want to watch the Ashes in the backyard shed but there isn't enough TV signal. By dedicating a digital tuner to the PC inside the house, you can access TV from the shed via Wi-Fi.

On the PC inside the house, install a digital TV tuner card or USB tuner and its associated software. Connect the antenna input of the device to an antenna (or antenna point) and start the digital TV software. Have the software scan for channels and view a few different channels to verify all is well.

In the configuration section of the software that deals with recordings, tell it to store all recordings in a location that has been shared on the network. The PC should be connected to the LAN the Wi-Fi is part of, and the Wi-Fi signal must be available in the shed.

Select the desired channel. Start time-shifting or recording and note the name of the file that appears on the desktop. Return to the shed and connect via Wi-Fi to the PC inside. Navigate to the desktop and open the file.

At this stage, either the media player program on the shed device will start playing the Ashes, or a warning will appear to say access is denied. This is because some media players will not allow files that are in use to be accessed. Media players such as VideoLAN and KMPlayer do not suffer from this limitation.

If the default media player says ''No'', close it. Right-click on the file again and choose ''Open with … '' from the context menu that appears. Open the file with other media players until the Ashes appears.

But what if the PC in the house is in standby or hibernation? Can you wake it up from the shed? And what if you want to change the channel?

To wake up a remote PC, Wake-on-LAN software is available. This allows a data packet to be sent over the LAN (of which your Wi-Fi is a part) to wake up the remote PC.

To change channels, install remote-control software such as RealVNC. Install the RealVNC server component on the remote machine (house) and the client component on the local machine (shed). You will then be able to view the screen of the house machine and control it with the mouse and keyboard.

You may now control the digital TV software from the shed. You can stop recording (or time-shifting), change channel and start recording again. Opening the new recording file over the network lets you view the new TV show.

Many traditionalists prefer to listen to ABC radio Ashes coverage while watching the TV broadcast. If you mute the volume in the digital TV tuner software, and tune in an AM radio to the Ashes broadcast, the sound from the radio will lead the TV picture by a few seconds. The explanation for this is technical. Digital TV broadcasting takes a finite amount of time to compress, assemble and transmit the bit stream that will arrive at our digital TV tuners. This results in the TV pictures arriving later than the radio audio. This annoyance has several possible solutions.

If an Ashes broadcast is available online, or via digital radio, try tuning in. Just like the digital TV broadcast, there will be a delay when compared to the AM broadcast. If the delays match, problem solved. If the digital radio has a timeshifting or review feature, use it to get the sound and picture perfectly in sync.

There are also special AM sports-lover radios that have an inbuilt audio delay feature to solve this problem. If buying from overseas, check that the AM radio supports a 9KHz station spacing, for use in Australia.

There is also PC software that can delay the audio. Buy a cheap USB audio input device and plug it into a PC. Run an AM radio into it using a lead with 3.5mm plugs. In the software, select this USB device as the input device and drag the delay slider until the TV picture and AM radio broadcast are in sync.

Streaming a digital TV recording over Wi-Fi does require a certain amount of data throughput to prevent stuttering or loss of frames. For maximum speed, ensure the Wi-Fi access point is located sensibly. Generally, higher is better and with a clear line of sight (if available) to the other location. The location of the Wi-Fi adaptor's antenna at the other location is also critical.  A USB Wi-Fi adaptor, connected via a USB cord of some length, often works better than an internal Wi-Fi adaptor embedded in a laptop. The USB cord allows the adaptor to be moved around until a reception sweet spot is found.

Start by turning off any internal Wi-Fi adaptors. Most laptops have a switch or button to do this. Now install a USB Wi-Fi adaptor on a USB cord. Move the adaptor around until the signal strength indicator in the software for the adaptor indicates a sweet spot. You will know it when you hit it. Use a blob of plasticine or other means to secure the adaptor at that spot.

You could try using wireless N technology, instead of G, or, if a common power line connects the two locations, power-line networking adaptors.

And don't forget that a laptop usually has an external video output. You can connect this to a big-screen TV for a larger picture.

Patrick Brennan is an ICT trainer and assessor.
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