Switched on to digital TV


South Africa officially switched on its digital TV signal on November 1 2008

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South Africa officially switched on its digital TV signal on November 1 2008. Wanting to be a part of the revolution, I acquired a digital TV tuner so that I could play...

I decided to get a digital TV tuner for my media center PC, the reasoning being that instead of the poor quality recordings I was getting off my analogue TV tuner, I wanted to be able to record TV programmes in perfect quality a-la PVR. I ended up buying a KWorld PlusTV hybrid USB stick, which is capable of both analogue and digital TV reception. As an added bonus, this stick works on laptops and even the XP-based EeePC. On switch-on day, I plugged in my USB stick at around 10am, expecting a quick Next -> Next -> Next -> Ok type of installation, followed by glorious digital pictures on my HD-ready LCD TV. At around 2pm, after losing about 10 clumps of hair and over 100Mb off my internet cap, I had a semblance of picture slideshowing in a little VLC window …

But more about that later; let’s focus on what this is all about. Firstly, digital TV is not HDTV (although it can be used to broadcast HDTV). It’s more like DStv, except that instead of broadcasting a programme via satellite, the programme is broadcast using the terrestrial transmitters that are used for analogue broadcasts such as the SABC channels and etv. Most HDTV sets and all HD-ready sets sold do not have a tuner that is capable of receiving the digital TV broadcast (in much the same way as they don’t have a built-in satellite receiver capable of receiving DStv), which is why you would need to buy a digital TV set-top box. One of the fundamental benefits of digital TV over analogue is that they can fit several channels in the same spectrum that a normal analogue station occupies. It is also possible to broadcast interactive content similar to DStv, such as the EPG (electronic programme guide). South Africa has standardised on the DVB-T standard, which is used in most places around the world, with the notable exception of the United States of America — they use the ATSC standard (very much like PAL vs NTSC). South Africa has chosen to use H.264/MPEG4 AVC codec to encode the video, and that was the source of my problems.

So, back to my foray into digital TV. It seems most DVB-T receivers assume MPEG-2 encoding (as used in DVD), which is why I couldn’t get a picture from the software that came with the tuner. Not that I’m complaining terribly — MPEG-4 offers much higher compression, meaning that we can potentially get several more channels than with MPEG-2. However, one must be careful when purchasing a set-top box or digital TV tuner and ensure that it supports H.264 decoding. In my case, neither the bundled software, nor the latest version of MediaPortal, nor two other DVB players I tried worked. Hence the hair-pulling. I eventually had to resort to using the latest version of VLC to play back the digital TV broadcast. However, my 1.7GHz Intel Celeron CPU could not cope with decoding the video, maxing out at 100% and dropping frames like hot potatoes.

Once I got it working on a beefier PC, these were my findings:

  • In the Midrand area where I live, I can receive six TV stations and six radio stations on one frequency — 554MHz. The TV stations are: SABC 1, SABC 2, SABC 3, etv, SABC Entertainment, and SABC News International. The radio channels are: Radio 2000, Lesedi FM, Ukhozi FM, SAFM, Umhlobo Wenene FM and Ikwekwezi FM. All stations are free-to-air.
  • I am unable to receive any signal with a bunny aerial or the external antenna that was bundled with the tuner. However, I did not need to re-orient my external TV antenna and the software showed 100% signal.
  • According to a thread on myadsl.co.za forums, some people can pick up more channels, including MPEG-2 versions of the channels at 770MHz. Maybe I need to re-orient the external antenna to pick up the other transmissions.
  • I was unable to get any EPG data, although some people on the afore-mentioned thread were able to receive now and next information on the 770MHz channel.
  • Quality-wise, it seems high levels of compression are used, so on a large screen some encoding artifacts are visible. However, on the whole the video looks about on a par with the analogue broadcast (and DStv in standard definition). The picture is clear and undistorted with no jerkiness or ghosting. The video was decoded at 785×576 in 24-bit colour, on my player. That equates to standard definition TV. Audio is in stereo and about the same quality as the analogue broadcast.
  • The video is interlaced. I had to enable a deinterlacer.
  • Unlike satellite broadcasts, there was no loss of picture quality during a storm.
  • Sometimes playback will just stop abruptly, as if the transmission has ended, and I then have to restart the playback to continue watching. This may be instability in the VLC software, which tends to crash a lot during channel switching.

So, should you rush out and buy a digital TV tuner? Absolutely not! For one, you will be hard pressed to find one available for purchase, let alone one that plays the H.264 video. It was fun (and at times frustrating) for me to play with digital TV and experience the start of a revolution in broadcasting, but as it stands, there is no significant advantage to getting a digital TV set-top box right now. Quality-wise, it is on a par with analogue, provided you have good analogue reception (if you don’t, you probably won’t pick up the digital TV broadcast). Content-wise, you get two additional TV channels. Future content providers may encrypt their channels using one of several encryption schemes, so a wait-and-see approach might be better in the long run, before plonking down for a box that might not be able to access those channels.

Bearing in mind that this is still a trial phase of digital TV broadcasting, I am sure there will be more content, EPG, interactive services (such as the intention of the government to provide public services), and better quality broadcasts (full HD, please!) to come in future when digital set-top boxes are launched. In addition, the DVB-T standard allows the broadcast of DVB-H content simultaneously, which will allow people to watch digital content on their cellphones or portable media players. This is certainly a technology to get excited about and I look forward to the day when the infrastructure is in place and the content providers come to the party.

UPDATE: South Africa has since changed to adopt the DVB-T2 standard, so old DVB-T receivers no longer work.

Read original article at ThoughtLeader