Here in Ireland, we have a terrestrial digital television broadcasting service called SaorView. There are eight TV channels available:
- RTÃ‰ One, which broadcasts in 576i
- RTÃ‰ Two, which broadcasts in 1080i
- TV3, which broadcasts in 576i
- TG4, which broadcasts in 576i
- 3e, which broadcasts in 576i
- RTÃ‰ News Now, which broadcasts in 576i
- RTÃ‰ Jr, which broadcasts in 576i
- RTÃ‰ One +1, which broadcasts in 576i
Channels 1 to 2 and 6 to 8 are owned by the state broadcaster, which also administers the SaorView service via its subsidiary RTÃ‰ Networks Limited (RTÃ‰ NL). Channels 3 and 5 are both owned by the TV3 Group. TG4 is a state-owned Irish-language channel separate from RTÃ‰. It is a DVB-T service, with all channels broadcasting H.264 streams.
Most of these channels are able to dynamically change the aspect ratio of their broadcasts, so 4:3 shows aren’t stretched to 16:9 (widescreen). Unfortunately, this is not the case for RTÃ‰ Two, which happens to be the channel where I watch most of my 4:3 programming. I was eventually motivated to figure out how to manually override the ratio on my decoder. This is actually rather easy, but it’s annoying, and changing it back afterwards is even more bothersome. Anyway, I assumed that, being a HD broadcaster, RTÃ‰ Two was locked to 1920×1080 and couldn’t do anything about it.
However, recently, I was using VLC to inspect the codec information of an MPEG file recorded from RTÃ‰ Two by MythTV, and discovered that the broadcast is actually anamorphic. It broadcasts at 1440×1080, which is a perfect 4:3 picture, then instructs the decoder to stretch it! Even normal widescreen programmes are squashed at RTÃ‰, then stretched back on my end. At first, I was enraged that this quality compromise was being made at all, but after doing a little research, I discovered that this is common on terrestrial broadcasts because of limited bandwidth. In fact, a quick inspection of recordings from SD channels reveals that they broadcast at 544×576, which is 17:18, but instruct the decoder to stretch to 768 (4:3) or 1024 (16:9) as required. 17:18 does seem like a strange aspect ratio, but I found a long-winded (yet satisfactory) explanation for it here.
So, rage against anamorphicity (if I may make up a word) is basically unjustified, but RTÃ‰ still have some explaining to do. If RTÃ‰ Two actually broadcasts a 4:3 signal, why on Earth can’t they let the decoder show it in 4:3 on appropriate programmes? It doesn’t make sense to me! All the other channels, as stated above, can dynamically change the degree of stretching, but this supposedly high-quality channel can’t simply change it to “no stretching at all”. Am I missing something here? These broadcasts are all standard MPEG-4 streams, using standard H.264/MPEG-4 AVC compression, so shouldn’t they all have the same capabilities?
At any rate, I suppose little to none of it matters to me, as the end result is a paltry 576i composite analogue signal, usually containing letterboxed widescreen video, which gets overscanned on purpose by my bloody LCD television!