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Enhancing OTA ATSC Reception Through Diversity

One of the goals of Project Entangle is to receive The Perfect Broadcast – a transport stream with no bits missing or in error. As anyone using OTA ATSC (and since you’re reading this you’re probably one of them) knows, this can be a challenging endeavor. Signals can be too weak, and ironically too strong. Multipath can turn an otherwise strong  signal error-prone. Dynamic multipath is even harder to deal with as the demodulator needs to adapt to the changing properties of the signal.

But hard doesn’t mean impossible. One of the methods for obtaining The Perfect Broadcast that Project Entangle has been investigating is diversity. Essentially, diversity involves receiving two or more versions of a broadcast in different ways. The various versions are then combined to yield a signal that’s better than any of the individually received ones.
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DIRECTV Now: A Good Start, Hoping For More Later

DIRECTV Now is a service I’d really like to succeed. After dropping Comcast there were a few channels that I missed. Like Science and BBC America. (We’ll ignore the little detail that one of the reasons I dropped Comcast, aside from their ever-increasing prices, was their seeming inability to actually deliver a reliable signal in the first place…) DIRECTV Now seemed like a godsend. Their initial promotion had the Go Big package for $35/month. No hidden taxes or fees. No years-long commitment. Plus, no cables to run or satellite dishes to mount.

I eagerly signed up for DIRECTV Now soon after it launched in late 2016, and was initially quite impressed. The video quality via AppleTV on a 55″ TV or on my iPad was quite good. No buffering or other issues which one might associate with streaming. There was the occasional bout of block noise, but these were infrequent and transient. But after waiting patiently for a year and a half for a decent DVR service, I finally cancelled my subscription. DIRECTV Now is a great solution for those of you who like to watch linear TV linearly. But it’s not so great if you’re used to trick modes or do a lot of time shifting.

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Update: The SiliconDust HDHomerun Connect Quatro

I’d like to thank all of you who commented or emailed about the SiliconDust HDHomerun Connect Quatro review posted in November of last year. I’m truly amazed at the amount of interest it garnered.

And there’s some great news for those of you who have the Quatro or been on the fence about getting one – the issue reported in that review has been addressed with the 20180327 firmware!

The HDHR5 Quatro now performs on par with the HDHR4 Connect. In fact, for certain types of impairments, it may perform a bit better.

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MPEG-2 Video Error Concealment

A lot of effort goes into making sure that the episode of America’s Funniest Home Videos you watched last night was as pristine as possible. From the network’s broadcast center to your local TV station’s transmission tower to that antenna on your roof, and finally to your DVR, a number of mechanisms ensure that all those 1s and 0s in the digital broadcast get to you unscrambled and in the right order.

But from time to time lightning storms, swaying trees, and stray cats will wreak havoc on the signal. Filters, error detection and correction codes, and even the most elaborate incantations of RF engineers struggle to make sense of the distorted waveform being received.  Inevitably the occasional glitch sneaks past and you end up recording some damaged audio and video.  The last bastion of defense for couch potatoes lies in the MPEG decoder and player’s ability to try to make some sense of the damaged programming. In many cases some sleight of hand can mitigate the visual effect of the damage, and occasionally the errors can be concealed so well that they’re invisible to the casual viewer.

We’re going to focus in this article on error concealment of MPEG-2 video. But the general principles apply to other video compression schemes such as H.264 and H.265.

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