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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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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Hard Drive Selection for DVRs

This and the next few posts will be focusing on hard drive selection for DVRs. This post will look at the type of workload that a DVR imposes on drives, using Project Entangle as an example. Subsequent posts will look at various system characteristics that can affect performance and performance measurements from some drives. And we’ll take a special look at shingled magnetic recording (SMR) drives, as they tend to have some very peculiar performance characteristics.

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Do You Need a VHF Antenna?

I’ve been in Las Vegas this week for the Amazon re:Invent conference. While there are enough sessions, receptions, and parties to keep you occupied day and night, I just couldn’t pass up a chance to check out the Las Vegas OTA airwaves. The Vdara staff was a bit mystified by my request for the highest south-facing room I could get, but very accommodating. So here I am on the 49th floor with good line-of-sight to the major towers (and a view of the desert instead of the Bellagio fountains, which apparently most people ask for.)

I had packed up a full Entangle development setup, including my trusty Silver Sensor antenna (aka the Zenith ZHDTV1). What I failed to do while busily packing was to check the RF frequencies of the Las Vegas broadcasts. As it turns out there are a few major channels in the VHF bands, including one on channel 2. Sadly the Silver Sensor is a UHF-only antenna.

This brings up an interesting point regarding the current state of OTA antennas: many of them, particularly the compact ones, are UHF-only. Even the ones that claim to be both UHF and VHF don’t handle VHF very well. At best they’ll pull in VHF-Hi. But can you make do with a UHF-only setup?

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