Is digital TV as bad as VHS?

This is a combo VCR-DVD player from Sony, SLV-D380P. There is nothing remarkable about this machine.

The DVD section can play DVDs, CDs, VCDs, as well as MP3s from Data CDs and Data DVDs. It is just a player, so it cannot record.

The VCR section can play standard VHS tapes; it can also play Super VHS tapes albeit at standard VHS quality; it cannot record in Super VHS mode; it cannot record from the DVD, so no dubbing whatsoever; it cannot record from TV because this machine has no TV tuner — it was made in 2007, two years before analog television shutdown. The date was known beforehand, and Sony figured it did not make sense to equip this machine with a TV tuner that would be used for two years only, if any.

But it can record from a composite input! This made me think — if I recorded from a digital TV tuner, how would the recording stack up to digital recording?

So I decided to test whether a VHS recording of these shows would look noticeably worse. Or, put it another way, would a VHS VCR be usable today? Twenty years ago the answer to this question was a resounding “No!”, because digital television was all about high definition. But the times have changed, and we are past the Golden Age of HDTV.

For the last five years or so, TV broadcasters have lost a lot of spectrum previously available for over-the-air TV programming.

Shrinkage of the spectrum coincided with increased proclivity of broadcasters to create more digital subchannels — colloquially known as “diginets” — within the spectrum previously used by a single analog channel. This does not come free. A single 6 MHz frequency band can transmit about 19 Mbit/s; good enough for one high-quality HD channel and one or two SD channels.

Improved efficiency of ATSC MPEG-2 encoders allowed reducing the bitrate without significant drop in quality. Ten years ago, JVC reported that 1080i bitrate could be safely reduced from 16 Mbit/s to 12 Mbit/s, while 720p bitrate could be reduced from 12 Mbit/s to 9 Mbit/s.

If JVC engineers could only know how their quest for compression efficiency would become abused by broadcasters. A single frequency channel now carries four, five, even eight subchannels! The best quality I get from local television stations is 9 Mbit/s for a 720p station, in accordance with JVC recommendations. There are several stations that broadcast 1080i at 7–8 Mbit/s, there are stations that broadcast 720p at 5 Mbit/s (at this rate it looks slightly better than DVD quality), and then there are stations that broadcast 480i at 2 Mbit/s (these look barely better than VHS).

You would think that the quality of standard definition channels is atrocious, and it is. On another hand, these channels target older viewers, whose eyesight is not good anyway. Between a barrage of cheap health insurance ads, these “diginets” transmit old TV shows, cheap fare like Sell This House!, Wheel of Fortune, Shipping Wars, Hardcore Pawn, Pawn Stars and reruns of crime dramas like NCIS, Major Crimes, Law & Order, Blue Bloods and Corrupt Crimes. Being broadcast in interlaced standard definition, these shows look dreadful on a TV with less than stellar deinterlacer.

I recorded mostly from SD channels, but I did some recordings from HD channels as well.

I recorded digital files off TV using my TV tuner/converter/recorder box and saved them onto an SD card. Then I played the saved digital files into the VCR over composite connection, recording on a VHS tape. Then I played the tape over composite connection into to an inexpensive A/D converter, Pinnacle Dazzle DVC100. I captured it with VirtualDub2 and made a split-screen version, digital on the left, VHS on the right.

Depending on your equipment you may see better result. My VCR records in regular VHS, not in Super VHS. Also, it does not have built-in time base corrector, so straight lines are not exactly straight.

In scenes with little motion, few details and low frame rate, digital looks good even at low bitrate. The background is uniform, the lines are straight, the colors are well-separated. The VHS version show fuzzies known as “dot crawl”, caused by crosstalk between brightness and color in composite signal. There is halo caused by oversharpening either in the VCR or in my digitizing hardware and software. There is characteristic for VHS color bleeding caused by very low chroma resolution.

Broadcasters try to save data everywhere they can by softening the image, by reducing frame rate, by avoiding fast camera movement and by blurring the background. Cinematic shows with shallow depth of field look good both in digital, constrained by low bitrate, and in analog, recorded to VHS.

Fast movement with lots of detail breaks digital video into macroblocks. These macroblocks are softened when recorded to VHS. This is probably the only case when VHS comes atop of digital.

The verdict? Despite that low-bitrate digital TV looks nothing like glorious HD promised us a quarter century ago, it still looks better than VHS most of the time, especially when there is little motion and few details.

The only reason to have a VHS machine is to play old titles that are not available in digital form.



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