HDTV Magazine
Welcome, Anonymous  •  Sign In  •  Register  •  Help

Today’s Show:

720p vs 1080p or More Compression vs Less Compression

Last September Apple released the AppleTV 2 and one of the things people complained about was that it was only 720p. We have talked on this program many times that resolution is not the most important specification of a good display or projector. Especially when you talk screen sizes less than 50 inches. There is study after study that says MOST people need to sit six feet away from a 50 inch TV to see the difference between 720p and 1080p.

So we set out to see if people could see the difference in resolution sitting 14 feet away from a professionally calibrated 100 inch screen. For this test we used an Apple TV and an Oppo  Blu-ray player. The movies we chose were Harry Potter Deathly Hallows and Beverly Hills Cop.

It only took us about ten seconds to see the flaw in our test. That flaw was that our experiment was more a test in compression than on resolution. Regardless we proceeded because everyone was already on their way over and there might be some decent conclusions anyway.

Process

The experiment was done by starting each movie at random scenes and switching between the AppleTV and Oppo player. This was done so that each individual was looking at each scene against itself and not in comparison to the other. A total of five scenes were selected for each movie. The subjects were given a score card with the name of the movie and two columns, 720p and 1080p. Ara kept the master. There were five people who participated in the test and only one of those was a self professed videophile who claimed he would be able to see the difference.

Results

The values below reflect the percentage of time the subject could correctly identify the difference between 720p and 1080p.

Harry Potter

  1. Subject 1 (Videophile) – 100%
  2. Subject 2 – 40%
  3. Subject 3 – 60%
  4. Subject 4 – 60%
  5. Subject 5 – 60%

Beverly Hills Cop

  1. Subject 1 (Videophile) – 100%
  2. Subject 2 – 80%
  3. Subject 3 – 80%
  4. Subject 4 – 100%
  5. Subject 5 – 60%

The Video expert nailed both tests. When we asked him what he keyed on he said, “The Macro Blocking”. In many of the scenes the Macro Blocking was a dead giveaway that the subjects weren’t watching Blu-ray. This ended up being the biggest tell to which source material was on screen.  So much so that watching Beverly Hills Cop most subjects could easily tell the difference in resolution.

But even with the compression issues the non experts were not able to see the difference between the two sources all the time. It did matter what scene was being displayed. If there was a lot of motion then there is typically less compression. In Beverly Hills Cop the office scenes were always a give away since there are large mono colored walls that compress easily and show macro blocking just as easily.  Bright outdoor scenes with a lot of motion were much harder to see a difference.

We figured that  because Harry Potter is darker it would be harder to see differences between the two sources. The results backed our initial thoughts with all but the videophile scoring lower.

What does this mean?

It essentially confirms what we have been saying all along. If you want the highest quality picture you will want to watch Blu-ray. At this point in time most streaming solutions will be a compromise in video quality. The one exception is Vudu HQX.  We will try to do a similar test with HQX video in the near future.

We conclude that for many people , streamed 720p will be an acceptable viewing experience. Even with the compression artifacts present some content will be difficult to see the difference between Blu-ray. If streaming providers were to reduce the compression (increase the bit-rate) the difference between 1080p and 720p material would be harder to distinguish and the resolution issue would go away.

The main reason the providers use highly compressed 720p content is because of bandwidth. It costs them more to stream all those bits to you. You may not want so much data streamed to you either. Some of you may be subject to data caps limited by your ISP. That would make watching high data rate 1080p content an expensive proposition.

Finally, just for grins we watched the same content on a 58 inch plasma. While the artifacts were still present they were much harder to see siting 12 feet away. The take away is that if you have a screen less than 50 inches, streaming video from Apple, Amazon, Netflix and Vudu will not only be convenient but will be of good enough quality for most people.

Next steps

The original intent of this experiment was to compare 720p vs 1080p at reasonable watching distances to see if most people could see the difference. What we didn’t consider was that our choice to use overly compressed streamed 720p content would taint the results. We will retry the experiment but only after we have secured high quality 720p content. Once we eliminate any compression artifacts from the equation we feel that it will be a much tougher test and only the true videophile will be able to see the difference.

Download Episode #481


Posted by The HT Guys, June 2, 2011 9:35 PM

About The HT Guys

The HT Guys, Ara Derderian and Braden Russell, are Engineers who formerly worked for the Advanced Digital Systems Group (ADSG) of Sony Pictures Entertainment. ADSG was the R&D unit of the sound department producing products for movie theaters and movie studios.

Two of the products they worked on include the DCP-1000 and DADR-5000. The DCP is a digital cinema processor used in movie theaters around the world. The DADR-5000 is a disk-based audio dubber used on Hollywood sound stages.

ADSG was awarded a Technical Academy Award by the Academy of Motion Picture Arts and Sciences in 2000 for the development of the DADR-5000. Ara holds three patents for his development work in Digital Cinema and Digital Audio Recording.

Every week they put together a podcast about High Definition TV and Home Theater. Each episode brings news from the A/V world, helpful product reviews and insights and help in demystifying and simplifying HDTV and home theater.