Posted Fri Jun 4, 2010 at 11:00 AM PDT by Joshua Zyber
Editor's Note: Each Friday, High-Def Digest's own HD Advisor will answer a new round of questions from our readers. If you have home theater questions you need answered, send an email to [email protected]
Answers by Joshua Zyber
24 fps Playback Problems
Q: When I watch films on Blu-ray through my Playstation 3 (connected to a Samsung LE40BDX) and set the output to 24p, I get a flicker/banding going up the screen, which is particularly noticeable in dark scenes or during the credits. It has become so annoying that I now watch films at 60 Hz. (I live in the UK.) The problem then disappears. Is there anything that I can do to eliminate this and be able to watch films as they were intended, or is it just a function of the low refresh rate? I know that my TV is 24p compatible and I cannot afford to replace it with a 120 Hz model (or any other one with a high refresh rate that is an even multiple of 24 Hz). My other friends have the same problem with their PS3s so I know that it isn't a faulty console.
A: Although 24 fps sounds like a low refresh rate, very few (possibly no) digital HDTVs actually display content that slowly on screen. Models with a so-called "24p" mode will instead convert the 24 frames to a higher even multiple such as 48 Hz, 72 Hz, 96 Hz, etc. These days, 120 Hz and 240 Hz are very popular. However, those really high refresh rates are primarily designed to combat LCD motion lag. That's a different issue than the flicker you describe. You shouldn't need 120 Hz to avoid flicker. Realistically, any refresh rate 60 Hz or higher should be free of flicker. (48 Hz is perhaps on the low end of tolerance for some sensitive viewers.)
I tried Googling the model number you provided, but couldn't find a lot of information on it. I think it's possible that the particular model designation may be retailer-specific. I did find references to similar Samsung models, however. This review of the Samsung LE 40B579 cites its "accurate 24p reproduction." Likewise, this review of the LD 40B650 claims that it, "handled 1080p/24 video signal from the Sony PS3 smoothly without any hint of telecine judder."
That latter review also states that the set has several "100Hz Motion Plus" modes that apply frame interpolation. (That's a topic that I've discussed previously.) If your set has these options in its menus, you might try adjusting the settings or turning off the feature, if you can.
The way that you describe the artifact as "banding going up the screen" makes me wonder if you're experiencing an electrical ground loop. A ground loop would cause an artifact known as "hum bars" that appear as vertical bands (of a different brightness than the rest of the picture) that scroll up the screen.
If you have cable TV connected to your set, try disconnecting it and then watching a Blu-ray. If the banding goes away, what you need is a small doodad called a Ground Loop Isolator. Check your local electronics stores. This should not be very expensive. Why a ground loop would only manifest during 24 fps playback and not 60 Hz, I don't know. But stranger things have happened. It's worth a try.
"Pure Direct" Audio Mode
Q: My Denon 4310ci receiver has a Pure Direct mode. In a nutshell, what does this mode do and are there real world benefits to using it during Blu-ray playback (PS3, original), mp3/aac streaming (via iTunes & Apple's Air Tunes), and for playing records (Musichall MMF 2.2)? Also, I read that Pure Direct disables bass management and such. Can you explain this in greater detail? It mentions stuff like "double bass" and "LFE+MAIN" which is confusing. Is double bass good? Is it a benefit to have LFE+MAIN enabled?
A: You actually have a couple of different questions mixed together here. We'll take them one at a time. "Pure Direct" is Denon's designation for an audio mode that disables all video output and extraneous digital processing. The idea is to provide the purest representation of the original audio signal with as little mucking around as possible. Theoretically, even something as simple as having video circuitry active could "pollute" the audio signal. (Realistically, the likelihood of this making an audible difference is next to nil; but it's something that makes audiophiles feel better about themselves.)
Because Pure Direct turns off video output, you certainly wouldn't want to use it when watching a Blu-ray movie. You won't get a picture on screen. This is specifically a music-listening mode.
You are correct that Pure Direct also disables bass management. If you have a typical home theater system with 5-7 limited range main speakers and a subwoofer, you're best off telling your receiver that you have "Small" speakers and setting an appropriate subwoofer crossover. Pure Direct bypasses that, and will send all bass to your main speakers, which may not be able to handle it or reproduce it accurately. I do not recommend using Pure Direct mode unless you have genuine full-range speakers.
Long story short: Pure Direct is intended primarily for audiophile applications. If you spent less on your speakers than you did on your car, and haven't seriously contemplated building an anechoic chamber in your home just for music listening, it probably doesn't apply to you.
As for the "LFE+Main" setting, that's a mode that will route bass in an audio signal to both your subwoofer and your main speakers simultaneously. This would be the "double bass" you mention. This is generally not recommended. First, your main speakers may not be able to reproduce the low bass frequencies, which could lead to distortion. Also, this may have the unintended consequence of causing the bass waves from two different directions to cancel each other out, resulting is less audible bass in your room. Again, you're better off telling the receiver that you have Small speakers and setting the crossover so that your subwoofer can do the heavy lifting when it comes to bass, which is what it's best at.
Correction: A couple of readers have pointed out that my response to the "LFE+Main" issue is precisely backwards. Rather than determining which bass and how much is directed to the main speakers, that setting determines which bass is routed to the subwoofer. "LFE" will route only bass information specifically encoded in the soundtrack's .1 channel to the subwoofer. "LFE+Main" will filter bass meant for the main channels and direct it to the subwoofer instead. So, if you have "Small" main speakers, you should use the LFE+Main setting. The name for this and the instructions in the Denon user manual are both confusingly worded.
After receiving these reader emails, I went into my own Denon receiver's setup menu and confirmed that I actually had it set for LFE+Main the whole time. Apparently, I knew the correct answer to this question at one point in the past, but had forgotten it over time. I set up my receiver when I installed it a couple years ago, but hadn't touched anything in the Setup menu or thought about it at all since.
Thank you to Clarke and Elvis for bringing this to my attention. I apologize for any confusion this may have caused.
The HD Advisor knows many things, but he doesn't know everything. Some questions are best answered with a consensus of opinions from our readers. If you can help to answer the following question, please post your response in our forum thread linked at the end of this article. Your advice and opinions matter too!
Connecting a Digital Camera to an HDTV
Q: I have a Canon digital camera #SD790IS and a Mitsubishi HDTV #WD73734. With the camera, I received a mini USB/composite A/V cable. The camera only has a mini USB connection. When viewing pictures and videos on the HDTV, the best resolution I can get is 480i. Can I get better resolution if I use a USB card reader or a mini USB/USB cable? Will I be able to view videos with sound with either of these? Is there a cable or converter that goes from mini USB to component or HDMI or is 480i the best I am going to get?
Check back soon for another round of answers. Keep those questions coming.
Joshua Zyber's opinions are his own and do not necessarily reflect those of this site, its owners or employees.
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