HD Advisor VI: The Undiscovered Country

Posted Fri Mar 13, 2009 at 11:40 AM PDT by

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Answers by Joshua Zyber


Q: How do movies get converted into HD? I saw 'Casablanca' last night on Blu-Ray and it looked amazing!

A: It's a common misconception that movies must be shot "in HD" (hence only recent productions) to benefit from Blu-ray. Since the dawn of cinema right up to the present day, the majority of movies have been shot on 35mm film, which has a higher potential resolution than any video format, even High Definition. Remember, movies are designed to be projected onto 50-foot theater screens. You need a high-quality source to hold up at that size.

The short version of this story is that, to make a Blu-ray, the film elements must be transferred to video using a machine called a telecine, which is sort of a fancy scanner that digitizes each frame of film. Once complete, sometimes color corrections and other image manipulations are performed in the digital realm, and then the results are exported to create an HD master, typically at either 2k or 4k resolution. That HD master will be used as the basis for any home video editions. The image will be scaled to 1080p for Blu-ray (or downconverted to Standard Definition for DVD), digitally compressed, and then authored onto a disc.

Assuming that the film elements have been maintained in good condition or can be restored, even very old movies like 'Casablanca' (1942) or 'The Adventures of Robin Hood' (1938) will look terrific on Blu-ray.

Some modern movies (such as 'Miami Vice' or 'Cloverfield') are shot on High-Def video rather than film. For obvious reasons, these movies can bypass the telecine process.

Even today, only a small minority of movies are shot on video. Most are still shot on 35mm film. However, recent 35mm productions often use a Digital Intermediate stage during production. After the movie has been photographed, the footage is telecined for color correction and visual effects in the digital realm, and then output back onto film stock for the theatrical release. In many cases, the DI will be used as the basis for the HD master, rather than putting the later film elements through another telecine transfer.

3:2 Pulldown

Q: I've noticed on three different Blu-ray discs now that on slow panning shots the picture seems to stutter once, quickly. It's as though the camera man has shook the camera briefly, do you know what causes this? And what is at fault? It has only happened on three discs out of about fifteen, but it's a little off-putting when it comes to adding new Blu-Rays to my collection. In fact, there's been a few times when I've opted for the DVDs instead!

A: What you're describing sounds like image judder, the side effect of 3:2 Pulldown. This occurs when 24 fps film is transferred to 60 Hz video. For more details, see my What's the Big Deal About 1080p24? article.

With that said, 3:2 Pulldown will affect Blu-ray and DVD video equally. You shouldn't see the artifact on one but not the other. If you are, there may be something else going on, such as a hardware problem in your equipment chain.

[Reader Michael responds: What’s probably going on is that he's turned on Cinemotion or some other non-Sony equivalent image enhancement technique on his TV, and then set his Blu-ray player to output 24p. When you turn on Cinemotion on a Bravia, it doesn't affect the output of anything running at 24p – only 60p/30i, which is why DVDs would pan smoothly though the Blu-ray does not. Tell him to turn 24p off on his Blu-ray player if he REALLY wants it to look that way.]

Brand Loyalty

Q: I have a Sony Blu-ray player that supports 24p picture. Do I need to get a Sony 1080p 120 Hz that supports 24p, or could I get any 1080p 120 Hz TV in order to watch my Blu-ray movies on the 24p setting.

A: There is no technical requirement that you must connect a Blu-ray player from one manufacturer to a TV from the same manufacturer. In fact, with many of these mega-corporations, the people making disc players and the people making TVs are in completely separate facilities and have little to do with one another, other than being owned by the same parent company.

The 1080p24 output from any Blu-ray player will work with any HDTV that supports 24 fps input and display, regardless of manufacturer. These days, that often means 120 Hz models, but not always. Any refresh rate that's an even multiple of 24 (e.g. 48 Hz, 72 Hz, 96 Hz, etc.) will display a 24 fps signal correctly. 120 Hz is only necessary for sets that offer a Frame Interpolation feature (see my earlier explanation of Frame Interpolation).

Lossless Audio and 7.1

Q: When playing a Blu-ray disc that has a DTS-HD Master Audio 5.1 track, I would like use all the speakers in my 7.1 setup, which means using the Dolby ProLogic IIx option on my A/V receiver. Will this mean that I'm not getting DTS-HD out of my first 5 speakers?

A: No, this will work fine. Even though Dolby and DTS are competitors, ProLogic IIx is designed to work with DTS audio tracks. ProLogic IIx will not downgrade the quality of the audio signal. Instead, it simply steers certain audio cues that were going to the left and right surrounds into the back center channels. It does this using a matrixing algorithm that analyzes the frequencies and their directionality to find an appropriate balance. The audio signals remain in full lossless quality, just redirected to more speakers.

Lossless Audio and HDMI

Q: I have a receiver with an HDMI 1.1 connection. I wanted to know if I am still getting HD sound because when I select Dolby TrueHD, the volume drops a little. My settings are on multi-channel and PCM. Regular Dolby on Blu-ray sounds louder.

A: In order to transmit the raw TrueHD digital bitstream from a Blu-ray player to a receiver, you'll need at least HDMI 1.3. If your receiver is limited to HDMI 1.1, it will only accept the bitstreams for standard Dolby Digital and DTS.

If you perform audio decoding inside the Blu-ray player, the player will convert TrueHD to multi-channel PCM, which can be transmitted over any version of HDMI. It sounds like this is how you have things configured.

This shouldn't result in any loss of sound quality if your Blu-ray player can decode the full TrueHD codec. Many Blu-ray players can't, and will instead only decode the standard Dolby Digital 5.1 backup track. You'll have to check your player's documentation. If your player will decode TrueHD, make sure you have it configured correctly in the Setup menu (every manufacturer is different, so you'll need to consult the owner's manual).

Assuming that everything is set up and working correctly, don't confuse volume with quality. One track being louder than another doesn't necessarily mean that it's better. Some high-res audio tracks are set to a lower default volume in order to leave enough headroom for a wide dynamic range. Always try to volume-match audio tracks (preferably with a sound level meter) before comparing them.


Q: What is up with the current status of 3-D at home? And by that I mean not the typical red/blue glasses but the new RealD type of stuff?

A: If this answer seems like a cheat, I apologize for that. However, I recently wrote a lengthy article on the subject of 3-D in cinemas and on Blu-ray for Home Theater magazine. It appears in the April 2009 issue, which should be on newsstands now (and is also available electronically with a digital subscription). Because the publisher owns the copyright to that text, I can't reprint any of the article here. But check out the magazine, and it can hopefully shed some light on the subject for you.

Homework Assignment: You Be the Advisor

Some questions that the HD Advisor receives 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!

A/V Receiver Recommendations

Q: My question is about receivers that support HD video/audio signals. Of all the choices out there, which is the least expensive option and which are the most recommended for the money? I'm looking for a receiver that will allow me to plug my PS3 via HDMI. I'm not looking for one with DTS-HD MA and Dolby TrueHD, just PCM 5.1 or 7.1 support and full 1080P passthrough. Can you help? Sony's seem to be about $350 give or take $50. Are there any other options that compete?

Be sure to check back next week for another round of answers. Keep those questions coming.

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Tags: Joshua Zyber, HD Advisor (all tags)