Common Confusion in Home Theater: Part 3

3d1As part of my mini-series of blog posts and Slideshare slideshows regarding topics of common confusion in home theater, below I cover PCM vs. bitstream and Blu-ray player upscaling/upconversion.

This series features excerpts from my new Kindle book Home Theater for the Internet Age.

  • Part 1: Volume in a zero dB world, updating firmware, and the disadvantages of Blu-ray
  • Part 2: Speaker resistance and analog vs. digital amps in AV receivers
  • Part 4: THX certification, DLNA network access, and distortion and THD
  • Part 5: HDMI (including cable length and controversial expensive cables)
  • Part 6: Closed-back vs. open-back around-ear headphones
  • Part 7: Understanding your room and room dynamics
  • Part 8: Room correction, speaker position, and more room dynamics
  • Part 9: Ethernet, component separates, and broadband internet routers

curtsig2 - trans
Curt Robbins


Upscaling / Upconversion

As you’ve already learned, DVDs feature a video resolution of 480 horizontal lines. When compared to Blu-ray’s 1080 lines, DVDs seem pretty wimpy. But if you have a large (and expensive) DVD collection, you probably don’t want to simply trash or sell them. Re-purchasing your collection is frustrating and expensive. Damn you, double-edged pace of technology!

Most Blu-ray players (and many AV receivers) automatically apply something called upscaling, or upconversion (both terms are used interchangeably) to DVDs in an effort to make them 1) fit on a 1080 TV, so they’re not displayed as a little box in the center of the display panel, and 2) appear to be higher resolution than they actually are (by simulating 1080).

In a nutshell, this means the Blu-ray player analyzes the video content of a DVD and adds more lines, creating a pseudo-1080 image. While upconverted 480 video doesn’t look as good as the native 1080 display of Blu-ray content (with 1080 unique lines, featuring none of the pixel redundancy that comes with upscaling), it does look better than standard 480. In terms of the end result, upconversion for video is akin to matrixed surround sound for audio: It’s all about optimizing legacy media formats on modern-generation equipment. (To learn more about matrixed and discrete surround sound formats, see the Surround Sound chapter.)

The quality of upconversion is determined entirely by your equipment (the hardware and software running within it; see the Video Processing section below for more info). Better Blu-ray players do a superior job of upscaling than their less-expensive siblings. The $300-$600 players offered by companies like Denon, OPPO, Onkyo, Pioneer Elite, and Marantz will do a considerably nicer job of upconversion than an entry-level $80 Sony or Samsung unit (which aren’t the best suited for home theater environments).

A standard definition DVD will never look better than when upconverted on a home theater with a decent Blu-ray player. So what’s your takeaway? Don’t sell those old DVDs on Craigslist or relegate them to a dusty box in a closet! If you’re willing to tolerate the slight decrease in quality between upscaled DVDs and native Blu-ray content (which many people don’t even perceive), upconversion can help you avoid rebuying your DVD movie collection. Also consider that the majority of discs available from your local video rental store or library—even in 2014—are DVDs, not Blu-rays.

Real-World Upscaling

One study claims that 39% of viewers can’t tell the difference between standard-definition video (480 lines of resolution, as featured on DVDs and old camcorders) and high-definition content (1080 on Blu-ray discs or streamed via a service like Netflix). If this is even marginally true, an even greater percentage of consumers will be oblivious to the difference between an upscaled DVD featuring “fake” 1080 resolution and a Blu-ray disc producing the real thing. If you’re one of them, keep your eyes peeled for those grocery store bargain bins full of clearance DVDs. (Your local brick-and-mortar video store—if your community still has one—is another great source of discounted new and used DVDs.)

Video Processing

Your Blu-ray player’s video processing is handled by a dedicated computer chip (or set of chips) and special software stored on it. Many manufacturers utilize fairly generic, average processing chips—which don’t always produce the best results, especially when upscaling DVDs to 1080 resolution. More potent models feature special leading edge video processing technologies licensed from third-party companies, such as Marvell’s Qdeo and Silicon Image’s VRS ClearView.

Many popular Blu-ray models, including those from Cambridge Audio, OPPO, Onkyo, and Pioneer Elite, feature Qdeo processing. Note that there are several generations of Qdeo, so one from three years ago won’t be as good as what’s shipping on current models. OPPO’s top Darbee models feature VRS ClearView video processing and upscaling.

PCM vs. Bitstream

If you’re connecting your Blu-ray player to your receiver via HDMI, there are two options for how data is sent from the player to the receiver. The first, PCM (Pulse-code Modulation,  sometimes called LPCM), is when your Blu-ray player performs all decoding of the compressed audio on the disc (a variant of either Dolby or DTS). In this scheme, the fully decoded audio is sent to your receiver, then passed along to your speakers. Many receivers allow you to select PCM output from the same menu from which you choose DLP sound fields (and will indicate the mode by displaying “PCM” on the front panel).

Bitstream, on the other hand, means your Blu-ray player does the opposite, performing no decoding of the compressed audio of the disc, instead sending along the raw, encoded bitstream to your receiver, where the decoding takes place. In this case, the receiver will display the exact encoding method employed by the disc (Dolby TrueHD or DTS-HD Master Audio, for example). The only disadvantage of bitstream is that any “secondary audio,” such as commentaries and other supplemental features of Blu-ray, will be lost. If you ever use these features, you obviously should lean on PCM.

Typically, both methods work equally well and, in practical applications, it doesn’t really matter which you employ. However, if you had a much nicer (and newer) Blu-ray player than receiver, you might choose to have it do the heavy lifting to improve the quality of the audio pumped into your speakers. If both your Blu-ray player and receiver are of relatively equal capability and age, the difference between these two schemes will almost certainly be negligible.


Curt Robbins is author of the following books from Amazon Kindle:

You can follow him on Twitter at @CurtRobbins, read his AV-related blog posts at rAVe Publications, and view his photos on Flickr.

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