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

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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.

Home Theater: More Surround Sound

3d1Today’s blog post is another excerpt from my new Kindle book Home Theater for the Internet Age. It further explores home theater surround sound (also check out Home Theater: Surround Sound Basics), diving into discrete vs. matrixed audio and lossy vs. lossless compression—topics that continue to confuse both casual fans and enthusiasts alike.

Also check out Surround Sound Basics and Surround Sound Formats.

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Curt Robbins


Standardized System

Surround sound isn’t merely a speaker arrangement for your living room, but rather a standardized system by which content producers can compose, or “encode,” their content so that consumers, with the proper equipment, can decode it to simulate a more realistic, immersive audio environment. The intent of surround sound is to create audio that radiates from all around the seating positions of the viewers, while giving content producers the ability to specify from which of those speakers a particular sound or audio stream is projected.

While basic surround sound involves three speakers in front and two in back, more sophisticated systems employ between eight and 12 speakers. The more speakers involved, the more immersive and “surrounding” the sound becomes (and, relatively speaking, the more expensive the speaker system and receiver).

Discrete vs. Matrixed Surround

This book strives to avoid the overly technical and speak in plain English. However, it’s helpful to understand the difference between discrete and matrixed surround sound formats. Discrete surround involves sound information that’s specific, or dedicated to, particular channels and speaker positions (and fully independent of other channels). Thus, if a movie features a 5.1 soundtrack, it means the producers recorded and mixed six separate sound channels, each intended for a particular speaker position in your living room.

dolby logo

Matrixed surround, on the other hand, involves your receiver producing sound information for six or more speakers that’s derived from a two-channel (stereo) signal. While not as good as discrete formats, matrixed surround can take standard stereo and make it pretty amazing—depending on the quality of your system. Assume you’re watching an old episode of Law & Order on cable TV and it’s encoded in stereo. If your AV receiver features a matrixed surround sound format, such as Dolby Pro Logic II or DTS Neo:6 (nearly all models for the past several years do), you can apply it to the stereo signal to direct sound to the other speakers in your home theater, not just the mains.

If a film or TV program features an audio mix that’s designed for surround sound, it will offer discrete channels. Dialog will be directed to the center channel, background noise like traffic, the din of a crowd, and sirens will come from the rear speakers, and the non-speech sounds and primary action will be directed to the main speakers. Because so much legacy content—be it music, TV episodes, or movies—features audio encoded in only stereo, you’ll find great benefit in applying matrixed surround filters to take advantage of those other speakers sitting in your living room. This is especially true for those who consume mostly TV content.

Lossy vs. Lossless Compression

When the audio portion of a video is created, it’s digitally compressed to make it smaller. Reducing the size of the data helps it stream smoothly from an internet video service (like Netflix) or fit on an optical disc (DVD or Blu-ray). However, there are different types of compression that impact the quality of the sound produced by any equipment, especially nicer systems.

Lossy Compression

Traditionally, data compression for audio has been lossy. This means that, during the compression of the audio, some information is lost—resulting in less data to play back. In a nutshell, less data equals lower sound fidelity. Different compression schemes produce distinct results in terms of sound quality. Overall, lossy compression is viewed as a bad thing. Music in MP3 (MPEG Audio Layer III) and AAC (Advanced Audio Coding) formats are good examples of lossy compression standards (and avoided by audiophiles). All music sold on standard compact discs (in CDDA format; see the Disc-Based Music chapter for more info) involves lossy compression (although of significantly higher fidelity than MP3 or AAC).

Lossless Compression

Lossless compression, on the other hand, is, well, lossless. It reproduces the original audio bit-for-bit, with no reduction in data or quality whatsoever (any decrease in fidelity reflects a deficiency in your equipment, not the audio itself). If you know an audio source is lossless, you don’t really need to learn anything else (except maybe the encoding standard employed to ensure that you can decode it on your particular Blu-ray player or AV receiver).

oppo bdp-103

The downside of lossless compression is that it results in significantly larger files than lossy schemes. This is why lossless audio is currently available only on high-capacity optical disc formats (like Blu-ray, which sports six times the storage of a DVD), but not in the form of internet streaming, where even the fastest broadband connections typically lack the bandwidth to support such high bit rates. Examples of lossless audio include Dolby TrueHD and DTS-HD Master Audio (both covered below). There are also internet-based download services that sell lossless music files in popular formats like FLAC and AIFF (higher quality than even regular music CDs, let alone MP3s).

Compression Levels / Bit Rate

Content compressed in a lossy format can be encoded at a variety of quality levels (measured in “bit rate” or bits per second, and sometimes called “compression levels”). For example, a 128 Kbps (kilobit per second) MP3 of Jessie’s Girl by Rick Springfield won’t sound as good as a 320 Kbps MP3 version. The 320 Kbps file contains nearly three times the data of the 128 Kbps version, enhancing the sound quality.

This is one reason that Blu-ray discs are so popular. While the video quality of Blu-ray (1080 lines of resolution) is certainly better than that of DVD, the audio improvement is even greater. Currently, there is no better sound that you can pump through your home theater than the lossless audio track of a Blu-ray movie or lossless music files like FLAC. (When it comes to audio only, there are also high-end music formats such as SACD, DVD-Audio, and Blu-ray Audio, which are covered in the Disc-Based Music chapter.)

Based on Standards

To clarify how this compression/decompression cycle works, it’s important to understand that content producers must encode their audio to a particular standard (like a United Nations interpreter choosing a language in which to speak). As you’ll learn below, for movies, this is typically a format from Dolby or DTS. Encoding makes files smaller for transport or distribution, regardless of whether it’s lossy or lossless. Your receiver or Blu-ray player incorporates a bunch of decoders. When you play a DVD or Blu-ray disc, the receiver applies the proper decoder, basically reassembling the audio data. In this respect, your AV receiver is just a specialized computer. (Some people will tell you that the audio on a Blu-ray movie is uncompressed, which isn’t necessarily true. Typically it’s compressed, but sometimes it isn’t. Even compressed, Blu-ray involves a lossless scheme.)

No Guarantees

It’s important to note that, simply because an audio source involves a lossless compression format, this doesn’t guarantee high-end fidelity. Technically, lossless compression simply means that the file reproduced by your playback equipment exactly matches the original, before it was compressed. If the original music file was of low quality to begin with (many movies and much music are poorly mastered or recorded in less-than-optimal live venues or studio environments), the best lossless format won’t make it sound good.


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

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