A Visual Comparison of CD, DVD, HD and iTMS

As noted in Why Apple is Winning in Media Downloads, there's a huge gulf between HD or even DVD quality video, and what can be effectively delivered over the web. Here’s a visual comparison of how much larger HD and DVD programming is, compared to what Apple is selling in the iTMS.

The Sound of Music

First, consider music: raw CD audio is compressed to about a tenth of its size by iTunes' AAC (or MP3). This creates dramatically smaller files for efficient use in audio players such as the iPod, or for distribution from the iTMS or similar download sites.

The iPod is designed to play back 128 kbit/s AAC audio, although higher bit-rates are available in iTunes, and the iPod can accommodate them.

For example, Apple also offers a lossless codec which only compresses CD audio in half, at about 700 kbit/s.

This results in a file that is about five times larger than a typical AAC file, but it retains all of the original quality of the raw CD information.

Higher compression formats, such as MP3 or AAC are called "lossy," because that they analyze and throw out the least important information in order to create the best sounding file at the smallest possible size.

Losing Something

While raw audio files, or lossless compression, might sound significantly better when played through high end equipment in a home theater sound setting, the actual difference in sound quality is lost when played back though standard headphones from a portable player, particularly in a gym, on a commuter train, or anywhere else where a typical iPod user might be exposed to ambient sound.

Users who attempt to fill up their iPod with lossless, CD-quality song files will find they are "losing" something else: five times as much disk space, and significant battery life. Bigger files means the iPod has to deal with more data to play back the same song: there is five times as much data to process, and five times as much disk activity. That extra work drains the battery significantly faster.

The iPod isn't the only device that benefits from smaller audio files: a music collection ripped from 100 CDs would take up around 50 GB of computer hard drive space; compressing that down to a tenth clearly saves a lot of disk space, backup resources, and unnecessary time lost copying excessively huge files around.

Sizing up the Network

Another benefactor of small audio files is wireless distribution. Apple's AirTunes feature encodes audio from iTunes and sends it wirelessly to an Airport Express unit, which then decodes it to regular audio for playback by remote speakers.

The fastest existing AirPort wireless standard, 802.11g, which Apple calls Airport Extreme, has a theoretical maximum of 56 Mbit/s. That should easily accommodate 128 kbit/s audio streams in theory, but in practice, wireless is not that fast. The typical data rate for Airport Extreme is really about half that: 25 Mbit/s; it only achieves that in close range, at full signal. Add any interference, and the top speed quickly drops in half.

Add in other overhead and network traffic, and the AirPort streaming audio system starts to struggle to maintain flawless playback of audio, despite its rated data transmission speed. If the fastest wireless system struggles to play back 128 kbit/s audio, it's not hard to figure out why Apple hasn't yet released video wireless distribution. Will they soon?

It appears likely. Apple is apparently making progress on a couple fronts. First, Apple has made a year's progress in refining their implementation of H.264 video compression. Further, newer decoding chipsets are available to efficiently decompress video streams for a new video enabled AirPort Express. The real jump will come when the much faster 802.11n wireless standard is finalized, but that's not slated to happen unit next year.

Sony's LocationFree and the Sling Media Slingbox both support wireless distribution of video data, so it's not impossible, but it does require a quality compromise. Existing wireless video products only support TV quality streaming in the low end of the same ballpark as what Apple is currently selling in the iTMS.

Wireless video is simply a big technology hurdle. Here's a look at how video bandwidth numbers compare to audio.

The Big Picture

Standard DVD video is already compressed, using MPEG 2, but is still seven times larger than uncompressed CD audio data.

In order to deliver DVD quality video as a web download, it needs far better compression than MPEG 2 can provide.

The newer H.264 (aka AVC, and part of the MPEG 4 specification) can compress the same video to half the size of the older MPEG 2 DVD standard, but at around 5000 kbits/s, it’s still far too big for practical and efficient downloading.

Further compromise has to be made in quality to arrive at a video size that can accommodate the download, portable, and wireless distribution market that Apple is targeting with the iTMS.

The Long and Short of It

Apple’s existing TV quality videos require around five times as much bandwidth (data/sec) as an audio only download (128 kbit/s vs ~600 kbit/s), but are still a tiny fraction of what DVD quality video would demand.

Another factor to consider is that, while music downloads are generally around five minutes, movies are commonly around 90 minutes, or 20 times longer than songs.

That makes even TV quality movie downloads 100 times larger than the typical music download!

DVD quality movie downloads, even with advanced H.264 compression, would be around 800 times larger.

That's a much longer download for consumers, and also requires much more bandwidth from Apple's servers. Clearly, the real hurdle in rolling out a download movie store isn't in lining up the content but rather finding out how to minimize the download time and expense while maintaining acceptable video quality at a price that isn't insane.

The price targets for movie downloads are around $10-15; thats only ten times as much as a single song, despite the fact that movies demand 100 times greater bandwidth and, of course, associated operating expenses.

Case of the Missing Profit

It's useful to note that Apple, despite being the clear leader in selling downloadable music and TV, is only reporting minimal profits for iTMS. If Apple can't make fat profits selling five minute songs for a dollar, how will they make more money selling 90 minute movies that are 100 times bigger for just $10? Clearly, Apple sees iTMS content as the lubricant to sell iPods and accessories, not a huge cash cow in itself.

Exploring Apple's motivation for running the iTMS helps explain why Apple doesn't have to be all that worried about being number one in media downloads. In fact, the primary reason Apple is leading the download media market is because few others have a good reason to enter the high risk, low profit market.

That’s a key element in Why Apple is Winning in Media Downloads.

I really like to hear from readers. What do you think? Leave a comment or email me with your ideas.

Next Article: How Apple’s iTV Media Strategy Works

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Tech: Online Music & Media