This is the second part of a post that started yesterday. I’m talking about some of the “marketing spin” that websites use to make their offering more compelling. I took the following line from the About HDTracks site.
“An HDtracks Master Quality file is typically either 96kHz/24-bit or 192kHz/24-bit, meaning that it has twice the bit depth of your favorite CD and up to 9612Kbps of sonic information!”
This one is particularly challenging to parse. When you begin to use specifications and technical terminology, things can quickly get fuzzy very quickly. I know I use numbers and charts a lot on this website. I understand the temptation to avoid the specifications that make your stuff look inferior and focus on the positive stuff.
Laura Sydell of NPR asked me several times if claim that DSD 64 files have 64 times the resolution of a CD was true? I said it was absolutely false. I tried to explain that standard DSD encoding uses a sample rate of 2.8224 MHz, which IS 64 times the sampling rate of a compact disc BUT that those numbers don’t mean anything if you don’t take into consideration the word lengths of each sample. It is necessary to understand the basics of DSD and PCM. Given the number of times she asked me about this, I don’t think she every really understood.
So let’s look at what HDTracks’ sentence is saying. The mastering facilities that they work with are delivering “96 kHz/24-bit or 192 kHz/24-bit” stereo PCM files to the HDTracks servers. However, unless I’ve got my math wrong…24-bits is NOT “twice the bit depth of your favorite CD”, which is 16-bits. If we do the math correctly, the actual relationship is 33% more information…or I should say potentially more. It only matters if the master that is being transferred uses 24-bits. We know that virtually ALL commercial releases don’t.
Figure 1 – A chart showing the bitrates associated with some common audio specifications.
Here’s how you get the 9216 kbps number (Actually, the number on the HDTracks site is wrong…it should be 9216…they mistyped 9612). Simply take the sample rate times the number of channels times the number of bits and presto you get a really big number. It’s a whole lot bigger than the measly 128 kbps you get with most digital download stores, right? So it must be 75,000 times better than your average music file from iTunes. This is numeric double speak.
First, HDTracks can only tell you what the size of the delivery container they’re offering you. And the maximum size of that container is a 192 kHz/24-bit stereo PCM file. But unfortunately it’s not full of “sonic information” as they claim. It’s mostly full of empty bits. Bits that you’re paying a premium price for.
The reason is because the source file that the folks at the mastering facilities are using doesn’t have enough “sonic information” to fill up the new over-sized container! A third generation “EQ’d master analog tape needs only 6-10-bits of dynamic range and doesn’t extend past 17-20 kHz…and sometimes much less. Take a look at Figure 2 below.
Figure 2 – A graphic showing the size of a source file and the delivery container you’re paying for. Is this real HD-Audio? (Click to enlarge)
What I would like to see is a serious effort on the part of labels, download services and music industry folks to be transparent with regards to their marketing messages. I know if it will happen but we can write and call the companies that are doing it and let them know we not going to take it anymore!
When I get my book completed, at least there will be a place that confused consumers can go to get information without so much hype.