HDCD: an investigation

No we shouldn't.

 

I forgot to mention that the song that I used the command line tool is again, Blue Rondo a La Turk from the HDCD remaster of "Time Out."

 

Yeah, the problem I had wasn't spaces in the filename afterall - I had assumed the <> was not actually to be typed in the command! In desperation I put those around the input filename and it worked I'm used to Unix where the input and output filename are not differentiated in this way in a command. Is the use of these <> normal in DOS commands?

The reason it didn't like the first attempt is that you missed the quotation mark at the end of the input filename (you don't actually need the quotation marks in your example anyway as there are no spaces in the filename). You don't need to take out the spaces in between each separate part of the command. In fact, I'm surprised it worked with all the parts running to gether like that! Another difference between DOS and Unix maybe?......

 

The good thing about using the hdcd.exe method is that the 24-bit wav file generated is a genuine wav file not the "wavex" file output by the WMP plugin. This is good for me as the Squeezebox wouldn't play the wavex file and I had to convert it using Audacity. Using hdcd.ex I can avoid that extra step and play the HDCD decoded 24-bit wav output file directly

OK, so I just ripped some HDCD Beach Boys.....

In both cases there is no peak extention evident

On the Pet Sounds Sessions track ("God Only Knows" backing track) the peaks are all intact on the 16-bit version anyway so no problem.

However, on the 16-bit "The Little Girl I Once Knew" from 2001 the tops of the waveform are shaved off so I was hoping to get those back but no such luck

Incidentally, in both cases my DAC reports the HDCD decoded "24-bit" wav files to be 17-bit in reality (I guess that means the last 7 bits are "0"s?). Sadly, it seems these Beach Boys HDCD encoded discs fall into SiriusB's "category one" definition.

Oh well.

[of course, this all assumes that the hdcd.exe code can decode peak extention - can we assume that is the case?]

 

Just checked using the WMP player method - same result

Is there any advantage to decoding "category one" discs apart from the -6dB attenuation that may give the DAC an easier time?

 

I don't think so Mal.

 

Mal, put up a Unix screen capture of the use of hdcd.exe sometime please, both a failed and a succeeded attempt, obviously with the censored default directory.

 

From my - limited - understanding, the only advantage to using the hdcd decoding over other filters is for discs that use peak extention.


At the very least we can now determine which discs those are.

 

Yep, we have the tools at our disposal.

 

I only have the hdcd.exe which runs in DOS - I was just saying that in Unix you wouldn't ever put the <> around a filename.

Sorry for the confusion!

 

That's what you'd think........

For some reason I am finding the "24 bit" decoded files from these Beach Boys CDs slightly easier on the ear than the normal 16 bit rips. Maybe the DAC does prefer the less hot level

I will do more critical listening when I get the chance as I could just be imagining it......

Then again, as I understand it Steve mastered the AP gold discs with HDCD without using peak extention and claims they are even better sounding decoded while sounding fine undecoded. Or am I remembering that wrong (why would he have used HDCD at all otherwise)?

 

Yes you do. It is a concept of standard input and output redirection, and it is interpreted by the shell you are running. Dos command prompt implements the same thing with same syntax for this simple case.

The idea is that a program has a standard input and output which by default go to the console, but < and > redirection directives tell the shell to use some other files. If you would leave out the > output.wav part it would print the result to your screen (not pretty).

Because hdcd.exe uses standard input/output, you could pipe the like

if you want to do flac to flac conversion. (The pipe | symbol tells the shell to chain standard output of the previous command to the standard input of the next one).

 

Whenever I type a commmand in Unix that involves input and output filnenames I don't use the <>, eg:

ps2epsi in.ps out.epsi

Is my Unix set up unusual?

 

Ah, you are talking about using > like this:

ls > t.txt

which would write the list to the text file t.txt rather than print it to the screen - I use that sort of thing all the time.

This isn't the same as the <> around the input filename in this hdcd.exe command line is it?

What is the < doing?

 

Yes.

There is no <> around filename, there is < infile and > outfile, you could even reverse them as
hdcd.exe > outfile.wav < infile.wav

< is same thing for input as > is for output.

Yes.

There is no <> around filename, there is < infile and > outfile, you could even reverse them as
hdcd.exe > outfile.wav < infile.wav

< is same thing for input as > is for output. It is more rare to have program behave like this, but hdcd.exe has decided to do it this way. More common is like flac encoder to have input file
flac infile.wav
but also
flac -o outfile.flac - < infile.wav
would do the trick because '-' as input file name tells flac to use standard input instead.

(Sorry if this is going bit off-topic..)

 

I see - that explains why Bradley's use of the command without any spaces worked!

Thanks - I thought it was odd having the <> seemingly around the filename. Now I understand it

 

I don't remember what he said, but the way I understand it many use the the Pacific Microsonics a/d converter because it's a great converter, not for the peak extention. The way I also understand it, even if you don't use the peak extention feature - the only feature that needs to be decoded, the ensuing result will still have the the hdcd flag.

Keep in mind - this is my understanding - I'd love for someone who really knows to confirm this.

 

We should write repost some of this stuff on the HDCD entry of Wikipedia.

 

Mac OS X users might be able to use the DOS Command Line tool by downloading this emulator for free: http://dosbox.en.softonic.com/mac

 

For some Mac users of the Command Line tool, VirtualPC for Mac and a copy of some Windows version installed in VirtualPC might be essential if the free DOS emulator for Mac OS X doesn't work for you.

 

For those Intel based Macs, it is recommended that you download Boot Camp at http://www.apple.com/macosx/bootcamp/ and buy a copy of Windows XP or Windows Vista for this purpose if the DOS emulator doesn't work for you. So for you Mac users out there, you have a few options if you want to try the Command Line tool.

 

Mac users should comment on their results with any of the methods and if they are using emulators or if they have an Intel Mac with Windows XP or Windows Vista

 

Well, I've done some more listening - the HDCD decoded "24-bit" file definitely sounds better than the regular undecoded 16-bit file!

I'm comparing the decoded and undecoded wav file extracted from the "God Only Knows" backing track on the Pet Sounds Session box here.

The difference is clear as day - the bass is lighter sounding with better definition on the decoded version. Also the track in general just feels less congested and more coherent. Is this due to better resolution or is there some EQ going on in the decoding process?? Maybe there was peak extention on this one - although I can't easily see it in the waveforms

Thing is, I hear the same thing on "The Little Girl I Once Knew" from the HDCD 2-fer and I can see the peaks are not extended on the decoded rip on that one!

What else could be the explanation? Is it just that my DAC performs better when not pushed to the limit - that is, with the -6dB drop does it make life easier for the DAC?

Seems unlikely but who knows. Is there another rational explanation? What exactly is the hdcd.exe code doing to the original 16.bit wav file?......

Anyone else finding similar results?

Anyway, I am convinced that it is worth ripping all the HDCD "Beach Boys" CDs using this decoding method now, even without evidence of peak-extention being used

Can anyone help me with a DOS batch process? I've got all the files already ripped to wav (stored as flacs). I'd love a batch process that could un-compress each original flac file, run the 16-bit wav file through hdcd.exe and then flac compress the output "24-bit" wav file......

 

Yah, that's a shame. But since I last posted I have found that foobar2000 has an option to convert any selected set of .flacs to wavs AND generate a Daemon-mountable cue file...something EAC can't do. That's made my HDCD digital decode project much simpler.

 

btw, check out this rancorous thread on HDCD tecnical details on audioasylum...

http://www.audioasylum.com/scripts/t.pl?f=dvda&m=24549