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Music Media

Software HDCD Decoding? 23

Posted by Cliff from the 16-1=20? dept.
Toshito asks: "I found that I have several CD's with HDCD encoding. I understand that these CD's contain a 20 bits stream encoded in the 16 bits (the original signal is truncated at 15 bits). A standard CD player will play the 15 bits version, but you have to get a HDCD compatible player to access the 20 bits version. My question is: do you know of any way to decode this stream on a computer with software only? Is the decodind method secret and only available in chip (hardware) form?"
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Software HDCD Decoding? More

Software HDCD Decoding?

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  • compatible? (Score:2, Insightful)

    by agnosonga ( 601770 )
    High Definition Compatible Digital (tm)

    when it comes to microsoft, the word compatible doesnt really come to mind

  • Suggestion (Score:2, Funny)

    by Copperhead ( 187748 )
    If you know the answer and you decide to respond, you may want to post your answer anonymously so as to keep the feds from beating down your door with a warrent.

    I would love to see the Taco, et al. fight a court order kindy requesting them to turn over the userid and ip of the poster who cracked their "encryption system".

  • My Toshiba DVD player plays HDCDs.....but this is the first time I've heard that it's a Microsoft technology. Did Microsoft maybe acquire this?

    -psyco

  • Software Only? Sure... (Score:4, Informative)

    by sheldon ( 2322 ) on Sunday September 29, 2002 @11:26PM (#4356861)
    Windows Media Player 9 as it comes with Windows XP supports HDCD number of other technologies such as SRS.

    If you want to write your own talk to Microsoft about licensing it, as they purchased Pacific Microsonics(makers of HDCD) several years ago.
    • talk to Microsoft about licensing it, as they purchased Pacific Microsonics....

      Okay, I know this is dumb, but at first I read this as, "the purchased Pacific Histrionics [dict.org], which seems very much like the sort of company Microsoft would want to purchase.

      Well, it amused me, anyway.

  • Good luck! (Score:4, Informative)

    by adolf ( 21054 ) <flodadolf@gmail.com> on Sunday September 29, 2002 @11:39PM (#4356921) Journal
    HDCD, while developed by a high-end audio company whose name currently escapes me, is now 100% owned by (you guessed it!) Microsoft along with the aforementioned original developer.

    It is also patented [uspto.gov].

    You can find an overview of how things work during the encoding process here [hdcd.com], but don't expect anyone to tell you how to do any of those things without you first handing them vast fistfulls of cash.

    You might be able to glean some useful information from the patent text, but probably the only sane way to go about this effort would be to read the bitstream coming from the CD. And while you should able to discern what the bitstream looks like without too much effort, it would probably be a fairly involved task to learn what it means.

    So. My only suggestion would be to give up now before you've wasted any effort on trying. But if you insist on putting real time into this project, here's a couple of nice encapsulated postscript HDCD logos [hdcd.com] you can illegitimately use to adorn any illegitimate HDCD products you produce.

    • Now I know exactly what CDs NOT to buy thanks to the logos! I wouldn't want to buy a CD and have some of my money go to Microsoft. Same reason I build all my computers from scratch instead of buying prebuilt with the m$ tax already on it... and yes... I do buy CDs :)
    • The same site has some technical papers up [hdcd.com]. From skimming them, it looks like they take the least audible bit of digital audio at set times for set durations, and encode suggested filters. The filters are most useful at times of extreme volume - loud or quiet. Even if you have to output to 16-bit depth, you might have a choice on dithering type, producing specific acoustic effects.

      Like albums and Dolby noise reduction cassettes, there are complementary filters for encoding or decoding; it's just more complex than an equalization.

  • Well... (Score:4, Informative)

    by TheSHAD0W ( 258774 ) on Monday September 30, 2002 @12:16AM (#4357053) Homepage
    Unless you're using some really amazing audio hardware, I wouldn't bother. Most any equipment you'd want to hook up to your PC will not be able to give the full dynamic range of the 16-bit signal, much less the HDCD audio. Most sound cards you use won't be able to either, and that includes ones with SPDIF output. Not to mention, once you encode to Ogg or MP3, all that extra quality goes out the window.

    Ripping tools may be desirable when they start putting "exclusive content" on the HDCD layer only, or start making them without the compatibility layer, but there's nothing like that in the pipe, so far as I know.
    • Most sound cards you use won't be able to [output 20 bit audio] either, and that includes ones with SPDIF output. Not to mention, once you encode to Ogg or MP3, all that extra quality goes out the window.

      I agree with the output part and in addition not that many consumer amplifiers have inputs for 20 bit digital audio either. However, I think that using 20 bit original for Ogg or MP3 should increase the resulting quality because you have more information to select from to discard unneeded pieces during compression. If you had 20 bit output I'd guess that 20 bit Ogg or MP3 (assuming 20 bit format is supported) would sound better than uncompressed sound dithered to 16 bit.

      But then, I don't have audio equipment or ears to hear even full 16 bits. Even NICAM [cs.tut.fi] sounds pretty nice to me.

    • Re:Well... (Score:3, Interesting)

      by adolf ( 21054 )
      I don't know about ogg, but MP3 is not at all tied to having things sampled at a specific bit-depth - it just doesn't matter to it whether it is 16, 20, or 24 bit - the format has sufficient dynamic range. I know of at least one free 24-bit MP3 decoder, but I've not run across anything for the encoding side just yet (and I haven't been looking, either).

      'sides, HDCD essentially only adds 4 bits worth of dynamic range, for a total of 20, which isn't such a stretch for current consumer audio gear. The human ear is likely to be a greater limiting factor than the equipment.

      And finally, there will never be any "exclusive content" on the HDCD layer, because there is no HDCD layer. The extra four bits are gleaned from unused space on a CD and interspersed with everything readable by a normal CD player. HDCD is an adjunct to a standard red book audio CD, not a replacement for it. Take away red book compatibility, and you not only remove 16 of HDCD's 20 bits, but eliminate compatibility with existing HDCD players (which are numerous indeed).

      You're thinking of Sony's SACD, which can include multiple layers, and currently lacks ripping tools and PC-compatible hardware. I'm sure that Sony would love to convert the world to SACD and then stop adding a red book layer to their music as a cost-saving measure.

      I doubt it will ever happen, however. Remember, this is the same company that brought you Beta, Minidisc, and Memory Stick. All of them are good, well-designed products, but lack of interoperability has always held them down, just as it will SACD.

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