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Thread: HDCD Decoder should NOT have the 6dB amplification gain set!

  1. #1

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    Exclamation HDCD Decoder should NOT have the 6dB amplification gain set!

    Hello!

    I just ripped the HDCD Danse Macabre by The Faint, and I noticed with +6dB amplification set on the HDCD DSP, I was getting some pretty severe clipping in Adobe Audition. I re-ripped the CD using the HDCD DSP without the +6dB setting, and ran amplitude statistics on the resulting file.

    The peak amplitude in the left channel is -2.80 dB, and the right channel is -3.27 dB. This suggests either enabling the +6dB amplification setting on the HDCD DSP should be avoided, or a routine should be implemented to scan for peak amplitude in the album BEFORE applying the amplification, and then ONLY applying enough to bring the peak amplitude to -0.3 dB.

    This may be an isolated case, but I am nervous now as to how many albums are being clipped due to this issue.

    Thank you for your time in this matter. :smile2:

  2. #2

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    Re: HDCD Decoder should NOT have the 6dB amplification gain set!

    I suspect whoever decided to make the +6dB amplify option for HDCD decoding forgot about the range extension option in the HDCD specifications, which probably was not used on many HDCD, but WAS used on The Faint "Danse Macabre" CD.

    Another example is the Disney "Tarzan" CD. When the +6dB option is checked, there is some slight clipping, and Adobe Audition measures the bit depth at 16 bits. When the +6dB option is NOT checked, there are higher peaks with no clipping (this indicates more dynamic range) and the measured bit depth is 20 bits per sample.

    IMHO +6dB should NEVER be checked when decoding HDCDs to 24-bit FLAC files. HDCD decoding is a non-reversible process, so it is better to leave the amplification setting off.

    Your files will be 6dB quieter, that is true, but with replay-gain enabled during playback on any software, this overcomes any issues. I would highly recommend adding the replay-gain (scanning only, not applying) DSP after the HDCD decode DSP. This will re-scan the replay-gain value for equal-volume playback on all devices.

    Oh, and for people worried decoding all their HDCDs will make their collection much larger in file size, don't worry. For example "Danse Macabre" by The Faint did grow by about 20%, but "Lazarus" by Tool, only grew a couple megabytes over the entire album, so FLAC is able to pack 24-bit audio very efficiently if their is not as much information added by the HDCD decoding process.

    Just a quick rant here, but replay-gain or something like it is used by most DJ's and is built in to most DJ software. Artists should NOT master their music so loud, or "hot" because all the software will do is turn down the volume on playback anyway. Better to keep all the pumping dynamic range instead!
    Last edited by Lynx_TWO; 06-05-2013 at 02:42 PM.

  3. #3
    dBpoweramp Guru
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    Re: HDCD Decoder should NOT have the 6dB amplification gain set!

    I assume you realize that ripping with hdcd DSP does not produce bit perfect rips. Lots of good info here.

    http://forum.dbpoweramp.com/showthre...best+practices

  4. #4

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    Re: HDCD Decoder should NOT have the 6dB amplification gain set!

    Quote Originally Posted by garym View Post
    I assume you realize that ripping with hdcd DSP does not produce bit perfect rips. Lots of good info here.

    http://forum.dbpoweramp.com/showthre...best+practices
    Of course it does not produce bit-perfect rips. It does however, produce bit-perfect rips first, then decodes those bit-perfect rips to 24-bit FLAC files with 17-20 bit actual resolution AND with greater dynamics if the compander option was used while encoding the CD. This is the same decoding process done by all HDCD compatible DVD and CD players on the market, as well as receivers that support it.

    The benefit of decoding the HDCD before compressing to FLAC is I do not need an HDCD compatable player since the decode is already done for me.

    There is a second benefit. CDs that did not use the compander option (such as Motley Crue's Dr. Feelgood (2003 Remaster), still have massive clipping, only the volume is around (not exactly) 6dB lower than the limit. This allows me to use RX Advanced 2 Declipper to analyse where the clipping starts, than restore the clipped peaks, while giveing the added benefit of working at native 20-bit resolution up to the 24-bit final resolution.

    CDs such as Green Day's - Nimrod have a huge visual difference when decoded using the HDCD plugin, and peaks are recreated appropriately. No more flat areas

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