Talk:High Definition Compatible Digital

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From VfD:

Duplicated in HDCD. My fault. Mandel 12:52, Aug 20, 2004 (UTC)

  • Do not delete. Readers will search for both of those titles. Instead, one article should be replaced by a redirect to the other one. (I think it should actually be HDCD redirecting to the full name.) Andris 14:27, Aug 20, 2004 (UTC)
  • Keep and redirect HDCD here. -- Grunt (talk) 22:47, 2004 Aug 20 (UTC)
  • Keep. Agree, HDCD should be redirected to High Definition Compatible Digital. Nothing to merge that I can see. Andrewa 00:53, 21 Aug 2004 (UTC)
  • Merge as necessary and redirect HDCD. -- Cyrius|✎ 01:13, 21 Aug 2004 (UTC)
    • Use the article in HDCD as it is better worded, then redirect. Mandel 13:50, Aug 23, 2004 (UTC)
  • Merge HDCD into this and make HDCD a redirect. -Sean Curtin 04:01, Aug 25, 2004 (UTC)

end moved discussion

Contents

[edit] "miniscule" reduction in range on normal CD player

Unless I'm missing something, shouldn't replacing the least significent bit with random numers (for the sake of a standard CD player, it is random) loose half the levels in the PCM signal?

I understand the difference wouldn't be obvious, but is loosing half the levels really a 'miniscule' drop?

WikianJim 17:08, 31 July 2006 (UTC)

Yes. Ears have a logarithmic, not linear curve, so removing one bit from a 16-bit recording only decreases the sound quality by about 7%. This decrease is probably not audio unless a CD has really quiet passages; double-blind tests have shown that people can't tell the sound quality of a 14-bit CD from a 16-bit CD. Samboy 22:04, 8 January 2007 (UTC)

Link for the above please.

Bad premise: HDCD adds dither and encodes a very low bitrate control signal into the lsb, using the lsb of 1-2% of the samples as is documented in the refs F5r5e5d 16:43, 2 June 2007 (UTC)

[edit] Question

  • Is there a way to check on one's computer to see if it is equipped with a 24 bit card? J-Dog 01:40, 14 October 2006 (UTC)


== Hello, I haven't registered with Wikipedia yet, but I have edited this article. Before reverting, please consider the information I have edited. That is: - the technical explanation for how Microsoft somehow get an extra 4 bits of dynamic range into a regular uncompressed PCM signal. This defies the laws of mathematics! I personally dispute this claim. Funny how Microsoft have removed the info from their website. You can't add more dynamic range to a regular audio CD without this taking up more space - yet, HDCDs claim to do this!

==

Yes, too bad Microsoft removed the information.

I remember reading some documents from the original Pacific Microsonic site. The audio signal carried by an HDCD is actually compressed. If I remember well, the top 9dB of the dynamic range is processed using a 3:1 compression, reducing it to only 3dB. That means the rest of the audio signal is shifted upwards by 6dB. (I am not too sure about the ratio or the actual figures). When used with an HDCD compatible machine, the D/A expands this top 3dB, giving back the full 9dB dynamic range, with some extra bits to spare at the lower end of the signal.

The reasoning behind this is because the decibel scale is logarithmic (based on the human perception of sound). The top end of the dynamic range takes up most of the resolution in a linear PCM signal, and the engineers who invented HDCD seemed to think that it was unnecessary, therefore compressing the top range into a much smaller resolution scale.

Note that this is not "data" compression (as in MPEG schemes) but rather "dynamic" compression, something very similar to what Dolby or dBx have been doing with noise reduction schemes. This (no data compression) is because it would have rendered the disc logically incompatible with existing players. The aim for HDCD is to make available "better" CDs for ALL players. Regular players treat the signal as normal linear PCM. It's just that the curve actually used for digital conversion was not linear. Therefore the quality of the audio heard from these non-HDCD players is rather compressed (radio-like).

Perhaps HDCD was aimed for some genres of music such as jazz or classical, which generally does not compress the music before (even during) mastering. But pop/rock music has relied on dynamic compression, from the moment the sound is recorded up to the final mixdown. With current trends of loudness war (who gets the loudest music on CD), there is only about 3-6dB of dynamic range in those mixes. Those albums cannot really benefit from the claimed advantages of HDCD.

Since 2 or 3 years the HDCD processor in the mastering room I frequent has been left alone, a simple glance at it makes every engineer/client a shiver... if you know what I mean. Dulldull 09:54, 21 February 2007 (UTC)

[edit] Fair use rationale for Image:HDCD.jpg

Image:HDCD.jpg is being used on this article. I notice the image page specifies that the image is being used under fair use but there is no explanation or rationale as to why its use in this Wikipedia article constitutes fair use. In addition to the boilerplate fair use template, you must also write out on the image description page a specific explanation or rationale for why using this image in each article is consistent with fair use.

Please go to the image description page and edit it to include a fair use rationale. Using one of the templates at Wikipedia:Fair use rationale guideline is an easy way to insure that your image is in compliance with Wikipedia policy, but remember that you must complete the template. Do not simply insert a blank template on an image page.

If there is other other fair use media, consider checking that you have specified the fair use rationale on the other images used on this page. Note that any fair use images uploaded after 4 May, 2006, and lacking such an explanation will be deleted one week after they have been uploaded, as described on criteria for speedy deletion. If you have any questions please ask them at the Media copyright questions page. Thank you.BetacommandBot 06:37, 5 June 2007 (UTC)

[edit] Dither and transcoding

I would appreciate if someone knowledgable could address the following:

1. How exactly is the term "dither" used in this context? Does this refer to the whole concept of representing 'more' data (the extra dynamic range) using the various HDCD control codes (filter options, etc) across multiple CDDA frames -- so you get the dynamic range scaling and other tricks, just at slightly more than a per-sample timescale -- or does it refer to adding noise to the LSB of all samples so that any effect from the "< N%" of samples with control coding in the LSB aren't noticeable as some audible artifact amidst the garbage?

2. Presume that one has the equipment or ability to process a CD with HDCD encodings via software DSP and output the result as a 24-bit-per-sample PCM stream. Would rounding the 24-bit stream back to a 16-bit stream produce a "better" result for playback on conventional CD players? "Better" is obviously subjective, elaboration on what is lost/gained via this form of reencoding is welcome. —Preceding unsigned comment added by 69.182.29.12 (talk) 04:14, 5 January 2008 (UTC)

[edit] ambiguation...

HDCD also refers to High Definition Compact Disk, which is a regular CD-R or CD-RW burned in a DVD burner with a half-width laser track. The resulting disc is 1.4GB and is only readable in another DVD driver or better (HD-DVD or Blu-Ray)