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Topic: More SACD gibberish (Read 15827 times) previous topic - next topic
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More SACD gibberish

Reply #50 –
If I had to guess what M$ was doing in Media Player when they play a CD it would be that they read a little piece of the first track and determine if the HDCD marker is in there (which is trivial), and if it is they turn on the indicator and don’t do anything else for the whole CD. That would explain why user saw that Media Player misidentified non-HDCD tracks on a CD with both kinds of tracks:

http://www.audiofora.com/yabbse/index.php?...y;threadid=2852

If someone had a soundcard with a non-resampling digital output it would be pretty easy to figure out what was going on. Or one could look at the CPU usage when playing HDCD vs. non-HDCD tracks.

BTW, does Media Player identify wav files with HDCD encoding, or must it be playing a CD?

Since that thread I have found another source of 24/96 recordings:

www.hiresmusic.com

I got their new Leon Russell release the other day and it sounds pretty good. And unlike DVD-A discs you have access to the full 24/96 digital audio data.

More SACD gibberish

Reply #51 –
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however it doesn't sound like the additional data encoded into the audio stream is used for this process.

It is :

Quote from http://www.hdcd.com/partners/proaudio/AES_Paper.pdf , page 15 :

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The information carried in the hidden code consists of the filter choice used for decimation to the final sampling frequency for each channel, whether the peak extend algorithm is on or not, and the nominal value of the gain for the low level compression algorithm.


page 17 :

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Finally, the signal is interpolated to twice the sampling frequency using a filter which is complementary to the anti-alias filter used in the encoder.


By the way, I stand corrected : 96 kHz is not needed, 88.2 kHz playback is enough

Emphasis is mine.

More SACD gibberish

Reply #52 –
As discussed in this thread, the HDCD signal needs hardware to be decoded. What WMP does is simply recognize the HDCD instructions that are embedded in the audio signal, nothing else.

/ Uosdwis

More SACD gibberish

Reply #53 –
Well, as said both WMP and HDCD is Microsoft, and I would assume WMP does actually decode it. And it doesn't need to issue a warning about 24/96 either, because it uses DirectSound, which will downsample it automatically (software or hardware, depends on card).

--edit--
Almost forgot it... Why shouldn't software be able to decode HDCD? It's digital data processing, so software is well able to do so.

More SACD gibberish

Reply #54 –
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Why shouldn't software be able to decode HDCD? It's digital data processing, so software is well able to do so.


I agree.

Quote
And it doesn't need to issue a warning about 24/96 either, because it uses DirectSound, which will downsample it automatically (software or hardware, depends on card).


I don't agree, it's like saying that a standard TV set can play HDTV because it just converts it to low resolution.
If you downsample HDCD, you get CD quality, not HDCD.

More SACD gibberish

Reply #55 –
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Why shouldn't software be able to decode HDCD? It's digital data processing, so software is well able to do so.


I agree.

If software can decode it, then it could be "ripped" too... I think (?).

More SACD gibberish

Reply #56 –
My guess is that it is possible in theory but no current software does it?

More SACD gibberish

Reply #57 –
In case of DirectSound, it does automatically downsample if the device caps are lower as the requested ones. That it serves of no purpose on HDCD playback, is right. But at least it doesn't need to care about anything or issue warnings about fucked up sound. Example: 96khz/24bit decode being played back on a soundcard that plays only 48khz/24bit.

More SACD gibberish

Reply #58 –
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If software can decode it, then it could be "ripped" too... I think (?).


Quote
That it serves of no purpose on HDCD playback, is right. But at least it doesn't need to care about anything or issue warnings about fucked up sound. Example: 96khz/24bit decode being played back on a soundcard that plays only 48khz/24bit.


Where do you want to come to ?
HDCD is perfectly compatible with all CD players, computer or not. An HDCD has inaudible info, in the 16 - 20 kHz range, at -90 db, that drives the dynamics and oversampling of the HDCD chip. Without HDCD decoding, you just get regular audio, a little compressed in dynamics, with just regular oversampling.
It is impossible to detect by ear if a CD is HDCD or not.

So I don't understand your remarks : ripped to what ? You can rip any CD, be it HDCD or not, and there is no issue warning when you play it in a CD player, or as a 44.1 kHz 16 bits wav file in Winamp.
You just won't notice the -90 db 18 kHz content, and there will be no HDCD algorithms used for D/A conversion, nor dynamics enhancement.
If you play the same wav file in Windows Media Player, it will read the 18 kHz signal, and light up the HDCD logo accordingly.
It doesn't seem to process the dynamics (it could at least do that), unless specified otherwise somewhere. But so far, there is no indication that Windows Media Player can perform the HDCD enhancement to 88.1 kHz, 24 bits.