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Re: HDCD Spotted - Post any rarities here

Reply #50
Is there anything released both as HDCD and as non-HDCD, for the same "mastering"?

I even forget that I posted a possible answer to that question myself. In this thread.
https://hydrogenaud.io/index.php/topic,112348.msg925894.html#msg925894

The ten seconds I mention there, is what a HDCD decoder should take to reset. Which is potentially a big issue; what happens in the following situation?
- A CD is compiled with HDCD tracks and non-HDCD tracks
- The "master" file is written to CD, with an arbitrary offset, slightly moving the track boundaries, so that the HDCD flags from track N find their way to the very first samples of track N+1
- and so the CD is pressed.
“It sounded bad to me. Digital. They have digital. What is digital? And it’s very complicated, you have to be Albert Einstein to figure it out.”
- Donald Trump, May 2017

Re: HDCD Spotted - Post any rarities here

Reply #51
The ten seconds I mention there, is what a HDCD decoder should take to reset. Which is potentially a big issue; what happens in the following situation?
- A CD is compiled with HDCD tracks and non-HDCD tracks
- The "master" file is written to CD, with an arbitrary offset, slightly moving the track boundaries, so that the HDCD flags from track N find their way to the very first samples of track N+1
- and so the CD is pressed.
There is supposed to be 200ms of "HDCD silence" at the beginning of each track, where the first packet is expected to appear. This is to give the decoder time to detect a packet and adjust levels if one is found.
I've seen that packets usually appear less than one second apart. The sustain timer in foo_bar uses 10 seconds, so if a non-HDCD encoded track is inserted, the last packet will continue to be used for the first 10 seconds of the track, but this is foo_hdcd specific. As the FFmpeg decoder is based on foo_hdcd, it inherited the 10 second timer, but I think it was chosen arbitrarily (but maybe kod54 will say otherwise). I've got an FFmpeg patch that allows it to be set as an option, and to lowers the default to 2000ms, but the patch hasn't been accepted/applied in master, yet. I'm still playing with it.


Re: HDCD Spotted - Post any rarities here

Reply #52
There is supposed to be 200ms of "HDCD silence" at the beginning of each track, where the first packet is expected to appear. This is to give the decoder time to detect a packet and adjust levels if one is found.

Beginning of each "track", are you sure? If the entire disc is HDCD, it would make much more sense to inherit the state from the previous track. (The decoder will reset in the time taken to switch a physical CD in a single physical player.) What if the beginning of track 2 is at volume above -6 dB?



I've seen that packets usually appear less than one second apart.

The Johnson/Pflaumer AES preprint mentions "in both channels within a one second interval". Makes sense.


As the FFmpeg decoder is based on foo_hdcd, it inherited the 10 second timer, but I think it was chosen arbitrarily (but maybe kod54 will say otherwise).

I just presumed that it was from hdcd.exe, which scans only the first 750 frames = 10 seconds to identify a HDCD (with the -i option). But that choice may in turn have been arbitrary.
“It sounded bad to me. Digital. They have digital. What is digital? And it’s very complicated, you have to be Albert Einstein to figure it out.”
- Donald Trump, May 2017


Re: HDCD Spotted - Post any rarities here

Reply #54
Is there anything released both as HDCD and as non-HDCD, for the same "mastering"?

Just got curious, and checked from this list.
Yngwie Malmsteen: Concerto for big ego and orchestra has two entries in the list, but mine is not HDCD.
Consistent with this. https://www.discogs.com/master/view/236975
My version is before the 2013 reissue, and I don't think the 1998-2000 versions were different mixes. So ... apparently a yes.


I even forget that I posted a possible answer to that question myself. In this thread.
https://hydrogenaud.io/index.php/topic,112348.msg925894.html#msg925894
Well maybe one more.
“It sounded bad to me. Digital. They have digital. What is digital? And it’s very complicated, you have to be Albert Einstein to figure it out.”
- Donald Trump, May 2017


 
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