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I read this whole thing twice and I now know what pregaps are and the history but still have no idea why people would put them on a CD or why they’re useful for

I read this whole thing twice and I now know what pregaps are and the history but still have no idea why people would put them on a CD or why they’re useful for hidden tracks.

dylan604 2y ago
Oh good, so I'm not the only one that thought the article failed to actually state what the superpower was. Some lame ass patent was granted?
monocasa 2y ago
Basically cd audio tracks have a base sector and a start specified. That allows sectors representing audio before timestamp 0:00 to be represented the track. The reason for this originally was probably to allow the drive to get synchronized before the track started. Enterprising cd masterers put actual hidden audio data in that area which would allow you on some CD players to rewind past 0:00 and then play the hidden audio at the negative timestamp.
- crazygringo 2y ago
  How much hidden audio could be stored? Was it limited to something negligible like a couple of seconds? Or could you store a whole five-minute recording in there or something?
  - boomboomsubban 2y ago
    There doesn't seem to be a limit, this https://en.wikipedia.org/wiki/List_of_albums_with_tracks_hidden_in_the_pregap https://en.wikipedia.org/wiki/List_of_albums_with_tracks_hid... mentions a 27 minute live recording.
    - jvan 2y ago
      Incredible! Songs in the Key of X was the only album I ever knew to do this, and it wasn't even the first. I had no idea so many others did the same thing. Edit: Son of a *, I've had a copy of Sister Machine Gun's Burn for almost 30 years and never knew there was a hidden track!
      - ChrisArchitect 2y ago
        Classic X-Files album is the one I think of too. And how they hinted to everyone that there even was a hidden track on the sleeve: "'0' is also a number". (and the technical fineprint about the disc possibly not being Redbook compliant)
    - croes 2y ago
      I guess the limit is some milliseconds short of 74 minutes.
- deleted 2y ago
  [deleted]
add-sub-mul-div 2y ago
As the article says its like an easter egg, putting a hidden song before the first track of a CD. If the song wasn't in the pregap it wouldn't be hidden. It's just for fun. (Sometimes songs can also be hidden in tracks at the end of the CD like 99, but that feels less mysterious.)
- mattl 2y ago
  Sometimes CDs would have a long piece of silence at the end of the last song and then another song on the same track. Other CDs really experimented with the shuffle feature. They Might Be Giants’ Apollo 18 had a bunch of very short tracks that would usually play between songs when shuffle was used.
  - add-sub-mul-div 2y ago
    I had that CD and remember the short tracks but never thought of playing it on shuffle that way. I think it was nine inch nails' Broken EP that had the hidden tracks on 98/99 rather than after a long silence, but I could be wrong.
    - mattl 2y ago
      I think it tells you in the liner notes that you should use the shuffle button. My copy in the UK at the time didn’t have the individual tracks. Just one track.
    - ssl-3 2y ago
      Broken was first released as a 2-disc set. It was still in a many-fold Digipak case, but also included was a 3" mini-CD that had Suck and Physical (You're So). The regular-sized CD looked about identical to the 99-track version, but had only 6 tracks. (It was expensive to do this, and was never intended for long-term production. Later versions were generally as you describe.)
  - gwbas1c 2y ago
    I remember getting surprised by one of those. I was at a friend's house and forgot to turn off the CD at the end. It was funny at first, but when every other CD I bought had one, it became tacky.
mikepavone 2y ago
An audio CD is mostly arranged like a single continuous recording. Tracks are added on top of this via the Q subcode channel that gives information about the current location and the ToC stored in the lead-in area (also using the Q subcode channel). In the ToC, each track will have one more indexes that points at a specific location on the disc by minute, second and "frame" (represents 1/75 of a second, basically a sector). If a CD is properly following the Red Book standard, index 0 will point to a 2 second pre-gap of silentce and index 1 will point to the actual start of audio of the track (additional indices are allowed, but not common). The purpose of the pregap is to make life easier for less sophisticated players that aren't able to seek to a precise frame on the disc. They just have to be able to hit a 150 frame region. However, just because the standard says the pregap is supposed to be 2 seconds and silent doesn't mean it actually has to be. Players generally don't care and by the time the format was popular, even inexpensive players could seek precisely. This allows you to stick audio data before a track that will be skipped by the player when it's trying to seek to that track. If you stick it before track 01, it will be skipped even when just playing the disc through unless you rewind.
- kevin_thibedeau 2y ago
  The key for a hidden track at the beginning is that players usually start playing track 1 from index mark 1 (1.1) rather than index 0 as with continuous play through all subsequent tracks. The lead-in area for 1.0 is a holdover from grooved phonorecordings never meant to be played. It's a way for the primitive hardware of early CD players to acquire the start of the data stream in a safe area that doesn't have to be faithfully reproduced. Some players permitted you to skip back from 1.1 to 1.0 to hear the lead-in as a hidden pseudo-track. Typically this was only possible with hardware index nav. buttons rather than the track nav. buttons, further obfuscating the presence of the hidden track. The other means of "hiding" tracks is to have a bunch of short silent tracks until you get to track 99 (inconvenient to reach on a player without numeric track entry) or to have a long section of silence starting on the last track from index 1.
  - crtasm 2y ago
    >Typically this was only possible with hardware index nav Holding the previous track button would "rewind" playback and get you into the pregap on all the CD players I remember using, but these would have been late 80s models onwards.
barrkel 2y ago
The writing is not good; I gave up part way through. It's weirdly elliptic and almost autistic in its focus on details and an almost complete absence of a big picture. It could do with some kind of proper context-setting introduction, at the very least.
- WarOnPrivacy 2y ago
  This mirrors my experience. It's good content but I'd barely land on one splainer before being segueded into the next one. I kept thinking I missed the part they delved into hidden tracks.
- nayuki 2y ago
  A CD audio frame is defined as exactly 1/75th of a second (588 samples per channel). I don't know why the article waffles around with these poor wordings (emphasis mine): > These albums all had a pregap of either 32 or 33 “frames,” with a frame representing a length of about 1/75th of a second, per Hydrogen Audio’s Wiki. > To offer a small correction to the original question now that we know we’re talking about 74 frames per second rather than 60 or 100 It's needlessly confusing and undermines my confidence of the entire article.

I read this whole thing twice and I now know what pregaps are and the history but still have no idea why people would put them on a CD or why they’re useful for hidden tracks.

dylan604 2y ago

Oh good, so I'm not the only one that thought the article failed to actually state what the superpower was. Some lame ass patent was granted?

monocasa 2y ago

Basically cd audio tracks have a base sector and a start specified. That allows sectors representing audio before timestamp 0:00 to be represented the track. The reason for this originally was probably to allow the drive to get synchronized before the track started. Enterprising cd masterers put actual hidden audio data in that area which would allow you on some CD players to rewind past 0:00 and then play the hidden audio at the negative timestamp.

crazygringo 2y ago
How much hidden audio could be stored? Was it limited to something negligible like a couple of seconds? Or could you store a whole five-minute recording in there or something?
- boomboomsubban 2y ago
  There doesn't seem to be a limit, this https://en.wikipedia.org/wiki/List_of_albums_with_tracks_hidden_in_the_pregap https://en.wikipedia.org/wiki/List_of_albums_with_tracks_hid... mentions a 27 minute live recording.
  - jvan 2y ago
    Incredible! Songs in the Key of X was the only album I ever knew to do this, and it wasn't even the first. I had no idea so many others did the same thing. Edit: Son of a *, I've had a copy of Sister Machine Gun's Burn for almost 30 years and never knew there was a hidden track!
    - ChrisArchitect 2y ago
      Classic X-Files album is the one I think of too. And how they hinted to everyone that there even was a hidden track on the sleeve: "'0' is also a number". (and the technical fineprint about the disc possibly not being Redbook compliant)
  - croes 2y ago
    I guess the limit is some milliseconds short of 74 minutes.
deleted 2y ago
[deleted]

add-sub-mul-div 2y ago

As the article says its like an easter egg, putting a hidden song before the first track of a CD. If the song wasn't in the pregap it wouldn't be hidden. It's just for fun. (Sometimes songs can also be hidden in tracks at the end of the CD like 99, but that feels less mysterious.)

mattl 2y ago
Sometimes CDs would have a long piece of silence at the end of the last song and then another song on the same track. Other CDs really experimented with the shuffle feature. They Might Be Giants’ Apollo 18 had a bunch of very short tracks that would usually play between songs when shuffle was used.
- add-sub-mul-div 2y ago
  I had that CD and remember the short tracks but never thought of playing it on shuffle that way. I think it was nine inch nails' Broken EP that had the hidden tracks on 98/99 rather than after a long silence, but I could be wrong.
  - mattl 2y ago
    I think it tells you in the liner notes that you should use the shuffle button. My copy in the UK at the time didn’t have the individual tracks. Just one track.
  - ssl-3 2y ago
    Broken was first released as a 2-disc set. It was still in a many-fold Digipak case, but also included was a 3" mini-CD that had Suck and Physical (You're So). The regular-sized CD looked about identical to the 99-track version, but had only 6 tracks. (It was expensive to do this, and was never intended for long-term production. Later versions were generally as you describe.)
- gwbas1c 2y ago
  I remember getting surprised by one of those. I was at a friend's house and forgot to turn off the CD at the end. It was funny at first, but when every other CD I bought had one, it became tacky.

mikepavone 2y ago

An audio CD is mostly arranged like a single continuous recording. Tracks are added on top of this via the Q subcode channel that gives information about the current location and the ToC stored in the lead-in area (also using the Q subcode channel). In the ToC, each track will have one more indexes that points at a specific location on the disc by minute, second and "frame" (represents 1/75 of a second, basically a sector). If a CD is properly following the Red Book standard, index 0 will point to a 2 second pre-gap of silentce and index 1 will point to the actual start of audio of the track (additional indices are allowed, but not common). The purpose of the pregap is to make life easier for less sophisticated players that aren't able to seek to a precise frame on the disc. They just have to be able to hit a 150 frame region. However, just because the standard says the pregap is supposed to be 2 seconds and silent doesn't mean it actually has to be. Players generally don't care and by the time the format was popular, even inexpensive players could seek precisely. This allows you to stick audio data before a track that will be skipped by the player when it's trying to seek to that track. If you stick it before track 01, it will be skipped even when just playing the disc through unless you rewind.

kevin_thibedeau 2y ago
The key for a hidden track at the beginning is that players usually start playing track 1 from index mark 1 (1.1) rather than index 0 as with continuous play through all subsequent tracks. The lead-in area for 1.0 is a holdover from grooved phonorecordings never meant to be played. It's a way for the primitive hardware of early CD players to acquire the start of the data stream in a safe area that doesn't have to be faithfully reproduced. Some players permitted you to skip back from 1.1 to 1.0 to hear the lead-in as a hidden pseudo-track. Typically this was only possible with hardware index nav. buttons rather than the track nav. buttons, further obfuscating the presence of the hidden track. The other means of "hiding" tracks is to have a bunch of short silent tracks until you get to track 99 (inconvenient to reach on a player without numeric track entry) or to have a long section of silence starting on the last track from index 1.
- crtasm 2y ago
  >Typically this was only possible with hardware index nav Holding the previous track button would "rewind" playback and get you into the pregap on all the CD players I remember using, but these would have been late 80s models onwards.

barrkel 2y ago

The writing is not good; I gave up part way through. It's weirdly elliptic and almost autistic in its focus on details and an almost complete absence of a big picture. It could do with some kind of proper context-setting introduction, at the very least.

WarOnPrivacy 2y ago
This mirrors my experience. It's good content but I'd barely land on one splainer before being segueded into the next one. I kept thinking I missed the part they delved into hidden tracks.
nayuki 2y ago
A CD audio frame is defined as exactly 1/75th of a second (588 samples per channel). I don't know why the article waffles around with these poor wordings (emphasis mine): > These albums all had a pregap of either 32 or 33 “frames,” with a frame representing a length of about 1/75th of a second, per Hydrogen Audio’s Wiki. > To offer a small correction to the original question now that we know we’re talking about 74 frames per second rather than 60 or 100 It's needlessly confusing and undermines my confidence of the entire article.