SEGA CD simple audio tech question

[ThugsRook]

how does SEGA CD (real hardware) handle the 2 second pre/post gap?
ive read/know that "space" is needed for seeking, but is it used during playback?



if someone would be nice enough to help me, i have a simple way to test this...

North American SEGA CD (real hardware)
North American Sonic CD (real disc, no CD-R stuff)

fire up Sonic CD and start a new game. dont play, just sit there and listen to the audio track. at 1:44 the track should end, loop, and restart at 1:47.


if someone could verify that for me id really appreciate it
TIA

(ill gladly explain more of what im getting at, but i need that verified first)

[evildragon]

Those 2 second things are determined when the CD is encoded, it's adjustable, so I'm fairly certain it does abide by this, as fast as the 1X drive can, because it DOES need to re seek at the beginning of the track.

[ThugsRook]

Those 2 second things are determined when the CD is encoded, it's adjustable, so I'm fairly certain it does abide by this, as fast as the 1X drive can, because it DOES need to re seek at the beginning of the track.

thats why i need to verify.

i have already fixed this in emulation, but im curious about the real hardware's default behavior.


can anyone run that test for me?
that will tell me EXACTLY what i need to know

[tomaitheous]

Understanding what the pregap is for and how it works in relation of, then it's pretty safe to assume that the SegaCD is not playing audio inside the 2 second pregap for track play mode. Btw, 2 seconds is the minimum and default size; it can be larger (legally according to spec). I think the only exception would be if track play mode had an ending track # other than the start (like a normal CD player) so playing through/across tracks sequentially would include the pregap in the CDDA playback, or if the BIOS took LBA addressing or MM:SS:FF addressing argument for the starting point for CDDA playback.

What is it that you're trying to do, exactly?

[ThugsRook]

Understanding what the pregap is for and how it works in relation of, then it's pretty safe to assume that the SegaCD is not playing audio inside the 2 second pregap for track play mode. Btw, 2 seconds is the minimum and default size; it can be larger (legally according to spec). I think the only exception would be if track play mode had an ending track # other than the start (like a normal CD player) so playing through/across tracks sequentially would include the pregap in the CDDA playback, or if the BIOS took LBA addressing or MM:SS:FF addressing argument for the starting point for CDDA playback.

What is it that you're trying to do, exactly?

KEGA Fusion plays the pregap as a postgap, noticable on tracks that loop. (Using a real Sonic CD, bin+cue, iso+wav, all formats)

I'm curious if real hardware does the same. youd think it wouldnt with all the trouble thats gone into marking pre/post gaps / end of tracks, etc. unfortunately im thinking real hardware is also gonna play the pre/post gap

if someone would run that Sonic CD test that i posted earlier... that will tell me exactly what i need to know.

[ThugsRook]

if someone would be nice enough to help me, i have a simple way to test this...

North American SEGA CD (real hardware)
North American Sonic CD (real disc, no CD-R stuff)

fire up Sonic CD and start a new game. dont play, just sit there and listen to the audio track. at 1:44 the track should end, loop, and restart at 1:47.

please, if someone could verify that for me id really appreciate it
this is all i need to know.
TIA

[Lastcallhall]

I'll look and see if I have my original Sonic CD tonight and test that out if I do.

[Lastcallhall]

Just a quick update - I don't have my sonic disc any longer, it would seem. I tore my loft apart looking for it and I've come to the conclusion that either the cats ate it, or it became part of a larger mess that seems to be growing daily up there... Sorry.

[Jax184]

How could a Genesis forum be this useless? I've got 2 CDXs and about 6 Sega CDs. I'll plug one in and do it for you later this afternoon.

[ThugsRook]

Just a quick update - I don't have my sonic disc any longer, it would seem. I tore my loft apart looking for it and I've come to the conclusion that either the cats ate it, or it became part of a larger mess that seems to be growing daily up there... Sorry.

NP ~ thx for the effort

hopefully JAX will come thru with some results. (thx JAX)

[Jax184]

Here we go, slightly later than expected. In addition to having to find my CDX power adapter, I had to find my copy of Sonic CD. Turns out both were with my other CDX.

I made you a recording of the entire sequence, from cold start to just after the first loop.
http://www.jax184.com/Sonic%20CD%20first%20loop.mp3

[ThugsRook]

Here we go, slightly later than expected. In addition to having to find my CDX power adapter, I had to find my copy of Sonic CD. Turns out both were with my other CDX.

I made you a recording of the entire sequence, from cold start to just after the first loop.
http://www.jax184.com/Sonic%20CD%20first%20loop.mp3

thank you very much

adjusting for time index, song faded out @ 1:44 and restarted @ 1:45. (compared to my 1:44-1:47 KEGA & real Sonic CD)

this means real hardware does NOT play pregaps.
this also means KEGA fusion DOES play pregaps. (bug!)

thx again

[ThugsRook]

ok, so KEGA fusion has a verified SEGA CD bug
this means ALL current BIN+CUE, ISO+WAV, and even home rips... are somewhat incorrect for emulator use

since PREGAP info doesnt work ~ all of the audio tracks need to be shortened by 2 seconds (some games its 1.74 seconds).

this can be done by ripping the BIN+CUE to ISO+WAV (or MP3) with IsoBuster, ommiting the pregaps.
IsoBuster is the only program i know of that can do this. cant be done from real discs, must be BIN+CUE.


i know i know, ive got balls claiming everything weve been doing for so many years is potentially wrong

id appreciate it if someone was interested in checking out my claims, trying my repair methods, and testing the results

[kool kitty89]

Isn't there an extra requirement for pre/post-gaps for CD-DA located outside of the normal data range of the Sega CD? (I forget what the specific limit is . . . 50 some minutes, or maybe the full 63 minutes of early/low density CDs)

[ThugsRook]

Isn't there an extra requirement for pre/post-gaps for CD-DA located outside of the normal data range of the Sega CD? (I forget what the specific limit is . . . 50 some minutes, or maybe the full 63 minutes of early/low density CDs)

im not sure about that.

but either way i dont think pre/post gap info is ever gonna work while using "data tracks" anyway.
Steve might get it working when using a real SEGA CD in KEGA Fusion, but data (audio) tracks are gonna be another animal entirely.

so ~ we need to correct the audio tracks for proper emulator usage.