Thread: What is a SBE?
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Old 2005-01-10, 05:40 AM
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Re: What is a SBE?

Audio CDs hold data in minimum block ("sector") sizes of 1/75th second (0.01333 seconds / 2352 bytes of data / 588 stereo samples). If you try to burn an audio file to an audio CD, and its length is not an exact number of sectors, the last sector will usually be padded with digital silence (zeros). This gap is referred to as a "sector boundary error" because it is an error caused by a large audio file having been split into individual tracks at places other than sector boundaries (1/75th second intervals).

As such, an SBE is a silence of less-than-but-not-equal-to 1/75th second found "between" audio tracks on a CD. I say "between" because technically it is at the end of the preceeding track and has nothing to do with the one that follows. In some cases, this flaw could be completely unnoticeable, as it could be only one sample, and could fit neatly into the current flow of samples. However, more likely it will leave an audible silence, or an audible click. The click is caused when the silence interrupts a "loud" part of the waveform, i.e. one that is not close to digital silence. The waveform makes a sudden jump from a loud value to silence, and then back up again to carry on when it left off. I'll add some images in a minute for clarification.

Once you burn an audio CD with SBEs, the silences become part of the audio data - they won't disappear again if/when you extract back to your computer. An audio file extracted from a CD can never have an SBE because it's come from a CD and is as such sector-boundary-aligned.

It should be noted that "SBE" has falsely become something of a catch-all term for anything that has a short (non-two-second) silence between tracks. There was an Ozric Tentacles show seeded on STG over summer straight from the master, which had silences at the end of each track that were maybe 0.05-0.1 seconds in length. I've no idea what the taper did to achieve these, but I've seen the show on tradelists noting "quite a large SBE between each track" - there's no such thing as a "large" SBE - it's by definition less than 1/75th second in length.

If you wish to avoid creating files with SBEs, split using CDWave. For assured reliability, don't actually split the files - just save the cuesheet and burn using software that can handle cuesheets (CDRWin, newer versions of Nero etc).

Thankfully, pure SBEs don't damage the audio data in any way, they just interrupt it, so with care can can be perfectly fixed by just removing the silence. The waveforms either side of the silence should automatically line up perfectly. TAO, and especially mp3 gaps, are not so easy to remedy as small parts of the audio data can be lost in the gap generation process.

I think that's pretty much everything!
see also http://www.cdrfaq.org and http://www.ambfaq.cjb.net
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