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is fading in/out a lossy process?, [moved from FLAC]
unicorn20
post Feb 19 2013, 18:09
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hey all you audio experts of the forum.
i've been interested in lossless music for a long time and i got almost all of my knowledge about it from this forum.
i have an issue that i'm trying to figure out, and i've searched everywhere possible for info about it but i couldn't find any.
so you guys are my last resort, i hope you can help...
here's the issue :

i download many lossless albums all the time (WAV,APE,ALAC,FLAC), but i only keep to myself those few songs (if any) from each album, those songs that i liked the most.
most albums are ripped with gap detection so they begin with silence and end with silence, but there are some albums that don't, albums such as :

mixed albums (where the songs dissolve into each other)
live albums (where the tracks begin and end with the audience clapping or shouting)
one track albums (where there are no gaps or pauses between tracks)

i find it very annoying to listen to songs that comes from albums like the above, so i fix it using audacity, i fade in, and fade out, add some silence if necessary (using the "generate - silence" option), the thing is i can't help thinking maybe i am turning this perfect lossless file into a lossy one, and by doing so actually creating a fake lossless (since i'm always exporting as flac), my ears can't hear any difference, but still, you know way more than i do about these things.

so please tell me, does the "fade in / fade out / add silence" processes make a lossless file lossy?

sorry if my english is bad, i hope it's understandable, and if you find any mistakes please correct me.

thanks smile.gif

This post has been edited by unicorn20: Feb 19 2013, 18:10
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mjb2006
post Feb 20 2013, 09:22
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unicorn20, in your original post, you mentioned gap detection. You seem to misunderstand what it is.

The audio on a CD is divided into tracks. Each track is divided into one or more sections called indexes. Usually there's only one section, index 01, which takes up the whole track. Sometimes there's two sections: index 01 for the main song, and before that, a brief section called index 00 (that track's "gap" or "pre-gap"). This is often silence, but might be an interlude, count-in, applause, or other filler. It is what you probably think of as being "between" the tracks, or perhaps at the end, audio-wise, of the previous track. Technically, though, it's the beginning of the current track. But since we always rip or play tracks starting at index 01, it's more natural to think of it as being at the end.

Only index 00 is what we call the "gap". There can also be indexes up to 99, but anything above 01 is uncommon (I think 2 or 3 out of 1000 CDs I own have index 02s) and anything higher than 03 is extremely rare (apparently it's mostly on sound effects CDs that would otherwise need to exceed the 99-track limit).

Now consider what happens when you're using a real CD player, and you reach the end of a song. As the gap/index 00 (if any) at the start of the next track plays, you see the track number go up by 1, and the time display switches to negative numbers, counting up to 0:00, at which point index 01 plays. You don't see this when playing files or even CDs in a computer; the gap is normally just at the end of the previous track's file.

For example, if there's a 5-second gap at the end of a song 3 minutes, 30 seconds long, in a computer you'll just see the counter go 3:29, 3:30, 3:31, 3:32, 3:33, 3:34, 0:00 (track number increments here). On a real CD player you would see 3:29, -0:05 (track number increments here), -0:04, -0:03, -0:02, -0:01, 0:00. The audio would be the same in either case.

Apparently there was some folklore on some excessively bureaucratic file-sharing forums that said to make the ripping software do a gap detection pass before ripping. There's no point to doing so. Ripping software that's capable of gap detection does it automatically when needed. And it's only needed for three situations: 1. when generating accurate cue sheets for discs that have gaps (so you can use the files to burn a CD that behaves as described above in a real CD player); 2. doing an index-based rip, where each index goes into its own file, rather than each complete track going into a file (useful for when you want interludes to be in files separate from the main songs); or 3. deliberately omitting gap audio from a rip, such as when you're ripping from a CD-R that has had silent gaps added in error (but you have to tell the ripper to do this; just detecting gaps doesn't make it omit them).

Gap & other index info isn't always possible or reliable (it's in the "subcode" alongside the audio data, harder to read). It all depends on the software, the drive, and the CD. When gap detection isn't done, the ripper just treats each track as if it only has one section, index 01. No audio is left out.

This post has been edited by mjb2006: Feb 20 2013, 09:24
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Posts in this topic
- unicorn20   is fading in/out a lossy process?   Feb 19 2013, 18:09
- - halb27   In a formal sense fading in/out is a lossy process...   Feb 19 2013, 18:16
- - Garf   Fade in and out is lossy. You cannot recover the o...   Feb 19 2013, 18:36
- - andrew_berge   Also, Audacity dithers everything by default, so i...   Feb 19 2013, 18:56
- - jensend   halb27, being different isn't what defines los...   Feb 19 2013, 18:57
- - extrabigmehdi   QUOTE (unicorn20 @ Feb 19 2013, 17:09) so...   Feb 19 2013, 19:32
|- - db1989   QUOTE (extrabigmehdi @ Feb 19 2013, 18:32...   Feb 19 2013, 20:01
- - halb27   As far as I can see the OP doesn't want to res...   Feb 19 2013, 19:34
- - dhromed   Andrew Berge's comment about dither is more im...   Feb 19 2013, 20:41
- - halb27   My problems with Audacity was when exporting to a ...   Feb 19 2013, 21:19
- - unicorn20   wow, you guys are quick hehehe well, thank you all...   Feb 19 2013, 23:11
|- - andrew_berge   I'm not so good at explaining this, so i'l...   Feb 19 2013, 23:29
|- - db1989   QUOTE (unicorn20 @ Feb 19 2013, 22:11) oh...   Feb 20 2013, 00:09
|- - yourlord   QUOTE (unicorn20 @ Feb 19 2013, 17:11) i ...   Feb 20 2013, 00:21
- - halb27   Dithering adds some noise to the least significant...   Feb 19 2013, 23:32
- - greynol   I think the world is better off to have them modif...   Feb 20 2013, 01:04
- - mjb2006   unicorn20, in your original post, you mentioned ga...   Feb 20 2013, 09:22
- - unicorn20   i'd like to begin by saying ***THANK YOU SO MU...   Feb 20 2013, 21:47
|- - pdq   QUOTE (unicorn20 @ Feb 20 2013, 15:47) QU...   Feb 20 2013, 22:01
||- - unicorn20   QUOTE (pdq @ Feb 20 2013, 22:01) db1989 s...   Feb 20 2013, 22:54
||- - greynol   QUOTE (pdq @ Feb 20 2013, 13:01) db1989 s...   Feb 20 2013, 23:03
|- - mjb2006   QUOTE (unicorn20 @ Feb 20 2013, 13:47) yo...   Feb 20 2013, 23:03
- - greynol   My point was not necessarily targeted exclusively ...   Feb 21 2013, 00:09
|- - mjb2006   QUOTE (greynol @ Feb 20 2013, 16:09) ther...   Feb 21 2013, 01:58
|- - greynol   QUOTE (mjb2006 @ Feb 20 2013, 16:58) The ...   Feb 21 2013, 02:10
- - db1989   If I make sure to include something like this in ...   Feb 21 2013, 00:46
- - greynol   You are too kind, db1989. I stopped aiding people...   Feb 21 2013, 00:49


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