AudioChimp wrote:here is an analysis one of the tracks you mentioned, i am not an expert on audio but is this a sign of an mp3 sourced file?
Even when looking at the entire file's spectrogram all at once like this, I do notice the telltale "gritty" look of lossy coding in the upper frequency bands. If you were to put just the first few seconds of the file into a file and run Spek on that, you could verify; you will see something similar to what I posted, where the upper part of the spectrum has had a lot of sound removed, and what remains behind is in discrete chunks, all the same size (the little dashes in the image I posted). This gritty texture actually extends all the way down into the lower bands but it's most noticeable at the top, due to the way MP3 deprioritizes that range. Audio that has never been subjected to lossy coding does not exhibit these characteristics.
AudioChimp wrote:remember all these songs are remixed by a dj they sometimes use various sources when creating mixes.
Yep, yep... absolutely correct. Some remixes are made from audio taken from different sources, e.g. some samples from MP3, some from CD, with freshly synthesized beats laid on top. This can explain why a spectrogram can have the look of lossless and lossy at the same time. That may have happened here. It's hard to say with certainty.
My point is just that this is one of those times when the fake-spotting tools are not entirely correct when they say this audio is "100% lossless". My experience with promo CD-Rs from this era (mid-2000s to mid-2010s) is that this kind of thing happened a lot, where they contain audio that's clearly from different, not entirely lossless digital sources.
AudioChimp wrote:i had the tracks all from varying lossless sources and added 2 seconds to each track to provide unity to the start of all the tracks (the 2 second segments were copied and pasted from the end of each track), using audacity i then selected the 2 second part i added and generated 'silence' so no noise would occur from the copied segment, ... no other part of the files were added to or altered
Depending on your Audacity settings, you may have accidentally added dither (very quiet, high-frequency hiss) to the non-silent parts when saving. In terms of what you hear, it's harmless, but for collectors it's not as ideal as sharing the completely unedited rip. This is one of the pitfalls of audio editors; they work with 32-bit floating-point samples, and then assume you want dither when quantizing to 16-bit integer. You might, depending on what you did to the audio. But if all you did was make simple cut-and-paste edits of audio that was quantized to begin with, then you probably
don't want dither when saving.
As for the 2nd rip you shared, yes, that's quite lossy, visibly worse than the first batch. It was converted to MP3 during/after the rip.
Posted: Tue Jun 16, 2015 7:57 am
