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  1. Member Cornucopia's Avatar
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    Originally Posted by kirkmc View Post
    Sorry I just assumed ppl here would know far more than me. AuCDTect is a tool to check if an audio file is lossless. Tau also does this (but from the CD itself).
    You would expect it to be lossless, but it won't be if the file (or CD) source is lossy e.g mp3.
    Someone may have extracted a file from CD (to wav) and then to mp3. Someone who doesn't know better might then convert that back into a flac (or wav).
    You may not know this by just listening, hence using a tool to analyse the file.
    So the "big picture" question is how good are these tools, how often is there a false positive. Or can they be considered (near to) 100%.
    I probably do know much more than you regarding recording, mixing, mastering, producing and pressing CDs, but it seems to me that this is all about using some hacker aftermarket tools to assist guessing the provenance of questionable sourced materials. Right there, you are already on a bad track. We have no data on how these tools are designed, or whether they follow good audio engineer best practices to analyse the files.
    I get my material only from reputable major publishers or from known audiophile or engineer friends, so would never need to encounter or look for such tools.

    But you never answered my earlier question: if this only works on SOME pychoacoustic models, how is it expected to be definitive to your judgement? Does it matter if it's 80% or 40% correct if it puts ANY of your judgements in question (positive or negative)?

    Also, if you cannot tell the difference via hearing, WHAT DOES IT MATTER? Seriously, if the quality is still great, isn't that good enough?
    If you CAN hear it, no need for a tool to tell you to return it.

    Me, depending on the kind of material, I can hear the difference somewhere between 320 and 256kps (on modern mp3s). I have a method of A/B'ing that makes very clear where that threshold is (need to have an uncompressed original for reference though), and this can be applied to test any form of compression.


    Scott
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    The argument about whether it matters if you can't hear it is very subjective. It's assumed one wants to know. I wouldn't call auCDTect a "hacker tool". We'll never know how its engineered but can look at its results. I asked here just in case someone else had used it and formed any opinions. I've never found it report CDDA for an mp3 (although now Dave here said one did) but quite a few the other way around - and from manufacturers like Spectrum, Bear Family, Universal - suggesting they may have been mastered from a lossy source. (They can vary considerably but relatively new stuff you'd expect to be ok). So far none before the advent of mp3 which would be a clue.

    I can't tell the difference between a 256 and 320 by listening, but would expect to with mp3 and flac. But to answer your question, it's to know if a track reports it's CDDA or not. Because I'm collecting a batch of flacs without the chance any might be MPEG.

    >Actually Flac is a confusing thing in this whole discussion, should stick to talking about WAV and mp3
    Apart from filesize, you could consider wav and flac to be the same. (As lossless).
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  3. Originally Posted by Cornucopia View Post
    Me, depending on the kind of material, I can hear the difference somewhere between 320 and 256kps (on modern mp3s). I have a method of A/B'ing that makes very clear where that threshold is (need to have an uncompressed original for reference though), and this can be applied to test any form of compression.
    My method doesn't require A/Bing in the traditional sense, but it suffers from a similar limitation. It requires the original for reference, although compressed is okay, as long as it's lossless.

    Take a lossless file and convert it to flac. Also convert it to MP3 or AAC etc. Convert the lossy file to flac using the same settings as before. The flac bitrate will be a little higher for the version that wasn't converted to a lossy format and back. Although full disclosure.... AC3 is the exception that proves the rule, at high bitrates. When converting AC3 back to flac, the flac bitrate can increase relative to the original. It should always be different though.
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  4. Member Cornucopia's Avatar
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    @hello_hello, can you explain your understanding of the science behind that? As it appears quite an anecdotal conclusion.

    It's a moot point, if the source is the unknown.

    Scott
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  5. I have no understanding. Only faith.

    I assume it's because lossy codecs throw stuff away and therefore FLAC doesn't have to compress it.
    Two CDs worth of bitrate.

    FLAC to FLAC.

    Image
    [Attachment 57329 - Click to enlarge]


    FLAC to MP3 to FLAC.

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    [Attachment 57330 - Click to enlarge]


    FLAC to AAC to FLAC.

    Image
    [Attachment 57331 - Click to enlarge]
    Last edited by hello_hello; 12th Feb 2021 at 19:09.
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