Software to provide REAL bit-rate
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  1. #1
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    Default Software to provide REAL bit-rate

    G'day,
    I have cleansed my collection of heaps of tracks lately and have some tracks that I need to re-purchase as the files I currently have are not up to scratch.

    A thought was to find all the "low bit-rate (less than 256)" files and start with going through them to decide if I needed the track (in which case buy a good copy) or get rid of it once and for all.

    I was hoping someone would be able to provide a reliable programme that will scan the "real" bit-rate as I feel I may have converted some low-res files to 320kbps when I was still an ignorant dumb-ass!

    Alternatively, is there a way to delete the stored bit-rate and re-analyse?

    Thanks for the help,
    DjCoops

  2. #2

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    You can use Audacity to detect lossy transcodes.

    Import a track, and then look on the left hand side of the waveform for a drop down menu (it will have the file name on it.)

    Then select "Spectrogram."

    A true 320 kbps track will have frequencies at 20k.

    If it cuts off a lot lower, then you have a transcode. Typically you'll find it cutting off at about 16k, which means a 128 kbps MP3 was transcoded to 320 kbps.

    Once you encode an MP3, that data is gone forever. There's no way to get it back. That's why most people recommend downloading only lossless (WAV, FLAC, AIFF) and then transcoding that to MP3s when needed, but keeping the original files for archival purposes.
    Last edited by Glitchwerks; 07-29-2014 at 09:22 PM.

  3. #3
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    Quote Originally Posted by djcoops75 View Post
    I was hoping someone would be able to provide a reliable programme that will scan the "real" bit-rate as I feel I may have converted some low-res files to 320kbps when I was still an ignorant dumb-ass!
    Depending on the original encoding and encoder, a spectrum analyzer might show some "obvious" signs. But even that is a horridly manual process.

    Quote Originally Posted by djcoops75 View Post
    Alternatively, is there a way to delete the stored bit-rate and re-analyse?
    The bit rate is the bit rate is the bit rate. There is no (general purpose) way to recover information about previous encoding rates.
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  4. #4
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    Quote Originally Posted by Glitchwerks View Post
    A true 320 kbps track will have frequencies at 20k.
    Maybe. If the original source material had 20kHz, then a single encoding to 320kbps with a reasonable codec will likely preserve that content. Transcoding multiple times can reduce or remove high(er) frequency content.

    Quote Originally Posted by Glitchwerks View Post
    If it cuts off a lot lower, then you have a transcode. Typically you'll find it cutting off at about 16k, which means a 128 kbps MP3 was transcoded to 320 cbr.
    LAME is well known for low passing the source material when encoding at or below 128kbps. BUT, if the encoding was done at 160kbps, or 192kbps, etc, then this signature might not be obvious. Other mp3 encoders (Fraunhofer) leave different fingerprints.

    Overall, there is no "definitive" way to determine previous encoding bitrates of a sound file.
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  5. #5

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    Quote Originally Posted by soundinmotiondj View Post
    Maybe. If the original source material had 20kHz, then a single encoding to 320kbps with a reasonable codec will likely preserve that content. Transcoding multiple times can reduce or remove high(er) frequency content.
    Lossless audio should be 22k.

    What exactly do you mean by transcoding multiple times? Like WAV > FLAC > ALAC?

    That shouldn't remove any content.

    Quote Originally Posted by soundinmotiondj View Post
    LAME is well known for low passing the source material when encoding at or below 128kbps. BUT, if the encoding was done at 160kbps, or 192kbps, etc, then this signature might not be obvious. Other mp3 encoders (Fraunhofer) leave different fingerprints.
    This is true, there are encoders that are problematic.

    Quote Originally Posted by soundinmotiondj View Post
    Overall, there is no "definitive" way to determine previous encoding bitrates of a sound file.
    No perfect way, but provided he was just using something common like iTunes, that sort of transcode should show up, especially if it cuts off dramatically.

  6. #6
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    Quote Originally Posted by Glitchwerks View Post
    Lossless audio should be 22k.
    The lossless formats can include content up to half the sampling frequency, which is 22k for "CD quality." That does not guarantee that the song was not low passed at some point in the original production process.

    Quote Originally Posted by Glitchwerks View Post
    What exactly do you mean by transcoding multiple times? Like WAV > FLAC > ALAC?

    That shouldn't remove any content.
    Your example was lossless to lossless conversion. That should be "clean," at least in theory.

    The conversion from lossy to lossless to lossy can introduce "artifacts" and can cause high and low frequency content to be compromised. The details depend on the details.

    While most people will not "intentionally" transcode "a lot" of times...it can happen accidentally. Most music editors will expand a file into a "wav" format. If you open an mp3 in an editor and save as an mp3, every time there is a mp3 -> wav -> mp3 conversion. Edit a song a mp3 a few times, and you have done something like this:

    mp3 -> wav -> mp3 -> wav -> mp3 -> wav -> mp3 -> wav -> mp3 -> wav -> mp3 -> wav -> mp3 -> wav
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  7. #7

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    Quote Originally Posted by soundinmotiondj View Post
    While most people will not "intentionally" transcode "a lot" of times...it can happen accidentally. Most music editors will expand a file into a "wav" format. If you open an mp3 in an editor and save as an mp3, every time there is a mp3 -> wav -> mp3 conversion. Edit a song a mp3 a few times, and you have done something like this:

    mp3 -> wav -> mp3 -> wav -> mp3 -> wav -> mp3 -> wav -> mp3 -> wav -> mp3 -> wav -> mp3 -> wav
    I see what you meant. Yeah, I know about that. If I'm editing a file I always make sure I start with a lossless source.

  8. #8
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    Thanks for the input... It would appear that some idiot (me) had the bright idea of converting some wavs and aiff's to 320kbps MP3's but instead of doing just those; decided to do anything that wasn't already 320... Like I said best intentions but done without the necessary knowledge... i.e. how did I think I 128 or 192 kbps MP3 would magically become a 320?

    Sometimes it amazes me that I can walk! LOL I was hoping someone would have a solution but it looks like I have a LOT of work to do.

    Thanks again...
    Coops

  9. #9

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    Quote Originally Posted by djcoops75 View Post
    Thanks for the input... It would appear that some idiot (me) had the bright idea of converting some wavs and aiff's to 320kbps MP3's but instead of doing just those; decided to do anything that wasn't already 320... Like I said best intentions but done without the necessary knowledge... i.e. how did I think I 128 or 192 kbps MP3 would magically become a 320?

    Sometimes it amazes me that I can walk! LOL I was hoping someone would have a solution but it looks like I have a LOT of work to do.

    Thanks again...
    Coops
    If it's any consolation, it does seem to be a common misconception.

  10. #10
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    we've all done it mate
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