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Audio quality/format info and some source links

Discussion in 'Audio' started by Mez, Apr 24, 2009.

  1. Mez

    Mez Active member

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    Lossy audio formats reduce the high frequency tones because high pitch requires much more data to preserve than low pitch tones. Humans can’t hear the tones and speakers to do not reproduce tones. Humans can’t hear above 20-22 kHz and adults normally can’t hear above 16 kHz. You really can’t even hear high pitch tones near your hearing threshold unless they are real loud (Fletcher and Munson). You will not discern these tones in your music even if they were present and your ear can physically hear it.
    Contains hearing limitations and Fletcher and Munson equal-loudness contours
    http://en.wikipedia.org/wiki/Psychoacoustics

    20,000 Hz contains 1,000 times more data than 20 Hz. To get a faithful reproduction the sample rate must be much higher to the total cost in bits is much more than 1,000 times. It is also believed by many and is supported in real life that ultrasonics are more damaging at the same db level than audible sound. If you are a speaker maker, you need to consider the liability for making a speaker that produces ultrasonics that no one can hear but will damage your hearing more effectively than if you left them out. It is foolish to use most of your band width for tones that will not be reproduced by any speaker or ear bud. The CBR mp3 uses that principle in making a lossy reproduction of the sound. It cuts off the highs to maintain a particular bit rate. For this reason there is not an absolute high end cut off but it normally runs about 20-22 kHz for a 320 CBR. Even a baby would not miss a note.

    Lossless -
    That is really a misnomer you always lose data going from an infinite stream to a digital stream. For this discussion you can just think of it as a 1200 - 1300 CBR. Persons I fondly refer to as analog junkies can point out vinyl holds more data than a CD, so it is better. They are correct about in holding more data. Better, I don’t think so unless you feel the pops and hiss need to be part of the listening experience. What good is data you will not use?

    Psychoacoustic compression VBRs, AAC, WMA and many more formats -
    See the Psychoacoustic reference for detailed info. These formats use the most advanced kind of compression removes tones your brain will not use even if it receives them from the ear.

    Formats using this technique have a better quality to file size ratio than formats that do not. I feel compelled to put my opinion forth since I think it might be helpful to some. I believe the VBR format is the best controlled format. It is the only audio format that the creator has the best control of the quality of the music. They do completely relinquish the control of the bit rate (Variable Bit Rate).

    Psychoacoustic compressionbeing complex, is the most prone to artifacts. An artifact is noise created by the encoder because it wasn’t built right. You need to be more selective in your choice of encoders if you want to avoid artifacts. LAME is the undisputed king in this realm. It was thoroughly debugged years ago. A pitiful few isolated finds were reported but no one as reported any artifacts in years. The next best still has artifacts. The last time I checked, Apple, M$ and Real Media formats have long lists of complaints.
    LAME quality settings
    http://wiki.hydrogenaudio.org/index.php?title=LAME#Technical_information

    I think I can hear tones you can't -
    What is the cut off frequency for me? There is a hearing test

    Mosquito tones and the student repeller device that resulted in Mosquito Ring Tones
    Mosquito Ring Tone Story

    http://www.freemosquitoringtones.org/


    Hearing test


    Ultrasonic tones damage ears even though the tones are below the loudness danger threshold.
    http://findarticles.com/p/articles/mi_hb6368/is_4_76/ai_n28968663/]Ultrasonic tones damage ears[/url]

    I just cleaned this up a bit since I am going to link it.
     
    Last edited: Nov 11, 2010
  2. 68vista

    68vista Guest

    I can see why no one's replied to this yet.
     
  3. Mez

    Mez Active member

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    This was an informational post not a query. This was in response to 2 different posts where the smart solution was to save as lossy. I was loled as only bush leagues listen to lossy. There are some good reasons to listen to lossless but sound quality is not one of them. I said I would post sources that supported lossy quality and they should post information supporting lossless actually sounds better than lossy.

    This was my post they never posted their info because there isn't any.

    Here is one more...
    http://en.wikipedia.org/wiki/Transparency_(data_compression)
    Transparency (data compression)
    This states that a 192 constant bit rate mp3s should the same as lossless to most adults. The constant bit rate mp3s are the simplest lossy format. The process eliminated the highest tones to meet the target bit rates. Adults do not hear high pitch tone well or not at all. High pitch tones account for most of the data in an audio file. It is obvious that by either using a higher bit rate or more advanced compression techniques, you can easily 'over-kill' the quality guaranteeing a perceptually indistinguishable product from the uncompressed input.
     
  4. djscoop

    djscoop Active member

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    i always use LAME and encode at VBR 192. anything above that is just pointless, with the exception of classical music due to the huge dynamic range
     
  5. Mez

    Mez Active member

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    djscoop you might be right about pointless. I max it out, V0, just because I can and the size difference does not matter to me. VBRs are pretty small. It is pretty much like listening to lossless. There really isn't any point to it but as long as you do not claim to be able to tell the difference, it is a free world.

    If you are trying to be sensible...
    VBRs are a tighter compression about 160 VBR is about the same as a 190 CBR. Even a -V3, target 175 BR, has the cut off of 17960 Hz - 18494 Hz is overkill for a even a 20 yr old male.

    The type of music does not matter with VBR. VRB, the choice of most audiophyles, is quality based. The quality never varies due to the complexity of the music because you set the quality not the bit rate. It compresses what it can within the setting. I have had a V0, target 190, go to 320 BR because the music was so complex. You only see that with classical. R&R often goes less than target.

    Billy Joel "The Piano Man" can be captured perfectlly at about 128. What a piece of crap that is. After listening to New Age music where they take care to capture the brilliance of the piano, "The Piano Man" is a piece of crap. Just last week I listened to it and thought the BR was a mistake. I re-ripped at lossless and it sounded the same. It sounds like 128 and that has a natural instrument.
     

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