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the Hz setting in Lame mp3 encoding

Discussion in 'Audio' started by hnyf, May 26, 2003.

  1. hnyf

    hnyf Guest

    Please tell me the difference between -- for example -- 16 kbits 8000 Hz Mono and 16 Kbits 16000 Hz Mono when recording mp3s with Lame. My question is: What difference does the Hz setting make? This is probably something simple but I can't get the info anywhere.
     
  2. tigre

    tigre Moderator Staff Member

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    There are 2 Hz things:

    - lowpass: It cuts all frequencies above a certain treshold, e.g. 16000 Hz to ensure there are enough bits left lower (=better audible) frequencies. At low bitrates lowering the lowpass can increase quality remarkably

    - sampling rate: This is what's displayed in some players on playback and probably what you're talking about. It's number of samples per second. E.g. if you have a sampling rate or 22050, 1/2 of the samples are thrown away (simplified) compared to CD source. The frequency range of a file can go up to 1/2 * sampling rate. So if your file has a sampling rate of 8000 Hz, there won't be any sounds above 4000 Hz which sounds somehow like you're wearing earplugs. Additionally to lowpassing low sampling rates save bits and usually increase quality on low bitrates.
     
  3. hnyf

    hnyf Guest

    Thanks for your help.

    Actually what I am doing at the moment is converting .rm files to .mp3.
    The .rm files are voice recordings -- lectures -- which are mostly recorded at 16000 bps.

    RealOne tells me that but doesn't tell me the frequency (Hz)

    I have been trying 2 different programs to change them to mp3s -- Total Recorder and Streambox Ripper. Both these offer different options for Kbps AND Hz.

    Obviously in changing the files to mp3s I keep them as 16000 bps but do I encode them as 16000 Hz or 8000 Hz?

    Any explanations or advice would be much appreciated.
     
  4. tigre

    tigre Moderator Staff Member

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    I don't have much experience about .rm, but an idea ... can you provide a link or a real audio file?

    Basically it's about using an audio player (XMPlay) that can use a Winamp Real audio input plugin and lame.exe as output "device" ...
     

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