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Bit-resolution decrease for internet

Discussion in 'General Electronics' started by Radium, Dec 3, 2003.

  1. Radium

    Radium Guest

    I would like to use an audio codec based on WAVE PCM. It should be a
    little different though. The bit-resolution should be set to equal
    1/(sampling rate X # of channels). The bit-rate should be set to equal
    1 bit per second. I would like to use this codec to transport audio
    files though the internet via email.

    I am looking for frequency response. In digital audio the sampling
    rate must be at least twice the highest frequency in the signal. It
    would like a highest frequency of at least 200 KHz. This would require
    a sample rate of at least 400 KHz.

    In this codec the bit-resolution is decreased to maintain a low bit
    rate of 1 bit/sec. The bit-resolution is divided by the sampling rate
    and the # of channels to acheive this.
     
  2. Ben Pope

    Ben Pope Guest


    You are clearly misguided.

    Ben
     
  3. Rich Andrews

    Rich Andrews Guest

    (Radium) wrote in
    1 bit per second? Wouldn't that equate to .5 hz or did I miss something?

    r
     
  4. Radium

    Radium Guest

    Wrong. 1 Hz sampling rate would equate to .5 Hz. Sampling rate must be
    at least 2x the maximum frequency.

    If in a wave file, the bit-resolution is made to equal 1 /(sampling
    rate X number of channels), then the bit-rate will definitely be
    1-bit/second. If the sample rate is 44,100 Hz in a stereo (2-channel)
    wave file of this type, the bit-resolution would be 1/(44100 x 2)-bit
    or 1/88200-bit.

    Bit-rate = sample-rate X bit-resolution X numbers of channels

    Multiply the 44100 X 2 X 1/88200 and you get 1!

    44100 Hz X 1/88200-bit X 2 channels = 1 bit per second

    1 minute of this file would comsume 60 bits of disk space.
     
  5. Radium

    Radium Guest

    1 Hz sampling rate would equate to .5 Hz. 1-bit/sec, however would
    not. Bit/time is the bit-rate. Sample rate is different from bit-rate.
    It is also important to know the difference between *bit-resolution*
    and *bit-rate*.

    1 byte = 8 bits

    If in a wave file, the bit-resolution is made to equal 1 /(sampling
    rate X number of channels), then the bit-rate will definitely be
    1-bit/second. If the sample rate is 44,100 Hz in a stereo (2-channel)
    wave file of this type, the bit-resolution would be 1/(44100 x 2)-bit
    or 1/88200-bit.

    Bit-rate = sample-rate X bit-resolution X numbers of channels

    Multiply the 44100 X 2 X 1/88200 and you get 1!

    44100 Hz X 1/88200-bit X 2 channels = 1 bit per second

    1 minute of this file would comsume only 60 bits of disk space. It
    would definitely work for the internet. Unlike conventional MP3s and
    WMAs, the high-frequency content of the PCM music will be restored due
    to the high sample rate.

    60 bits = 60/8 bytes
     
  6. Hello Radium,

    At this rate, a 700MB CD will hold 177 years' worth of music!!
    Why don't you compress some music to be just 1 bit per second and see if
    anyone would be willing to listen to it more than once. I think you need to
    check how you are handling your units. The Hz times 1/Hz units cancel out.

    Clay
     
  7. Ben Pope

    Ben Pope Guest

    OK, so whats the maximum frequency you would like to capture? (More to the
    point, what sampling rate do you propose)
    Only if you could represent the samples in fractions of a bit.
    And how do you propose to represent such fractional bits?
    Fine, but you can't have less than one bit per sample.
    Well done.
    Yes, but even if it was possible, it would not really be classed as sound,
    would it?

    The reason the "bit resolution" is 16bits in CD Audio is because then you
    can represent the varying wave with some degree of precision. If you took
    that down to one bit, you would be turning sinusoids into square waves,
    which would introduce just a tiny bit of odd-harmonic distortion. That
    would result in bps = sampling rate * channels.

    Ben
     
  8. Bevan Weiss

    Bevan Weiss Guest

    Consider this logically for a second...
    The lowest possible bit depth for a single sample is 1 bit, hence you must
    have at least 1bit per sample.
    If you want 400kHz sample rate then you must have a minimum of 400kbps data
    rate.
    1 minute of this data would consume 2400kb.
     
  9. Simple question: What is or how do you make a fractional bit? Digital
    systems are quantized. One bit implies quantising to two levels On or
    Off. What are the quantization levels of a fractional bit and how
    would you represent it?

    Regards,


    Paavo Jumppanen
    Author of AtSpec : A 2 channel PC based FFT spectrum analyzer
    http://www.taquis.com
     
  10. Radium

    Radium Guest

    1 Hz sampling rate would equate to .5 Hz. 1-bit/sec, however would
    not. Bit/time is the bit-rate. Sample rate is different from bit-rate.
    It is also important to know the difference between *bit-resolution*
    and *bit-rate*.

    If in a wave file, the bit-resolution is made to equal 1 /(sampling
    rate X number of channels), then the bit-rate will definitely be
    1-bit/second. If the sample rate is 44,100 Hz in a stereo (2-channel)
    wave file of this type, the bit-resolution would be 1/(44100 x 2)-bit
    or 1/88200-bit.

    Bit-rate = sample-rate X bit-resolution X numbers of channels

    Multiply the 44100 X 2 X 1/88200 and you get 1!

    44100 Hz X 1/88200-bit X 2 channels = 1 bit per second

    1 minute of this file would comsume only 60 bits of disk space. It
    would definitely work for the internet. Unlike conventional MP3s and
    WMAs, the high-frequency content of the PCM music will be restored due
    to the high sample rate.
     
  11. Radium

    Radium Guest


    From the responses to my above message I found it is impossible to
    have less than 1-bit/sample. After the bit is the quantum of digital
    info.

    What about sampling rate? Is it possible to have less than 1
    sample/bit?

    Lets say a codec with:

    Sample rate = 1/(bit resolution X number of channels)

    Since:

    bit-rate = sample rate X bit-resolution X number of channels,

    The sample rate would cancel with the bit-resolution and # of
    channels.

    After all AB X 1/AB = 1

    Plug in CD quality bit resolution (16-bit) and # of channels (2),

    sample rate = 1/32 = 0.03125 Hz

    I know this codec would be impractical but is it possible?

    I'm just in it for the science. No application.
     
  12. Robert Baer

    Robert Baer Guest

    In the very remote past, "Ug" took a sample of the La Brea tar pits,
    and died in the muck.
    He never took another sample, and that was thousands of years ago.
    How is *that* for a sample rate???

    Actually, in real life, photographers have used one sample per day
    with a movie camera, to show the growth of a plant.
    Also, a sample rate of once every 15 minutes (i am guessing) to show a
    flower opening in the morning, turning to follow the sun, and closing at
    night.
    Another real case: to show cloud movement over a day or many days.
     
  13. Hello Radium,

    At this rate, a 700MB CD will hold 177 years' worth of music!!
    Why don't you compress some music to be just 1 bit per second and see if
    anyone would be willing to listen to it more than once. I think you need to
    check how you are handling your units. The Hz times 1/Hz units cancel out.

    Clay
     
  14. Ben Pope

    Ben Pope Guest

    OK, so whats the maximum frequency you would like to capture? (More to the
    point, what sampling rate do you propose)
    Only if you could represent the samples in fractions of a bit.
    And how do you propose to represent such fractional bits?
    Fine, but you can't have less than one bit per sample.
    Well done.
    Yes, but even if it was possible, it would not really be classed as sound,
    would it?

    The reason the "bit resolution" is 16bits in CD Audio is because then you
    can represent the varying wave with some degree of precision. If you took
    that down to one bit, you would be turning sinusoids into square waves,
    which would introduce just a tiny bit of odd-harmonic distortion. That
    would result in bps = sampling rate * channels.

    Ben
     
  15. Bevan Weiss

    Bevan Weiss Guest

    Consider this logically for a second...
    The lowest possible bit depth for a single sample is 1 bit, hence you must
    have at least 1bit per sample.
    If you want 400kHz sample rate then you must have a minimum of 400kbps data
    rate.
    1 minute of this data would consume 2400kb.
     
  16. Simple question: What is or how do you make a fractional bit? Digital
    systems are quantized. One bit implies quantising to two levels On or
    Off. What are the quantization levels of a fractional bit and how
    would you represent it?

    Regards,


    Paavo Jumppanen
    Author of AtSpec : A 2 channel PC based FFT spectrum analyzer
    http://www.taquis.com
     
  17. Bevan Weiss

    Bevan Weiss Guest

    I honestly think you're going about this all wrong:
    Ask any audiofile and they'll say that the sound is much better with a
    higher sample rate and bit resolution....
    Clearly the answer is to reduce the number of channels of audio.

    If you have the number of channels as
    num channels = bit-rate / (bit-resolution X sample-rate)
    then you can still have a 1bit per second for the bit rate, but you can now
    have a huge sample rate and an awesome bit resolution. I mean you could
    easily get 192bits per sample, and some 6MSPS with this system. You would
    just have to only use 868.056x10^(-12) channels.

    I'm pretty sure that everyone else in this newsgroup will agree with me that
    this is more the approach that you should utilise radium...

    lol
     
  18. Randy Yates

    Randy Yates Guest

    Hey Radium,

    If you're so sure about your analyses, then knock yourself out. Go ahead and
    construct a CODEC that will blow the socks off WMA, MP3, etc. and show us
    all up.
    --
    % Randy Yates % "...the answer lies within your soul
    %% Fuquay-Varina, NC % 'cause no one knows which side
    %%% 919-577-9882 % the coin will fall."
    %%%% <> % 'Big Wheels', *Out of the Blue*, ELO
    http://home.earthlink.net/~yatescr
     
  19. Rich Andrews

    Rich Andrews Guest

    (Radium) wrote in
    Methinks something is wrong with the math and/or definitions.

    The way I understand it, if one samples at 44.1kc that means that 44
    thousand times per second you have a 16 bit word. Thus, in one second,
    you have 44,100 16 bit words of data. Put another way, in one second you
    have 44,100*16*2(for stereo) or 1,411,200 bits of data.

    1,411,200 / 8 = 176400 8 bit bytes per second.

    Now if you are wanting to change the sampling resolution or depth from 16
    bits to something like 8 or even 4, the result would not be very good. I
    believe that there are examples of 4 amd 8 bit on the net.

    r
     
  20. Dick Pierce

    Dick Pierce Guest

    Kind people, stand up and give Radium a hearty Huzzah!, for he
    has volunteered for the role of Village Idiot, a job for which
    has has proven himself truly qualified.
     
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