[Linux4christians] Audio tape to MP3 ideas
akaimbatman at gmail.com
Wed Jul 16 14:38:24 EDT 2008
Just a minor correction: The rate of the MP3 is a data rate, not a kilohertz
measurement. 16K is 16 kilobits (2 kilobytes) per second, not 16KHz. With a
data rate like that, it's up to the encoder to figure out how to make the
data fit. Thus it will drop audio data left and right until it gets down to
the desired size.
This is a feature of the format that goes back to the days of hard-wired
lines with specific data transfer capacity. Since MP3 was designed to
digitally move audio data for existing markets (e,g, streaming a song from a
storage facility to the transmitter facility at a radio station), having a
fixed rate of transmission was a very desirable feature. Given that times
have changed, most follow-ups to the original MP3 format include a feature
called "Variable Data Rate" whereby the data rate setting is merely a
guideline for the encoder.
Otherwise the information is correct. 64Kbits for voice, 128Kbits for music,
and 192Kbits for High Quality recordings is the standard.You may also want
to consider the AAC format as it is far superior to MP3 at the same bit
rates. It's also supported by most popular tools these days, including
FFMPEG and iTunes.
Good luck with your encoding adventures! :-)
On Wed, Jul 16, 2008 at 1:30 AM, Rob Mitchell <didaskw at comcast.net> wrote:
> For spoken word, 64K will give you reasonably good quality
> and reasonably small file size. I've had good results with 32k. Even
> 16k should accommodate spoken word well - the max frequency of the human
> voice is about 8khz, and 16K is twice that, the minimum you need, but
> at that bit rate you will hear some artifact in the sound (it sounds
> like someone is talking through a high speed fan). Stay at 32k or 64k.
> For music you want 64k minimum - preferably 128 or 192 if you are using
> digital input.
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