[icecast] Akos...Darkice questions

Akos Maroy darkeye at tyrell.hu
Wed Aug 28 23:56:33 PDT 2002



Geoff Shang wrote:
> On Wed, 28 Aug 2002, Matthew Mencel wrote:
> 
> 
>>I'm using liveice and lame on another stream...
>>
>>sample rate of 22050
>>bitrate of 24000
> 
> 
> urrr.. Bitrate and bits per sample are *NOT* the same thing.  Bitrate
> refers to the data rate of the resulting audio stream (MP3 in this case).
> Bits per sample refers to the number of bits in each PCM sample read from
> your soundcard.  You'll usually want to use 16.  Generally, only
> professional soundcards will do anything higher.

yes. in brief:

bits per sample: the number if bits describing each audio sample. 
usually 8 bits or 16 bits

ample rate: number of samples (each sample the number of bits as above) 
per second describing the audio. usually one of 11025, 22050 or 44100, 
but there are other values possible, e.g. 16000, 48000.

for example an audio CD contains sound at 16 bits/sample, 44100 samples 
/ second, stereo, thus will consume 1411200 bits/second.

bitrate: this is the number of bits per second the encoded audio (mp3 or 
Ogg Vorbis) will consume. as you see, uncompressed audio takes a lot of 
space, and this is where compression algorithms come in.

for example, an Ogg Vorbis stream with a bitrate if 96000 will take 
96000 bits/second of space, but can still encode an audio of 16 
bits/sample, 44100 samples per second, stereo. This is what you win with 
the compression: instead of 1411200, it only takes 96000 bits per second 
(about 7% of the original), and still sounds good.

<p>Akos

<p><p>--- >8 ----
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