Re: Digital audio stream terms?

[Richard Crowley]

"DaveC" > wrote in message
al.net...
> I'm listening to a stream via WMP. The Get Info box says:
>
> Bit Rate: 24 Kbps
> Audio Codec: Windows Media Audio 9
> 20 kbps, 32kHz, mono 1-pass CBR
>
> Can someone please clarify what the bit rate means and what the audio
codec
> numbers (20 kbps & 32 KHz) mean?

I believe they mean...

20 kbps = 20,000 (or 20480?) bits per second of data
through the network into your computer for this stream.

32kHz = the (original?) sample rate implying absolute
maximum 16KHz high frequency limit (likely lower).

CBR = constant (vs. variable/dynamic) bit-rate.

[Stimpy]

DaveC wrote:
> On Thu, 20 May 2004 20:26:29 -0700, Richard Crowley wrote
> (in article >):
>
>>
>> "DaveC" > wrote in message
>> al.net...
>>> I'm listening to a stream via WMP. The Get Info box says:
>>>
>>> Bit Rate: 24 Kbps
>>> Audio Codec: Windows Media Audio 9
>>> 20 kbps, 32kHz, mono 1-pass CBR
>>>
>>> Can someone please clarify what the bit rate means and what the
>>> audio codec numbers (20 kbps & 32 KHz) mean?
>
>> I believe they mean...
>>
>> 20 kbps = 20,000 (or 20480?) bits per second of data
>> through the network into your computer for this stream.
>
> My guess would be that the 24 Kbps is the network stream speed...
>
>> 32kHz = the (original?) sample rate implying absolute
>> maximum 16KHz high frequency limit (likely lower).
>>
>> CBR = constant (vs. variable/dynamic) bit-rate.
>
> Anyone else?

Both definitions are correct...

With streaming audio, the kbps figure represents the number of Kilo Bits Per
Second being streamed down into your computer. The kHz figure represents
the sample rate, i.e. the number of samples per second when the source was
sampled.

CBR = Constant bit rate. That is to say the sample/rip was taken at a fixed
kbps value. Some encoders can calculate the 'best' (a-hem) bit rate on the
fly, this is known as VBR (Variable Bit Rate).

[Tim S Kemp]

DaveC wrote:

> An audio CD is digitized at 44.1 KHz, but there's no Kbps rating
> associated with the digitizing, that I'm aware of.

16 bits per sample, two seperate channels no compression therefore
1411.2Kbps. The data rate from the disk though is higher as each byte is
encoded as 14 bits for resilience, so 2469.6Kbps.

You did ask.

[Les Cargill]

DaveC wrote:

> On Fri, 21 May 2004 10:44:41 -0700, Stimpy wrote
> (in article >):
>
>
>>>>>Bit Rate: 24 Kbps
>>>>>Audio Codec: Windows Media Audio 9
>>>>>20 kbps, 32kHz, mono 1-pass CBR
>>>>>
>>>>>Can someone please clarify what the bit rate means and what the
>>>>>audio codec numbers (20 kbps & 32 KHz) mean?
>
>
>>With streaming audio, the kbps figure represents the number of Kilo Bits Per
>>Second being streamed down into your computer. The kHz figure represents
>>the sample rate, i.e. the number of samples per second when the source was
>>sampled.
>>
>>CBR = Constant bit rate. That is to say the sample/rip was taken at a fixed
>>kbps value. Some encoders can calculate the 'best' (a-hem) bit rate on the
>>fly, this is known as VBR (Variable Bit Rate).
>
>
> So the 24 Kbps is how fast it's being delivered over the 'net;
> 32 KHz is the sample rate it was digitized at the source;
> and 20 Kbps is ... hmm, I'm getting a bit lost here.
>

I think 20 kpbs is the encodde rate, and 24 is the
delivery/streaming rate - 4 kbps of overhead.

I *think*.

> An audio CD is digitized at 44.1 KHz, but there's no Kbps rating associated
> with the digitizing, that I'm aware of.

Sure there is. It's 1.44 M(bit)ps or something. It shows
up in Winamp when you play back 44.1 .wav files.

>
> Clarification?
>
> Thanks,


--
--
Les Cargill

[Logan Shaw]

DaveC wrote:

> On Fri, 21 May 2004 18:52:15 -0700, Les Cargill wrote
> (in article >):
>
>
>>>An audio CD is digitized at 44.1 KHz, but there's no Kbps rating
>>>associated
>>>with the digitizing, that I'm aware of.
>
>
>>Sure there is. It's 1.44 M(bit)ps or something. It shows
>>up in Winamp when you play back 44.1 .wav files.
>
>
> So it's 44.1 x 8 (or whatever a byte is) x 2 (stereo) + overhead +
> errorchecking = encoding kbps?

44.1 kilo-samples per second x 1000 kHz/Hz * 8 bits/byte * 2 bytes/sample
* 2 channels + overhead = encoding bits/second.

So for CD-quality, it's 1,411,200 bits/second + overhead, which
could be in the neighborhood of 1.44 megabits/second if you
only have a few percent of overhead (which is feasible in
some cases).

- Logan