[audacity4blind] Re: Constant Versus Variable Bit Rate

  • From: Steve the Fiddle <stevethefiddle@xxxxxxxxx>
  • To: audacity4blind@xxxxxxxxxxxxx
  • Date: Wed, 5 Sep 2012 07:25:34 +0100

VBR (Variable Bit Rate) adjusts the bit rate depending on the
complexity of the audio. "Simple" data can be encoded in high quality
with low bit rate, thus allowing more bits to be used for "complex"
audio that requires more bits while keeping the average bit rate
approximately within the range specified.

The fundamental difference between CBR and VBR is that CBR uses
exactly the same number of bits per second regardless of what the
audio is, whereas VBR aims to achieve a certain level of sound quality
and adjusts the bit rate as necessary to achieve that quality level.
In most cases VBR will achieve better accuracy (better quality)
overall than CBR because CBR is "wasting" some bits on audio that
could be encoded at the same quality with less bits. The exception to
this is when you get to very high bit rates. At 320 kbps (the highest
available bit rate), all of the audio is encoded at the highest
possible rate of 320 kbps, so this is always CBR.

Steve

On 4 September 2012 04:32, JM Casey <crystallogic@xxxxxxxxxxxx> wrote:
> I always understood that variable encoding uses an algorithm to determine
> the required bitrate for specific sorts of audio output, and varies the size
> of each sample according to that data. If you want a more exact copy of your
> audio file: if, for example, you are editing music, , I would not choose
> this method. However, for most things it'll probably be fine.
>
>
> ----- Original Message ----- From: "Steve the Fiddle"
> <stevethefiddle@xxxxxxxxx>
> To: <audacity4blind@xxxxxxxxxxxxx>
> Sent: Sunday, September 02, 2012 7:35 PM
> Subject: [audacity4blind] Re: Constant Versus Variable Bit Rate
>
>
>
>> VBR with joint stereo will usually give a better trade-off between
>> file size and sound quality than other combinations.
>> The "Preset" options are generally a very good choice for music
>> recordings.
>> Some MP3 players will report the duration of tracks incorrectly for
>> VBR encoded MP3s, though virtually all MP3 players will be able to
>> play both VBR and CBR correctly.
>> CBR is able to provide smaller file size than VBR by selecting a very
>> low bit-rate but the sound quality will be very poor.
>>
>> Steve
>>
>> On 3 September 2012 00:08, Rich De Steno <ironrock@xxxxxxxxxxx> wrote:
>>>
>>> What are the considerations in choosing either constant or variable bit
>>> rate
>>> when saving a file as an MP3?  While I am at it, what are the merits of
>>> choosing joint stereo?
>>>
>>> --
>>> Rich De Steno
>>>
>>>
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>
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