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Bit Rate all over the map


Mike19
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I'm confuded about Bit Rates.

 

First, my system: Viper custom desktop PC; Windows XP Home (SP3); ASIO4ALL; EAC; JRiver Jukebox > USB out to Behringer U-Control (for conversion of USB to optical)> optical out to Musiland MD10 DAC (set at 24bit/48kHz)> analog preamp.

 

MP3 tracks downloaded from HD Tracks show 320 kpbs on the file and playback at 320. However, their more expensive tracks downloaded in FLAC show 729 on the file, but on playback the bit rate is constanlty fluctuating between 711 and 1055 and everything in between. Why?

 

The better Internet radio stations stream at up to 128 kpbs w/ no flutuation during palyback.

 

MP3 tracks downloaded from Walmart show 256 kpbs on the Jukebox file and play back at 256 w/o fluctuation.

 

Someone gave me a burned Norah Jones CD. This shows on the file as WMA @ 858. It plays back @ 729 w/o fluctuation. Why is playback different from file?

 

For comparison purposes, I selected a particular CD track and ripped it to FLAC w/ the Jukebox. The file shows 714, but playback constantly fluctuates between 711 and 1055. I then ripped the same track to WAV using EAC: file shows 1411 and playback is 1411 w/ no fluctuation.

 

Strangest of all: I ripped 2 tracks from The B-52's new CD on the Jukebox in WMA. The first track file shows 1122 and it plays back @ 1122 w/ no fluctuation. The 2nd track shows 128 on file and plays back @ 128 w/ no fluctuation. Not surprisingly, the 1st track sounds better than the 2nd. How can 2 tracks ripped off the same CD have different bit rates?

 

I do not hear any fluctuations in sound quality on playback w/ the fluctuating bit rates. However, intuition tells me this is not supposed to happen. I have a feeling I'm doing something wrong, but I don't know what.

 

Any advice would be appreciated.

 

Mike

 

 

 

 

 

 

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There a two types of compression, CBR= Constant and VBR= Variable Bit Rate.

WAV is CBR (small wonder, no compression at all), FLAC is VBR (compression is dependend on the complexity of the music)

Your observation that VBRdoesn't have impact on sound quality is correct.

http://en.wikipedia.org/wiki/Variable_bitrate

 

How can 2 tracks ripped off the same CD have different bit rates?

Very uncommon, before you rip you set the conversion, in this case WMA Lossless and it should stay that way.

Is it a audio CD or has somebody burned tracks on it with different compression rates?

 

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also,

lossless can be variable compression rate.

 

 

with regards to two songs on the same physical CD having different rates, that would be due to the rate at which they were ripped by the software.

 

 

 

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It throws away what it can mathematically, so each frame is different, and each track is different.

 

With prewar recordings in mono, the data rate often gets below 300 in my experience. It can throw out half the frequency range and one channel.

 

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