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View Full Version : How does 160 bps = 256 bitrate?



JoeRip
11-05-2006, 03:39 PM
Using dbpoweramp's idtag explorer extension, I see the following information for some of my WMA's:

Codec = Windows Media Audio 9.1
Compression = 160 kbps, 44 kHz, stereo 2-pass VBR
Bitrate (Kbps) = 256

So when listed in Windows Media Player, this file song shows "256" in the Bitrate column. However, when played, the stream is identified as "Playing: 160 Kbits/second (Variable bit rate)"

What is the relationship between "256 Kbps" and "160 kbps" here?

LtData
11-05-2006, 05:09 PM
256Kbps is probably the max bitrate, the 160 is probably the average or current bitrate as it plays?

neilthecellist
11-05-2006, 06:09 PM
I second LtData's response. I've noticed this in the past as well. It's nothing serious to worry about, though :).

JoeRip
11-05-2006, 08:30 PM
But I *am* interested in the difference. I'm looking at the WMA files produced by various music services, and I'm trying to figure out which music service to use.

(Please, I'm not loooking for a discussion of the best music services here, I'm just looking to find out more about how to establish which ones emit higher quality WMA's by looking at the metadata).

All of the files produced by Service A have "Bitrate = 256 Kbps", but WMP and dbPowerAmp extensions all identify the Compression as exactly "160 kbps" (note small k, by the way). How would this occur, if they are all ripped as 2 pass VBR?

LtData
11-05-2006, 09:57 PM
Actually, I seem to remember that the big music services (Napster, Rhapsody, Wal-Mart) do either 160kbps or 192kbps and I was under the impression that the songs were CBR. Where are you getting VBR, let alone 2-pass VBR?

JoeRip
11-06-2006, 12:11 AM
Most of what I'm getting from MSN Music express the following in WMP, if you select Properties:

Windows Media Audio 9
160 kbps, 44 kHz, stereo 2-pass VBR

although the Bitrate column says "256".

In dbPowerAmp's "Edit Tag" pane under Explorer Properties, they say:

Codec: Windows Media Audio 9
Compression: 160 kbps, 44 kHz, Stereo 2-pass VBR
Bitrate (Kbps): 256

JoeRip
11-06-2006, 12:17 AM
Oddly enough, a couple of them list as "159" or "161" in WMP's Bitrate column :-). In any other location where they are not listed as "256", they are listed as 160.

DudeBoyz
11-06-2006, 02:21 AM
Variable Bit Rate gives wanky results. Som apps may list the Min, some list Avg, some list Max.

I use Constant Bit Rate and avoid the whole thing. :)