Roman
ubw newbie
Joined: Jan 25, 2007
Posts: 3
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| Posted: Tue Feb 13, 2007 9:41 am |
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Hi, I just created a little streamsize calculator in Excel to calculate what size a file should be for a certain bitrate and a certain period of time (and vice versa)...
For example, if a song runs for 5 minutes and has a bitrate of 192 kbps, its filesize should be 7031 KB...
Just had a quick look thru some of the songs in my collection and noticed that some files are of wrong sizes... and not just by few bytes, which is acceptable, but some differences are as big as 2-3 MB... For example I have a file of 192 kbps and 5 minutes that has a size of only 5MB... Since the song does run for 5 minutes, does it mean that the bitrate is displayed wrong? According to my calculations, 5MB & 5mins song would be running at a bitrate of 140kbps, not 192kbps as its displayed in the file's properties. Does this mean that some audio converting programs tamper with music... Or could soemthign else casue this variation?
Any thoughts? |
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smili
moderator
Joined: Sep 11, 2004
Location: Nashville TN
Posts: 1223
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| Posted: Wed Feb 14, 2007 9:14 pm |
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That does sound like a big difference.
I think there's variable bitrate encoding - where the encoding uses more bits where needed and maybe less when not needed. I remember reading about some of it when I was trying to figure out what different bitrate files sounded like (thought 128 was pretty good tradeoff of filesize/sound), but I think there's a way in some encoders to force fixed bitrates to test.
fwiw, I've noticed fairly predictable file sizes in most of the conversions I've done although I haven't calced out to the second. |
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