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Topic: Why mp3 rip is shorter than WAV (Read 1527 times) previous topic - next topic
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Why mp3 rip is shorter than WAV

I double ripped (first in WAV, then in 320 kbps mp3) same track from the same audio CD on my PC via standard Windows media player and got these files in mm:ss:msms :

Wav duration - 04:18:720
Mp3 duration - 04:18:577

As I know mp3 should add some extra length in ms to uncompressed audio so why I got this?

Re: Why mp3 rip is shorter than WAV

Reply #1 –
So it seems that something is wrong with mp3 encoder in Windows media player.

Re: Why mp3 rip is shorter than WAV

Reply #2 –
My guess is a ripping error/difference.    Audio CDs don't have regular computer files (that's why they have to be "ripped" and not just copied like you can copy a WAV file or an Excel file).     The error detection-correction is not as robust as computer files.

What happens if you repeat the experiment?   Do you get different results every time?

You might want to switch to a ripping application that supports AccuratRip.   You can still get errors but it's less-likely, and you are more-likely to know that you're getting errors.

Re: Why mp3 rip is shorter than WAV

Reply #3 –
MP3 length can't be accurate without the encoder writing accurate length information in Xing/Lame header. Pretty sure WMP doesn't support anything like that. You should probably use something else to encode the files to MP3, LAME or Helix for example. And you'd probably have faster and better ripping experience with some other CD ripper, perhaps Exact Audio Copy, Cue Tools or dBPoweramp.

Edit: it's probably worth mentioning that what ever tool is used to read the length must also support this additional metadata. One such program is foobar2000.

Re: Why mp3 rip is shorter than WAV

Reply #4 –
UPD:

First time I checked durations in Soundforge. But then I decided to try another tools and got different results. I had no clue that Soundforge may lie like that...

Soundforge:

MP3 = 4mn 18s 577 ms
WAV = 4mn 18s 720 ms

Audacity:

MP3 = 4mn 18s 717 ms
WAV = 4mn 18s 720 ms

Wavelab:

MP3 = 4mn 18s 716.73 ms
WAV = 4mn 18s 720 ms

But still mp3 is slightly shorter than WAV which is kinda strange..

Re: Why mp3 rip is shorter than WAV

Reply #5 –
I went ahead and tested WMP's MP3 writing. It doesn't support the gapless information and thus the lengths in MP3s are not accurate. And afaik none of the audio tools you tried support it either so no loss there.