Thank you for your advice.
I understood that part2_3_length is supposed to be the number of
substantial sound data.
Then, how can I calculate the size of total main data in *last* frame
in mp3 file? I think the following calculation is for non-last frame.
the size of main data = frame size - frame side information -
granule side information
e.g.
frame size = 1152 * 128000 / 44100 / 8 = 418 byte (if padding = 1)
(128kbps,44.1kHz,MPEG-1 Layer-3)
frame side information = 4 byte
granule side information = 2 + 59bit * 4 / 8 byte = 31.5 byte ?
-> the size of main data = 418 - 4 - 31.5 = 382.5 byte ?
> > Why are there mp3 files in which the value of part2_3_length is zero?
> > e.g. http://php.s3.to/bbs/up/img/216.png
> > Isn't the part2_3_length length of main data per 1granule, 1channel?
>
> Because the frame contains totally no sound (the frame is digital silence).
>
--
Miyoko Shioda <[EMAIL PROTECTED]>
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