Compression - MP3 File Format

Author

MP3 File Format - Size/EOF?

Jackson

2004-09-15, 3:55 pm

I've been reading information on the MP3 Format but can not find any
reference to an EOF tag. I want to be able to view the HEX of an mp3
file and find out the size of the file OR locate an EOF tag within
that file.

From what I have read it's my understanding an MP3 is made up of
several independent frames which have their own header. There is not
one unified header, or footer, for an MP3 file, so how do I find the
End of the file or the size of the file?

Any ideas?

Thanks
Jackson

Willem

2004-09-15, 8:55 pm

Jackson wrote:
) I've been reading information on the MP3 Format but can not find any
) reference to an EOF tag. I want to be able to view the HEX of an mp3
) file and find out the size of the file OR locate an EOF tag within
) that file.
)
) From what I have read it's my understanding an MP3 is made up of
) several independent frames which have their own header. There is not
) one unified header, or footer, for an MP3 file, so how do I find the
) End of the file or the size of the file?

The MP3 format is a streaming format that basically doesn't have an
end as such. The end is when the data stops coming.

Try splitting an MP3 file in two and/or concatenating several MP3 files.

On the other hand, finding the size of a file is a simple operation
on moset operating systems, as evident in the fact that the ID3 tag
is 128 bytes appended at the end of an MP3 file.

SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something..
No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT

Jackson

2004-09-16, 4:01 pm

Willem <willem@stack.nl> wrote in message news:<slrnckh8d8.22vf.willem@toad.stack.nl>...
> Jackson wrote:
> ) I've been reading information on the MP3 Format but can not find any
> ) reference to an EOF tag. I want to be able to view the HEX of an mp3
> ) file and find out the size of the file OR locate an EOF tag within
> ) that file.
> )
> ) From what I have read it's my understanding an MP3 is made up of
> ) several independent frames which have their own header. There is not
> ) one unified header, or footer, for an MP3 file, so how do I find the
> ) End of the file or the size of the file?
>
> The MP3 format is a streaming format that basically doesn't have an
> end as such. The end is when the data stops coming.
>
> Try splitting an MP3 file in two and/or concatenating several MP3 files.
>
> On the other hand, finding the size of a file is a simple operation
> on moset operating systems, as evident in the fact that the ID3 tag
> is 128 bytes appended at the end of an MP3 file.
>
>
> SaSW, Willem

Thanks for the info. Just curious, is the ID3 tag appened @ the end
of ALL mp3 files? If not, what would you say is the % of MP3's that
have the ID3 tag at the end? Again, it's my understanding there are
different vers of the ID tags out there..?

Thanks,
Jackson

cr88192

2004-09-16, 4:01 pm

"Jackson" <jsmith193300@yahoo.com> wrote in message
news:680af4.0409160653.1016758e@posting.google.com...
> Willem <willem@stack.nl> wrote in message
> news:<slrnckh8d8.22vf.willem@toad.stack.nl>...
>
> Thanks for the info. Just curious, is the ID3 tag appened @ the end
> of ALL mp3 files? If not, what would you say is the % of MP3's that
> have the ID3 tag at the end? Again, it's my understanding there are
> different vers of the ID tags out there..?
>
my guess is it has a lot to do with the nature of the mp3 files...
they are much more likely, say, for copied music than for, say, sound
effects or misc clips created by someone for utilitarian purposes.
it is hard to say really. if one were just to assume mp3's in general, it
could be guessed that a majority have them, in the same way that a majority
are likely copied music...

there are 1.0, 1.1, and 2.* variants.

1.0 and 1.1 are appended to the end of the file, and differ only in that one
has a 30 char comment and the other a 28 char comment and a track number.

v2 tags are actually found at the start of the file, and have a chunked
structure (and are apparently added automatically by windows in some cases,
which annoys me, and forced me to alter my copy of mpglib to make it resync
with said files...).

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