JJZolx;576130 Wrote:
> Can't it be properly verified mathematically? Is there something unique
> about doing MD5 checksum calculations on compressed audio data that
> increases the probability of non-unique checksums?
>
We aren't calculating the whole file, just a section of it. If we did a
checksum of the whole file the limitation would just be the MD5
algorithm, when we do a checksum of a smaller section other factors
affect the result. As a sample, in the first implementation we took x
bytes from the beginning of the compressed audio segment, the result
was duplicate because the LAME encoder adds some padding in the
beginning that is the same on all files. The current solution takes a
section of the middle of the file which instead moves the problem to
how the compression algorithm work.
However, I agree, a mathematical specialist in all compression formats
used and expert in acoustics would probably be able to verify it
mathematically. Unfortunately, I haven't seen anyone with that
knowledge in this thread yet, so until then, testing is the way to do
it.
JJZolx;576130 Wrote:
>
> Speaking of unique identifiers... What about allowing users to create
> their own unique identifiers for files? Say SbS recognized a tag
> field, maybe something named "UUID" that the user populated randomly.
> Instead of computing a checksum, just use that field. The only
> important thing is that they be unique and unchanging; they don't have
> to correlate in any way with the audio data. Wouldn't this speed up
> the scanning process?
>
1. People can't be trusted.
2. It requires writing to the music files which I would like to avoid
if possible.
If we can't get decent performance on this, we can calculate the
checksum and write it to a tag. However, I'm not convinced that's
needed yet. In FLAC files we basically already do that, because the
latest version uses the MD5 built into the FLAC format, so FLAC should
be really fast already now.
--
erland
Erland Isaksson ('My homepage' (http://erland.isaksson.info))
(Developer of 'many plugins/applets'
(http://wiki.slimdevices.com/index.php/User:Erland). If my answer
helped you and you like to encourage future presence on this forum
and/or third party plugin/applet development, 'donations are always
appreciated' (http://erland.isaksson.info/donate))
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