Re: [freebsd-questions] Scanning MP3 files for skips

2006-06-13 Thread Howard Jones

Chuck Swiger wrote:

Kyrre Nygard wrote:

I'm curious whether there's a tool out there that will scan through
audio files looking for patterns that resemble skips and other nonos
in the world of music.

I have MD5 checksums for all my MP3 files, but that doesn't
guarantee that they were fine before the checksums were generated.


Sort of...GraceNote and a few other companies (Shazam, seems to be
from India?) sell a service where music files can be fingerprinted and
identified.  Good audio files ought to ID as what they are; bad music
files with skips or garbage will fail to ID.


Shazam (at least) works on a fragment the song. In the UK they provide a
phone-based service, which only needs 20-30 seconds of clear music to
identify a song. MusicBrainz is a similar type of thing that is
available as a plugin for a number of media players, which I think works
on a whole song, but I don't know that it's precise enough to detect the
odd tick and burp.

I'm also looking for a blip-detecting MP3 tool. I haven't had time to
look at it yet, but I was going to try something like libmad on the
assumption that somewhere internally it knows when it's only had half an
frame of data, even if there is no CRC. That way, it'll work on any
obscure music I have, without relying on some external giant database of
correctness.
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Re: [freebsd-questions] Scanning MP3 files for skips

2006-06-13 Thread Chuck Swiger

Howard Jones wrote:

Chuck Swiger wrote:

[ ...ID'ing skips in music... ]

Sort of...GraceNote and a few other companies (Shazam, seems to be
from India?) sell a service where music files can be fingerprinted and
identified.  Good audio files ought to ID as what they are; bad music
files with skips or garbage will fail to ID.


Shazam (at least) works on a fragment the song. In the UK they provide a
phone-based service, which only needs 20-30 seconds of clear music to
identify a song.


Yeah, that's right.  But there's also a fingerprinting tool which creates 
something called QCF files (Qualcom something-or-other) which analyses the 
entire song and should notice major skips or distortions better.


[ ... ]

I'm also looking for a blip-detecting MP3 tool. I haven't had time to
look at it yet, but I was going to try something like libmad on the
assumption that somewhere internally it knows when it's only had half an
frame of data, even if there is no CRC. That way, it'll work on any
obscure music I have, without relying on some external giant database of
correctness.


That's the rub of the matter: most home-grown tools are going to find it hard 
to recognize a skip from Trent Reznor or a lot of rap music, or a dropout with 
silences common in classic music, etc.  :-)


With the external giant database of correctness, you've got something which 
actually can tell that a song isn't correct, rather than making guesses, even 
if you have to break your samples down into 10 to 30 second pieces and check 
them all individually.


[ Again, I would try using the QCF fingerprinting tool instead of exhaustive 
submatch checking.  On the other hand, if you can manage to put together 
something which can guess well, I'd be interested in seeing it... ]


--
-Chuck
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