Using TLH test for MPEG evidence?
Glad I finally found you guys! This has been bugging me for a minute and I was hoping some might share their thoughts. This started in another thread so I am going share below, then follow up. Thanks for any information you might have!
Re: Trader's Little Helper
This might be a question that has been answered, but for the life of me I cannot find. If so, please forgive me!
I think I know of someone who is testing .flac files converted to .wav files for evidence of MPEG... can you speak to why a genuinely recorded .wav file that has been converted to flac, then back to .wav might produce a report that the audio came from MPEG??
Thanks !!
Re: Trader's Little Helper
Quote:
Originally Posted by Drgiggles1
Most likely a false positive. That's why it is recommended when checking for lossy you use Cool Edit Pro to check the spectral and frequency analysis preferably zoomed in on a 2 second area of the file. Also a file that has been recorded on a DAT recorder with a 16K drop off may be confused for a lossy file when indeed it is not.
Interesting... is there any information to tell what TLH actually tests?? If there is a likelihood of false-positives, then this would not necessarily be a "go-to" tool for testing if FLACs are sourced from MPEG then would it?? as you say, the only way to truly tell is to see where the freq. roll-off exists....
So in your opinion is spectral analysis the ONLY definitive way to test?
Do you think the false positive comes from the codecs involved in going wav>flac>wav and are leaving some sort of artifact that TLH is sensing??
There is a site right now that is promoting the TLH test on files that have gone wav>flac>wav to test if they are not from MPEG.... I posted a recording that went from wav to flac, using the TLH codecs, and that very recording tested positive for MPEG in the TLH test!!
I might be the only one, but I stand by my statement that flac is NOT lossless and converting it back to a wav for anything other than a qualitative exam is worthless....
This is very bizarre and I am trying to decide if I should challenge this method since it seems very flawed to be the definitive test for their overall QC....
Any thoughts??
So, I guess what I am asking is on a scale of 1 to 10, how sensible is it to use the TLH test as your overall QC screen? (1 being not, and 10 being definitely smart)
Thanks!!
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Last edited by TomB; 2010-10-20 at 09:20 PM.
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