--- Harry Sack <tranzedude@gmail.com> wrote:> 2007/7/25, Harry Sack <tranzedude@gmail.com>: > > > > Hi > > > > I have downloaded a FLAC file somewhere and when trying to decode > it to > > WAV it gives the error message: ERROR, MD5 signature mismatch > > So my question is now: are FLAC files that give the error message > above > > still decodable to WAV (and how can you do this, because flac.exe > doesn't > > want to decode the file), even if there is a MD5 signature > mismatch, or is > > this not possible at all?if that is the only error given even when decoded with -F, then it got all the samples back. they are also highly likely to be the same samples that were encoded. most likely they were encoded on a machine with bad hardware (bad ram, aggressive overclocking), less likely is that the file was corrupted or tampered with.> An additional question: what happens if you re-encode a FLAC file, > that > gives the error message 'ERROR, MD5 signature mismatch' while trying > to > decode to WAV, to another FLAC file using a later version of the FLAC > encoder? I tried this and it seems to work, but I'm wondering if the > audio > data is still the same in the new file as in the old file? Or what > happens > in the re-encode process when such a input FLAC file is re-encoded to > another FLAC file?the audio data is the same, otherwise it is highly likely that you would get other errors along the way decoding. the MD5 is just a hash of the audio data. whether the audio was corrupted during the original encoding takes some investigation to figure out. Josh ____________________________________________________________________________________ Looking for a deal? Find great prices on flights and hotels with Yahoo! FareChase. http://farechase.yahoo.com/
2007/7/25, Josh Coalson <xflac@yahoo.com>:> > --- Harry Sack <tranzedude@gmail.com> wrote: > > 2007/7/25, Harry Sack <tranzedude@gmail.com>: > > > > > > Hi > > > > > > I have downloaded a FLAC file somewhere and when trying to decode > > it to > > > WAV it gives the error message: ERROR, MD5 signature mismatch > > > So my question is now: are FLAC files that give the error message > > above > > > still decodable to WAV (and how can you do this, because flac.exe > > doesn't > > > want to decode the file), even if there is a MD5 signature > > mismatch, or is > > > this not possible at all? > > if that is the only error given even when decoded with -F, then > it got all the samples back. they are also highly likely to be > the same samples that were encoded. most likely they were encoded > on a machine with bad hardware (bad ram, aggressive overclocking), > less likely is that the file was corrupted or tampered with.But how is it possible then the FLAC encoder allows files which have a bad resulting MD5 to be encoded? Is it because of the bad ram, ... this incorrect MD5 is not detected during encoding? Can you also give me an example of an error message that would occur when the file is corrupted? -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.xiph.org/pipermail/flac/attachments/20070726/b13f3be6/attachment.htm
--- Harry Sack <tranzedude@gmail.com> wrote:> 2007/7/25, Josh Coalson <xflac@yahoo.com>: > > > > --- Harry Sack <tranzedude@gmail.com> wrote: > > > 2007/7/25, Harry Sack <tranzedude@gmail.com>: > > > > > > > > Hi > > > > > > > > I have downloaded a FLAC file somewhere and when trying to > decode > > > it to > > > > WAV it gives the error message: ERROR, MD5 signature mismatch > > > > So my question is now: are FLAC files that give the error > message > > > above > > > > still decodable to WAV (and how can you do this, because > flac.exe > > > doesn't > > > > want to decode the file), even if there is a MD5 signature > > > mismatch, or is > > > > this not possible at all? > > > > if that is the only error given even when decoded with -F, then > > it got all the samples back. they are also highly likely to be > > the same samples that were encoded. most likely they were encoded > > on a machine with bad hardware (bad ram, aggressive overclocking), > > less likely is that the file was corrupted or tampered with. > > But how is it possible then the FLAC encoder allows files which have > a bad > resulting MD5 to be encoded? Is it because of the bad ram, ... this > incorrect MD5 is not detected during encoding?it happens like this, x.wav gets encoded with flac.exe on a machine with bad ram. flac.exe reads some audio data from x.wav into memory and encodes it. samples are buffered to md5 checksummer which writes intermediate checksum to bad memory. md5 is corrupted but samples were encoded ok. the user will not know unless the --verify option was used during encoding.> Can you also give me an example of an error message that would occur > when the file is corrupted?you would get errors about lost sync, frame crc mismatch, bad header, or unparseable stream. Josh ____________________________________________________________________________________ Fussy? Opinionated? Impossible to please? Perfect. Join Yahoo!'s user panel and lay it on us. http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7
On Jul 26, 2007, at 1:24 PM, Harry Sack wrote:> But how is it possible then the FLAC encoder allows files which > have a bad resulting MD5 to be encoded? Is it because of the bad > ram, ... this incorrect MD5 is not detected during encoding?In your original email you mentioned that you had downloaded the FLAC file with these errors; you don't know that the reference encoder was used. I mention this because I have encountered such errors with third-party encoders. For example, at least one release of Max wrote incorrect checksums. (See <http://sbooth.org/tracker/view.php?id=222> for details.) Cheers, - Andrew