M4A to FLAC adds Noise

[street_samurai]

I've just had an extremely annoying experience of converting Apple Lossless files to FLAC using DBPowerAmp. Since I assumed this process would be pretty much foolproof (lossless to lossless conversion), I deleted the source files as I converted (a collection of over 50gb of music). None of the M4A files had DRM protection.

Much to my annoyance, the newly created FLACs have extremely noticable and extremely grating digital noise in them. The noise seems to occur randomly throughout the tracks.

Converting the FLAC back to Wav and opening in Wavelab shows that the noise is encoded into the file and not an artifact of playback.

Any thoughts on why this might be happening?

ss.

p.s. I'm using Release 11 of DBpa, Flac Codec 5.2 (using FLAC 1.1.2) and Release 3 of the m4a FAAC codec.

p.p.s. this sounds exactly like: http://forum.dbpoweramp.com/showthread.php?t=7741 so I'd imagine this is a FLAC encoding issue and not a M4A decoding issue... but I could be wrong.

[LtData]

Re: M4A to FLAC adds Noise

Do you have any more ALAC files to test with? Channels of your ALAC files, frequency?

By the way, its a good idea to not delete the source files unless you can remake them by remaking it from the source or another backup of it. Sorry to hear about the noise.

[street_samurai]

Re: M4A to FLAC adds Noise

Do you have any more ALAC files to test with? Channels of your ALAC files, frequency?

By the way, its a good idea to not delete the source files unless you can remake them by remaking it from the source or another backup of it. Sorry to hear about the noise.

Hi, thanks for the prompt response!

I'll be getting the same files again. These were masters for a series of CDs that I am working on from a remote friend so they are recoverable but a pain to get again. I'm not super familiar with ALAC because I never use it at home but the files were all CD quality: 2 channel, 16 bit 44.1khz.

I've learned my lesson about keeping the source. Naively figured that dBPA would do some kind of consistency checking when doing a lossless-to-lossless conversion. In my mind at least, it seemed like a simple thing to do... although I realize that technically, its really quite complex.

I should get another copy of the original ALAC files by tonight.

Any thoughts on what the problem might be?

ss.

[LtData]

Re: M4A to FLAC adds Noise

Unsure. You were making the usual 44100Hz, 2 channel FLAC files, right? 16-bit?

[Spoon]

Re: M4A to FLAC adds Noise

Try convert ALAC m4a to wave, then alac to flac and wav to flac (give each final filename a unique name). Then convert both flac files to wav and use a CRC checking program to check the 3 wave files, are they all the same or different? also check that no DSP effects are being used in dBpowerAMP.

[street_samurai]

Re: M4A to FLAC adds Noise

Thank you for the help.

Right now I'm thinking that this isn't a poweramp issue but something else (possibly an issue with the portable drive that I'm getting the files on). I realized that the original versions on the disk had errors even when played in iTunes. But the originals on my friend's disk are prestine. I tried the various conversions mentioned and everything CRC32s fine.

Its an extremely annoying problem to troubleshoot because the errors occur randomly and rarely across many files. Which means I have to listen through a number of tracks before I notice the errors.

I'll write back later if I figure out exactly what the problem is... but right now it appears not to be a PowerAmp issue. Sorry for the confusion!

ss.

[street_samurai]

Re: M4A to FLAC adds Noise

Ok. Definitely not a poweramp problem.

I believe the issue was a problem with my external usb enclosure. It seems that when I do the conversion on the enclosure hard disk, I get errors. But when I copy the files to a local HDD, no problem at all.

There is an updated firmware for my enclosure which I haven't yet tested... this may fix this particular problem.

Sorry to lay blame where it wasn't deserved!

ss.

[dcoberlin]

Re: M4A to FLAC adds Noise

What HD USB enclosure were you using? Did your firmware upgrade heal the unit. I am poised to buy a unit. I have an AMS Venus for my photos and am considering an SATA compatible one like one from COOlDrive or AMS that would allow at least the HD to be forward compatible.