Hydrogenaudio Forums > Something I don't understand with the converter...

Olaf

Mar 3 2007, 04:58

Hi,

I have all my albums ripped in APE on my computer, and for some reasons I'm currently thinking about converting them to image albums with embedded cuesheets. The option "Convert in Album Images with Cuesheets of Chapters" works great, but there's something weird that's bothering me : with the same encode profile (Monkey's Audio Normal), the album images are at least 50mb smaller than the separate APE files.

If I convert the album images back in separate files, they are still smaller than the original ones. So... what's wrong ?

I'm currently listening to an album image and it seems ok. I'm just wondering where have gone my 50mb...

Synthetic Soul

Mar 3 2007, 07:11

What version were the source files encoded with? I started using 3.99 - maybe 3.97 or lower compressed a lot worse?

Additional tagging would account for a few KiB, but not that much!

Olaf

Mar 3 2007, 14:40

They are all encoded with the same version (3.99), the same profile (-c2000) and the same way (foobar converter).

I just did a test :
- "Open Audio CD..." -> Rip -> using preset "Monkey Audio, Normal" : 244mb
- Load the files in foobar -> "Convert in Album Images with Cuesheets of Chapters" -> using the exact same preset : 215mb
- Load the image in foobar -> "Convert to..." (separate files again) -> still using the same preset : 215mb

30mb are gone... That's good for me, I will save space on my hard drive, but I'd like to know what happen exactly...

Olaf

Mar 6 2007, 14:01

I've tested with FLAC, that's exactly the same...

Tich

Mar 6 2007, 16:20

You should probably consider ripping with EAC instead of foobar and test your results there.. seems weird though.

kanak

Mar 6 2007, 16:35

QUOTE(Olaf @ Mar 4 2007, 02:40)

They are all encoded with the same version (3.99), the same profile (-c2000) and the same way (foobar converter).

I just did a test :
- "Open Audio CD..." -> Rip -> using preset "Monkey Audio, Normal" : 244mb
- Load the files in foobar -> "Convert in Album Images with Cuesheets of Chapters" -> using the exact same preset : 215mb
- Load the image in foobar -> "Convert to..." (separate files again) -> still using the same preset : 215mb

30mb are gone... That's good for me, I will save space on my hard drive, but I'd like to know what happen exactly...

Did you bit compare the files? If they're identical, you should be very happyfor getting 30 mb per album

Borisz

Mar 6 2007, 16:38

Have you tried bitcomparing the resultant files? If the decoded audio doesn't match, you have something very fishy going on.

Olaf

Mar 6 2007, 17:01

CODE

differences found: 24830528 sample(s), starting at 0.0175510 second(s), peak: 0.6390381 at 262.8719728 second(s), 1ch

That's the result of the bitcomparing test with one track before and after the "Convert in Album Images with Cuesheets of Chapters". Don't understand what that means though, first time I use this component.

I'll try to rip with EAC tomorrow, but I think it will still be the same.

buktore

Mar 6 2007, 20:46

QUOTE(Olaf @ Mar 7 2007, 06:01)

CODE

differences found: 24830528 sample(s), starting at 0.0175510 second(s), peak: 0.6390381 at 262.8719728 second(s), 1ch

That's mean.. you got a different data. so 2 track is different.

something going wrong.

fluffy

Mar 6 2007, 21:23

you did do the bitcompare after you'd decoded both of the files back to wav, right?

Olaf

Mar 7 2007, 01:15

QUOTE(fluffy @ Mar 7 2007, 04:23)

you did do the bitcompare after you'd decoded both of the files back to wav, right?

Ha ha, that would be a good idea. Indeed I did the bitcompare with the APE files, and now I think about it after a good night of sleep, I see that was totally stupid.

I'll do the thing again tonight when I'm back home.

david_dl

Mar 7 2007, 02:22

QUOTE(fluffy @ Mar 7 2007, 16:23)

you did do the bitcompare after you'd decoded both of the files back to wav, right?

Shouldn't make a difference. bitcompare compares the _decoded_ data.

Olaf

Mar 7 2007, 08:05

Indeed, I still have an error after converting back to WAV.

I just did some more tests :
1 - rip in WAV with EAC
2 - convert to any formats (tried with APE, FLAC & WV)
3 - use the magic "Convert in Album Images with Cuesheets of Chapters"
4 - convert back to single files, then to WAV

The result is always the same : the WAV files after the whole process are different from the original ones. If I skip step 3, the files are ok.

kanak

Mar 7 2007, 13:26

one suspect: have you enabled the "use dsp during conversion" thing? because the resultant file seems to be mono (i'm assuming your source wasn't mono).

Olaf

Mar 7 2007, 14:08

That wasn't enabled, but I've done some more testing with ReplayGain, and I finally found the problem :
- if my original APE files don't have ReplayGain info and I apply ReplayGain when converting to an album image, that's ok
- if my original APE files have ReplayGain info and I don't apply ReplayGain when converting to an album image, that's ok
- if my original APE files have ReplayGain info and I apply ReplayGain again when converting to an album image, the image is screwed up

I still don't understand why, and what happen to the lost megabytes, but at least I know where it comes from.

Anyway, thanks to those who helped. I'm glad I didn't rush to convert all my files before investigating.

Moguta

Mar 7 2007, 21:56

QUOTE(Olaf @ Mar 7 2007, 15:08)

That wasn't enabled, but I've done some more testing with ReplayGain, and I finally found the problem :
- if my original APE files don't have ReplayGain info and I apply ReplayGain when converting to an album image, that's ok
- if my original APE files have ReplayGain info and I don't apply ReplayGain when converting to an album image, that's ok
- if my original APE files have ReplayGain info and I apply ReplayGain again when converting to an album image, the image is screwed up

I still don't understand why, and what happen to the lost megabytes, but at least I know where it comes from.

Anyway, thanks to those who helped. I'm glad I didn't rush to convert all my files before investigating.

That's because applying ReplayGain isn't the same as copying RG tags or calculating the gain. It's actually applying the gain info to the actual audio before converting to the image. Or so it would seem. It's usually best to disable ReplayGain application when converting.

And I have a feeling that the gain is a negative gain... which would round some audio data off to zero, and probably kill the dithering too. Thus making the files a little simpler to encode.

Olaf

Mar 8 2007, 03:52

Hmm... That's a good thing to know. Thanks.