[smartins]

I have two FLAC files of the same album/track with about the same size but that came from two different sources.

Is there any way to visually compare the amount of information each one has to see if they are equal or one just has more details than the other?

I have the feeling that one is slightly less detailed than the other and would like to confirm if it might have been transcoded from a MP3 file.

Thanks!

 

[hYdrociTy]

Quote:

Originally Posted by smartins /img/forum/go_quote.gif I have two FLAC files of the same album/track with about the same size but that came from two different sources. Is there any way to visually compare the amount of information each one has to see if they are equal or one just has more details than the other?

Sometimes flac files encoded with different settings yield different sizes, and even sometimes with the same settings. I think the frontend has a validation feature.

Quote:

Originally Posted by smartins /img/forum/go_quote.gif I have the feeling that one is slightly less detailed than the other and would like to confirm if it might have been transcoded from a MP3 file. Thanks!

That would be hard to say, until gather the original wav file, the two flacs, and decompress and see what it turns into. One of them should be the same exact waveform, the other should be slightly different.

Try playing around with the the flac frontend

 

[Ross1]

There is an ABX testing feature in foobar, I think that sounds like exactly what you want.

Otherwise, you can check the spectral analysis of them both in something like adobe audition, audacity (free), or even EAC if you decode to wav first.

 

[smartins]

Thanks for the replies. The thing is I have an album already in FLAC and decided to grab a track from allofmp3 also in FLAC format to see if they were exactly the same.

Converting to wav results on my original flac file being around 100 Kb bigger than the allofmp3 flac file.

I've also did a comparison with EAC and audacity and indeed they are not exactly the same.

Unfortunately i couldn't really find a way to actually see if one just had more information available than the other. When opening on audacity they look very similar.

 

[Alleyman]

If one is transcoded from an MP3 file, then it should display a lowpass in the frequency spectrum analysis. Have you tried that?

 

[ShadowVlican]

it's extremely difficult to end up with identical rips from different sources

different model optical drives all have different read offsets (google EAC and offsets for more info) this explains your rips and allofmp3's rips are different

encoding with FLAC with same settings will yield identical files, given your source is also identical..... and of course if you change settings the output will change

you can test for identical files using RapidCRC, which will output a checksum of the files so you can compare easier (i did this with foobar converting lossless files into one type then into another then etc........ then finally back to uncompressed wav... and it was exactly the same as the original... meaning lossless really is lossless!)

 

[smartins]

Quote:

Originally Posted by Alleyman /img/forum/go_quote.gif If one is transcoded from an MP3 file, then it should display a lowpass in the frequency spectrum analysis. Have you tried that?

Sorry, I have no idea of what you said

Can you share some more information on how to detect if the flac might have been transcoded from an MP3?

 

[Alleyman]

What I meant was open the file in Audacity, select a few seconds of the waveform and goto analyze>plot spectrum. Check the right most value on the x-axis where there is data present. Do this for both files.

During encoding of MP3 the audio data over a certain frequency is cutoff since human ears cannot discern them. Thus one transcoded from a MP3 will show a lower frequency cutoff than the one that is losslessly encoded from the source. I hope I exaplained it well (I'm not so good with words)

 

[Kees]

If they are both genuine lossless (not derived from an MP3 file) they should be identical if converted to WAV. This way you can see if the file size difference is only from a different FLAC encoding setting (same wav result) or from an MP3 > FLAC conversion (less information: smaller WAV file).

 

[thomaspf]

There is a wav file comparison tool on sourceforge. It deals with additional samples at the beginning and end that are artefacats of ripping.

I would expand to WAV and give this a try

Cheers

Thomas

 

[katalyst^]

Foobar has a bit-compare component. It won't tell you a great deal unless you know that both come from the same pressing and know that at least one is a bit-perfect rip.

 

[hilikus]

coming from another form.

Also look into http://www.accuraterip.com/ . It checks to see if anyone else in the world with accuraterip got the same results as you did for your rip.

Quote:

What is a Transcode? Put simply, a transcode is any audio file that wasn't encoded from an original lossless source, such as a retail CD (not created from lossy files) or a properly made lossless rip. Why is transcoding bad? Whenever you encode a file to a lossy format (such as mp3, m4a(AAC), ogg, or mpc) information is permanently lost. It doesn't matter what you do, it's impossible to get this information back without making a new rip from the original lossless source. If you reencode it to a different format or bitrate, all you're doing is reducing the quality. This applies to any lossy to lossy conversion, so even if you convert from 320kbps to 192kbps, the final file will still sound worse than if you had just ripped to 192kbps in the first place. FhG VS. LAME Most lossy encoders use a low-pass filter when encoding. The filter is set to cut frequencies above a certain point and leave those below. The reason they're doing it is, that high frequencies are more difficult to encode and hearing is less sensitive in higher frequencies. MP3 encoders at 128kbps will typically use a LPF at 16kHz. As you raise the bitrate, the frequency threshold raises. At 192kbps the LPF is usually set at 18kHz or higher.

Quote:

How to view the Spectral Analysis of songs using Adobe Audition To view the spectral analysis of audio files in Adobe Audition, first ensure you are in Edit Waveform View by pressing the number 8 on your keyboard. Then, go to File > Open and select the file you wish to test. Adobe Audition will open the audio file in the "Waveform View" by default each time, so you'll need to choose View > Spectral View or press F9 to switch to Spectral View. The following section contains a list of common bitrates and their audio spectrum. The LAME were all done using dbpoweramp from a flac source, and they are all encoded using LAME version 3.97. The FhG were all done using Adobe Audition 1.5 FhG. The shape of the screen-shots differ due to different screen resolutions. Original (FLAC): 128 LAME: 128 FhG: 160 LAME: 160 FhG: 192 LAME: 192 FhG: V2: preset standard: 224 LAME: 224 FhG: 256 LAME: 256 FhG: 320 LAME: 320 FhG: V0: preset extreme: Typical Webrip: (notice the gap) As you can see, LAME uses 'full resolution' up to the frequency threshold, whereas FhG, encodes at 'full resolution' up to 16kHz, and uses 'low resolution' at higher frequencies. This is an easy way to tell which encoder was used. At 128kbps, LAME uses a LPF at ~17kHz and FhG at ~16kHz. I have included a screenshot of FhG at 128kbps without the LPF. At 160kbps FhG's LPF is set at 20kHz. At 192kbps, LAME stops at 19kHz and FhG encodes upto 22kHz. FhG looks like it's not doing its job right, but if you listen to the 192kbps samples, you can hardly tell which is LAME and which is FhG. At 128kbps, LAME sounds a bit better, more 'clear'. FhG encoding at 128kbps without the LPF sounds bad, you can certainly listen to the artifacts. LAME APS will typically use a LPF at 18.5kHz, whereas APX will go up to 19kHz.

Quote:

I've seen a lot of discussion here about how to spot transcodes. Many people have suggested using a spectral analysis from programs like Cool Edit / Adobe Audition / EAC and looking at the 'cut off' point. There is some disagreement about how effective this is, but those who recommend it suggest looking for cut-offs between 1600 Khz as the signature of a 128kbps mp3 source and 2100 Khz as the signature of Lossless. One counter argument to this 'cut off' level method is that the same cut off which characterises lossy encodes may also be the result of a poor quality recording - a bootleg of a live show or a 'third world' vinyl master. A number of spectral views have been posted and linked to, but nearly all of these have been analyses of entire tracks... which IMHO is NOT the most effective way to use spectral analysis to detect transcodes. What I haven't seen anyone discuss is the 'blocky' appearance of the spectral analysis of lossy rips which is noticeable only when you zoom in close enough. IMHO this is a more reliable way to detect whether a file which purports to be lossless has in fact been transcoded from a lossy rip, and may even be a useful way to detect re-encodes from lower to higher bitrate mp3s (although this is much harder whatever method you use). The image below illustrates what I mean. The track (from an album by Philip Glass) was ripped from CD to flac and a 1 second sample was saved to 320 kbps LAME mp3 and 128 kbps FhG mp3 and then in each case saved again to flac. The spectral analysis was done at full screen on a monitor with resolution of 1280 x 1024. Each of the three strips below is of the same 0.15 of a second. [size=medium]FLAC / 320 mp3 / 128 mp3 compared[/size] And here are bigger strips of the three spectral analyses. The zoom level is the same - bigger simply means that what is shown here is around 0.5 of a second - and NOT the whole track! [size=medium]FLAC[/size] [size=medium]320Kbps LAME mp3[/size] [size=medium]128Kbps FhG mp3[/size]

 

[smartins]

Thank you for all the replies especially hilikus for the detailed one.

I've just analyzed the track with Adobe Audition and here's the results (click any image for the full image:

FLAC from allofmp3 (converted to WAV)


FLAC from my rip (converted to WAV)


MP3 320 CBR (from someone else's rip)


WAV transcoded from MP3 320 CBR


So it seems that at least with this album allofmp3 hosts the full lossless version. I've read some comments about the FLAC downloads actually being transcoded from MP3 320 but I guess the albums with the OEEX are indeed lossless.

Thanks again for all the explanations you guys posted.