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Topic: Help with detecting real 320kbps and FLAC (Read 2619 times) previous topic - next topic

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  • GamerX
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Help with detecting real 320kbps and FLAC
I do it with SPEK but how do I detect shelves ?
Please Help.

  • JunkieXL
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Re: Help with detecting real 320kbps and FLAC
Reply #1
Buy the music from legitimate sources or make your own from the original CD.
JXL

  • j7n
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Re: Help with detecting real 320kbps and FLAC
Reply #2
Regardless of the tool used, you need to lower the floor to -120 or -130 dB and make a spectrogram that is big enough to discern detail. Have at least 20 pixels per second. If Spek can only make small images, use SoX instead. Analyze at the difference channel for stereo files, which will reveal more artifacts.

I use the following command line for SoX for analysis. The remix effect adds one more channel with the difference between L and R.

sox.exe "INPUT.WAV" -n remix 1 2 1v0.5,2v-0.5 spectrogram -x 5000 -y 257 -Z -10 -z 120 -o "INPUT.WAV-lrs.png"

Instants where the signal falls below the "shelf" will show as black. You want the spectrum between 16 and 20 kHz to be quite "dense", and show no blocking at all for lossless sources. Encode a few 320 kbit files of different music genres yourself and analyze them to learn what to expect.

  • DVDdoug
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Re: Help with detecting real 320kbps and FLAC
Reply #3
If your goal is to fool someone, I assume it's easy to fake-out the software by using an exciter effect before encoding to FLAC.

  • GamerX
  • [*]
Re: Help with detecting real 320kbps and FLAC
Reply #4
If your goal is to fool someone, I assume it's easy to fake-out the software by using an exciter effect before encoding to FLAC.
really its that easy to fake a mp3 encoded to FLAC?

  • GamerX
  • [*]
Re: Help with detecting real 320kbps and FLAC
Reply #5
Regardless of the tool used, you need to lower the floor to -120 or -130 dB and make a spectrogram that is big enough to discern detail. Have at least 20 pixels per second. If Spek can only make small images, use SoX instead. Analyze at the difference channel for stereo files, which will reveal more artifacts.

I use the following command line for SoX for analysis. The remix effect adds one more channel with the difference between L and R.

sox.exe "INPUT.WAV" -n remix 1 2 1v0.5,2v-0.5 spectrogram -x 5000 -y 257 -Z -10 -z 120 -o "INPUT.WAV-lrs.png"

Instants where the signal falls below the "shelf" will show as black. You want the spectrum between 16 and 20 kHz to be quite "dense", and show no blocking at all for lossless sources. Encode a few 320 kbit files of different music genres yourself and analyze them to learn what to expect.
I will try this and tell you, thanks.

Re: Help with detecting real 320kbps and FLAC
Reply #6
Spectro (FLAC & MP3)
http://spectro.enpts.com
Screenshots: http://spectro.enpts.com/screenshots.php

Also, Lossless Audio Checker [UI or CLI]. No shelf but it just tells you if the FLAC is clean or upsampled.
http://losslessaudiochecker.com
Mp3tag beatport WSS creator (◣_◢)     https://goo.gl/YsJF8w

  • ErnestS
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Re: Help with detecting real 320kbps and FLAC
Reply #7
Also, Lossless Audio Checker [UI or CLI]. No shelf but it just tells you if the FLAC is clean or upsampled.
http://losslessaudiochecker.com
No it doesn't. 

  • GamerX
  • [*]
Re: Help with detecting real 320kbps and FLAC
Reply #8
Regardless of the tool used, you need to lower the floor to -120 or -130 dB and make a spectrogram that is big enough to discern detail. Have at least 20 pixels per second. If Spek can only make small images, use SoX instead. Analyze at the difference channel for stereo files, which will reveal more artifacts.

I use the following command line for SoX for analysis. The remix effect adds one more channel with the difference between L and R.

sox.exe "INPUT.WAV" -n remix 1 2 1v0.5,2v-0.5 spectrogram -x 5000 -y 257 -Z -10 -z 120 -o "INPUT.WAV-lrs.png"

Instants where the signal falls below the "shelf" will show as black. You want the spectrum between 16 and 20 kHz to be quite "dense", and show no blocking at all for lossless sources. Encode a few 320 kbit files of different music genres yourself and analyze them to learn what to expect.
How to run it? I am sorry I am a noob
  • Last Edit: 16 August, 2017, 11:15:32 AM by GamerX

  • polemon
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Re: Help with detecting real 320kbps and FLAC
Reply #9
I don't know if what you want is a spectrogram, if you do, I'd suggest having a look at http://www.baudline.com/
It's my go-to spectrum analyzer for quickly checking audio sources, etc.

  • shayzee101
  • [*]
Re: Help with detecting real 320kbps and FLAC
Reply #10
Hi guys,

I got one of my producer friends to create me some remixes, he used original itunes songs as the base which I sent him myself so know these remixes have not been created from a low quality source. Looking at the two examples of my remixes, are these high quality audio? Because I notice a weird visible line at 16khz.

  • j7n
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Re: Help with detecting real 320kbps and FLAC
Reply #11
How to run it?
I didn't see your post. I use Frontah as a frontend, and have customized it with more options. The SoX folder must be in the system %path%. To process compressed formats directly, the respective command-line decoders must be in the path too. SoX understands flac by itself among a few others. The "stdin" option will force use of flac.exe and create detailed spectrograms that exceed 5000 pixels in width. The list will still say 'error' because how I appended the resolution to the output filename. You can see if it is working anyway. Don't use Unicode characters in filenames.

Let it process a good number of tracks and later check through the generated images.

The above files might be fine. The MP3 format has limited precision above 16kHz, and LAME will keep this range sparse at lower 'q' settings. The signal needs to be quite loud to get over the coding threshold, and it looks like that it isn't most of the time. With a small spectrogram you see an average over time. If you were to zoom in, you'd see that in instances when there is percussion or s-sounds, those get encoded. I would be concerned if black gaps were to appear in the lower bands, which at 320 kbit/s should be solid.

  • shayzee101
  • [*]
Re: Help with detecting real 320kbps and FLAC
Reply #12
Hi sorry im a bit confused. I have a  Mac not sure really what your reply means. LOL its too technical for my small brain. I am just concerned these mixes are not 320kbps :(

  • j7n
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Re: Help with detecting real 320kbps and FLAC
Reply #13
The first paragraph was in reply to the Original Poster whom I quoted. The line appears because of a design limitation of the MP3 format and the fact that high pitched sounds happen to be too quiet to be heard in this sample. Encode similar music style of music yourself and compare. If you can only have MP3 as an option for these original mixes, this might be the best quality. If a similar line was to appear in other formats, it would indicate that MP3 was used during processing.

  • shayzee101
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Re: Help with detecting real 320kbps and FLAC
Reply #14
Ah i see! So this line does not mean my remix is poor quality. Because tbh they sound decent its just ive seen forums saying that line means it is 128kbps upscaled. But if it just a deaign flaw and is actually 320kbps then its all good !

  • j7n
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Re: Help with detecting real 320kbps and FLAC
Reply #15
At 128 kbit/s sounds in the audible range would break up on the spectrogram. Look at the area below the 16 kHz line, if it is solid.

Example SoX spectrograms:
128 kbit, 320 kbit/s q0, 320 kbit/s q-default

Maybe the remixes were encoded with a "high quality" (q0) setting, which makes the shelf more pronounced.

  • shayzee101
  • [*]
Re: Help with detecting real 320kbps and FLAC
Reply #16
Hello!

Yes - Looking at your graphs the qo filter spektogram matches my files. So therefore my remixes are not high quality audiothen ! :(

  • julf
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Re: Help with detecting real 320kbps and FLAC
Reply #17
So therefore my remixes are not high quality audio then ! :(

How do you define "high quality audio"?

  • shayzee101
  • [*]
Re: Help with detecting real 320kbps and FLAC
Reply #18
Basically,

I am an aspiring bedroom dj. So these mixes will eventually be played at functions / venues on loud roadshow systems. Therefore the songs need to be good quality to prevent any distortion / cracking when played loud. They need to be crisp and sharp.

  • j7n
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Re: Help with detecting real 320kbps and FLAC
Reply #19
It is possible that the author has selected a "high" or "maximum" quality setting in his software, overriding the default, which counter-intuitively causes thinning of the spectrogram and lower effective bitrate. However, 320 kbit has a considerable quality margin in any case, and slight differences in spectrogram aren't a sufficient reason to raise doubts about quality of a lossy encoding. I am not able to hear a difference between a q0 or q3 setting. Different encoders and versions fill in the top part of the spectrum to variable extent, and it is by itself an unreliable indication of quality. If you would like to use specific settings, then request a lossless format and encode the files yourself.

Distortion and crackling is usually caused by hot levels and limiting, not by standard lossy codecs.

  • Aldem
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Re: Help with detecting real 320kbps and FLAC
Reply #20
Also, Lossless Audio Checker [UI or CLI]. No shelf but it just tells you if the FLAC is clean or upsampled.
http://losslessaudiochecker.com
No it doesn't. 

Care to explain your thoughts ?

  • julf
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Re: Help with detecting real 320kbps and FLAC
Reply #21
I am an aspiring bedroom dj. So these mixes will eventually be played at functions / venues on loud roadshow systems. Therefore the songs need to be good quality to prevent any distortion / cracking when played loud. They need to be crisp and sharp.

"Good quality" has nothing to do with avoiding distortion and cracking when played loud. That is up to your sound system. 320k mp3 is just as crisp and sharp as uncompressed audio.

  • DVDdoug
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Re: Help with detecting real 320kbps and FLAC
Reply #22
Quote
I am an aspiring bedroom dj. So these mixes will eventually be played at functions / venues on loud roadshow systems. Therefore the songs need to be good quality to prevent any distortion / cracking when played loud.
In that case, just judge the quality with your ears!     Use a decent pair of headphones if you don't have good speakers/monitors in your bedroom.   And, listen to some known-good music in the same genre to "calibrate your ears".     If it doesn't sound quite right, try some equalization.*    And of course, if you buy the CDs or buy MP3s (or AACs, or FLACs) from a legitimate site you know they are not "poor quality" copies.

And yes...   The quality of your speakers/PA system and the room acoustics are super-important.    In many venues with reverberation ("echo") or noisy crowd, you're never going to hear any MP3 compression artifacts.  ;)   You might hear too much bass, or not enough bass, or not enough highs, or distortion, etc., but usually not MP3 artifacts.




* EQ doesn't fix everything,  but unless you've got rather-bad distortion or noise, EQ (frequency balance) is usually the biggest "sound quality" factor.

BTW - If you EQ digitally (with your player software or with an audio editor) watch your levels!    If you boost any frequencies you can end-up clipping (distorting) the digital audio, and you may have to reduce the overall (digital) volume to compensate.    Then if your amplifier is powerful enough, you can compensate for any loss of volume by cranking-up the analog volume.

  • Last Edit: 09 September, 2017, 04:34:23 PM by DVDdoug