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Topic: Comparing quality between different bitrate recordings (Read 5141 times) previous topic - next topic
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Comparing quality between different bitrate recordings

Hey there, I'm sure this comes up for a number of you as well... You'll have the same recording in different bitrates, you may have a 128MP3 of say, Cookie Monsta's Optimus Prime and also have a 320MP3 version. Upon further listening you can clearly tell that some bozo has tried to convert the 128MP3 to 320 and the 320 doesn't sound nearly as clear as the 128kbps.

Is there a scientific way to compare different bitrates of the same recording to assess clarity aside from aural examination? Let's talk about it.

I've got a VBR MP3 in the mid 200kbps and I'm having difficulty aurally comparing it with the 320MP3 version I've got. I would only assume the same thing that some undereducated fool has gone and transcoded upto 320kbps but it would be nice to understand the science behind the analysis. Hope you can help

Comparing quality between different bitrate recordings

Reply #1 –
Quote from: _Slipstream on
Is there a scientific way to compare different bitrates of the same recording to assess clarity aside from aural examination? Let's talk about it.


No.

Comparing quality between different bitrate recordings

Reply #2 –
Transcoding evidence takes quite a bit of sleuthing, in which automated processes are generally unreliable.

Take your example: if you could positively identify the encoder used (LAME, FhG etc) in the 320kbps file; and identify the version of the encoder; then positively know that encoder+version encodes above 16KHz at 320kbps (meaning, that it encodes over 16KHz more often than not); and then notice a spectrograph of your 320kbps file has a pretty clear 16KHz lowpass-- chances are the file is a transcode.

Also, some older encoders just sound bad even at the maximum bitrate, so that could be why it some files sound shredded/warbly.

Good luck!

edit: oops, managed to get myself a bit off-topic. Comparison of files at different bitrates are kindof an 'ears-only' territory.
"Something bothering you, Mister Spock?"

Comparing quality between different bitrate recordings

Reply #3 –
Only got back to this now, thanks for the input

Comparing quality between different bitrate recordings

Reply #4 –
Quote from: Destroid on
Take your example: if you could positively identify the encoder used (LAME, FhG etc) in the 320kbps file; and identify the version of the encoder; then positively know that encoder+version encodes above 16KHz at 320kbps (meaning, that it encodes over 16KHz more often than not); and then notice a spectrograph of your 320kbps file has a pretty clear 16KHz lowpass-- chances are the file is a transcode.

This is correct because a typical, original 320kbps MP3 should had a lowpass of 19kHz-20kHz. The only problem in this is when someone knowledgeable enough to add high frequencies to the 16kHz MP3 to make it "look" like a 20kHz MP3. This is one example why you should not trust spectral analysis in this situation. A simple listening test or ABX will do 
sin(α) = v sound/v object = Mach No.