IPB

Welcome Guest ( Log In | Register )

lossyWAV vs MP3
chrizoo
post Sep 13 2011, 07:40
Post #1





Group: Members
Posts: 345
Joined: 25-March 08
Member No.: 52274



Hi. I very much like the theoretical concept of lossyWAV. But being skeptical by nature, I always like to try for myself and verify.

This is my test set-up:
file1: the source wav file
file2: file1 processed with lossyWAV --extreme
file3: file1 compressed with LAME mp3 320CBR and decoded back to wav
file4: file1-file2
file5: file1-file3

Results:
Regarding the waveform, I generally noticed,
that file4 is always "centered" at the zero line (while file5 strays from it), i.e. positive and negative half of the wave are quite symmetrical
but
that file4 generally has considerably higher amplitudes than file5.
Hereafter is a screenshot sample to illustrate that.

sample from file1 which includes the part shown in the screenshot:
http://www.hydrogenaudio.org/forums/index....showtopic=90776


Now the question is:
While mp3 (of any bitrate) is generally not recommended to transcode to another lossy format, lossyWAV --extreme is:

QUOTE (http://wiki.hydrogenaudio.org/index.php?title=LossyWAV)
--quality extreme: (-q E or -q 7.5) Higher quality preset, disc space-saving alternative to lossless archiving for large audio collections, considered to be suitable for transcoding to other lossy codecs;

So the lossyWAV's loss should without doubt be considerably less than the loss/distortions introduced by mp3.
The comparison doesn't exactly suggest that (if anything, it would suggest the contrary).

On the one hand waveform comparison allegedly cannot reliably inform about quality loss (according to HA),
but on the other hand I am asking myself HOW it can be possible, that file4 COULD even somehow be closer to the original file (than file5) when we see that it is in fact more different?



This post has been edited by chrizoo: Sep 13 2011, 07:45
Go to the top of the page
+Quote Post
 
Start new topic
Replies
chrizoo
post Sep 13 2011, 09:21
Post #2





Group: Members
Posts: 345
Joined: 25-March 08
Member No.: 52274



Look, of course none of you is forced to explain anything to me or to talk about the waveform at all. But simply saying "only listening to differences is accepted here, but looking at the waveform is not", does not make me (or anyone else who is looking for answers) understand anything. I've been here long enough to know that the consensus here is that only listening matters (But WHY that is so is a different matter). However, I find the theoretical background interesting too (plus I don't hear so well).

It's not like the waveform doesn't depict exactly the acoustic signal we are dealing with here. And if in the difference graph, the amplitude is higher, it means, there is more difference from the original audio. Correct me if I am wrong, but I think that is a fact.

The answers included explanations of how lossyWAV works - which I think I broadly know already - but this is irrelevant (because not intrinsic) to explaining why difference graphs in general don't matter. And this point just is not understandable to me (so far).

This post has been edited by chrizoo: Sep 13 2011, 09:27
Go to the top of the page
+Quote Post
saratoga
post Sep 13 2011, 19:01
Post #3





Group: Members
Posts: 4868
Joined: 2-September 02
Member No.: 3264



QUOTE (chrizoo @ Sep 13 2011, 04:21) *
I've been here long enough to know that the consensus here is that only listening matters (But WHY that is so is a different matter). However, I find the theoretical background interesting too (plus I don't hear so well).


The ears are basically a nonlinear spectrometer, reading out spectral differences in waveforms, while the eyes are spatial domain instruments, reading out spatial variations with little spectral resolution. If you try to interpret audio data in a domain other then the one its measured in, the results are likely to be weird if not completely meaningless because not all differences in one domain will map into changes in measurements in the other.
Go to the top of the page
+Quote Post

Posts in this topic


Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



RSS Lo-Fi Version Time is now: 1st August 2014 - 09:02