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Observing the loss., How good a criterion for quality measure
atici
post Jul 12 2003, 20:35
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Ok after some other discussion that prodded me into this I decided to give it a try again.

That is, I calculated the pure loss with mp3 and mpc encoders in CoolEdit (Mix Paste, both channels inverted & Overlap) and listened the pure loss in each case with different quality settings. I observed that with mp3 standard preset, I can still figure out the melody because I can still hear some instruments (probably because of low pass filter). With MPC I hear the swoosh sound intensifying in some parts of the sample esp. when the original sample's volume is high. The average volume of the loss decreases as I increase the quality setting.

Could you tell me your points why this is not a good way of objectively evaluating how successful a lossy codec is? I think it's nice because the difference is not masked by the rest of the sample (which is usually higher in volume and dominates). But I can also imagine that using this way one cannot figure out stereo separation artifacts and even though when the pure loss is listened as a sample and sounds tolerable, the actual encoding result might have noticeable differences and is non-transparent. But isn't this also a reasonable method to supplement the results about which encoder is more successful? Can't we conclude anything objectively or subjectively by observing the pure loss? It sounds to me the discarded information is more tolerable a loss in q4 MPC than lame standard mp3 3.93.1.

This post has been edited by atici: Jul 12 2003, 20:51


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guruboolez
post Jul 12 2003, 23:52
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QUOTE (atici @ Jul 12 2003, 08:35 PM)
(...) I observed that with mp3 standard preset, I can still figure out the melody because I can still hear some instruments (probably because of low pass filter). With MPC I hear the swoosh sound intensifying in some parts of the sample(...)  It sounds to me the discarded information is more tolerable a loss in q4 MPC than lame standard mp3 3.93.1.

Just a question : have you decoded your mp3 first with LAME, in order to remove the additional samples ? If not, your test is biased : Fhg decoding engine will maintain the 'gap'.


I had fun some times ago with this tool. I find interesting to mesure the real loss of the encoding process. Nevertheless, you can't evaluate the quality of two encodings by this way. The stronger difference (= noise) isn't necessary the most ABXable file. I tried to oppose MPC and Vorbis by this way ; mpc seemed to be the most degraded one, but after a carefully blind listening test, I only heard a difference (hiss) for the vorbis file.

Note that this tool is interesting in order to detect artifacts similar to the erhu effect.
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Posts in this topic
- atici   Observing the loss.   Jul 12 2003, 20:35
- - upNorth   QUOTE (atici @ Jul 12 2003, 09:35 PM)I think ...   Jul 12 2003, 20:59
- - Xerophase   QUOTE (atici @ Jul 12 2003, 02:35 PM)Ok after...   Jul 12 2003, 21:20
- - atici   Once there was a program called eaqual. I guess it...   Jul 12 2003, 21:25
- - 2Bdecided   Haven't we been here very recently, in a joint...   Jul 12 2003, 22:21
- - tigre   QUOTE Can't we conclude anything objectively o...   Jul 12 2003, 22:56
- - atici   @tigre: For point 1) we may assume the lossy enco...   Jul 12 2003, 23:27
- - Jebus   Look, The more bits you throw away, the more info...   Jul 12 2003, 23:30
- - atici   Jebus, I guess you missed my point. Because I agre...   Jul 12 2003, 23:36
- - lucpes   Blah... take a wave file. Apply wave gain or norma...   Jul 12 2003, 23:50
- - guruboolez   QUOTE (atici @ Jul 12 2003, 08:35 PM)(...) I ...   Jul 12 2003, 23:52
- - atici   QUOTE Just a question : have you decoded your mp3 ...   Jul 12 2003, 23:58
- - ErikS   QUOTE (atici @ Jul 12 2003, 11:27 PM)I think ...   Jul 13 2003, 02:08
- - Pio2001   Personally, I would be less worried by a differenc...   Jul 13 2003, 03:13
- - tangent   Look around for the "masking effect", I...   Jul 13 2003, 07:34
- - Pio2001   But... masking effects occurs when two frequencies...   Jul 13 2003, 11:21
- - tangent   Obviously you do the frequency analysis over time,...   Jul 13 2003, 13:24
- - 2Bdecided   It's not the same question, but it's close...   Jul 14 2003, 10:08
- - DonP   Here's another issue to chew on.. Even allowi...   Jul 14 2003, 12:38
- - Vietwoojagig   QUOTE (atici @ Jul 12 2003, 02:27 PM)@tigre: ...   Jul 14 2003, 12:46
- - 2Bdecided   QUOTE (DonP @ Jul 14 2003, 11:38 AM)Here...   Jul 14 2003, 12:54
- - Pio2001   QUOTE (Vietwoojagig @ Jul 14 2003, 02:46 PM)H...   Jul 14 2003, 14:13
- - tigre   QUOTE (2Bdecided @ Jul 14 2003, 03:54 AM)You ...   Jul 14 2003, 14:13
- - ErikS   This is interesting... Diff1 = -Diff2 by your own ...   Jul 14 2003, 14:33
- - Vietwoojagig   QUOTE (ErikS @ Jul 14 2003, 05:33 AM)This is ...   Jul 14 2003, 15:11
- - ErikS   QUOTE (Vietwoojagig @ Jul 14 2003, 03:11 PM)T...   Jul 14 2003, 15:19
- - Gecko   In the past Microsoft used the wave substraction m...   Jul 14 2003, 15:30
- - atici   QUOTE (2Bdecided)Unfortunately, this measurement i...   Jul 14 2003, 16:27
- - PoisonDan   QUOTE (atici @ Jul 14 2003, 03:27 PM)I know H...   Jul 14 2003, 16:39
- - atici   @ PoisonDan: Funnily, I just gave examples in my ...   Jul 14 2003, 16:42
- - DickD   QUOTE (atici @ Jul 14 2003, 04:27 PM)I'd ...   Jul 14 2003, 18:15
- - atici   QUOTE You might be surprised to learn that the amo...   Jul 14 2003, 18:18
- - DickD   QUOTE (atici @ Jul 14 2003, 06:18 PM)QUOTE Yo...   Jul 14 2003, 18:25
- - atici   QUOTE I thought it as more like L2 Ultra dither, w...   Jul 14 2003, 18:44
- - DickD   QUOTE (atici @ Jul 14 2003, 06:44 PM)The defa...   Jul 15 2003, 09:37
- - wkwai   QUOTE (Pio2001 @ Jul 14 2003, 05:13 AM)QUOTE ...   Jul 18 2003, 07:51
- - Gabriel   The first problem with the diff is the potential p...   Jul 18 2003, 09:47


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