It's probably worth noting that the tenure track can be 25+ years long in some universities. I knew a guy who joined a dept as asst/associate professor (I forget which) in the mid 80s, and only got his tenure after I graduated in '02.

It's a really messed up system and I wouldn't belittle any professor who wasn't tenured.

Quote from: Pio2001 on 2005-11-17 20:19:58

I finally found an example : in Europe, when we watch a movie in the theatre, then several monthes later on DVD, the sound track is speeded up, because the movie runs at 25 fps (video PAL) instead of 24 fps (theatre).

Just because the FPS change, there's no necessity for the pitch or timing to change. People working with films and video have been managing this situation for several decades.

This article explains how FPS changes are have been managed for decades so that they don't affect the length or running speed of film or video:

http://www.zerocut.com/tech/pulldown.html

In the old days, the production paths for sound and video were separated, the video or film was altered using pull down techniques, and the audio was added back into the finished product with  no changes. Or, the sound was added back into the finished product with a different FPS from a more origional source.

These days, most video production software manages things like this automagically.  You just specify the FPS of the finished product, and it is produced in accordance with your spec under the covers, as it were.

In short, your example has a rather serious flaw.

Quote from: Pio2001 on 2005-11-17 20:19:58

I finally found an example : in Europe, when we watch a movie in the theatre, then several monthes later on DVD, the sound track is speeded up, because the movie runs at 25 fps (video PAL) instead of 24 fps (theatre).

Just because the FPS change, there's no necessity for the pitch or timing to change. People working with films and video have been managing this situation for several decades.

This article explains how FPS changes are have been managed for decades so that they don't affect the length or running speed of film or video:

http://www.zerocut.com/tech/pulldown.html

In the old days, the production paths for sound and video were separated, the video or film was altered using pull down techniques, and the audio was added back into the finished product with  no changes. Or, the sound was added back into the finished product with a different FPS from a more origional source.

These days, most video production software manages things like this automagically.  You just specify the FPS of the finished product, and it is produced in accordance with your spec under the covers, as it were.

In short, your example has a rather serious flaw.

If you've heard the content before, the pitch shift is quite obvious. Even if it's weeks later that you hear it again.

Quote from: 2Bdecided on 2010-03-01 15:23:36

If you've heard the content before, the pitch shift is quite obvious. Even if it's weeks later that you hear it again.

Personally, I have to disagree with this. My tonal memory is pretty awful even though I'm playing piano and guitar since I was 8.

With the spoken voice, vowel formant frequencies tend to sound too light and high if the playback is 4% fast.

A verification method if you suspect audio has been subjected to 25/24 speedup, is to subject it to 24/25 slowdown (i.e. a 4.000% slowdown).  It will then either sound right, or too low in pitch and too slow.

Another method is to wait for music in the audio, sing a note of the melody and go to a piano.  The note you sing will lie in between the notes, about 0.7 sharp of one note, and 0.3 of a semitone flat the semitone above, if the music has been sped up by 25/24, i.e.  by 4.166%.

Other things get in the way with this comparison though - instruments are not guaranteed to be "in tune" (your piano, and/or the ones on the recording) - music is not guaranteed to be played into the soundtrack at the correct speed. Also different releases of the same music (especially older music) sometimes have slightly different speed.

I have compiled a number of articles that provide anybody here resources and empirical support for the various claims David and I have been making. I claimed that there is a distinction between sensory and decision processes. This recent Nature article provides empirical support for this. Cognitive scientists have understood this distinction for decades, but here is recent evidence demonstrating the neurological basis for it. This is a fundamental issue in our criticism of the validity of ABX testing as the last word on ultimate differences in the auditory processing of lossy audio. Acoustic differences that could matter for a listener’s overall experience might not be audible.

Here are two articles that show the difference between decision processes linked to the discrimination of stimuli versus sensory processes that are affected when there is no discrimination. There is clear enhanced brain activity that occurs during the presentation of noisier stimuli even when it cannot be distinguished from a less noisy counterpart.

Effects of Low-Pass Noise Masking on Auditory Event-Related Potentials to Speech
The Effects of Decreased Audibility Produced by High-Pass Noise

Woodinside claimed that no filtering processes happen after the ear. This is definitely incorrect, as filtering processes do happen in the auditory cortex (one of the many analogues between auditory and visual processing), but I’ll assume he meant that the relevant filtering for audio codecs involves processes that happen only in the ear. This is fine, as there’s no reason to distinguish peripheral (inner and outer ear) processes from central processes (auditory cortex) when talking about metabolic costs of neural effort. The neurons must work harder (wherever this happens) to resolve the signal and encode it for later processing. And this does not deal with the likely possibility that the resulting representations might differ depending on stimulus quality (not a necessary feature of our argument).

There has been quite a bit of skepticism regarding the claim that compressed or degraded stimuli require more effort to process. I could cite a list of papers a mile long showing reaction time increases as a function of stimulus complexity (which heavily imply that processing difficulty increases), but there is also work showing that neurons respond to increased attention demands. Additionally, there seem to be specialized neural systems for resolving degraded signals, which in turn contribute to learning. These processes require effort, and have associated metabolic costs. This is exactly the sort of thing we have been arguing.

I think it is quite plausible that greater neural activity could be associated with processing compressed audio relative to uncompressed counterparts, and ABX decision tasks would not reflect it. Just saying it's possible.

Quote from: duff on 2010-03-04 06:29:25

I think it is quite plausible that greater neural activity could be associated with processing compressed audio relative to uncompressed counterparts, and ABX decision tasks would not reflect it. Just saying it's possible.

Consider also that the reverse might apply: lesser neural activity.

I find if listening to conventional Dolby 5.1 from a DVD that the sound is "neater" than an uncompressed version.  The compression removes less important sounds (potential distractions) and may thus help guide human hearing towards perception of the "significant and relevant" audio content.

Assuming there actually is one?

Quote from: greynol on 2010-03-05 09:28:21

Assuming there actually is one?

For simplicity let's assume there is a brain
What puzzles me is that training is an essential aspect of perceptual DBT (audio, wine etc.) and can make a difference in the results. An athlete can train his/her body for (visibly) better performance, but what makes a trained ear ? We probably can't train to hear things beyond the physical limitations of our ear. I've always assumed that the trained ear has to do with brain activity. What else can it be ?

Quote from: Arnold B. Krueger on 2009-12-19 15:11:13

Quote from: Pio2001 on 2005-11-17 20:19:58

I finally found an example : in Europe, when we watch a movie in the theatre, then several monthes later on DVD, the sound track is speeded up, because the movie runs at 25 fps (video PAL) instead of 24 fps (theatre).

Just because the FPS change, there's no necessity for the pitch or timing to change. People working with films and video have been managing this situation for several decades.

This article explains how FPS changes are have been managed for decades so that they don't affect the length or running speed of film or video:

http://www.zerocut.com/tech/pulldown.html

In the old days, the production paths for sound and video were separated, the video or film was altered using pull down techniques, and the audio was added back into the finished product with  no changes. Or, the sound was added back into the finished product with a different FPS from a more origional source.

These days, most video production software manages things like this automagically.  You just specify the FPS of the finished product, and it is produced in accordance with your spec under the covers, as it were.

In short, your example has a rather serious flaw.

It's in fact your example that has a serious flaw, because the method you posted a link to (2:3 pulldown) is for NTSC and not for PAL. All PAL movie DVDs I've encountered so far (old and new) have been speed-up. This means the tempo of the audio always has been speed-up (with or without pitch correction, personally I prefer without). From capturing I know that long ago movies in PAL were broadcoasted with fieldshifting which didn't require to change the audio tempo, but nowadays this technique isn't used anymore, at least not with the movies I have captured.

Quote from: MLXXX on 2010-03-04 09:11:28

Quote from: duff on 2010-03-04 06:29:25

I think it is quite plausible that greater neural activity could be associated with processing compressed audio relative to uncompressed counterparts, and ABX decision tasks would not reflect it. Just saying it's possible.

Consider also that the reverse might apply: lesser neural activity.

I find if listening to conventional Dolby 5.1 from a DVD that the sound is "neater" than an uncompressed version.  The compression removes less important sounds (potential distractions) and may thus help guide human hearing towards perception of the "significant and relevant" audio content.

You never know, but... the Dolby 5.1 differences are above threshold -- we're talking about differences you can't necessarily hear. Still, I agree that it's unclear what the relationship is between subjective sound judgment and brain activity.

So, if you are getting PAL media whose pitch is different from the corresponding NTSC media, the core problem is that the production people did not avail themselves of any number of different approaches that are available for a reasonable cost and in general use, at least by people who have a clue and have the resources to exercise that clue.

For simplicity let's assume there is a brain

@duff,

The correlate of the flicker example you give would be finding a task which was impaired by lossy coding, despite the lossy coding being inaudible in an ABX test. e.g. "write down the words that are spoken", or "identify the instrument", or "sing the tune" etc.

I'm not convinced by the flicker example anyway - whether you see a difference between different flicker rates depends on whether the flickering device is in the centre or periphery of your field of view, whether your eyes are moving or stationary, and whether your eyes are following something (eye-tracked motion), or moving across something that isn't itself moving.

Hence if you can't ABX a difference when simply staring at a screen, but can perceive a difference when reading from that screen, it doesn't necessarily tell you anything about ABX vs reading - because you've introduced another variable (eye movement) which you would expect to interact with the flicker anyway.

There are (possibly) four categories:
1. differences we can short-term ABX
2. differences we cannot short-term ABX directly, but which yield different results in some task
3. differences we cannot short-term ABX directly, which do not yield different results in any known task, but which reveal consistent differences in some kind of brain respond
4. differences which are undetectable on all three counts

The thing with (2) is that the task itself becomes the ABX test - you merely have to ask the correct question.
The thing with (3) is that, if there really is no question or task or anything else that can reveal any kind of conscious knowledge of the difference, over any time scale, why would any one care when listening to music? (It's nice research, but...!)
Obviously (4) self evidently doesn't matter.

Cheers,
David.

You've missed my point. My point is that in 2010 there is no need to accept a pitch shift in the accompanying audio when changing the frame rate of A/V media. The general problem has been around for decades, and the means for solving it have only become more sophisticated, economical and undetectable over the years.  You have fastened your attention on a particular implementation (2:3 pulldown) of a particular technique (pulldown) and mistakenly invalidated the general comment because of some variations in impementations of that technique. There are also other techniques.

If perchance a piece of video actually has  its running time changed, there is still no need to change the pitch of the accompanying audio. For decades there have been means for changing the running time of audio without changing its pitch. Currently, this is a standard feature of a number of reasonably-priced audio editing programs. I personally do this sort of thing every once in a while.

So, if you are getting PAL media whose pitch is different from the corresponding NTSC media, the core problem is that the production people did not avail themselves of any number of different approaches that are available for a reasonable cost and in general use, at least by people who have a clue and have the resources to exercise that clue.

This seems like a good time to shoot or at least beat up the messenger - the messenger being the video media distributor who is foisting these A/V kludges off on you. He's taking your money and feeding you crap. Tell him that you are madder than %$## and won't take it any more! ;-)

If there's no time to check this carefully, it's better to introduce a known flaw (wrong pitch), rather than introduce a potential serious unknown flaw (e.g. mangling the sound of some strings).

It's a bit like noise reduction - it is possible to remove hiss from older recordings - but sometimes it's better not to, given what's available. Just because someone chooses not to doesn't mean that they can't - not doing something can be a sign of great care, rather than great incompetence.

Anyway, many PC-based home theatre enthusiasts are thankful for 25p masters with a speed up - they can easily slow them down again and get the original sound - something which is impossible with pitch "corrected" versions!

Doesn't matter with BluRay - most are 24p even in "PAL" countries.

Dolby digital is itself a perceptual coding technique.  It is not necessarily even a outstandingly good perceptual coding technique. It is reliatively old, but apparently the coders in general use have been upgraded somewhat over the years. There are blind tests that show that audible degradation due to it can be heard, at least in some cases.