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Can lossy encoding create audible clipping not present in the source?
Takla
post Jan 3 2012, 02:02
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re: http://www.hydrogenaudio.org/forums/index....showtopic=92690

Apparently it's hard to know even established facts, and every statement must be proven again as if new if it's not made by a suitable person. Pure science of course, nothing to do with groupthink or the innate religious mindset of the human being.....

Attached is a 30 second sample of uncompressed wav.

http://wiki.hydrogenaudio.org/index.php?title=Clipping

QUOTE
Clipping

Clipping is a phenomenon that occurs in digital audio when the amplitude value of a signal exceeds the maximum level that can be represented by the current bit resolution. In 16bit digital audio (cd-audio), the sample values can be presented between the values of -32768 to 32767.

Any sample which should get higher or lower value than this (for whatever reason), will get the maximum/minimum value instead. This causes the signal to distort, and appears in the waveform display as a "chopping-off" of the top or bottom of the waveform. The audible result of sequential max or min values is a static-like distortion.

A correctly mastered CD does not have sequential max or min samples. Also, clipping is not always audible. It depends on how severe the clipping is, in other words how many samples are getting the same maximum/minimum values sequentially. Maximum/Minimum values are considered as "possible clipped samples" by analysis tools, but only one max or min value doesn't mean clipping.

Lossy audio encoding and decoding can cause the highest/lowest sample values to go over the allowed limit (in practice having the sequential max/min values), which may lead to clipping seen by analysis tools, or even audible clipping. But whether the clipping is truly audible or not is a totally different thing. There are different methods to avoid clipping in lossy audio. Look at the specific audio format answers how to best avoid clipping in each case.


But of course you don't need to try to avoid it because it has been retrospectively decreed to be unpossible!

This post has been edited by Takla: Jan 3 2012, 02:09
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db1989
post Jan 3 2012, 02:22
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Didn’t you get in enough of the childish jibes about religion in the main thread? Either way, please stop it now and stick to the discussion. This passive aggression in several of your recent posts is entirely unconstructive and is perhaps reducing your chance of receiving thoughtful replies. In this case, the context and the tenor of your repeated metaphor makes you seem rather paranoid, as only one person expressed doubt [in a way that seemed to refer to clipping in general, not specifically to yourself or your example] and asked whether you had tested your claim. You were not mobbed by a fanatical horde, and krafty did not denounce you, insult you, or call you a liar or any other name. Please remain on-topic and avoid baiting people with irrelevant aspersions; further such asides will be binned in observance (see what I did there?) of TOS #2 and/or #5.

This post has been edited by db1989: Jan 3 2012, 03:22
Reason for edit: adding clarification in square brackets
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Takla
post Jan 3 2012, 03:20
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QUOTE (db1989 @ Jan 3 2012, 01:22) *
Didnít you get in enough of the .....


I guess I developed a reflex at some point and it became a habit......

When someone says "I don't believe you" or "It's not possible" in preference to "Can this be shown?" or "Do you have any data?" then it looks like the expression of an orthodoxy and a bit of unthinking reaction, not an exchange or a prelude to a conversation (especially when the original unwelcome assertion turns out to be demonstrably true). I have seen it lots of times and been on the wrong end of it on occasion (complete with unannotated post deletions, unmentionable warnings, ill feeling carried over into unrelated forums and so on) so I guess I developed a tendency to assume the worst. HA's vigour has sometimes in the past contracted into something less than rational. Perhaps this has changed (I didn't visit or log-in for many months until the last few weeks) and I am being overly defensive; in fact I'm sure I am, so I'm sorry: I'm in the wrong and will modify my future responses, but there were reasons I arrived at that place.
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