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Old October 4th, 2002, 12:35 AM   #1
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What does clipping mean when filming?

What does clipping mean when filming?
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Old October 4th, 2002, 12:44 AM   #2
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Generally it refers to audio recording, where the signal is so overmodulated that it's distorted. See this link:

http://www.audiovideo101.com/dictionary/clipping.asp
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Old October 4th, 2002, 12:53 AM   #3
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isn't it a video term also?
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Old October 4th, 2002, 01:20 AM   #4
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Definately. it applies to both audio and video as a term. In video it is usually refered to when the luminance in a image goes over the max white level (or below the max black level). This means that anything that is above that is "clipped" and lost forever.

/Henrik
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Old October 5th, 2002, 08:45 AM   #5
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Lots of camera's apply a "soft" kind of clipping (soft knee) in order to handle high contrast scenes. Lots of other electronic circuits apply hard or soft clipping techniques as well,..TV modulator, analog VCR recording circuits, medical ultrasound equipment, Secam encoders...
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Old October 5th, 2002, 12:25 PM   #6
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Hi,
Not sure if this applies to the audio part, but in the phone business, the more bits you have, like 16 bit vs. 12 bit, the less occurance of clipping.

Bruce
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Old October 5th, 2002, 01:19 PM   #7
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Compression -vs- Clipping

Is the video clipped, or compressed?

Clipping is what happens when the value of a signal exceeds the maximum level that can be represented by the current bit resolution. This is supported by Bruce's phone example. The greater the bit depth the greater range you can represent. If you look at a clipped waveform it will be squared off rather than rounded. Any sample which should get higher or lower value than this (for whatever reason), will get the maximum/minimum value instead, this causes distortion.

Compression can be applied to avoid clipping. By compressing a signal to reduce the overall dynamic range or detail, you can avoid clipping certain detail entirely. This is compression of the analog waveform, not to be confused with the digital compression we do to reduce bandwidth (and file size) requirements.

In theory anyway. I understand how this works in the analog audio domain a lot better, but it seems like it would translate. So...

Do these cameras apply controlled white compression to preserve detail that would otherwise be clipped, at the expense of some detail across the entire range of compression, or do they maintain full dynamic range up to the clip point, after which everything is effectively chucked, detail-wise? (is the "soft knee" dre refers to actually compression rather than clipping?)

lyd
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Old October 5th, 2002, 01:42 PM   #8
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"Soft knee" is indeed a treshold based form of gradual compression belonging to the domain of non linear compression techniques. Grayscale resolution (depth) is mainly being reduced in the highlights and hard clipping is thus avoided.
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