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Knowledge Hardware Software DV-Movies HowTo Misc A DV(L)-FAQ [e] DVL-Digest 534 - Postings: Index Audio dynamic range Exaggeration - (2) - (3) - (4) Headphones for Canon GL-1 JVC or DVCPRO or XL1 Audio dynamic range - "Perry" Steve Mullen posted: >"Wouldn't 16-bit sound have a usable dynamic range of about 96 dB. The softest non zero sound sample being 1, and the loudest being 2^16-1, or a ratio of about 65535:1 or 96 dB." Which would mean that a symphony orchestra with its over 100dB peaks, would not quite fit the dynamic range offered by 16-bits. But, I very sure anything that can be handled by the type of MIC used in video would stay within 96dB. In other words, a MIC has a maximum dynamic range. Above a certain sound pressure, the voltage output doesn't get any greater.< Steve is muddying the waters somewhat by confusing dynamic range with maximum level. Although an orchestra could well peak over 100dB of audio level (SPL) the quietest music level would be much higher than 0dB, more likely around 40-50dB. The dynamic range of the music is thus less than 60dB and easily encompassed with 16bits. Recent moves towards 24 bits and higher for audio recording are for increased accuracy, not dynamic range. Professional microphones have a maximum level way above these limits, the popular Sony electret clip-on jobbies can cope with about 130dB SPL which is well into the threshold of pain. Studio mics can reach 150dB which is a level needing ear defenders to avoid permanent injury. There are even mics available capable of recording modern rock bands at a typical concert!! A mic's dynamic range is usually more realistically set by the minimum level it can detect, and this is determined mostly by noise. The best mic in a Sony catalog to hand has a noise 'floor' equivalent to 18dB SPL, but this uses very esoteric vacuum tube techniques in the built in pre-amp. I would guess that a typical system as used in a video camera would have a floor of around 30dB SPL and thus an effective dynamic range with an orchestra max level of around 70dB. Most consumer camcorders are limited to the 12bit 32kHz option of the DV format. This would give a maximum dynamic range of 72 dB with no headroom. To put all this into context, a few years ago the very best broadcast video tape machines had a dynamic range of perhaps 50dB with a following wind! Perry Mitchell Video Facilities http://www.perrybits.co.uk/ Exaggeration - "Perry" Elliot posted: >** ten thousand million times. (My mum said, "If I've told you once, I've told you a million times. 'Don't exaggerate!' ")< If my mental arithmetic still serves, that's 190dB! Perry Mitchell Video Facilities http://www.perrybits.co.uk/ Exaggeration - "Perry" From: Elliott Roper [mailto:elliott@yrl.co.uk] Sent: Monday, June 26, 2000 03:48 To: DV-L@dvcentral.org Subject: Re: Exaggeration Perry wrote: >Elliot posted: >>** ten thousand million times. >(My mum said, "If I've told you once, I've told you a million times. >'Don't exaggerate!' ")< >If my mental arithmetic still serves, that's 190dB! Nah, you are still in voltage mode Perry! 100dB is 10^^(100/10) = 10 000 000 000 ------(cut off when replying)------------------------------- All about DV-L: http://www.DVCentral.org/thelist.html Exaggeration - Perry Mitchell Ric posted: >You've got me worried, because you're rarely incorrect, but I think I disagree with you here. I believe decibels are ratios of power. Power is (voltage times current.) 3dB is double the power, 10 dB is ten times the power. (logarithmic, not linear.) So 20 dB is 10 times 10, or a hundred, and 30 dB (not 60) is 10x10x10 or a thousand times the power. Or did I miss something?< decibels(dB) are indeed a ratio of power. If you look at my original 'thesis' last Sunday, I stated that IF one was talking about a fixed value load then it was possible to use dB as a ratio of voltage as well. Since power is proportional to the square of the voltage (for the fixed load) then a 3dB power ratio is equivalent to a 6dB voltage ratio. Since Elliot was talking about a noise floor, and therefore a signal voltage, it is appropriate to talk in terms of the larger numbers. I DID make a mistake in my mental arithmetic, I should have stated that 10x=20dB. The grand total should therefore be 200dB for 10 thousand million times. Exaggeration - "Perry" Ric posted: >You've got me worried, because you're rarely incorrect, but I think I disagree with you here. I believe decibels are ratios of power. Power is (voltage times current.) 3dB is double the power, 10 dB is ten times the power. (logarithmic, not linear.) So 20 dB is 10 times 10, or a hundred, and 30 dB (not 60) is 10x10x10 or a thousand times the power. Or did I miss something?< decibels(dB) are indeed a ratio of power. If you look at my original 'thesis' last Sunday, I stated that IF one was talking about a fixed value load then it was possible to use dB as a ratio of voltage as well. Since power is proportional to the square of the voltage (for the fixed load) then a 3dB power ratio is equivalent to a 6dB voltage ratio. Since Elliot was talking about a noise floor, and therefore a signal voltage, it is appropriate to talk in terms of the larger numbers. I DID make a mistake in my mental arithmetic, I should have stated that 10x=20dB. The grand total should therefore be 200dB for 10 thousand million times. Perry Mitchell Video Facilities http://www.perrybits.co.uk/ Headphones for Canon GL-1 - "Perry" Headphones for this type of camera are pretty easy, you need good noise exclusion and good comfort. Absolute quality is not important but they should sound natural on voices, and have enough bass response to be able to hear wind noise and background rumble as well as the dreaded hum. Remember you are using headphones to hear problems, not to hear the overall sound quality. Just take your camera along to the shop and try a few, I've always got on well with Sony models. Headphones for Betacam type camcorders are a lot more difficult since they tend to get in the way. I use a relatively thin Sennhuiser model. I once asked a sound engineer why recording artists nearly always wore Sony headsets (but the engineers didn't). He told me the Sony ones were the most comfortable for the artists and that the engineers only used headphones to listen for problems so they tended to use ones with the most detail. Perry Mitchell Video Facilities http://www.perrybits.co.uk/ JVC or DVCPRO or XL1 - "Perry" Geoffrey McKell posted: >There is a noticeable white rim to the left and right of areas of all images, eg a scene of my wife and daughter sitting on a lounge suite with coloured balloons in the bg, then a medium c/u of my wife's face...in each case there is a distinct rim on the edges of the clothing, face and balloons...it is not an impressive look.< (Keep your head down Eric, here comes another one!) This is due to what us old timers call 'Aperture Correction', that is commonly now called 'Sharpness' in camera menus. Untreated video pictures tend to look a bit flat, even when they have good resolution. Manufacturers include an edge enhancement circuit to boost the apparent sharpness. This circuit is based upon something called a 'cosine equaliser' which is centred on a target frequency. The lower this frequency then the more obvious the effect. If the frequency is below the video pass band cut-off (known as 'in-band' correction) then there will be a visible 'rim' as described. If the frequency is out of band then the resolution is boosted but the image still retains a somewhat flat look. Some of us actually like this look and positively detest the edginess alluded to in Geoffrey's post! Incidentally, most cameras have a single equaliser driven by the green signal and then added to all three channels. Don't expect to get much 'edge' from a pure red or blue object like a balloon. The boosted signals are also limited to larger signals away from black to avoid increasing noise, this is more extreme on consumer cameras which can thus have very 'dead' looking shadow areas with no detail. The best consumer cameras (like the VX2000) have an adjustable sharpness to suit your taste. Many professional cameras, including the GY-DV500 have the possibility to change the frequency of the correction; higher frequency gives less obvious 'rim' effects. The very best broadcast cameras have two adjustable correctors; one 'out of band' to boost basic resolution and one 'in band' to give an apparent 'sharper' image. The bottom line is if your GY-DV500 is set to factory default, I would agree that the sharpness is intrusive. The default is apparently tuned for wedding videographers with an end product on vhs. A few simple adjustments of the menu will give what you and I would consider a much more attractive picture, and this can then be saved to be the norm for your camera. One last caveat: the above theory is based upon analog techniques, many cameras now use digital signal processing (DSP) which could give a whole new ball park! Perry Mitchell Video Facilities http://www.perrybits.co.uk/ (diese posts stammen von der DV-L Mailingliste - THX to Adam Wilt and Perry Mitchell :-) Match AllAny term in Search Index: [ All ] ADVLFAQ DV-L Digest Forum Site [up] last update : 21.Februar 2024 - 18:02 - slashCAM is a project by channelunit GmbH- mail : slashcam@--antispam:7465--slashcam.de - deutsche Version