What Audio Levels are best on the XH A1?

Petri Kaipiainen · November 5th, 2008, 01:21 AM

Just be aware that only fairly expensive recorders get anything out of 24 bits. Most if not all sub $2000 recorders have so much noise that 24 bits is not any better than 16 bits. The recorder does put out a 24 bit file, but tha extra 8 bits are just noise. Even the best recorders like SD7xx, Nagra, Cantar and Deva at 2500-20000 dollar price range have about 20 bit resolutions in reality.

XH-A1 has very good audio if fed from a good mixer. I have achieved over 90 dB S/N ratios with Sound Devices 302 mixer. That is about 25 dB better than analog Nagra recorders 20 years ago, which were the absolute top pro equipment at that time. But for some people getting 500 times more dynamic range is not enough?

Stuart Graham · November 5th, 2008, 02:43 PM

I'm confused now :(

Audio is too complicated.

Is it still worth using a 24 bit recorder if it only gives you 20 bit really?

Or is it better to buy a mixer and plug it into the XH-A1?

At the moment I have my shotgun microphone plugged straight into the XH-A1 XLR socket.

Petri Kaipiainen · November 6th, 2008, 03:26 AM

1) Mic straight to Camera
Pro: cheap, simple, good quality (about 80 dB S/N)
Con: difficult to set levels on the fly, no limiter, only 2 mics maximum at one time

2) Mic(s)->mixer->camera
Pro: Better S/N ratio with good mixers with line in (about 90 dB with SD302), better metering, better mic pre-amps, good limiters, possibility to mix from many mics, gain riding possible during the shoot.
Con: costs more, more cables, needs usually a soundperson.

3) 24 bit recorder capable of 20 bit true resolution (something like SD7xx)
Pro: safer level setting with 24 dB extra headroom, better mic pre-amps, no cable to camera.
Con: needs either TC (not available on cheap cameras like XH-A1) or slate for every take, more work in post. Costs as much or more than the camera.

Stuart Graham · November 6th, 2008, 07:35 AM

Quote:

Originally Posted by Ivan Mosny

Quality of the sound depend not from a thing that only record a digital data. A laptop works here as good as another recorder. With a good 24bit soundcard you have an excellent sound recorder. But you need microphone preamplifier with phantom power for condenser mic.
Behringer BCA 2000 ist a cheap mixer with mic preamps an integrated 24bit soundcard - but there are some smaler units there.
I am using it as a mobile soundstudio - most for recordings voice overs. I have 2 such units by my "artists" directly at they home for recordings small projects an sending it per email to me.
But by filming i am recording directly to the camera - of course by maximal possible level.

Thanks Petri, that's was very enlightening. Would the 24bit soundcard recorder that Ivan recommended (see above) be equivalent to 20 bit too?

How much is an SD7xx? I couldn't find them on Google Shopping. Would it be better than the sound card?

The no cables to camera option is very attractive as they are very awkward and get in the way on dolly shots. They also make moving the camera between shots much more laborious. I have someone operating the sound equipment on set so a recorder operator is not a problem.

Petri Kaipiainen · November 6th, 2008, 10:18 AM

Quote:

Originally Posted by Stuart Graham

Thanks Petri, that's was very enlightening. Would the 24bit soundcard recorder that Ivan recommended (see above) be equivalent to 20 bit too?

How much is an SD7xx? I couldn't find them on Google Shopping. Would it be better than the sound card?

Only the better and best recorders achieve 20 bit resolution, I doubt any soundcard recorder does. Maybe 17-18 bit resolution, just guessing. By the way, even the VERY BEST rack mounted AD converters like Lavry and Weiss costing around 10k$ get 127 dB = 21 bit resolutions. So thinking about getting real 24 bits form a $300 pocket thing is absurd.

SD7xx refers to Sound Devices 700 series recorders (702, 722, 744 and 788 in different variations). They cost from $1875 to $5995 (B&H prices). Generally considered the best field recorders there are, in top 3 anyways. I have SD722 recorder and SD302 mixer, great tools.

Sound Devices, LLC | Professional, Portable Audio Products

Ivan Mosny · November 6th, 2008, 03:16 PM

Quote:

Originally Posted by Petri Kaipiainen

Most if not all sub $2000 recorders have so much noise that 24 bits is not any better than 16 bits. The recorder does put out a 24 bit file, but tha extra 8 bits are just noise.

Definitelly NO. 8 bit "extra" are not 8 LED of levels even not higher levels ranges - but abot 366 times higher resolution.
Most of equipment noise comes from their analog devices - specially mic preamps. This will be of course quantisated too and saved in digital form and this makes smaller dynamic range - not the ADC, not the 24 bit recorder.
There is much much less digital - quantisation noise in 24bit as in 16bit (shown on my first figure) and even 18bits give you much more quality and important here - much more headroom (enabling lover levels recording) to avoid oversteering as a 16 bit system. Even 18 bits are 4times more resolution.
24 bit are not "8 extra" bits or extra levels. Its a diference between 65 536 levels and 24 Million Levels.
You don`t wanna really say that in 24bit they are 23,93 millions of levels only noise?
Yes - its right - most of microphone preams are definitelly not in possible dynamic ranges of 24 bit recorders. ( by recording live you will not a find dynamic ranges about 60dB) Here - by recording to lover levels to avoid oversteering is ist everytime better to record in 24bit and avoid adding quantisating noise. Remember: recording to -6dB ist recording with HALF resolution. Its still better to record with 12 millions levels than with 33 000 levels. Recomended Behringermixer ist of course the cheapest thing and it has in this pricelist excellent mic preamps. Such XHA1 is an excellent camera but has no chance i comparison with a HDW 750 for 60 000 Euro.

"Only the better and best recorders achieve 20 bit resolution"
No. Only the better and best recorders achieve maximal dynamic range theoretically allowed by 20 bit recording.

Ivan Mosny · November 6th, 2008, 03:43 PM

Here is an article to shown a difference by size (amplitude) of the signal relative to full scale (full amplitude) by comparison between 8 and 12 bit. Difference between 256 values (8 bits) and 4096 values (12bits). 16timer more resolution. This is exactly the some principe as a difference between 16 and 24 bits. But the dynamic range is a difference between max. possible amplitude and noise level. If there is a high noise level from the mic preamp - even horrible to -12dB - you will have only 12dB of dynamic range but this quantisated to 6 million levels (24bit) or only 16 000 levels (16 bit)
Resolution Compromise 8 to 12-bit
I will try to say - 24 bit vs 16 bit is like HDTV vs SD in audio. Or better 4K vs SD. If you wanna zoom in twice the picture (volume adjustment from -6dB to 0dB) and convert to SD (to 16 bit) - its always better to shoot in High Definition. Still better to shoot with XHA1 in HDV - even if not soo good as with the RED 4k.

Stuart Graham · November 6th, 2008, 05:05 PM

I see what you're getting at. Thanks Ivan.

The laptop and 24 bit soundcard/mixer sound like the best option to me at the moment. It seems it would record much better quality audio and there would be no need for cables connected to the camera. As long as I use a clapper board to synchronize the sound with the video in editing. The other possibilities for improving audio quality are too expensive for me.

What's ADC by the way? Analogue to digital converter?

Petri Kaipiainen · November 7th, 2008, 12:38 AM

There is a basic misunderstanding about digital audio floating around here, Ivan.

The fact is, that this "umpteen million more levels of resolution" all reside at the bottom of the dynamic range scale. That is why with more bits you get more dynamic range; i.e. smaller details and quieter sounds can be resolved. Mathematically it is measured in dynamic range and expressed in dB, ONLY. Calling it "detail" or "resolution" is misleading.

If we have two systems, 16 bit and 24 bit, which both are fed with 90 dB S/N electronics, we get a digital file with 15 bit equivalent dynamic range. One file has 1 bits worth of noise, the other 9 bits worth. The useable audio signal is identical on both. This is what I meant by "just having 8 bits of noise".

Now, this 24 bit file mentioned above has no extra "detail" or "resolution" in the top 90 dB clean range. All that imagined extra resolution and detail is in that 8 bits of extra noise compared to 16 bit file. For this reason the analog electronics are the limiting factor and thinking that using a cheap 24 bit recorder is giving a huge improvement in quality is just fallacy. If using more bits would do what misinformed people here are proposing, we would not have stopped at 24 bits, but would be using 30, 36, 42 bit systems. But we are not, because engineers designing the AD converters and systems know better.

This is getting too far from the original topic, so I'll stop here.

Stuart Graham · November 7th, 2008, 04:05 AM

I thought I kind of understood. But now I'm completely confused.

Doesn't the signal to noise ratio depend upon the conditions you are recording in - not whether you use a 16 bit or 24 bit recorder? For example, if you record in a room with air conditioning you would have a lot of unwanted background noise effectively lowering the dialogue's s/n ratio. Will a 24 bit recorder give a massive decrease in s/n ratio compared to a 16 bit one? Noise would also originate from poor electronics I imagine.

Why would the extra 8 bits all be filled with noise? Wouldn't that make 24 bit recording completely pointless?

Surely a 24 bit recorder will allow the signal from the preamps to be captured more accurately than a 16 bit recorder even if it's not delivered to the recorder in 24 bit format?

Petri Kaipiainen · November 7th, 2008, 05:01 AM

No reason for confusion.

The recording systems makes no judgements on what is wanted signal and what is noise. It attempts to record everything as well as it can. How could it tell what is dialog and which is unwanted machinery noise, for example?

Noise in this context is not the noises we hear on set which we try to avoid recording (that is another matter more to do with miking practises, choosing the location etc), but noise caused by the less than perfect recording system: mics, mixer, mic preamplifiers and AD converter. It is all electronically generated and we hear it only on the recording or when monitoring it.

Sampling bit depth, either 16 or 24 bits, dictates the accuracy of the samples. Simply put, how small are the smallest voltage variations in the incoming signal which can be recorded. AD converter system measures voltages, for that reason one additional bit can describe twice as big voltage differentials and thus one bit more gives 6.03 dB more dynamic range potential to the system.

There is no other measurement tool for this accuracy, only the difference between smallest and largest possible voltage (waveform) and the relative logarithmic unit dB is used. If you want to use "normal" number ratios, you just raise 10 to dB/10 power (10^(dB/10)).

Dymnamic range does not mean only the difference between the quietest sound and loudest in a given recording, but also the difference between the smallest detail and the general level of the signal. Remember that the sound wave is very complex single waveform which contains all the levels and frequences in one single wave.

Now, let's imagine a perfect clean mic signal with 144 dB dynamic range going to a cheap 24 bit recorder. Cheap electronics add so much noise, that the finest 48 dB/8 bits of detail is buriend under it. We have 96 dB of clean signal and if we listen loud enough (this is important, we never do...), we hear just noise under this good signal. Feeding this same signal to a 16 bit recorder we get the same 16 bits worth of good signal, and if we turn up the volume, we hear just noise just like before. Both recordings are of same quality.

The misunderstanding about this "resolution" and dynamic range thing is that people forget that this dynamic range is the relative measurement of the smallest detail level piggybacking the large amplitude waveforms. If the dynamic range is large (like in good 24 bit systems), then there is more "resolution". If the noise level is high, then in a 24 bit signal these minuscule details piggybacking the waveform is not real signal, but random noise. It can not be called "detail" or "resolution".

Like I said before, if just using more bits for sampling would really improve the signal quality regardless the noise floor provided by the less than perfect analog circuits, we would certanly be using 48 bit systems by now. But we are not. That is because there is no point in using more bits than what the other parts of the chain can feed. With the best analog electronics and microphones the limit is around 130 dB which translates to 22 bit sample depth (For this reason 24 bit AD converters are plenty good enough and nobody even tries to use more).

Back to cheap recorders: with high noise electronics these recorder's 24 bit AD converters are not fed with a signal which has more than 96 dB or so dynamic range. So there is NOTHING those 8 extra bits compared to 16 bit recorders can do exept record this random noise faithfully. For that reason 24 bit files have exactly the same data content in the top 16 bits as a 16 bit file of the same signa, and ONLY noise in the last 8 least significant bits. That makes using 24 bit recording pointless, UNLESS the electronics & mics actually are capable of more than 96 dB dynamic range. With most cheap recorders they are not.

And finally, to put this all into perspective: 16 bit recording is wastly better than any analog recorders are capable of. Tens of thousands of high quality movies have been recorded in not-so-distant past using $15000 analog Nagra recorders, with ONLY about 65 dB dynamic range (11 bits...). Now, amateurs are panicing if they are not getting true 24 bit resolutions = 144 dB dynamic range from their $300 pocket recorders! Come on, in XH-A1 we have qualitywise a much better audio recorder than those glorified Nagras. That surely can not be the reason why we can not make great movies with great audio?

Ivan Mosny · November 7th, 2008, 07:54 AM

1.
If we have two BW pictures - one in 8 bit resolution and the some with 24 bit resolution. Both have he some dark poinst at zero black level, brithness and full white points. Both pictures have the some dynamic range. But the 24bit picture has 24 million levels between black and white - 24millions of grey levels. 8 bit picture has only 256 levels. This is the some as a difference between recorded audio signal.

2.
To be exactly - dynamic range is difference between max and min possible writable level.
By 24 bit resolution - we can write 0000.....001 and this - lovest writable level will be 1/24million of possible max level. By 8 bit resolution we have 00000001 and this is 1/256 of possible max level. The lovest level about zero is 366 times bigger than by 24 bit! This is the difference. Lower first step = greater dynamic range. Finer details just about zero = greater dynamic range. If we have not a really deep black in our pictures - because dark areas are noisy - we have pictures with lover dynamic range - but the 24bit picture has still finer grey graduations.
The some in audio. We record to max level - to 0dB. Every 6dB to minus is a half of the level. Logarithmic. -24dB ist a 1/16 of max. possible level. -30dB 1/32 of maximal level.
What if we have a ground noise level on -30dB? We have very low dynamic range - only 30dB. But how much possible levels - how fine steps are about noise level? We can`t use 1/32 of all levels - because this area is only noise. 24millions/32= 750 000. This is what we can`t use. Usable area has still 23,25 million levels.
Horrible dynamic range - but still much greater quality due to excellent resolution above the noise level.
Its mistake to say - we record with only 30dB dynamic range - so we have only ~8bit resolution and 16 bits are only noise. The difference in dynamic range makes the "quality" in lovest audio levels - but better resolution works in whole area - even to loudest 0dB.
Audio resolution and audio levels are linear - but dynamic range logarythmic and we have to different this.
3. Back to the point here.
We record audio - but not to 0dB to avoid oversteering by unexpected louder sounds.
We record to -6dB - to half of a full possible level. We record a real life sounds - probably nothing will have a dynamic about 60-70 dB. Yes - for this dynamic range in full levels will be 16 bit still more than enough. But by recording to -6dB we use only a half of 16 bit resolution!
In postproduction we have to do sound levels twice as louder - to have in final levels to 0dB. So - we make all sound louder - even noise = it will be no better dynamic range. But even quantisation steps will be twice as bigger! This is the some as scaling to different range here:Resolution Compromise 8 to 12-bit
We have here a final sound - with twice as big quantisation steps as by recordings directly to 0dB! And this is the problem.
If we record in 24 bit to -6dB an makes normalising to 0dB - every quantisation step is still 366times finer. After downconversion to 16bit - the is much better quality.
Even postproduction makes sense to use 24bit recording. This is still not enough. Probably ever better music software uses 32bit resolution and temporary files for every processing -even on 16bit files.

Ivan Mosny · November 7th, 2008, 08:59 AM

Quote:

Originally Posted by Petri Kaipiainen

16 bit recording is wastly better than any analog recorders are capable of.

Absolutelly NO. Dynamic range is not the only one aspect of quality.

Quote:

Originally Posted by Petri Kaipiainen

Now, amateurs are panicing if they are not getting true 24 bit resolutions = 144 dB dynamic range from their $300 pocket recorders!

There is definitelly no problem today for any recorder to have true 24 bit resolution. The problem is on analogue devices side on recording equipments. Its no a technical problem to produce smalest 24bit ADC with an precise 1bit technology - but its a problem to deliver them analogue signals with 144dB dynamic range. Its a problem to find any signals wit 144dB dynamic range.
If minimal noticeable for peoples ear sounds are by 0dB - a jet airplane products still only 120dB about this! A normally conversation is at 60dB. Remember - this is a logarithmic range.
120dB is not twice as loud as 60dB. 66dB is it. 72dB is 4 times louder as 60dB.
So 144dB is 16 times louder as a jet airplane with 120dB!
So - why in the hell would anybody produce a recorder with 24 bit if there were nothing more as a dynamic range? To record simultaneously lovest sounds and 16 starting Jets?
If we had ability (mics preamps and recorders) to record simply even half of this dynamic range - the audio level regulators are useless.

Petri Kaipiainen · November 8th, 2008, 06:29 AM

Quote:

Originally Posted by Ivan Mosny

1.
If we have two BW pictures - one in 8 bit resolution and the some with 24 bit resolution. Both have he some dark poinst at zero black level, brithness and full white points. Both pictures have the some dynamic range. But the 24bit picture has 24 million levels between black and white - 24millions of grey levels. 8 bit picture has only 256 levels. This is the some as a difference between recorded audio signal.

This analogy is invalid. In audio having more sample depth means the quetest parts can be more quiet. In photography this would mean that blacks would be blacker. Zero blackness is called "black body" in physics, theoretical term impossible to achieve in reality. If your photograph would be analogous with audio, black in the the 24 bit photo would have a reflectance of 0.00000596% and in 8 bit photo 0.39%. Quite a difference. In photography first the dynamic range is set governed by the sensor quality (typically 7 to 12 bit equvalency = 42 to 72 dB dynamic range), then this range is quantified with certain accuracy, typically 8 bits, sometimes 14 or 16. In audio one bit is always 6 dB.

Case 2 is a complete mess. Hopeless. You have the math upside down. Fine gradiations in the signal are the bottom part of the dynamic range. If it is noise, it is noise.

Petri Kaipiainen · November 8th, 2008, 06:36 AM

Quote:

Originally Posted by Ivan Mosny

So - why in the hell would anybody produce a recorder with 24 bit if there were nothing more as a dynamic range?

There is no other measure or unit of this quality than dynamic range. It all boils down to dynamic range: ratio between the total maximum amplitude and the finest details in that waveform.

24 bit recorders are made for 2 reasons: 1) because we can, and: 2) using 24 bit sample depth with good front end gives more latitude and safety in recording when aiming for maximum quality end result, even if the said result is usually 16 bits (which in real life is much better than the reproduction systems and listening rooms).

November 5th, 2008, 02:43 PM	#32
Stuart Graham Major Player Join Date: Aug 2008 Location: Selby UK Posts: 274	I'm confused now :( Audio is too complicated. Is it still worth using a 24 bit recorder if it only gives you 20 bit really? Or is it better to buy a mixer and plug it into the XH-A1? At the moment I have my shotgun microphone plugged straight into the XH-A1 XLR socket. __________________ Stuart Graham www.magentapictures.com

November 6th, 2008, 05:05 PM	#38
Stuart Graham Major Player Join Date: Aug 2008 Location: Selby UK Posts: 274	I see what you're getting at. Thanks Ivan. The laptop and 24 bit soundcard/mixer sound like the best option to me at the moment. It seems it would record much better quality audio and there would be no need for cables connected to the camera. As long as I use a clapper board to synchronize the sound with the video in editing. The other possibilities for improving audio quality are too expensive for me. What's ADC by the way? Analogue to digital converter? __________________ Stuart Graham www.magentapictures.com

November 7th, 2008, 04:05 AM	#40
Stuart Graham Major Player Join Date: Aug 2008 Location: Selby UK Posts: 274	I thought I kind of understood. But now I'm completely confused. Doesn't the signal to noise ratio depend upon the conditions you are recording in - not whether you use a 16 bit or 24 bit recorder? For example, if you record in a room with air conditioning you would have a lot of unwanted background noise effectively lowering the dialogue's s/n ratio. Will a 24 bit recorder give a massive decrease in s/n ratio compared to a 16 bit one? Noise would also originate from poor electronics I imagine. Why would the extra 8 bits all be filled with noise? Wouldn't that make 24 bit recording completely pointless? Surely a 24 bit recorder will allow the signal from the preamps to be captured more accurately than a 16 bit recorder even if it's not delivered to the recorder in 24 bit format? __________________ Stuart Graham www.magentapictures.com

November 7th, 2008, 07:54 AM	#42
Ivan Mosny Regular Crew Join Date: Sep 2007 Location: Poland Posts: 141	1. If we have two BW pictures - one in 8 bit resolution and the some with 24 bit resolution. Both have he some dark poinst at zero black level, brithness and full white points. Both pictures have the some dynamic range. But the 24bit picture has 24 million levels between black and white - 24millions of grey levels. 8 bit picture has only 256 levels. This is the some as a difference between recorded audio signal. 2. To be exactly - dynamic range is difference between max and min possible writable level. By 24 bit resolution - we can write 0000.....001 and this - lovest writable level will be 1/24million of possible max level. By 8 bit resolution we have 00000001 and this is 1/256 of possible max level. The lovest level about zero is 366 times bigger than by 24 bit! This is the difference. Lower first step = greater dynamic range. Finer details just about zero = greater dynamic range. If we have not a really deep black in our pictures - because dark areas are noisy - we have pictures with lover dynamic range - but the 24bit picture has still finer grey graduations. The some in audio. We record to max level - to 0dB. Every 6dB to minus is a half of the level. Logarithmic. -24dB ist a 1/16 of max. possible level. -30dB 1/32 of maximal level. What if we have a ground noise level on -30dB? We have very low dynamic range - only 30dB. But how much possible levels - how fine steps are about noise level? We can`t use 1/32 of all levels - because this area is only noise. 24millions/32= 750 000. This is what we can`t use. Usable area has still 23,25 million levels. Horrible dynamic range - but still much greater quality due to excellent resolution above the noise level. Its mistake to say - we record with only 30dB dynamic range - so we have only ~8bit resolution and 16 bits are only noise. The difference in dynamic range makes the "quality" in lovest audio levels - but better resolution works in whole area - even to loudest 0dB. Audio resolution and audio levels are linear - but dynamic range logarythmic and we have to different this. 3. Back to the point here. We record audio - but not to 0dB to avoid oversteering by unexpected louder sounds. We record to -6dB - to half of a full possible level. We record a real life sounds - probably nothing will have a dynamic about 60-70 dB. Yes - for this dynamic range in full levels will be 16 bit still more than enough. But by recording to -6dB we use only a half of 16 bit resolution! In postproduction we have to do sound levels twice as louder - to have in final levels to 0dB. So - we make all sound louder - even noise = it will be no better dynamic range. But even quantisation steps will be twice as bigger! This is the some as scaling to different range here:Resolution Compromise 8 to 12-bit We have here a final sound - with twice as big quantisation steps as by recordings directly to 0dB! And this is the problem. If we record in 24 bit to -6dB an makes normalising to 0dB - every quantisation step is still 366times finer. After downconversion to 16bit - the is much better quality. Even postproduction makes sense to use 24bit recording. This is still not enough. Probably ever better music software uses 32bit resolution and temporary files for every processing -even on 16bit files. Last edited by Ivan Mosny; November 7th, 2008 at 08:33 AM.

November 5th, 2008, 01:21 AM	#31
Petri Kaipiainen Major Player Join Date: Apr 2007 Location: Espoo Finland Posts: 380	Just be aware that only fairly expensive recorders get anything out of 24 bits. Most if not all sub $2000 recorders have so much noise that 24 bits is not any better than 16 bits. The recorder does put out a 24 bit file, but tha extra 8 bits are just noise. Even the best recorders like SD7xx, Nagra, Cantar and Deva at 2500-20000 dollar price range have about 20 bit resolutions in reality. XH-A1 has very good audio if fed from a good mixer. I have achieved over 90 dB S/N ratios with Sound Devices 302 mixer. That is about 25 dB better than analog Nagra recorders 20 years ago, which were the absolute top pro equipment at that time. But for some people getting 500 times more dynamic range is not enough?

November 6th, 2008, 03:26 AM	#33
Petri Kaipiainen Major Player Join Date: Apr 2007 Location: Espoo Finland Posts: 380	1) Mic straight to Camera Pro: cheap, simple, good quality (about 80 dB S/N) Con: difficult to set levels on the fly, no limiter, only 2 mics maximum at one time 2) Mic(s)->mixer->camera Pro: Better S/N ratio with good mixers with line in (about 90 dB with SD302), better metering, better mic pre-amps, good limiters, possibility to mix from many mics, gain riding possible during the shoot. Con: costs more, more cables, needs usually a soundperson. 3) 24 bit recorder capable of 20 bit true resolution (something like SD7xx) Pro: safer level setting with 24 dB extra headroom, better mic pre-amps, no cable to camera. Con: needs either TC (not available on cheap cameras like XH-A1) or slate for every take, more work in post. Costs as much or more than the camera.

November 6th, 2008, 03:43 PM	#37
Ivan Mosny Regular Crew Join Date: Sep 2007 Location: Poland Posts: 141	Here is an article to shown a difference by size (amplitude) of the signal relative to full scale (full amplitude) by comparison between 8 and 12 bit. Difference between 256 values (8 bits) and 4096 values (12bits). 16timer more resolution. This is exactly the some principe as a difference between 16 and 24 bits. But the dynamic range is a difference between max. possible amplitude and noise level. If there is a high noise level from the mic preamp - even horrible to -12dB - you will have only 12dB of dynamic range but this quantisated to 6 million levels (24bit) or only 16 000 levels (16 bit) Resolution Compromise 8 to 12-bit I will try to say - 24 bit vs 16 bit is like HDTV vs SD in audio. Or better 4K vs SD. If you wanna zoom in twice the picture (volume adjustment from -6dB to 0dB) and convert to SD (to 16 bit) - its always better to shoot in High Definition. Still better to shoot with XHA1 in HDV - even if not soo good as with the RED 4k.

November 7th, 2008, 12:38 AM	#39
Petri Kaipiainen Major Player Join Date: Apr 2007 Location: Espoo Finland Posts: 380	There is a basic misunderstanding about digital audio floating around here, Ivan. The fact is, that this "umpteen million more levels of resolution" all reside at the bottom of the dynamic range scale. That is why with more bits you get more dynamic range; i.e. smaller details and quieter sounds can be resolved. Mathematically it is measured in dynamic range and expressed in dB, ONLY. Calling it "detail" or "resolution" is misleading. If we have two systems, 16 bit and 24 bit, which both are fed with 90 dB S/N electronics, we get a digital file with 15 bit equivalent dynamic range. One file has 1 bits worth of noise, the other 9 bits worth. The useable audio signal is identical on both. This is what I meant by "just having 8 bits of noise". Now, this 24 bit file mentioned above has no extra "detail" or "resolution" in the top 90 dB clean range. All that imagined extra resolution and detail is in that 8 bits of extra noise compared to 16 bit file. For this reason the analog electronics are the limiting factor and thinking that using a cheap 24 bit recorder is giving a huge improvement in quality is just fallacy. If using more bits would do what misinformed people here are proposing, we would not have stopped at 24 bits, but would be using 30, 36, 42 bit systems. But we are not, because engineers designing the AD converters and systems know better. This is getting too far from the original topic, so I'll stop here.

November 7th, 2008, 05:01 AM	#41
Petri Kaipiainen Major Player Join Date: Apr 2007 Location: Espoo Finland Posts: 380	No reason for confusion. The recording systems makes no judgements on what is wanted signal and what is noise. It attempts to record everything as well as it can. How could it tell what is dialog and which is unwanted machinery noise, for example? Noise in this context is not the noises we hear on set which we try to avoid recording (that is another matter more to do with miking practises, choosing the location etc), but noise caused by the less than perfect recording system: mics, mixer, mic preamplifiers and AD converter. It is all electronically generated and we hear it only on the recording or when monitoring it. Sampling bit depth, either 16 or 24 bits, dictates the accuracy of the samples. Simply put, how small are the smallest voltage variations in the incoming signal which can be recorded. AD converter system measures voltages, for that reason one additional bit can describe twice as big voltage differentials and thus one bit more gives 6.03 dB more dynamic range potential to the system. There is no other measurement tool for this accuracy, only the difference between smallest and largest possible voltage (waveform) and the relative logarithmic unit dB is used. If you want to use "normal" number ratios, you just raise 10 to dB/10 power (10^(dB/10)). Dymnamic range does not mean only the difference between the quietest sound and loudest in a given recording, but also the difference between the smallest detail and the general level of the signal. Remember that the sound wave is very complex single waveform which contains all the levels and frequences in one single wave. Now, let's imagine a perfect clean mic signal with 144 dB dynamic range going to a cheap 24 bit recorder. Cheap electronics add so much noise, that the finest 48 dB/8 bits of detail is buriend under it. We have 96 dB of clean signal and if we listen loud enough (this is important, we never do...), we hear just noise under this good signal. Feeding this same signal to a 16 bit recorder we get the same 16 bits worth of good signal, and if we turn up the volume, we hear just noise just like before. Both recordings are of same quality. The misunderstanding about this "resolution" and dynamic range thing is that people forget that this dynamic range is the relative measurement of the smallest detail level piggybacking the large amplitude waveforms. If the dynamic range is large (like in good 24 bit systems), then there is more "resolution". If the noise level is high, then in a 24 bit signal these minuscule details piggybacking the waveform is not real signal, but random noise. It can not be called "detail" or "resolution". Like I said before, if just using more bits for sampling would really improve the signal quality regardless the noise floor provided by the less than perfect analog circuits, we would certanly be using 48 bit systems by now. But we are not. That is because there is no point in using more bits than what the other parts of the chain can feed. With the best analog electronics and microphones the limit is around 130 dB which translates to 22 bit sample depth (For this reason 24 bit AD converters are plenty good enough and nobody even tries to use more). Back to cheap recorders: with high noise electronics these recorder's 24 bit AD converters are not fed with a signal which has more than 96 dB or so dynamic range. So there is NOTHING those 8 extra bits compared to 16 bit recorders can do exept record this random noise faithfully. For that reason 24 bit files have exactly the same data content in the top 16 bits as a 16 bit file of the same signa, and ONLY noise in the last 8 least significant bits. That makes using 24 bit recording pointless, UNLESS the electronics & mics actually are capable of more than 96 dB dynamic range. With most cheap recorders they are not. And finally, to put this all into perspective: 16 bit recording is wastly better than any analog recorders are capable of. Tens of thousands of high quality movies have been recorded in not-so-distant past using $15000 analog Nagra recorders, with ONLY about 65 dB dynamic range (11 bits...). Now, amateurs are panicing if they are not getting true 24 bit resolutions = 144 dB dynamic range from their $300 pocket recorders! Come on, in XH-A1 we have qualitywise a much better audio recorder than those glorified Nagras. That surely can not be the reason why we can not make great movies with great audio?