Sound ?!

[Steve Sherrick]

The "filters" that provide noise reduction etc in SoundTrack Pro are about in a par with what comes in other low cost audio programs like Sound Forge, Audition etc. They are not on a par with higher cost plugs available for ProTools etc or dedicated outboard systems like Cedar. What I mean by this is that they can do less work for you reducing noise and distortion before the artifacts they cause in the resulting audio file start to make the whole exercise not worth it. It is VERY easy to improve a piece of noisy audio into a ruin with these tools.

One of the new entries from a software perspective is Cube-Tec. Pretty impressive stuff, but expensive, very expensive.

The fact that an audio file is 24 bit tells you nothing about how it really sounds. I can record 24 bit via the analog audio input of my laptop or on a low-cost file recorder and end up with audio that is inferior in every way to that recorded by a used DAT machine @ 16 bit. The bit width is like a videotape format--just a container. You can record very nice looking video on DVCAM and you can record unwatchable crap with a low end camera--the format is the same. As I've mentioned, there is not yet available a 24 bit A-to-D that gives you a real 24 bits of resolution, even in the ultra high end audio world. And as I've also opined, the audible difference between a good 16 bit recording of most field production audio and a 24 bit recording of the same scene would be nil. Why? 1: The background noise floor of this noisy world we live in. 2: the analog audio electronics in all video camcorders and most audio recorders under $2000 or so have so much noise and distortion themselves that the added resolution is wasted--the only real difference in a 16 bit and a 24 bit recording they'd make is that the 24 bit one would take up more storage. (By the way, there are no 24 bit DAT machines--the DAT spec is 16 bit.)

Good points. 24 Bit can help minimize artifacts and quantization noise, but as mentioned the noise floor of the location and the signal chain can all impact any benefits you might gain with 24 bit. I have found 24 bit to be very useful in post. You can do a lot with nicely recorded 24 bit 48K tracks.

For taking the signal of a microphone and recording it on a camcorder (F900 was mentioned), using an external mixer makes for an audibly better recording. There are two major reasons for this: first, the preamps in even a small mixer like a SD 302 or even a Shure FP33 are far cleaner and lower distortion that those in the F900, and there is the previously discussed matter of low-level analog audio amplification going on within the chassis of a device also doing high speed digital image processing--the proximity to those circuits is a real problem. The control of the audio signal in the mixer is more precise, low roll-off filters are available and easily auditioned, the headphone circuit of the mixer is much cleaner and capable of higher levels w/o distortion. Metering is immediately available. Dynamics control is usually included, either on output (FP33) or both (302, 442). The 2nd reason for using a mixer is that having worked the audio as discussed within the mixer, the user can now feed it to the camera as a much more easily recordable signal, at a good level (stay out of the noise floor mud), without big peaks (momentary distortion) and with a way, via a return feed, to immediately evaluate if there is a problem with the mix feed or how the camera is dealing w/ the sound by switching between the two on the mixer. Recording a mic directly to the camera will always have its place on certain sorts of shoots, but it will never make for as high fidelity and easily controlled and monitored track as one done via a mixer.

Red will cross into many shooting situations, so I guess we'll see a wide variety of audio approaches. For narrative and any kind of controlled shooting situation it is highly recommended that an audio professional be brought in to handle the task as it will almost always improve the audio being recorded and save time in post. Obviously, there are times when run and gunning just does not allow for this kind of thing. In those cases, care should still be taken to make sure you have a proper run and gun audio system in place. Solutions will appear in the next few months I'm sure. The pimping of the Red camera has barely begun. By this time next year, there will be some cool products on the market.

Steve
Philip Perkins CAS[/QUOTE]

 

[Elizabeth Lowrey]

A limiter is not a compressor. Please look more closely at the functions of these tools, how they operate and what those terms mean in the audio world. Again, a limiter only functions on the peaks of a signal, while a compressor works on the whole mix according to its settings, which look at the average level of the mix. There are places where the functions blur together, but only in the most sophisticated of studio processors, not on inexpensive video camcorders.

Philip, while very respectful of your obvious knowledge and credentials, it seems you are striving to prolong an artificial debate when I don't think there is any substantive difference of understanding (and apparently you are selectively doing so, as the post of mine you quoted was merely an affirmation of something 10s posted). A limiter IS like a one-legged compressor -- it does exactly the same thing to signals exceeding a specified amplitude that a compressor does but usually does it at a much sharper curve/faster rate and usually kicks in at a higher threshold frequency. Most dedicated hardware limiters are not called "limiters": they are called "limiter/compressors", and that's because the functionality between the two systems is so overwhelmingly similar. Specifically WRT software compressors, you could program one to do exactly the same thing to a file that you could do with a limiter, and you are very likely to not even FIND a plugin in major programs today called a "limiter" but rather one unified plugin that manages dynamic range and fulfills the overlapping functions of a limiter and a compressor.

If, for example, you look at the flagship DAW from Cakewalk Audio, Sonar, you will see that it doesn't offer a "limiter". Limiter functions are subsumed within and are a subset of the functions of their Sonitus compressor. (See the attached screenshot.) In Sony Vegas, you will get a choice of several "dynamics" plugins (ExpressFX Dynamics, Multiband Dynamics, Graphic Dynamics), all of which feature the same basic parameters for adjustment.

With a programmable limiter (hardware or software), you are setting the level at which you wish to begin amplitude attenuation, you specify the ratio of attenuation to be applied to amplitudes exceeding that threshold, and you set the amount of time in milliseconds over which you will allow the gain reduction to reach its maximum and return to passivity (when signal input again falls below the threshold). With compression, you do exactly the same thing, attend to exactly the same parameters, only you also specify some amount of input boost, which may or may not be constant and the implementation of which (attack, release times, low threshold levels, etc.) will vary depending upon the compressor. The continuum of dynamic range control typically connoted by the respective terms ranges from "brick wall" attenuation of only very, very high peaks with an overall preservation of wide dynamic range to a very consistent, compact dynamic range with ample input boost and often an increase in both perceived volume and actual average amplitude.

With what part of that description do you take issue? If you google the words "limiter compressor differences", the first 5 hits you get will say essentially what I've said above, and most make a point of acknowledging the pronounced kinship between the two terms and devices. I really don't see what you are so determined to refute or what I've said that should seem in any way controversial to a seasoned audio professional.

 

[Steve Sherrick]

Perhaps a case of semantics. Compression changes the sound much more than limiting does. The goal of limiting is to be transparent. When you want to raise the overall level of sound without changing the character of the sound too much. Fast attack times and release times can help make it transparent. Technically limiting is a form of downward compression but with a high ratio. But they do serve different purposes to an extent. So, you are both probably right, but just phrasing it somewhat differently.

Steve

 

[10s]

Eclaire, I'd suggest you get away from using software as a reference and instead look at analog hardware. The software is based on these tools. You might want to look up optical limiters such as Manley, etc. The LA2 has been used for decades and is a fav of many recording artist. These tools are for studios so they don't apply very well to cameras because they're large bulky boxes full of tubes, but there is plenty or reading material to enjoy.

http://www.manleylabs.com/containerpages/langdualoplim99.html

The debate over compression / limiting is getting a little silly. Yes, one can view limiting as one leg of compression, but they're two different processes.
Limiting in field production is acceptable and is used often while compression isn't. There is a difference. Differentiating between the two will serve you, but if you insist they're the same, then for you, it is. But of course, audio engineers might view it differently.

Back to RED: This camera has great potential to be an excellent tool for artists. Let's hope they figure in the need for limiting. They're bright folks.

 

[david farland]

Well said....Let's drop it.......Back on topic.

Be excellent to create a new Reduser Audio section.....Jarred!!!

But whilst we're waiting for a Red solution what interium measures do people suggest?

Dave,

 

[philper]

Philip, while very respectful of your obvious knowledge and credentials, it seems you are striving to prolong an artificial debate when I don't think there is any substantive difference of understanding (and apparently you are selectively doing so, as the post of mine you quoted was merely an affirmation of something 10s posted). A limiter IS like a one-legged compressor -- it does exactly the same thing to signals exceeding a specified amplitude that a compressor does but usually does it at a much sharper curve/faster rate and usually kicks in at a higher threshold frequency. Most dedicated hardware limiters are not called "limiters": they are called "limiter/compressors", and that's because the functionality between the two systems is so overwhelmingly similar. Specifically WRT software compressors, you could program one to do exactly the same thing to a file that you could do with a limiter, and you are very likely to not even FIND a plugin in major programs today called a "limiter" but rather one unified plugin that manages dynamic range and fulfills the overlapping functions of a limiter and a compressor.

If, for example, you look at the flagship DAW from Cakewalk Audio, Sonar, you will see that it doesn't offer a "limiter". Limiter functions are subsumed within and are a subset of the functions of their Sonitus compressor. (See the attached screenshot.) In Sony Vegas, you will get a choice of several "dynamics" plugins (ExpressFX Dynamics, Multiband Dynamics, Graphic Dynamics), all of which feature the same basic parameters for adjustment.

With a programmable limiter (hardware or software), you are setting the level at which you wish to begin amplitude attenuation, you specify the ratio of attenuation to be applied to amplitudes exceeding that threshold, and you set the amount of time in milliseconds over which you will allow the gain reduction to reach its maximum and return to passivity (when signal input again falls below the threshold). With compression, you do exactly the same thing, attend to exactly the same parameters, only you also specify some amount of input boost, which may or may not be constant and the implementation of which (attack, release times, low threshold levels, etc.) will vary depending upon the compressor. The continuum of dynamic range control typically connoted by the respective terms ranges from "brick wall" attenuation of only very, very high peaks with an overall preservation of wide dynamic range to a very consistent, compact dynamic range with ample input boost and often an increase in both perceived volume and actual average amplitude.

With what part of that description do you take issue? If you google the words "limiter compressor differences", the first 5 hits you get will say essentially what I've said above, and most make a point of acknowledging the pronounced kinship between the two terms and devices. I really don't see what you are so determined to refute or what I've said that should seem in any way controversial to a seasoned audio professional.

I would say that it is you who are prolonging a debate by insisting that two things that are different are the same. I take issue with not calling things what they are and correctly describing what they do in the real world. Limiters and compressors, when the terms are correctly used, do not do the same thing, which is why they have different names. The fact that low-cost software plugins mislabel them or appear to work as some blend of the two doesn't change that. They may be able to function as both a limiter and a compressor at the same time, but what is going on are separate processes if what they are doing is exactly limiting and compressing. If these apps work for you I am glad, but that doesn't change the fact the processes of compression and limiting as they are understood in the audio industry are separate and distinct things. Calling them the same thing merely causes more confusion, like saying that black level and iris are the same thing in a camera because they change the apparent exposure of part of the picture.

Philip Perkins CAS

 

[S. Um]

But whilst we're waiting for a Red solution what interium measures do people suggest?

Here are my thoughts. I may be wrong, so I welcome other suggestions.

There are 2 cases. If you have a line input, then there's no gain adjustment available. But if you have a line input, then you're probably feeding the signal from a mixer, and hopefully your sound guy will feed you the proper levels.

For mic levels, you can adjust the gain on the preamp to give you some headroom that you're comfortable with. Even the best limiters will clip when the audio is loud enough, so here you decide what loud enough is. I think Red is counting on the 24-bit A/D converter having enough resolution to cover the signal and the headroom.

Here's an example. Let's say the signal you're recording has 96dB dynamic range (or 16-bits). Because there's no limiter, you want to give yourself, say, 12dB of headroom (or 2-bits) for unexpectedly loud sounds. In a 16-bit system, 2-bits of headroom will only leave you with 14-bits of data. But in a 24-bit system, you still have 22-bits of data possible. Even if the A/D is only accurate to 18-bits, you can still capture your 16-bit signal.

But once you have the data, you will need to do some processing in post. Most likely it will require adding gain, compression, and limiting. But we normally do this anyway, so it's not really additional work.

I think this is how Red intended the workflow to be. In a sense, it's analogous to recording RAW video with no gamma curves. You can add as much gain as you want (by opening the iris), but you have to be careful because there's no gamma curve to keep you from blowing out the picture. Same for audio.

In the real world, the problem with setting your gain too low (in order to get some headroom), is that your signal may get lost in the noise. That's why they have limiters.

 

[10s]

Sumfun, good point. We'll just have to wait and see how the testing goes.

One thing we can count on, Jannard & team are not afraid to improve their designs, we all know that lesson vey well. I'm sure there will be a few audio bugs that the RED team will pounce upon.

My concern is that the camera allows one to operate w/o others, i.e., sound man (even though I myself do sound gigs) I would like the option of creating without the constraints of needing additional crew. If one person can get great image and audio, and it also works well with a complete production team, then we are set to do some serious work.

Jannard & team will not let us down.

 

[Elizabeth Lowrey]

edited as double post

 

[Elizabeth Lowrey]

I would say that it is you who are prolonging a debate by insisting that two things that are different are the same.

Please quote one passage anywhere in this thread where I said they are the "same" thing. And when you realize that you cannot do so, please have the courtesy to admit that the above statement is a mischaracterization.

Being able to see overlap and similarity between two phenomena where there is such is as indicative of a sense of discrimination and nuance as is the ability to discern differences. They are two sides of the same coin of evaluation and comparison. The fact that you chafe at the suggestion that limiting is like "one legged compression" or covers a subset of tasks falling within the purview of compression is your prerogative, but you are absolutely baseless to suggest that your propensity to emphasize their differences is any more "correct" than my propensity to see their similarities and to acknowledge the fact that one is, in effect, a subset of the other.

I'm more than satisfied that we BOTH know what the terms really mean and, more importantly, what the effects of each sound like and the continuum of dynamic range control that connects them. And I think it's very instructive that you chose to ignore my express attempt to take semantics out of it (as much as possible in any verbal endeavor) and focus on our respective understandings/definitions rather than on the terms themselves. I asked what part of my carefully specified understanding did you take issue with, and you responded not with equal specificity but with the very terms under discussion and the simple conclusion that they are "separate and distinct". That solidified once and for all that this "debate" is born far more out of didacticism and ego than out of genuine intellectual disagreement.

The only reason I'm still in this is because you have consistently read my posts carelessly, first ignoring an introductory disclaimer of subjectivity and then ignoring the part of my references to limiters that spoke to their customary differences vis-a-vis compressors. And your selectivity was not just evident in picking and choosing from within my posts but from within this thread. For example, you chose to quote only my post, though it was chronologically later than these remarks by sumfun and to which I was only responding in affirmation:

BTW, a compressor and a limiter actually perform similar functions. With a compressor, you set a threshold or knee (where the compression kicks in), and a compression ratio. With a limiter, the threshold is usually set just under the limiting level, and the ratio is usually very high. So essentially, a limiter is a type of compressor.

I could have sworn he just said essentially the same thing I said, yet you addressed your remarks only to me.

Not wishing to further divert this thread or try the patience of other posters, this will be my last word on the subject. I persevered this long only because I resent manufactured arguments and egos that motivate lectures when there is no need. A pity, too, because I sense there is much I could genuinely learn from you and many lectures I would happily indulge if offered in good faith and with a modicum of humility.

 

[Phil Becque]

How about impeadance (english spelling)? Are there any specs for the mic and line inputs? Also - if you can reconfigure a mic input to a line input at the mini XLR connector; does the impeadance change to match what you'd expect?

Thanks for any info or opinion, Phil

 

[philper]

How about impeadance (english spelling)? Are there any specs for the mic and line inputs? Also - if you can reconfigure a mic input to a line input at the mini XLR connector; does the impeadance change to match what you'd expect?

Thanks for any info or opinion, Phil

I think on the existing cameras the impedance stays the same, and the real diff between the mic level an the line level input is a pad that is switched in for line level. But to be sure I would have to check the spec again. In any case WE don't actually DO anything different between connecting mic and line levels to the cameras--if I had to guess I would say it was low, between 200-600 ohms.

Philip Perkins CAS

 

[Phil Becque]

I think on the existing cameras the impedance stays the same, and the real diff between the mic level an the line level input is a pad that is switched in for line level. But to be sure I would have to check the spec again. In any case WE don't actually DO anything different between connecting mic and line levels to the cameras--if I had to guess I would say it was low, between 200-600 ohms.

Philip Perkins CAS

Hi Phil,

You were saying earlier in this thread that there were not any 24bit ADC's. Wolfson seems to have a very good range:

http://www.wolfsonmicro.com/products/WM8786/

I'm not saying this is what RED are using but the specs look very good.

Like you say though, claiming you have a 24 bit convertor and then only getting - 111dB SNR make you wonder what's going on. Although for most people 111dB SNR is probably more than enough.

All the best, Phil

 

[philper]

Hi Phil,

You were saying earlier in this thread that there were not any 24bit ADC's. Wolfson seems to have a very good range:

http://www.wolfsonmicro.com/products/WM8786/

I'm not saying this is what RED are using but the specs look very good.

Like you say though, claiming you have a 24 bit convertor and then only getting - 111dB SNR make you wonder what's going on. Although for most people 111dB SNR is probably more than enough.

All the best, Phil

I think what I said is that there aren't (yet) any convertors that can give you 24 whole bits of resolution. Putting an ADAC inside the chassis of a digital video camera makes it hugely more challenging to make anything useful of the higher bits--there is too much system noise and hash. I'm hoping Red has beaten this and if so that will be a great thing, since most of my clients will want to continue recording production sound on the camera as they have w/ the cameras they currently use.

Philip Perkins CAS

 

[Elizabeth Lowrey]

For those who, like me, missed this thread when it was first posted, Evin Grant has posted what I think must be the first clip of RED-acquired audio:

http://www.reduser.net/forum/showthread.php?t=7151

I hope there is an explanation for the pronounced hiss that lies outside the RED camera.:sad:

 

[philper]

I'm hoping it was just a quickie test and they weren't being careful about levels or muting unused inputs.

Philip Perkins CAS

 

[Bryan Golder]

I'm a long time lurker here. My background is as a record producer/recording engineer, slowly moving into "multimedia" production, hence my interest in Red.

A couple points:

24 bits - Bits represent dynamic range, but dynamic range is always limited by the noise floor, and the quality of the A/D electronics and the environment they are housed in. You will always run into "too much noise" before you run into "not enough bits". Forget about the number of bits as a practical matter. Worry about the noise floor and the dynamic range, same as you do with your light.

A compressor and a limiter are the same dynamics processing function, but each addresses a different part of the signal. The distinction between the two terms is more a function of historical terminology than a technical definition. Typically, a limiter has a fast attack and release time, a higher compression ratio, and a higher signal threshold so it sharply decreases the amplitude of the loudest transients for brief periods of time. A compressor may have a somewhat slower attack & release, a lower threshold, and a lower ratio so it affects the average level of the program material and lets transients through unaffected.

 

[Shawn Nelson]

Back to the original post, I recently got audio working on Red #27. It took me a while, as the lasering is wrong! Port 2 is really Port 1 and Port 4 is really Port 2, but after that it wasn't too hard. I can't find any audio adjustments in Build 12 but using my SD302 I generated a 1khz tone and it landed perfectly, so they seem to be well calibrated for the Sound Devices stuff. Chazmo made me two kick ass mini to full cables and I recorded to both channels and easily brought it over to the Mac.

Notes:
-Like the meters, small but easy to read
-We need volume adjustment for at least initial configuration
-I hate miniXLRs

 

[Alexis Hanawalt]

I'm not sure whether this part of the manual has been posted here, but it reiterates the radical notion that the 24bits allow enough resolution to prevent clipping without a limiter.

Audio:
This sub menu allows microphone input levels to be adjusted via a high quality pre-amplifier.
Audio is sampled at 24bits, which provides high audio fidelity and ample dynamic range to
prevent clipping without the use of an analog domain input limiter.
Each microphone input is provided with a high fidelity pre-amplifier that maybe adjusted for
optimal level to match different microphone sensitivities and sound pressures.
Input Level. Range +20dB to +54db Default value is +28dB
Note: Input level adjustment does not apply to line level audio inputs.

Shawn, any thoughts about running a few tests with and without the SD 302?

 

[Jason Sinclair]

So the options?

So the options?

OK, we have some audio pros here and we have had a great discussion on limiters and compressors etc... and we get the message about the delicate nature of sound recording and problems associated (and i for one am extremly happy with the learning available in these discussions) and i'm sure teamred will listen carefully to how they can improve on the camera but at the end of the day, workable solutions given the equation of cost versus quality needs to be addressed.
Now, there is going to be comprimises in sound production as by the sounds of it there always are. Even with the best equiptment and best ops. So there to me must be a optimal working condition given the inherent floors with technology trying to recreate reality. Red has it's own particular limitations and lets say technology itself will always have some limitations. So i'm asking you pros and enthusiastic soundphiles what in your opinion is the best solutions given the technology available under the circumstances that are available.

There seems to be two different areas,1. run and gun single or two person operation and 2. small low budget crew looking to make feature films, theatrical productions etc....

I think it is obvious that anyone with budgets higher than this will just hire a pro and let them deal with it... I think it also obvious that the revolutional aspect of red is it's ability for low budget and the reason at least 80% of us are here.

So what set ups would you employ for 1. run and gun and 2. low budget (but aiming for the highest quality, ie. the best cost versus quality ratio)

How would your work flow operate from production (and even pre production) and in post?. Give your reasoning while always attributing discusion towards the cost versus quality ratio.

Please