Forums » Production Techniques

1. ralck
   Member

   

    So I feel really stupid about this... but I need some help with using the color bars with the tone at the begining of a video.

   Basically, up until now I've just done my own video stuff and gotten it to the sound level/color correction that I like and exported it to whatever format I wanted/needed at the time.  However, several friends and I are thinking of entering a film festival and part of the submission rules are to have the color bars at the begining.  I'm much more concerned about the tone.

   From what I understand, the film fest will calibrate their audio equipment to the level of that tone to ensure the audio in the project is at the proper levels.  Do I adjust my audio so it's at the right level according to that tone, or do modify the level of that tone to match it to my audio?  One last question... how "loud" do they make the tone be in the theatre (like, if you could give a comparison to something in real life... a fire alarm or wrist watch alarm, etc?).

   This will be the first festival I'll be entering, so I want to make sure I understand how the tone should be setup. :)

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2. robgrauert
   Member

   

   By default in FCP, tone is -12dB, but you can change it to anything. Also, when I do freelance work, I've been told to ensure that audio in the final edit is around -12dB and doesn't peak over -6db. So I'm assuming it's industry standard to assume tone is -12db.

   However, tone can be anything. It's just used as a reference. If you set tone at -20db AND TELL THEM IT'S -20dB, they will then set up their equipment so that your tone reads -20db when they're watching. If you allow them to assume it's -12db, your audio will be very loud and they won't be psyched. 

   This is my understanding of tone and what other's have told me. My advice is to put the bars and tone like they ask and inform them what your tone is set to. 

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3. robgrauert
   Member

   

    I just thought of something.

   They will most likely be viewing your stuff on a TV or pro monitor, so you should be editing with video going out from your NLE to an external monitor (it can be a TV since you're not broadcasting). If you have your external monitor calibrated correctly, aka set color bars, and reference that when doing color correction or whatever, all you will have to do is insert the color bars at the beginning of your tape and you'll be good to go.

   The reason for this is because the video on your computer screen will not look exactly like the way it does on a monitor. So you reference the external monitor. The only time you don't need a monitor is when you are absolutely positive that your video will only be viewed on the web, because it will be viewed on a computer screen then. The term they use in the industry is "wysiwyg" (pronounced wiz-e-wig). It stands for "what you see is what you get."

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4. ralck
   Member

   

   Okay, so I've been googling a bit here to try and get more information...

   It seems like the common place in digital video is for the tone to be set at -12dB, but it can be anywhere between -24 and -6 as long as the playback is set to the correct levels.

   Now, the average sounds in your video should be around -16 to -12 dB, loud sounds shouldn't peak past -6 and quiet sounds can be as quiet as you want (but generally don't go less than -24 unless you don't want it to be heard).

   So this is starting to make a lot more sense to me... except for one thing.  How exactly do I know what -12dB is?  I know I can tell my NLE to set it the audio to -12, but if my recorded audio was very quiet to begin with? For example, using the inverse square rule, if my mic wasn't close enough to the subject to pick up "normal" loudness audio... in this case I wouldn't just want to set it to -12, I'd want to increase it to make it easier to hear... right?

   Or am I making this way too complicated?  Am I just supposed to set my audio levels so that the "average" sound is the same as the tone?  Is the -12/-6/-24/etc refering more to the levels during playback?  If I think about it that way, and use my receiver as an example (it does audio from -99 to 0dB) that sort of makes much more sense.  That way, it's more important of the loudness of the tone for setting up their equpment than it is for what my NLE says the "negative dB" is?

   So does that mean I can just set the tone to be about the same as my "average" audio instead of setting the audio to the default tone?  They have provided their own bars and tone, so does that make audio setup different than using my NLE's bars and tone?

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5. ralck
   Member

   

    I just thought of something. They will most likely be viewing your stuff on a TV or pro monitor, so you should be editing with video going out from your NLE to an external monitor (it can be a TV since you're not broadcasting)."

    I know about this... I'm not worried about the color part.  I actually don't have an NTSC monitor... but my computer monitor is an 8-bit panel, so properly calibrated it gives great color reproduction (also, the out-of-the-box calibration was actually very good, based on a lot of user reviews, so until I can afford color calibration hardware, it will have to do).  For the meantime, I do "verify" on an NTSC TV to help make sure it's as accurate as possible (and I've always been pleased with the results).

   Thanks for the tip, though.  Hopefully it will help someone else reading the thread. :)

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6. robgrauert
   Member

   

   "How exactly do I know what -12dB is? I know I can tell my NLE to set it the audio to -12, but if my recorded audio was very quiet to begin with? For example, using the inverse square rule, if my mic wasn't close enough to the subject to pick up "normal" loudness audio... in this case   I wouldn't just want to set it to -12, I'd want to increase it to make it easier to hear... right?"

    

   The audio meters in your NLE should be telling you what your audio levels are. If they are low, yes you want to increase them. But be aware that you will also be raising the noise too. So be prepared to do some sound editing/noise reduction in a program specifically made for sound, such as Soundtrack Pro. 

   I don't really know how to answer your next question. I'm getting confused reading it myself, haha. But I know in studio classes at school we would send tone to the tape deck and then adjust the levels on the deck so that the tone was reading 0db (you set it to 0dB when working in analog.) This way, when we did sound checks for the people that had mics on, they too would generally be at 0db when we were recording. So if I understand your question correctly, it's probably a good idea to set your tone to -12dB if that is the average level of your sequence. 

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7. robgrauert
   Member

   

   "For the meantime, I do "verify" on an NTSC TV to help make sure it's as accurate as possible (and I've always been pleased with the results)."

    

   Yep, since you're not working in broadcast a regular ol' TV will serve you well. I used to use one too until I saw someone selling a real monitor on Craig's List for $300.  

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8. ralck
   Member

   

    Yeah, I know about the audio meters in NLE's... I guess I've never paid enough attention to them...

   If I import a clip, does the audio meter act as that clip is at 0dB because I haven't increased or decreased it yet?  Or does it actually measure the amplitude of the audio waves and somehow calculate the dB from that?

   I don't know how I'm going to set audio levels on a DV deck... I use a camera to capture my footage because I'm poor and decks are way too expensive right now. :-/

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9. robgrauert
   Member

   

    "If I import a clip, does the audio meter act as that clip is at 0dB because I haven't increased or decreased it yet?  Or does it actually measure the amplitude of the audio waves and somehow calculate the dB from that?"

    

   I'm not sure about then engineering how the audio meter works in an NLE, but it's one of those "what you see is what you get" things. So if you imported a clip and it's reading -X on your meter, then thats what it will be when you export to tape. So adjust accordingly.

    

    "I don't know how I'm going to set audio levels on a DV deck... I use a camera to capture my footage because I'm poor and decks are way too expensive right now. :-/"

    

   Sorry. I'm a bit out of it from editing for long hours. They didn't adjust audio on the deck itself. They sent tone from the mixer and adjusted it on the mixer until it read 0 on the meter of the deck.

   How they did it is irrelevant to what I was making a point about anyway. I was trying to make the point that tone was set to the average level of what we were recording. So to take that situation and compare it to yours, set tone to match the average dB level of your sequence. 

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10. ralck
    Member

    

    Any audio gurus out there that might be able to help clarify this up any more?

    I'm still confused if there's a specific set of steps I need to follow or if I'm a little more free?

    Do I need to set all my audio based on what their tone is?

    Or... if my audio is lower than normal, but I set my tone to be lower than normal, they will calibrate their audio equipment a bit higher to normalize it for playback?  Same kind of thing for if my audio is higher... just that they would calibrate lower?

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11. robgrauert
    Member

    

     It has nothing to do when them compensating whether or not your audio is too high or too low. It's there as a reference for them so that they are viewing and hearing the way you intended it to be viewed and heard.

     So if you tell them your tone is at -12dB and they set tone from your tape on their equipment to -12dB, they will be hearing your sequence the way you were hearing it while editing. 

     You could tell them that tone is at -100db, then when they set the tone on their equipment, they will be hearing your audio from the sequence properly, whatever your average dB level of your sequence may be. 

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12. robgrauert
    Member

    

     Think of it like this:

    If your average audio is -12db, you want them to view it at that, and giving them something to reference allows them to do so. 

    So if your average audio is -12 and you tell them tone is -20, for example, they will set tone to -20. Tone will probably sound low to them because -20 is low, but that's fine because when it gets to your video, your average audio will be at -12. If they didn't have tone to use as a reference, they wouldn't know what you intend your sequence audio to be. So if they assume your -20 tone is -12 they will have tone too loud and when it gets to your video, your sequence audio will be too loud. 

     

    I don't know what else to say if you still dont understand. sorry. 

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13. D0n
    Member

    

     " Think of it like this:

    If your average audio is -12db, you want them to view it at that, and giving them something to reference allows them to do so. 

    So if your average audio is -12 and you tell them tone is -20, for example, they will set tone to -20. Tone will probably sound low to them because -20 is low, but that's fine because when it gets to your video, your average audio will be at -12. If they didn't have tone to use as a reference, they wouldn't know what you intend your sequence audio to be. So if they assume your -20 tone is -12 they will have tone too loud and when it gets to your video, your sequence audio will be too loud. 

     

    I don't know what else to say if you still dont understand. sorry. "

     

     At first it didn't make a whole lot of sense..... so I went dipped into a bottle of scotch, and came back to it..... but now....

    ....I'm gonna need more scotch... 

    ;0) 

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14. ralck
    Member

    

     Hey guys,

    So I was talking to a film student I know hoping to get a little more clarity on this.  He explained it fairly simple and I'll try to repeat what he said for those out there using this as reference.

    Basically, digital video uses a tone signal at -12 dB for reference.  This is measuring the amplitude of the signal.  The #1 goal of this tone is to ensure properly calibrated audio equipment for playback (so it can be played back as intended by the post crew).  This tone (which is generally 1200 Hz or 1000 Hz) should correspond to the average audio levels in your video.  Your loud sounds shouldn't excede -6 dB and your quiet sounds can be as low as you want (but generally isn't lower than -24 dB).  Okay, I think that summarizes most of this thread so far.  Now for the fun stuff...

    So basically, the best thing to do is calibrate your tone and average audio to be -12 dB.  You can, if you really want, set your tone and audio to be -20 dB if you really choose so (with the idea that you crank your speakers or headphones up so that your hearing a "virtual" -12 dB).  The same idea applies if you really wanted to set your tone/audio to -6 dB.  Note that in both cases your tone still meets the average audio in your video.  This will NOT mean they hear your audio any louder or softer than you inteded.   Instead, they will recalibrate their audio equipment (increasing or decreasing the audio levels as necessary) to set your tone to -12 dB in which case they will hear your audio as you intended.  This will, however, make you look like a very big n00b to them if they have to recalibrate their equipment because you were too lazy to set tone/audio to -12 dB.

    So the moral of the story is, the best thing to do is set tone to -12 dB and set your average audio to a range of -16 to -12 dB.  The biggest thing you need to worry about is that your tone matches your average audio.  If their equipment is already calibrated properly, they can just pop in your tape and hit play and they will hopefully think of you as less of a n00b. :-P

    I hope I've explained this correctly... I understand how to use bars and tone now... I'm just not sure I can translate that to words.

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15. BarefootMedia
    Member

    

    I'm not sure who came up with the notion of setting tone to your "average" audio level.  But that ain't how we use tone in master control, the place where all TV signals start their trip to viewers.  Tone is assumed to be at 0 db and will be as loud as the loudest sound on the tape.  Master control operators are charged with insuring that the audio or video portion of the RF signal do not cause interference with each other.  (If you don't understand how they can do that, I can explain it again.)

    It is assumed professionals already know what dynamic range they want for their program, so tone is at the same level as the maximum sound that occurs during playback.  If you set your tone to -12db or -6 db, master control operators will boost your audio to 0 db for playback, which works fine as long as you never exceed the level you set.  The general rules of having your audio bounce between -6 db and -12 db are there to provide some headroom for louder sounds.  Say you have an interview with several people and when any one is speaking normally, they are bouncing between -6 db & -12db.  But when anyone speaks up or if everyone begins laughing, your audio levels can jump up to 0 db without causing RF signal problems.  But ANYTHING over 0.0 db will cause distortion in TV playback.

    Audio only recordings & movies may deal with peak audio in a different manner.  In sound recording or amplified performances, your audio can bounce above 0 db with little to no distortion.  So audio recordings are adjusted differently than audio/video recordings.  While I'm sure that there have been changes since video recording switched from analogue to digital, it seems unlikely that professional practices have radically changed since I used to work full-time in master control.  Back when HiFi audio was introduced, the audio signal was laid between the tracks of the video signal (low hi audio continued to reside on the edge of the tape.)  If the audio was too loud, it would encroach upon the actual video signal and cause video & audio distortion on the source tape.   To prevent distortion, professional video productions would place an audio limiter/compressor between the mixer & the record deck.  But film productions never put the audio & video signals in contact with each other.  Audio is recorded on tape until a final print is made, so distortion occurs only when it is overdriven in recording or, more often, when overdriven to speakers.

    So while I can't speak to film production practices, industry convention in TV is tone should be recorded at 0 db, to correspond to the loudest sound in the program.  SMPTE color bars are used in conjunction with a vectorscope & a waveform monitor to adjust the time base corrector (TBC) output.  Which should make the playback signal look exactly like the video signal you saw when editing.  Provided you viewed your program on a properly adjusted monitor.  Film playback does not require a color/luminance/contrast reference signal as there are no adjustments made to the projected image.

    I hope this clears up the confusion on this issue.

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16. ralck
    Member

    

     That actually caused a little more confusion for me. :-P

    Barefoot, are you refering to analogue equipment?  I did read somewhere that analogue was set at 0 dB, but when you are talking about DV it went down to -12.  I don't really know why.

    Now I'm wondering again if my tone should be average or maximum loudness. :-P  I suppose I could try and contact the film fest people to get a little more clarification on what exactly they want...

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17. D0n
    Member

    

     I agree ralck, there was an old way of doing things, and now there's a new way. But do share what you learn from the film fest organizers!

    I'm finding the default settings on my software work pretty good. But so far none of my clients are t.v. broadcasters. I assemble my projects, that have clips done in final cut express (composites for eg) iMovie hd, iPhoto, and then to Garageband before going to iDVD/iWeb.

    I believe that net, and direct to end user (ie dvd/downloads) will circumvent the old tv broadcasters. They may be endangered.

    So the filmfest idea is something I've not yet had to learn about. But I'm curious.

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18. arby
    Member

    

    Each TV organization has its own requirements try this website

    http://www.outdoorchannel.com/downloads/NewShowTechReqs2009.pdf

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19. BarefootMedia
    Member

    

    WOW, maybe standards did change with the switch to digital signals.  I have to admit that digital camcorders were just getting into the prosumer/cable production markets.  But ALL our video playback came from analogue machines, although we did have computers generating the interstitial "coming up next" kind of stuff.

    I still think master control operators are most interested in the peak or loudest signal to adjust the modulator.  The Outdoor Channel describes the audio tone to be at 0 VU.  Then later on it describes the standards for transient peaks, in digital terms, with reference tone set to -20dBFS the peaks can reach -12dBFS.

    So now I'm confused.  But I'm thinking that translating the Outdoor Channel into English pretty much describes what ralck described before I added my two cents worth.  Sorry!

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20. ralck
    Member

    

     So last week at the festival I talked to the people about the tone.  They were very understanding since everybody seems to want tone submitted slightly differently.

    They said that they wanted a -12dB tone at the maximum audio level and everything else should be lower than that.

    This of course isn't going to be the same for every festival or broadcast submission, but maybe it will help someone else out there.

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