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#1
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I transferred a tape from a DVcam to add reverb. What's the purpose of the
test tone at the start of a video? Should it be at any particular level? I notice the tone on the original tape show to be -8.5 on the left channel and -8.4 on the right, per the meter on Soundforge. The sound is 2-channel mono. Also, what about the short "beep" that occurs on "2" of the countdown in the leader? I had to lower the level a tad when applying reverb to keep it from clipping. The highest levels after applying the reverb are about -.7 If I bring the highest peak back to 0db which is what it appears to be on the original tape, what considerations should there be regarding the test tone? Is it imperative to bring it back to the exact same level it was at on the original tape, which was transferred from a DVCam? Thanks for all shared wisdom. |
#2
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![]() "Doc" wrote in message ink.net... I transferred a tape from a DVcam to add reverb. What's the purpose of the test tone at the start of a video? Should it be at any particular level? It is for the TV station. To make sure the sound level is correct for replay on their system. The level should not be in the red I notice the tone on the original tape show to be -8.5 on the left channel and -8.4 on the right, per the meter on Soundforge. The sound is 2-channel mono. Also, what about the short "beep" that occurs on "2" of the countdown in the leader? It lets the editor know when to slice the video if they plan to put the segment int their own tape I had to lower the level a tad when applying reverb to keep it from clipping. The highest levels after applying the reverb are about -.7 If I bring the highest peak back to 0db which is what it appears to be on the original tape, what considerations should there be regarding the test tone? Is it imperative to bring it back to the exact same level it was at on the original tape, which was transferred from a DVCam? No. It needs to be set to your levels on your equipment Thanks for all shared wisdom. |
#3
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"Doc" wrote ...
I transferred a tape from a DVcam to add reverb. What's the purpose of the test tone at the start of a video? Should it be at any particular level? Frequently, the tone is used as an indication of where the "0dB reference point" is. The levels of the sound track(s) on the tape are referenced to this level. I notice the tone on the original tape show to be -8.5 on the left channel and -8.4 on the right, per the meter on Soundforge. The sound is 2-channel mono. That is why it is there. So that you can tell where the reference point is relative to YOUR setup. Also, what about the short "beep" that occurs on "2" of the countdown in the leader? It is a (optional) tradition with the "Academy Leader". It serves several purposes, not the least of which is to wake up the operator when it is time to switch. :-) I had to lower the level a tad when applying reverb to keep it from clipping. The highest levels after applying the reverb are about -.7 If I bring the highest peak back to 0db which is what it appears to be on the original tape, what considerations should there be regarding the test tone? Is it imperative to bring it back to the exact same level it was at on the original tape, which was transferred from a DVCam? Your new peaks should have the same ratio to your reference tone as the original peaks had to the original reference tone. OTOH, I don't think I would be all that obsessive about 0.7dB. They'll likely not even notice. |
#5
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On Wed, 15 Jun 2005 21:46:23 -0700, "Richard Crowley"
wrote: Frequently, the tone is used as an indication of where the "0dB reference point" is. The levels of the sound track(s) on the tape are referenced to this level. -8.5dB. That's an odd value, ain't it. -martin- -- "Now I want you to say it thrice daily and don't dress a bun" |
#6
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Doc wrote:
I transferred a tape from a DVcam to add reverb. What's the purpose of the test tone at the start of a video? Should it be at any particular level? I notice the tone on the original tape show to be -8.5 on the left channel and -8.4 on the right, per the meter on Soundforge. The sound is 2-channel mono. Also, what about the short "beep" that occurs on "2" of the countdown in the leader? The tone should be at - 20dBFS for standard reference. It really only matters that nothing clips and that you dub the thing back to DV at the same level, though. The 2-beep is to synchronize sound and picture. I had to lower the level a tad when applying reverb to keep it from clipping. The highest levels after applying the reverb are about -.7 If I bring the highest peak back to 0db which is what it appears to be on the original tape, what considerations should there be regarding the test tone? Tone at -20. Always. Is it imperative to bring it back to the exact same level it was at on the original tape, which was transferred from a DVCam? Probably. It would certainly be a good idea. That's why post houses have everything set up at the same level and why there is tone on tape. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#7
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"Scott Dorsey" wrote ...
Doc wrote: I had to lower the level a tad when applying reverb to keep it from clipping. The highest levels after applying the reverb are about -.7 If I bring the highest peak back to 0db which is what it appears to be on the original tape, what considerations should there be regarding the test tone? Tone at -20. Always. We sometimes use -8dBFS or -10dBFS with consumer equipment with marginal SNR. Is it imperative to bring it back to the exact same level it was at on the original tape, which was transferred from a DVCam? Probably. It would certainly be a good idea. That's why post houses have everything set up at the same level and why there is tone on tape. The context was a local TV station with minimal audio equipment. Previous discussion cast doubt whether there were any on the staff that could even read a VU meter. |
#8
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In article ,
Martin Heffels wrote: On 16 Jun 2005 08:52:59 -0400, (Scott Dorsey) wrote: Tone at -20. Always. YMMV ![]() Again, it doesn't really matter as long as yoou don't clip and you have the same levels going in as you have coming out. But it's worth putting a sticker on the tape if it's at -12. Or even if it's at -20. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#9
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"Scott Dorsey" wrote ...
Martin Heffels wrote: (Scott Dorsey) wrote: Tone at -20. Always. YMMV ![]() Again, it doesn't really matter as long as yoou don't clip and you have the same levels going in as you have coming out. But it's worth putting a sticker on the tape if it's at -12. Or even if it's at -20. I always specify the ref level in the slate. Slate : SMPTE bars & tone : Academy Leader : Program... |
#10
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On 16 Jun 2005 10:07:29 -0400, (Scott Dorsey) wrote:
In article , Martin Heffels wrote: On 16 Jun 2005 08:52:59 -0400, (Scott Dorsey) wrote: Tone at -20. Always. YMMV ![]() Again, it doesn't really matter as long as yoou don't clip and you have the same levels going in as you have coming out. Tell that to the posthouse guys who adjust your -20 to -12 when they dub it ;-) But it's worth putting a sticker on the tape if it's at -12. Or even if it's at -20. That sticker is a must! cheers -martin- -- "Now I want you to say it thrice daily and don't dress a bun" |
#11
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On Thu, 16 Jun 2005 04:04:54 GMT, in 'rec.video.desktop',
in article What's the purpose of the test tone in a video?, "Doc" wrote: I transferred a tape from a DVcam to add reverb. What's the purpose of the test tone at the start of a video? Should it be at any particular level? I notice the tone on the original tape show to be -8.5 on the left channel and -8.4 on the right, per the meter on Soundforge. The sound is 2-channel mono. Also, what about the short "beep" that occurs on "2" of the countdown in the leader? I had to lower the level a tad when applying reverb to keep it from clipping. The highest levels after applying the reverb are about -.7 If I bring the highest peak back to 0db which is what it appears to be on the original tape, what considerations should there be regarding the test tone? Is it imperative to bring it back to the exact same level it was at on the original tape, which was transferred from a DVCam? Thanks for all shared wisdom. Doc: It's SOP (standard operating procedure) to place bars and tone at the head of a tape intended to be submitted for broadcast. These reference levels are used to properly set levels in playback equipment. Personally, I use a Horita CSG-50, which is a low-cost device that I can recommend. It's a combination color bar (selectable split-field SMPTE or full-field bars), blackburst at +7.5 IRE (U.S. NTSC standard), sync, audio tone generator (1 kHz sinewave at 0 dBu or 0 dBV) and is also useful for blackening tapes prior to use. Horita CSG-50 http://www.horita.com/video.htm#Colo...one_Generators -- Frank, Independent Consultant, New York, NY [Please remove 'nojunkmail.' from address to reply via e-mail.] Read Frank's thoughts on HDV at http://www.humanvalues.net/hdv/ |
#12
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Whoa there Scott . . .
My analog roots may be failing me here. Or I may just not be understanding you. My operator's understanding - - as opposed to an audio engineer's understanding - - is that db is a measure of the relative difference between two audio sources. With that in mind (and correct this underlying assumption here if it's wrong) . . . . Are you saying to record the tone 20 db below program audio peaks ? Or at -20 relative to some external reference. Or some arbitrary voltage level, etc. ? In practice - - I'm a operator, remember - - when I make a tape (beta SP) for a TV station (at least a weekly occurrence at our shop here), I always reference the tone to 0, and then make sure the peak audio levels make only brief excursions into the red, never exceeding +4 or so. The audio is compressed as it's recorded, and handled well along the production chain, so this isn't too difficult at this stage. Am I doing something wrong ? I don't think so. Inquiring minds want to know . . . Steve "Scott Dorsey" wrote in message ... Doc wrote: I transferred a tape from a DVcam to add reverb. What's the purpose of the test tone at the start of a video? Should it be at any particular level? I notice the tone on the original tape show to be -8.5 on the left channel and -8.4 on the right, per the meter on Soundforge. The sound is 2-channel mono. Also, what about the short "beep" that occurs on "2" of the countdown in the leader? The tone should be at - 20dBFS for standard reference. It really only matters that nothing clips and that you dub the thing back to DV at the same level, though. The 2-beep is to synchronize sound and picture. I had to lower the level a tad when applying reverb to keep it from clipping. The highest levels after applying the reverb are about -.7 If I bring the highest peak back to 0db which is what it appears to be on the original tape, what considerations should there be regarding the test tone? Tone at -20. Always. Is it imperative to bring it back to the exact same level it was at on the original tape, which was transferred from a DVCam? Probably. It would certainly be a good idea. That's why post houses have everything set up at the same level and why there is tone on tape. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#13
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#14
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Steve Guidry wrote:
Whoa there Scott . . . My analog roots may be failing me here. Or I may just not be understanding you. My operator's understanding - - as opposed to an audio engineer's understanding - - is that db is a measure of the relative difference between two audio sources. With that in mind (and correct this underlying assumption here if it's wrong) . . . . Right. Are you saying to record the tone 20 db below program audio peaks ? Or at -20 relative to some external reference. Or some arbitrary voltage level, etc. ? In the digital world, the tone is recorded so that it is 20 dB below the full scale level at which the digital system clips. In practice - - I'm a operator, remember - - when I make a tape (beta SP) for a TV station (at least a weekly occurrence at our shop here), I always reference the tone to 0, and then make sure the peak audio levels make only brief excursions into the red, never exceeding +4 or so. The audio is compressed as it's recorded, and handled well along the production chain, so this isn't too difficult at this stage. Right. You're using an average-reading meter, and you're seeing levels 4 dB above the tone mark. This means you're seeing peak levels that are a good bit higher than that, maybe as much as another 6 dB. Remember, there is no plus-anything on the digital meter. It gets up to zero, and then it clips. So the digital reference needs to be high enough so that the tone is -10dBFS with your tape or it'll clip. Setting it at -20 dBFS gives you another 10dB of safety margin. Am I doing something wrong ? I don't think so. Not at all! You're doing things perfectly. The problem comes in that your meters are reading in a different way than the digital meters, so if you dub your tape to a digital recorder, the metering has to be set differently on the digital recorder. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#15
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Oh. That just reflects the 16 db or so headroom that analog gear usually
has. Plus an extra margin. In practice, on our 'truck shoots" when we record the camera ISO's to DV, we usually set our decks 10db down. I'm assuming that we are able to get away with it because of our extreme attention to the program audio levels and compression before it even gets to the decks. It would be very rare that we'd ever have a 10db spike. Steve "Scott Dorsey" wrote in message ... Steve Guidry wrote: Whoa there Scott . . . My analog roots may be failing me here. Or I may just not be understanding you. My operator's understanding - - as opposed to an audio engineer's understanding - - is that db is a measure of the relative difference between two audio sources. With that in mind (and correct this underlying assumption here if it's wrong) . . . . Right. Are you saying to record the tone 20 db below program audio peaks ? Or at -20 relative to some external reference. Or some arbitrary voltage level, etc. ? In the digital world, the tone is recorded so that it is 20 dB below the full scale level at which the digital system clips. In practice - - I'm a operator, remember - - when I make a tape (beta SP) for a TV station (at least a weekly occurrence at our shop here), I always reference the tone to 0, and then make sure the peak audio levels make only brief excursions into the red, never exceeding +4 or so. The audio is compressed as it's recorded, and handled well along the production chain, so this isn't too difficult at this stage. Right. You're using an average-reading meter, and you're seeing levels 4 dB above the tone mark. This means you're seeing peak levels that are a good bit higher than that, maybe as much as another 6 dB. Remember, there is no plus-anything on the digital meter. It gets up to zero, and then it clips. So the digital reference needs to be high enough so that the tone is -10dBFS with your tape or it'll clip. Setting it at -20 dBFS gives you another 10dB of safety margin. Am I doing something wrong ? I don't think so. Not at all! You're doing things perfectly. The problem comes in that your meters are reading in a different way than the digital meters, so if you dub your tape to a digital recorder, the metering has to be set differently on the digital recorder. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#16
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On Thu, 16 Jun 2005 17:32:56 GMT, "Steve Guidry"
wrote: It would be very rare that we'd ever have a 10db spike. With normal dialogue, and even a slightly excited one, that would be a safe margin, and you keep the maximum from the noise-floor. If I'm in an environment where I don't know what to expect (e.g. vox-pops), I stay at -18, while for doco-stuff with more control, I even tend to be a bit safer, and stay on -12. 16dB headroom on analogue, is a bit too much. A Nagra IV tends to keep it up till +4dB, and then the lot gets saturated. But, if analogue gets saturated, at least it's legible, unlike digital. cheers -martin- -- "Now I want you to say it thrice daily and don't dress a bun" |
#17
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Steve Guidry wrote:
Oh. That just reflects the 16 db or so headroom that analog gear usually has. Plus an extra margin. You can think of it that way. Some of the "headroom" though, comes from the difference between peak and average metering and some of it comes from the fact that the 0dB mark on the meters is not a hard limit with analogue recorders. In practice, on our 'truck shoots" when we record the camera ISO's to DV, we usually set our decks 10db down. I'm assuming that we are able to get away with it because of our extreme attention to the program audio levels and compression before it even gets to the decks. It would be very rare that we'd ever have a 10db spike. That's fine, as long as you have the tapes marked that way so when you send them to another facility their levels are correct. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#18
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![]() "Scott Dorsey" wrote in message ... Not at all! You're doing things perfectly. The problem comes in that your meters are reading in a different way than the digital meters, so if you dub your tape to a digital recorder, the metering has to be set differently on the digital recorder. Let me bounce this off you. So far I've left the test and timing (?) tones alone (they're at -8.5) and processed only the performance itself. The hottest signals on the original file are right at 0db. Well, actually there are a couple of spots where it actually clips, but for the most part they're right at 0db according to what the Soundforge meter says. I had to lower the overall level a bit to allow for the acoustic mirror processing. Then again using the volume utility, I brought the whole thing (except for the tones) up to where it peaks at exactly 0db. I used the volume utility instead of compression (Wave Hammer) to avoid altering the overall character of the file beyond the reverb. So, now the test tone is exactly where it was as they gave it to me, and the highest peaks, though in slightly different places, are back at 0db. The responses in here indicate that -8.5 is an oddball level for the test tone, but that's where they had it. |
#19
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#20
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Doc wrote:
So far I've left the test and timing (?) tones alone (they're at -8.5) and processed only the performance itself. The hottest signals on the original file are right at 0db. Well, actually there are a couple of spots where it actually clips, but for the most part they're right at 0db according to what the Soundforge meter says. A lot of consumer DV Cams have a built in limiter so you don't get "overs". When you work with a Tape on a true mixing desk (as opposed to a DAW), you adjust the trims on your audio channel inputs so that the tone coming off the tape reads 0VU on your mixing desk. Thing is that DAW's are a somewhat different paradigm than working on a classic mixer, and people learning audio on them kind of miss a stage of learning that you get from working on a real console. A lot of DAW's don't have the "solo in place" or "prefade listen" functions that a real console has either. I had to lower the overall level a bit to allow for the acoustic mirror processing. Then again using the volume utility, I brought the whole thing (except for the tones) up to where it peaks at exactly 0db. I used the volume utility instead of compression (Wave Hammer) to avoid altering the overall character of the file beyond the reverb. So, now the test tone is exactly where it was as they gave it to me, and the highest peaks, though in slightly different places, are back at 0db. The responses in here indicate that -8.5 is an oddball level for the test tone, but that's where they had it. I might label the tape "0VU = -8.5dbFS" to give a heads up to the next guy who has to deal with the tape not to take anything for granted when he does a transfer. 8.5db is about the "crest factor" that cassette tapes require, that is peak levels not exceeding the VU (average) levels by more than that. Also if you feed a -10 level device (like a consumer DV Cam's rca jacks) a +4 line level signal, what is 0VU @ -20dbFS at a +4 level now hits your -10 device around -6dbFS. So I might suspect something like that kind of "cheating levels" was happening for one reason or another when they tracked the audio on your DV Tape. Will Miho NY Music and TV Audio Guy Staff Audio / Fox News / M-AES "The large print giveth and the small print taketh away... " Tom Waits " |
#21
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#22
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On Jun 16, 2005, Martin Heffels commented:
YMMV ![]() --------------------------------snip---------------------------------- Not the UK, and not the USA. Standard levels for all digital VTRs I know of (D5, HDCam, D1, D2, etc.) have been -20 for tones for over a decade. Sony and Panasonic also put that in the manual. The BBC typically requests -18, but they're the only exception to my knowledge. Tell me the country that uses -12 and the name of the broadcast venue that asks for that level. I have seen -14 used for audio mastering tones, for creating CD master tapes, but not for video. --MFW |
#23
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Doc, please understand I am not trying to insult you, but frankly, I
don't see how you can offer yourself as an audio sweetening business if you are only now just learning really elemental basics like setting tone. This is like a roofing contractor bidding to re-do my house and asking me what the heavy silvery thing next tot he nails is for. I think maybe you're being ambitious, and rather than see you get in over your head, I think you should re-think the "business proposition" with the TV station and just work on these at a non-cash "hobby" level while you build up more experience. Shutting up now, because you're absolutely right, I don;t know you or anythign about you, but what say, i say out of genuine desire to help. |
#24
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On Thu, 16 Jun 2005 23:54:29 GMT, Marc Wielage
wrote: Tell me the country that uses -12 and the name of the broadcast venue that asks for that level. Australia, all of it. -martin- -- "Now I want you to say it thrice daily and don't dress a bun" |
#25
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Tell me the country that uses -12 and the name of the broadcast venue
that asks for that level. Australia, all of it. Not true, -14 down here. |
#26
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On Sat, 18 Jun 2005 20:43:38 +1000, "John T"
wrote: Not true, -14 down here. Where here? At the post-houses we used frequently, The Lab, Video 8, and the one whose name I always forget in Sydney, it was -12. And they told me it was -12 all over the country. Maybe I should go back and kick some arse ;-) cheers -martin- -- "Now I want you to say it thrice daily and don't dress a bun" |
#27
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"C'est un Nagra. =A0C'est suisse, et tres, tres precis."
That was a heck of a good movie. After that, I got into listening to Delibes. |
#28
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![]() "nobody special" wrote in message oups.com... Doc, please understand I am not trying to insult you, but frankly, I don't see how you can offer yourself as an audio sweetening business if you are only now just learning really elemental basics like setting tone. This is like a roofing contractor bidding to re-do my house and asking me what the heavy silvery thing next tot he nails is for. I think maybe you're being ambitious, and rather than see you get in over your head, I think you should re-think the "business proposition" with the TV station and just work on these at a non-cash "hobby" level while you build up more experience. I didn't actually offer myself as an audio sweetening business. I happened to mention to a musician friend during the course of conversation that I was transferring my family movies and video tape to DVD. When she heard this her ears perked up and she asked if I could convert a VHS tape of her performance to DVD. I knew this would be a simple enough task. When I got it, it occurred to me to ask her if she wanted me to add reverb to it since the sound was dry. She didn't realize you could do that. She was so tickled with the results that she asked if I could do the same with the master tape at the studio. I captured that first project with my DC-10 capture card. In the interim I had acquired a Digital8 camcorder. All research including a number of inquiries on Usenet indicated that it should be no problem to capture the DV cam footage It just happened to be good timing that I had only a few days earlier acquired a cam that could do it. So, I did it. Great thing about people, they have the capacity to learn. That's why I'm asking questions. Despite the fact that I had never touched a digital camcorder until a couple of weeks ago, and had never actually used the Firewire port before, and admittedly only have a peripheral understanding of the various issues involved, it's just as captured and treated using my eBay consumer digital cam as it would have been by some $200/hr production house. Keep in mind, it's a pretty basic project. I didn't have to learn to use an editing suite, just add reverb and take out a few mic thunks in the sound track using software I was already familiar with. The station manager was completely aware of all of this, I wasn't trying to pull the wool over his eyes. I was just doing a project for a friend. He actually never even mentioned the test tone issue. It's something I thought to ask about on my own. Since then, he's asked me if I want to work on some other music programs they have. He hasn't even seen the results of my first project yet. What can I say. An opportunity has presented itself. |
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