Ahhh! I'm officially terrified! Recording audio do

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c.g._eads

Veteran
Okay, the scariest thing I just read about, is if you're recording audio on a seperate recording device, you must make sure that recording device is set to record audio at the same rate/speed as your camera. I'm shooting on an HV20 at 24p. What settings should I enter?

This brings me to my next question, which likely stems from your resulting question -- "What are you recording on?" The answer is... I don't know.

I'm not even sure how all this audio stuff works. You send your mic into your mixer, right? And adjust the levels there. Then you have your mixer connected to your audio recorder (which in this case will be something digital, right?) And you record your audio onto that "hard drive" recorder. And that's how you get your audio. Well, I'll probably be using one of the cheaper mixers and audio recorders then (any suggestions welcome) and hopefully that will be enough information to answer my first question - what settings should I enter in order to record at the same rate as my HV20 at 24p?

Oh, and if I change it to 60i, I would then have to change my audio settings as well?
 
Often the camera preamps are not the best, thats why we use a mixer to record for instance quieter sounds such as ambience or foley, the mixer usually has better preamps than the camera, therefore you can go into mixer then into the camera.

Second, you dont need a mixer going into the recorder unless you want to use more than one mic and hence the name "mix" the signals as one channel or seperate channels (c,r,l)

if you have a seperate recorder, and will only be using one microphone, you dont really need the mixer and can plug right into the recorder.

Sound is usually recorded at 30 frames non drop, but if you're using a 23.976 camera, then you can choose that rate on the recorder (if it supports it), most recorders now do.
 
Often a halfway decent mixer will still have better preamps than a cheap recorder... so that too can be a reason to be a mixer and recorder. Especially with the latest crop of tiny compact-flash recorders, on the low end, the preamps are the weak point.

As to the audio format matching - sounds like you're not using timecode, so you don't have to worry about those issues... and if you have a decent piece of software to do it, you can convert the output of the recorder to the sample rate of your video without much of a problem. It's an extra bit of conversion, but not at all likely to be the defining factor of your audio quality. I do this all the time with critical classical music video, and with decent conversion (I usually use ProTools "TweakHead" conversion), I see no more drift from converted 44.1 than I do with native-recorded 48... at most, a frame or so per hour.

Howeever, if you can, record at 48Khz, and you won't have to do the conversion. However, that doesn't mean you won't have to at least check for drift.. unless clocked together, audio from different devices will drift to some degree... but again, with decent equipment, we're talking a frame or two per hour.

Regardless of shooting mode (60i/24p, etc), the standard for video these days is 48Khz.
 
ullanta said:
Often a halfway decent mixer will still have better preamps than a cheap recorder... so that too can be a reason to be a mixer and recorder. Especially with the latest crop of tiny compact-flash recorders, on the low end, the preamps are the weak point.

As to the audio format matching - sounds like you're not using timecode, so you don't have to worry about those issues... and if you have a decent piece of software to do it, you can convert the output of the recorder to the sample rate of your video without much of a problem. It's an extra bit of conversion, but not at all likely to be the defining factor of your audio quality. I do this all the time with critical classical music video, and with decent conversion (I usually use ProTools "TweakHead" conversion), I see no more drift from converted 44.1 than I do with native-recorded 48... at most, a frame or so per hour.

Howeever, if you can, record at 48Khz, and you won't have to do the conversion. However, that doesn't mean you won't have to at least check for drift.. unless clocked together, audio from different devices will drift to some degree... but again, with decent equipment, we're talking a frame or two per hour.

Regardless of shooting mode (60i/24p, etc), the standard for video these days is 48Khz.
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All of this is correct, but here's a couple of additional points:

To clarify and emphasize what you said about frame rates and audio, they are entirely unrelated. Audio is sample rate based only. All you need to know to record audio that will be entirely compatible with your video, and will import directly without any conversion whatsoever is the following:

1) Sample rate, usually 48KHz for video, but sometimes 96KHz for Dolby Digital/DTS etc. Some camcorders record at 32KHz, which should be avoided if at all possible. The other choice is usually 44.1, which is usually wrong for video.
2) Bit depth, usually 16 bit, but sometimes 24 bit for Dolby Digital/DTS etc.
3) File format, usually either AIFF or WAV (or BWAV whic is time-stamped WAV).

If you can get the audio specs for the project (or camera) in advance, just set the audio recorder to the same settings. If some of the choices are unavailable, come as close as you can. The most important of the settings by far is sample rate, which will cause huge timing errors if it's wrong, and can affect quality if a poor conversion scheme is used later.

Next in importance is bit rate, in particular if you capture at 24 bit but need 16 bit in the end. Then you'd want to apply dither, which is a whole other topic. Truncating 24 bit to 16 is a no-no, but truthfully, in practice you can often get away with it. Best to set it where it should be from the start though, unless you or someone else in the workflow understands the dithering process.

File format is least important - any of them will convert quite easily to the other, including some I didn't mention like SDII. Apple's ".caf" Core Audio Format format is an exception, and can't be directly imported into apps like Pro Tools for example, which is actually a major pain, but don't get me started on that : )

BWAV can be especially handy if the camera and audio recorder are synced to one another via time code. Then the audio files can be easily spotted into the correct location in many apps like FCP and Pro Tools (PT will also do it with SDII files).

Also:

Pro Tools' "Tweakhead" sample rate conversion is among the best in popular systems nowadays (BIAS Peak is also excellent), but many lesser systems do it rather badly, like Digital Performer for example. I don't know about something like FCP, but I wouldn't expect much from it if it. Unless you have access to a quality sample rate conversion system, make every effort to record initially at the same rate as the video.
 
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Often a halfway decent mixer will still have better preamps than a cheap recorder... so that too can be a reason to be a mixer and recorder. Especially with the latest crop of tiny compact-flash recorders, on the low end, the preamps are the weak point.
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true, but thats with a cheap recorder, if you got a good recorder with nice preamps (the 702 has the same preamps as the 302) a mixer is not necessary. i did a test recording yesterday with the recorder only using a shotgun, and compared to a recording made with a mixer/recorder combo, nothing different, its amazing how quiet the 702 was while doing some foley.

A mixer is helpful when doing ms recording(302) but for a mono boom mix, going straight into the right recorder is plenty
 
Record at 16/48 and use a clapper or anything that makes a sharp, fast sound. Be sure that object is visible on camera when it smacks (even clapping your hands works).

Line up audio manually in post using your clap as a reference.

Double check that your camera is recording at 16/48... the only other setting it will have is 12 bit, but if it's still a 48 sample it may not matter. The default "best setting" is 16/48 in most cameras.

Time code is for the editor... and in this case that's you. Since most prosumer users don't have the luxury of TC anyway... don't worry about it for now.
 
Great advice guys. Killfilm, what product is the "702"? Can you give me the pros/cons between the 702 and the 302?
 
the drift is not because the frame rate but as the difference in stability of the clock between 2 devices - you can run what ever frame rate in your camera and sync everything with clapper .
dont sure the 24 p on your camera is not 23.98
also -are you editing it as 23.98 or pull up to 24

about recording to camera or not - depends on your camera - yours is probably - not
 
702 is sd 2 channel recorder with 2 preamps so you can connect the mic directly , 302 is 3 channel amp with mixing capabilities - no recording
 
ok . im a pro sound guy so I think i can help in this post.
Sound Devices 702 is the non timecode version of their top of the line recorders. It will record to flash based media in almost any applicable frame rate. the going rule for video is that if you are recording audio separately for video here is the breakdown

always go for 24 bit 48k (unless the post super says they want something else)

30fps video - record audio at 29.97
24fps video - record audio at 23.976

24fps FILM - record audio at 30fps nd

there are some variations with this and you should always check with the post super or editorial dept to make sure as there are always variations in the post gear that places use.

i have a sound devices 302 (mixer) and 702t (timecode recorder) for sale as well if anyone is looking.

thats my 2 cents.
 
rezamatix said:
ok . im a pro sound guy so I think i can help in this post.
Sound Devices 702 is the non timecode version of their top of the line recorders. It will record to flash based media in almost any applicable frame rate. the going rule for video is that if you are recording audio separately for video here is the breakdown

always go for 24 bit 48k (unless the post super says they want something else)

niot nessery for dialog recording -16/48 is more then enouth

30fps video - record audio at 29.97
29.97 as cameras do real 30

24fps video - record audio at 23.976
23 .98 not 24
24 video should be recorded in 24 ( cina alata f-900, any flahbaced camerawith true 24)

24fps FILM - record audio at 30fps nd
24 fps could be recorded 24 or 25
30nd /48.048

23.97edited as 24 could be recorded 29.94 /47.952
thats you work in the states doesnt mean you should get uncomplite unswears

there are some variations with this and you should always check with the post super or editorial dept to make sure as there are always variations in the post gear that places use.

i have a sound devices 302 (mixer) and 702t (timecode recorder) for sale as well if anyone is looking.

thats my 2 cents.
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my 2 shekels from the pal world
 
Ted Spencer said:
Next in importance is bit rate, in particular if you capture at 24 bit but need 16 bit in the end. Then you'd want to apply dither, which is a whole other topic. Truncating 24 bit to 16 is a no-no, but truthfully, in practice you can often get away with it. Best to set it where it should be from the start though, unless you or someone else in the workflow understands the dithering process.
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Most software used for sound mixing these days will handle 24-bit audio and have some facility for dithering, so it's best when possible to capture at 24 if you can, and get the associated benefits.



Killfilm - the preamps in the 702 may be good (I'm sure they are, though I haven't tried 'em) - but they're not "the same" as in the SD mixers - they're SD's "next generation" preamps... (no transformer...)
 
this is a direct reply from sound devices

​
"The 302 has extended functionality for processing that the recorders do not include. For an example, panning(like you mentioned), but also faders in addition to course gain, multiple phantom powering options, analog outputs, camera returns, and a slate mic. These are just a few of the options available on the 302. Depending on the application, not all functionality might be utilized, so it really depends on your individual needs. We try to cover as many bases as possible.​
Thanks"​


Sound Devices LLC​
 
c.g._eads said:
Great advice guys. Killfilm, what product is the "702"? Can you give me the pros/cons between the 702 and the 302?
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As Oleg said. Just adding a note, in many pro audio situations BOTH devices (or their equivalents) would be used. Mics would feed to the 302 (mixer) to take advantage of its superior preamps, limiters, level controls, etc. The 302 would in turn send mixed stereo line level audio the 702 (recorder) for the actual recording.
 
Steve House said:
As Oleg said. Just adding a note, in many pro audio situations BOTH devices (or their equivalents) would be used. Mics would feed to the 302 (mixer) to take advantage of its superior preamps, limiters, level controls, etc. The 302 would in turn send mixed stereo line level audio the 702 (recorder) for the actual recording.
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I don't know about "superior" preamps - someday, hopefully I'll have a chance to test; or maybe someone else can report. SD claim the ones in their recorders to be a next-generation, better design. I'm not sure either of the difference in the limiters, either... anyone have a comment? The 302 certainly has some benefits as stated in the SD quote above, but I don't think sound quality and limiter performance are among them...
 
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i prefer the 7xx preamps , the only ***** is the meter bar graph resolution
i often work with 744 directly to camera if i dont need more then 2 inputs and check the return on channels 3 and 4 inputs - so if you have a perfect match on the meters you not really need to go and actually listen to returns
 
ullanta said:
I don't know about "superior" preamps - someday, hopefully I'll have a chance to test; or maybe someone else can report. SD claim the ones in their recorders to be a next-generation, better design. I'm not sure either of the difference in the limiters, either... anyone have a comment? The 302 certainly has some benefits as stated in the SD quote above, but I don't think sound quality and limiter performance are among them...
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You're probably right about the relative quality of the preamps in SD's mixers and recorders. I was thinking more in terms of generically why you'd interpose a mixer if the recorder already had mic inputs.
 
To go back to the original question for a moment. Despite all the various numbers there are only two speeds (well three sort of with PAL), Film speed and video (NTSC) speed. Drift on any modern recorder is going to be insignificant in all but the most extreme cases. The time code settings only make a difference if everyone is using TC and it can be used in post. Also if everyone is on the same TC it is a bit easier to find related material. If your shooting video AND your staying in video OR your shooting in film and staying in film everything is cool. THe one exception would be some strange scenario where you were working in (true) 24 frame video for some reason. The trouble comes when you switch from film to video because there is a speed change. The change is a bit different in PAL than it is in NTSC but the concept is the same.
The confusing part comes because current video format names often don't reflect reality. For instance 24p (with a few exceptions) does not run at 24 FPS (film speed) it runs at 23.976 FPS (video speed). 30 and 60 whatever do not run at 30 FPS or 60 FPS (long story but this also translates to film speed) they run at 29.97 FPS (video speed).
The jist is if your shooting video and your not going to film 99.999% of the time you should be at 48k and whatever TC matches the video folks. If your shooting Film the same is true (swap film folks for video folks). If you shooting one format but going to the other it gets complicated and everyone needs to sit down WITH the post folks and decide how to shoot it. You will most likely record audio at some "pull up (down)" rate in this case. Which depends on which direction things are going. And depending on when they make the conversion you may not have to do anything special.
 
rezamatix said:
ok . im a pro sound guy so I think i can help in this post.
Sound Devices 702 is the non timecode version of their top of the line recorders. It will record to flash based media in almost any applicable frame rate. the going rule for video is that if you are recording audio separately for video here is the breakdown

always go for 24 bit 48k (unless the post super says they want something else)

30fps video - record audio at 29.97
24fps video - record audio at 23.976

24fps FILM - record audio at 30fps nd

there are some variations with this and you should always check with the post super or editorial dept to make sure as there are always variations in the post gear that places use.

i have a sound devices 302 (mixer) and 702t (timecode recorder) for sale as well if anyone is looking.

thats my 2 cents.
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Good info but it could be a bit misleading to say "record audio at xx.xx". That implies some kind of speed sample rate relationship, and there is none. Your recording "time code at xx.xx" not audio. A bit nit picky but folks are constantly getting TC and speed confused so I think it's important to be extra clear.
 
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