What Audio Levels are best on the XH A1?

[Stuart Graham]

Does anyone know what range you should aim to keep the audio level bars between on the Canon XH A1?

For instance if you are recording a normal conversation what should be the minimum number of bars you want to see for quiet speech and what is the maximum number of bars you want for the loudest speech?

And what should be the maximum number of bars for very loud sounds like shouting, gunshots or a glass smashing?

The reason I ask is that I don't want to have distorted loud sounds or to have to boost the volume in post-production on quiet sounds and pick up background hum.

Thanks!

[Mark Fry]

Audio levels need to be adjusted to make the most of the sound information, whether loud or soft. Try to make the level meters peak without lighting the last (right-most) segment. You can't just set them and forget them. As with everything, it depends on what you are shooting and what sort of a crew you have.

As discussed in this thread, adjusting the XH-A1 audio level controls while shooting is too fiddly to be practical. If you are shooting on a well-controlled set, you can re-adjust the levels during the rehearsal of each scene. However, if you are running and gunning, so-to-speak, you have three choices:
1) Use Auto. As these things go, the XH-A1 ALC is not bad, and it's the safe option. This is what I usually do. In noisy environments, such as a factory or a busy city street, try switching in the MIC ATT, too. However, it's usually possible to improve on what ALC gives you (as with most Auto functions), provided you've got enough hands!
2) Feed one mic into both channels and set different manual levels on each, one for "normal" sound, the other for loud sound. In post, use the "normal" one unless it's distorted, and hope the "loud" track is OK throughout. You'll still have to keep a careful eye on the levels and adjust as you go along, but at least you have a bit of a safety net. (This will work with the internal mics too, so long as the source is more-or-less in front of you.)
3) Get a mixer with limiters, which attenuate loud sounds, like ALC, but without boosting things when it's quiet. The SD302, which is a proper portable mixer with a lot more to offer than just limiters, seems to be the bees knees, but it's not cheap. Somewhere I've seen a smaller gadget that bolts under the camera, possibly a version of the famous "Beechtech" box, that provides in-line limiters between the mic and your camera. This only works with external mics.

The position of your mic relative to your subject can make a huge difference to your levels, as well as to the quality of the sound (reverb, etc.) If you hear things distorting, take a couple of steps away. If it's too quiet, get in closer (consider using a lapel mic?)

The "pro" solution is to hire a sound operator, with a boom, mixer and headphones, but good ones are not cheap.

One last thing - wear headphones, preferably good ones that will let you hear when the audio starts to distort, so that you can shout "cut", or at least adjust the dials a bit.

BTW I'm no expert. This is basically advice I've picked up from the DVi audio forum and similar places. As I say, because I work by myself 99% of the time, I stick to ALC. I always use headphones, though, just to be sure.

[Bill Pryor]

Good info. I think Stuart was asking about specific levels. I try to keep voices between a -20 and -12, letting things peak up to about a -6. With most DV/DVCAM cameras I used in the past, I never peaked over about a -10, but this one seems to have more latitude. For really loud sounds, like applause. car horns, etc., you could probably let them peak at close to zero. The meter in the VF only gives you bars and a little green dot at -12; check the side readout for real numbers.

[Stuart Graham]

Thanks Mark and Bill. That's just what I needed.

Bill: I didn't realise there were audio levels on the side panel readout, I haven't really looked at it before. I'll look when I get home.

Is zero where the red bar is on the viewfinder monitor?

Mark: I have someone doing sound, but they are not trained. But we will have time to do audio tests before filming so I'll do it that way and adjust gain with the wheel on the camera. We don't have a mixer I'm afraid, can't really afford one, but we do have some good headphones at least to listen for distortion.

I notice the levels you suggest are very different to those I have been suggested to use in Adobe Premiere with speech between -6 and -3 db, background music at -18 to -12.

You can find this info in the following thread:

http://www.dvinfo.net//conf/showthre...848#post930848

Is this just because the Premiere and XH A1 audio volume scales are different?

[Stuart Graham]

I didn't know the dots on the XH A1 audio level meter correspond to the units on the side display panel. Thanks for that Bill. Now I know what each dot signifies it will be easy to monitor the audio and get the levels right!

[Tripp Woelfel]

One caveat about using ALC on two different sources. The A1's ALC will tie both channels together somewhat. By that I mean a very loud input from one channel will drive down the audio on the other. I know this from experience.

I tried ALC once whilst shooting races. Track announcer on CH1 and race ambient on CH2. Worked OK when the little 4 pots were running, but when the big V8s came out, it lowered the announcer volume when the engines got loud.

Not saying your shouldn't use it, but you might want to test it out in your conditions before you commit to it.

[Ivan Mosny]

The ground idea is always to record as loud as possible. -6dB uses only a half of the possible dynamic range (this is logarithmic scale) and resolution of 16 bit. -12db only a quarter of them.
There ist always a quantisation noise and noise from mic preamp etc. It is important to record with highest amplitude to have a greater difference to noise amplitudes.
So if you record voice to 0dB - ist qauntizated always to one of the 65535 levels of 16bit resolution.
If you record the some voice to -12dB - you use only a quarter of the amplitude an you have only 16383 levels of quantisation.
Due to this uses recordings studios 24bit resolution. To have enough resolution with lower audio levels and bigger precision with postproduction.

[Stuart Graham]

Thanks Ivan. You've explained that very well. I had no idea you lost audio resolution at lower volumes. So basically you need a high signal to noise ratio. Will try to record as loud as I can without hitting the dreaded red -0 dB!

[Bill Pryor]

Make sure you listen carefully for distortion going that high.

[Stuart Graham]

Will do.

Cheers Bill.

[Jeff Kellam]

Those are a lot of great reasons to use a 24 bit digital audio recorder with a limiter.

But the XHs usually work just fine. If Canon just incorporated a really good limiter, it would really be great.

[Ivan Mosny]

Originally Posted by Jeff Kellam

Those are a lot of great reasons to use a 24 bit digital audio recorder with a limiter.

With 24 bit recording you have a lot of reserve of dynamic range - compare to 65536 levels of 16bit - there is over 16,7 millions of quantisation levels by 24 bit. You don`t really need a limiter for recording. Recording "safely" to -12dB in 24bit makes still better quality as 16bit at maximum level.

[Stuart Graham]

24 bit sounds like the way to go. Will think about getting a 24 bit audio recorder for the next film. I guess they are rather expensive?

What do they record onto? Hard drives?

[Richard Gooderick]

Originally Posted by Stuart Graham

24 bit sounds like the way to go. Will think about getting a 24 bit audio recorder for the next film. I guess they are rather expensive?

What do they record onto? Hard drives?

Hi Stuart
I use a Fostex FR2 LE which isn't ridiculously expensive for what it is - about £360. It records to standard flash cards (but you need to get one that's on their recommended list).
If you decide to go down this route it may be worth buying a Tamiya battery (from a model shop - used for toy cars etc) and charger and 8GB flash card. That adds a lot to the cost (another £120 or so I think) but it means that the recorder will run for 8 hours without charging or changing the media. That's what I did.
I used it to record a double bass at close range - a notoriously difficult thing to do according to the engineer at Fostex because the lower frequencies are massive - and got a slightly muffled result.
However I got a sound engineer to look at it he pulled the rabbit out of the hat and produced an excellent end product.
I think he could do this because I recorded 24 bit.
The only fly in the ointment is that Jay Rose in his excellent book 'Producing Great Sound for Film and Video' refers vaguely to thousand dollar units by Tascam and Fostex and says 'These prosumer units have fewer features; and while they boast 24-bit recording, our measurements have shown this mode to sound about the same as 16-bit when you use their analogue inputs'.
(expletive deleted) marvelous.
It's a minefield buying sound kit. It's so technical and so much jargon and so much of what you read is contradictory.
I buy what Ivan says above.
I hope Jay Rose is wrong (in this case he seems to be from my experience).
I've been meaning to post a thread about this and will now do so as it seems appropriate to start a new one rather than take this thread off at a tangent.

[Ivan Mosny]

There is a lot of external USB an Firevire 24bit Soundcards to use with laptops.
For "portable" use i am working with little Behringer mixer with integrated Soundcard and CAD condenser Microphones.