Audio Help !

[John Benton]

I am doing a job
& keep having audio problems...
obviously I am not understanding something.
It most probably is an H1 problem (but might be a Final Cut thing):

I have recorded a scene
with a wireless mic and Boom coming out of the XLR's (16bit 48khz HDV)
when I press the Audio Monitor on the side of the Cam it shows no signal for 1 &2
but a full signal the next time I press it for 3 & 4
and also for 1/3& 2/4
Though I know the audio monitor has no baring on what is pulled in Final Cut

When I do pull it into Final Cut
the sound is barely there. It's not really a level thing.

The sound Is In the Camera I am just having trouble getting it into FCP
Does this make any sense?

Help !
Thank You,
John

[Daniel Epstein]

Hey John,
It is possible you recorded on 3 +4 and Final Cut is only picking up 1+2. I am not sure how to get Final Cut to pick up the audio from 3+4 but it might be in Log and Capture settings. See Page 157 of XLH1 manual to see about how the routing works on the camera. Depending on your set up you might need to digitize the audio from 3+4 channels using the RCA outs and keeping the monitor switch set to 3+4. If you are seeing a level but not hearing anything in Final cut . It possible there is a phase issue between the wireless mic and boom so you should try and listen to single channel at a time and see if you can hear the audio in Final Cut. HTH

[John Benton]

Thanks Dan,
Yeah the audio is on 3&4 but Final Cut is evasive here.
(I posted something in the FCP forum...)

and I am wondering if there is anything on the Camera (like the audio monitor switches back between the 4 channels - though no Firewire output)
to chose what you send

I found nothing in the manual...

How do people record 4 channels of audio (say you want 2 Lav's AND the on camera mic) ??
48khz & 16bit
it seems 4 channels only is a 32Khz option
correct?
but doesn't HDV need to be 48khz?

?
ugh

[Daniel Epstein]

You should check out this Apple Support Search. It looks like Final Cut only captures 1+2 Audio channels unless you have the third party HDSDI board. You will probably have go in analog from the RCA's or some other workaround. Sorry

http://support.apple.com/kb/index?pa...HDV%20%20Audio

[John Benton]

Dan, Thank You!

How do you work with 2 XLR's (wireless lavs & Booms) AND the on Cam mic?
Do people Use the 4 Audio channels > 2 channels with FCP?

John

[Daniel Epstein]

Hey John,
You should just forget about the cam Mic or get an external 4 track recorder or switch to a different format camera like DVCPRO 100 which does allow you two external xlrs plus the internal cam mic or the internal slot radio mic. Of course this raises the cost compared to the the XLH1.

Dan Epstein

[Dave Gosley]

Hi Guys, sorry to interlude but you raised something interesting which brought the question to me.
Canon obviously designed the camera to be able to record 4 channels of audio and I could be forgiven for thinking their folks would have taken into account the quality of the audio being recorded would be required to be representable if not good when using the camera in SD or HD.

Can the ear tell the difference between sound recorded at 48Khz and 32Khz (I'll forget the 16Bit stuff as I believe that is purely computer tech) and is it really that important to an audio visual production as opposed to an audiophile product such as a Super CD?

As normal CD audio is recorded at 44.1Khz I would have thought the 32Khz stuff is still going to be very very good - or Canon would not have been able to pass it for use with the cam. I know others will say that Super Audio CD is at 96Khz etc but is this necessary for those of us using a Canon XL-H1?

The other thing of course is "TRY IT". Go ahead, try recording at 32Khz while in HD mode with four mics plugged in and see what you get. This of course does not get over the possible problem of audio not being configured 100% on the receiving computer.

Hope you don't mind me putting in my pennyworth and that it is seen to be constructive.
regards
Dave..

Originally Posted by John Benton

Thanks Dan,
Yeah the audio is on 3&4 but Final Cut is evasive here.
(I posted something in the FCP forum...)

and I am wondering if there is anything on the Camera (like the audio monitor switches back between the 4 channels - though no Firewire output)
to chose what you send

I found nothing in the manual...

How do people record 4 channels of audio (say you want 2 Lav's AND the on camera mic) ??
48khz & 16bit
it seems 4 channels only is a 32Khz option
correct?
but doesn't HDV need to be 48khz?

?
ugh

[Mike Teutsch]

Read most all of the posts, but did not see the answer posted.

Most NLE's do not capture channels 3 & 4. You will need to use a third party solution such as Scenalizer to get 3 & 4.

Mike

[Grayson L. Wideman]

You need to get into the theory of digitally representing an analog audio signal. The sampling rate will decide the highest audio frequency you can record using the system, this frequency will be no higher than ½ the sampling frequency. Any audio with a frequency higher than this will result in the production of artifacts called aliases. These are rightly regarded as noise and are not harmonically related to the source frequency. To prevent the input Analog to Digital converter from seeing audio frequencies beyond the maximum allowable frequency we use a low pass filter called an anti aliasing filter, these are very steep skirted filters. When a filter has deep skits it will ring if it is fed the right frequency, in the case of a low pass filter this will be high frequencies in the neighborhood of its cut off frequency. That is why both the CD and the DV/HDV formats use a sampling rate in the 40,000 Hz range. The bit depth will determine the available dynamic range of the recording.
A sampling rate in the 40 to 48 kHz range will allow for recording a pretty good representation of an audio signal with a maximum frequency of 20 kHz. Yes this is more than the range of the human voice when you look at the fundamentals and the principle harmonics. It is more than the range of most known musical instruments. But if you look at the envelopes of the sounds you are recording you will find many with very steep rise times. To accurately represent these transients you might need to go to even much higher sampling rates. This is part of the reason you should back off your input levels when recording things like drums that have a high peek to average ratio.
The reason that camcorders will record 2 channels using 48 kHz/16 bit and 4 channels using 32 kHz/12 bit is that is the DV and the HDV specification. The specification was developed to use the amount of data that can be recorded on the tape used in the systems.


Grayson

[Don Palomaki]

Can the ear tell the difference between sound recorded at 48Khz and 32Khz (I'll forget the 16Bit stuff as I believe that is purely computer tech) and is it really that important to an audio visual production as opposed to an audiophile product such as a Super CD?

A good ear (e.g., that is young and not suffering from the hearing losses associated with aging or abuse by too much loud sound) can, depending on the program material and the reproduction system. The 32 kHz/12 bit sound is roughly equal to the of typical FM broadcast sound and better than the reproduction capability of most typical home TV sets, and probably as good as much of the commonly used field-recording gear such as wireless mics and popular moderate cost shotgun microphones.

The trick is to establish a good quality balance among all of the elements in the sound capture and reproduction chain. FYI, the optional Hi-Fi digital audio track associated with Hi8 recording was 32 kHz/10-bit.

32 KHz/12-bit was the default audio mode for many MiniDV camcorders, and offered the ability to dub in sound later - a capability seldom used I suspect. The Canon XL series was one of the few that offered the capability to do 4-channel recording when shooting - a nice feature for some event work.

[Nick Hiltgen]

I'll double check when I get back into the studio but I'm pretty sure when you open up the capture window in FCP there's a section that let's you choose audio or video and with video it should let you choose tracks 1+2 or 3+4 maybe I'm making that up I'll look and let you know.

[Per Johan Naesje]

You need a capture card attached which support multiple track capture to make this possible. With firewire capture there's only 2 channels audio available!

[John Benton]

exactly.
I went through the manual where they show a picture of this, but not having a card attached it wasn't accessible to me
:(
Alas,
How am I going to get sound recorded in channels 3&4
to be the 2 that Final Cut sees?

I recorded the sound out separately via the headphone jack into Quicktime
but it sees to be slightly out of sync with the 24F
?

What if I down-converted in camera (now that I have the HD Video files)
would that be a possibility?

Thanks,
John

[Per Johan Naesje]

Originally Posted by John Benton

How am I going to get sound recorded in channels 3&4
to be the 2 that Final Cut sees?

John,
I think the best solution for you will be to get a capture card with this future built-in! Blackmagic or Aja cards will do, but they ain't cheap!

I think this thread has been more fcp specific than xlh1, so it maybe vice to move it over in the other forum?

[A. J. deLange]

Originally Posted by Grayson L. Wideman

... artifacts called aliases. These are rightly regarded as noise and are not harmonically related to the source frequency.
Grayson

Aliased energy is harmonically related to the source. If you put in a sin wave at ff + delta Hz where ff is the folding frequency (half the sampling rate) it appears (aliases) as a sin wave at ff - delta Hz. That's why it's called aliasing. The fact that aliasing has the same envelope as the signal being recorded is one of the most annoying (IMO) things about it.