MoviePlus X5: Audio Levels

[mac]

After some horrifying results with Cello and Guitar on a DVD I realised my audio levels were too high.
The help file suggests peaking at -20Db which is way down in the green area of the levels meter. Should they really be that low?

[ericlnz]

Interesting question which I've searched several times for answers on. There appears to be mixed opinions. Some say you should always record with a peak that low whilst others say keep it below zero. In MVPX5 I keep my peak at around -0.5. Played loud on big speakers my audio is no better or worse than others. When I play my DVDs on my TV my volume comes out around the same as digital TV broadcasts and at the same volume as commercial DVDs so presumably I cannot be doing it wrong. However occasionally I come across some commercial DVDs which are recorded very low with the result I have to turn my TV way up.

No doubt there are some audio experts on the forum who can comment.

Eric

[chrsbrss]

I just started volunteering at a local Christian Television station and edit material for broadcast. When we adjust the audio we have our peaks at between -14 and -16. I also thought that seemed awfully low but when I applied that same philosophy to MoviePlus, I have found that when I save material to be streamed to my Television that the audio sounds much better that way.

[DeanLach]

Originally Posted by chrsbrss I just started volunteering at a local Christian Television station and edit material for broadcast. When we adjust the audio we have our peaks at between -14 and -16. I also thought that seemed awfully low but when I applied that same philosophy to MoviePlus, I have found that when I save material to be streamed to my Television that the audio sounds much better that way.

Hi, I'm putting together a project for broadcast as well as distribution on other venues. I'm wondering what advise you have for audio. For example, if I try to keep my audio between a level of -14 and -16...when I output and then deliver the movie file to aggregators, will the audio be "legal" for broadcasters???

[ericlnz]

Originally Posted by DeanLach Hi, I'm putting together a project for broadcast as well as distribution on other venues. I'm wondering what advise you have for audio. For example, if I try to keep my audio between a level of -14 and -16...when I output and then deliver the movie file to aggregators, will the audio be "legal" for broadcasters???

There is a heap of discussion over this on the web. Try these for starters.

http://en.wikipedia.org/wiki/Broadcast-safe
http://community.avid.com/forums/p/68675/384155.aspx
http://www.lafcpug.org/phorum/read.php?1,193504,193534

The short answer is probably check with your broadcaster to see what their required audio (and video) specs are.

Eric

[chrsbrss]

I would think that those levels would be fine, If it isn't, it should be of sufficient quality for them to make any tweaks they need to make for broadcast.

[Greyfox]

Originally Posted by mac ..The help file suggests peaking at -20Db which is way down in the green area of the levels meter. Should they really be that low?

Mac,
The figure of -20dB which appears on page 146 of the PDF user guide for MvPX5 was not present in the user guide for MvPX3. In the MvPX3 guide it simply made the point that the loudest part of your audio clip should be set to peak below 0dB.

I'm temped to say that -20db might be a typo, because for me that's too low. I normally aim to peak mine at around -3dB, so perhaps it was intended to be -2dB, not -20dB.
That said, I also consider what is happening at the other end. Sometimes I find that the dynamic range of a clip needs to be reduced so that the volume at the lowest level is still acceptable when the max level is at -3dB.

The older I get, the more I find I'm having to jack up the bottom end. I guess that should be telling me something.

[mac]

My googling shows differing opinions- but it seems making it a bit lower is better than making it a bit louder.
Ian M - re jacking up the bottom end:-
plastic surgery for a butt lift is more expensive than paying someone to walk behind holding it up!

[jamesf]

If you are recording your musical instruments along with the video you have little control.
I would suggest a separate microphone/s to record the soundtrack into an audio application such as Audacity, wherein you can make level adjustments. The best 'effect' in an audio editor, for your 'low bottom end' is compression. This has the effect (in simplification) of controlling the top end whilst boosting the lows.

JamesF

[AlfredP]

Originally Posted by jamesf If you are recording your musical instruments along with the video you have little control. I would suggest a separate microphone/s to record the soundtrack into an audio application such as Audacity, wherein you can make level adjustments.

Although there are advantages to the 'separate microphone/s' approach, James, there's no reason why you couldn't export the audio from MoviePlus, edit it in Audacity and then bring it back into MvP. Just a thought.

Alfred

[RichardS]

Originally Posted by AlfredP Although there are advantages to the 'separate microphone/s' approach, James, there's no reason why you couldn't export the audio from MoviePlus, edit it in Audacity and then bring it back into MvP. Just a thought. Alfred

I think that the problem here is that most (non professional) camcorders and audio recorders use automatic gain/level control. These must always be a compromise and will not suit all types of sounds.

Something recorded at too low a level can be boosted, although this will also boost any noise etc.

Something which overloads the recording circuits will remain distorted... rather like a photo where the whites are "burnt-out."

I remember long, heated discussions about the relative merits of different types of level and VU meters.

[opampman]

One of the problems if you are encoding to AC3 or Dolby Digital sound is the setting for Dialogue Normalization and Dynamic Range Compression. Many programs allow you to vary these settings when rendering for DVD. Here is a link to some reading on the subject that, if nothing else, explains what you are dealing with when encoding for a DVD:

http://www.hometheaterhifi.com/volum...on-6-2000.html

Kent

[mac]

In my recording of the cello guitar duet I used the camera's built in stereo mike and a standalone (mono) flash mike with great recording quality.
I added both sources as separate tracks and got them in sync.
The mike got a good sound from the cello and the camera seemed to get a nice bright sound from the guitar.
I played with the track volume control to find a balance which seemed to my inexperienced ear to work well.

[GoneToPlaid]

I would suggest setting the audio level such that peaks are between -3 to 0 dB in order to prevent clipping of loud sounds. Different audio codecs handle clipping differently and sometimes horribly. And needless to say, exporting with the audio set to 16-bit instead of 8-bit provides much greater dynamic range for the audio portion of your exported video.

[ohernie]

The question is: How quiet is your recording device?

Cheap chips have allowed the cheapest dedicated recording devices to be 16 bit/96 db. The old thumbnail for "hifi" was anything above a 60db s/n ratio. 72 db is superlative and you don't need to go beyond that for recording. In fact, unless you have access to an anechoic chamber or a wind tunnel with a jet engine you'll probably never record in a room that has a 72 s/n ratio.

At the same time digital, unlike analog, is absolutely unforgiving of overloads. Exceed the input by one bit, 1/65536th of the full scale, and you get a loud unmusical "clack".

I've learned the hard way to stay low, yes, as in 15 or more db, even though it runs agains my "analog" mind. Again, remember that one "clack" and your video is destroyed. Remember too that as performers get warmed up they get louder, so that 10 db margin you had when they started is going to shrink to five. And if they get excited ... one hard bow on the cello is all it will take.

The bottom line is that the modern solid state recording devices, like the Zoom H1 that I have, are dead quiet so how low you go doesn't really matter much. I often record in 24 bit mode (actually 22 bit s/n). I then chop off any start and end transients, normalize and convert to 16 bits. That way I can have a large safety margin.

Note that camcorders may not be so forgiving. I've seen reports of high end camcorders with motor and handling noise. That annoyance would set the lowest level you can record.

You will need software, like Audacity, that lets you normalize the audio, that is, adjust the volume so the highest peak is at or near "0". I'm actually shocked that MoviePlus doesn't include a function that scans the audio and set the gain accordingly (hint, hint). I would normalize before applying compression.

Compression is another can of worms so I would suggest taking a short class at Google U before messing with it.

My $.02

[opampman]

I would suggest not using normalization, especially at the default 0dB setting. This leave no room for equalization or other track adjustment. In fact, the normalization tool in Audacity or any program for that matter is of dubious use. All it does is raise the track level of the highest peak to the normalization setting. Compression and limiting is much better and,as suggested, educating yourself on the use of these two tools is wise. When dealing with voice, I suggest the free "Levelator". It is an amazing tool for voice (and actually works on some music tracks, but be wary of routinely using it for music. It's available here: http://www.conversationsnetwork.org/levelator

Kent

[DeanLach]

Thanks Eric and Chris. The articles Eric refers to are old and refer to analog, so although the discussions are interesting, I'm wondering if the specs are up to date.
I've decided to use MP's vol meter. It indicates when audio peaks, so I'll try lower the volume of my audio under 0db, with consideration towards a peak ranging -11 to -14 unless another point of fact sways me different.