ATTN rs170a - Separate Audio & Video

bbrooks wrote on 7/3/2004, 4:39 AM

Considering the issues I've had w/ the audio and video actually being different lengths due to one being an analog to digital and the other digital to digital, what would be my option with the potential problem:

I want to capture some video of a live band. Audio wise, I would like to come from the board to a different recording medium. I've noticed when using the cameras mic, the audio is very compressed and loses a lot of bass, thus recording from the board.

#1) If I go direct to the board to the camera using the stereo input will the sound be any better?
#2) If I have to record to a different medium or device what would be my best option for syncing up then considering the problems that I've had

Can you record just audio going through the camera firewire input i.e using the camera as a digital pass through and not have to record the video. (video of course taking up much more realistate on the computer is why I wouldn't want to record a dummy video track). I suppose I could record it as video and save just the audio as a new track but the initial process would still take up G's on my hard drive.

Your take on this?

Brandon

Comments

Chienworks wrote on 7/3/2004, 6:36 AM

#1 - depends on the input to your camera. If you're connecting to a mic input then the sound will probably be processed by the camera's mic circuitry (ie. squashed) anyway. Yes, it may be a little better, but not a lot. The big advantage is that you will get a good signal from the band's mics up close rather than from your mic far away. On the other hand, if your camera has line inputs then you should get a very good signal.

I don't recommend it though. If something goes wrong with the connection you will possibly end up with no audio and this wouldn't be good at all. I definately recommend :

#2 - Recording to a different device is a good idea. This way you have two sets of audio and redundancy is always a good thing. Take a look at the current forum thread about portable recorders: Sony's new CE toys... for lots of discussion in this area. It looks like the iRiver devices could be perfect for this application. Since both your camcorder and the audio recorder would be digital recordings (presumably with locked sample rates), sync should be a breeze. Find one identifiable event such as a hand clap or a big drum beat, line up the audio peak to the video frame, and the whole recording should then be in sync.

#3 - (you didn't number this one, but i'm taking the liberty ...) Vegas' VidCap utility can't do this. It will always capture the video with the audio. So yes you can capture the whole thing and then save the audio to a new .wav file. You only need the space on your drive until you've finished saving the .wav file and then you can ditch the capture. There are other capture softwares out there that can probably get just the audio.

rs170a wrote on 7/3/2004, 7:01 AM

One drawback of tying into a band's board is that if the guitars are fed to on-stage speakers only, the mix you get out of the board will be low on this part. You'll still get some sound from the on-stage mics but it won't be as good. When I've done this before, I've used a mixer myself which then feeds the camera. I'll feed it a pair of lines from the band's board as well as a pair of mics from out in the audience somewhere. Careful mixing here is critical.

Another choice, as you mentioned (and Chienworks agreed with), is to feed the audio to another device, ideally a multi-track device of some kind, although this may not be in your budget. A lot of folks have been using mini-disc recorders successfully for some time - quite often for events such as weddings which can be over an hour. If lip sync does drift a bit, matching it back up isn't hard to do at all. With a band, it's even easier because the songs are so short in comparison to a wedding.

Mike

farss wrote on 7/3/2004, 7:45 AM

If you've got the money the Fostex FR-2 is very nice looking bit of kit, soon to have the ability to record TC as well. Also Alesis make a nice multitrack HD recorder but you'll need your own mic pres as well. Nothing wrong with using the mics already on the stage if you can get them split into your own mixer as well.
I've been burnt just about every time I've used a feed from a desk. They're mixing for sound AMPLIFICATION not recording, two very different things. The only time we have it come out OK is when they're mixing for live broadcast.

bbrooks wrote on 7/3/2004, 8:52 AM

All of these suggestions are great. My concern was the sample rates being slightly off but I guess with both being digital that wouldn't be as much of an issue. I have recorded from the board to my MP3 player. The archos jukebox recorder 20g is what I've been using. It will capture at up to the 160 rate. I've only tried to sync it up once and it was a shorter show (30 min's). That is of course only a stero feed.

I have been fortunate to get good leads from boards so far (I'm in Nashville and there are a pleathora of decent sound guys and sound systems - and an equal amout of, shall we say, less skilled).

I have a firewire multi track interface and have not tried to use it live yet (MOTU 828 mk II). Can vegas record a separate set of audio track simultaneously with a separate video track being done through vidoe capture?

You are all so immensley helpful.

Brandon

Chienworks wrote on 7/3/2004, 9:04 AM

Sample rates aren't an issue. The camera's audio will probably record at 48KHz and will play back on Vegas' timeline at 48KHz. External audio may be recorded at 44.1KHz and will play back at 44.1KHz. In other words, each source will playback at the speed it was recorded at. In other other words, it's not an issue.

John_Cline wrote on 7/3/2004, 9:45 AM

Taking a mix exclusively from the live sound mixer is problematic at best. As was already pointed out, the PA mixer is for reinforcement, not recording. It's what I call the "inverse mixing rule." If the guitar player happens to be playing a bit loud that night (and when aren't they?) then the guitar will be more than loud enough coming off the stage and not turned up in the mix through the audio mixer. Generally speaking, in a smaller room, the PA mix will contain a LOT of vocals, kick and snare, then the rest of the instruments much lower in level. Obviously, the best way to do it is to record each microphone input on a multi-track machine and mix it in a studio later. Or split the mics to a separate audio mixer located in an acoustically isolated room at the venue and have a good audio engineer mix the tracks live for the video. Failing all of this, you can record the output from the audio mixer to DAT or MiniDisc AND use the out-front camera's audio in post-production to "fill in" the direct feed from the house PA mixer.

When using the direct feed and out-front audio trick, it is also important to slip the out-front audio track in Vegas to match the direct feed audio track in time. Otherwise, there will be some obvious echo if the camera's mics were more than 40 feet from the stage (anything longer than 40 milliseconds will be detected by the human ear as discrete echoes.) Having the audio lined up in time makes a very nice recording with some "room tone" without the delay mucking up the intelligibility of the audio track. Basically, sound travels about 1 foot per millesecond, so if the camera's mics were 50 feet away from the stage, you would move the camera's audio track 50 milleconds earlier on the timeline to match up with the audio mixer track and then mix the direct and out-front audio to taste. It really is a great effect when done right.

Also, strictly speaking, when using separate video and audio recording devices, even if they're digital, does not guarantee that they will sync up. The only way they would have "locked sample rates" is if they were running off the same crystal clock sync reference. However, it works more often than not.

John