Recording multiple audio sources in realtime

[Cyber Akuma]

Pretty much all my encoding experience is either from encoding from a raw/obscure format into another more common one or recording video in realtime from a capture device then encoding it into a more common format.

Point is, all my previous encodes were from static material with one video and one audio source.

I have never actually had to use any software to edit video beyond decomb/interlace filters or cropping, I never had to add/delete different video clips together into one movie or mess with the audio track.

I want to be able to record video and on top of the video's own audio, I want to add my own audio AS it is recording, possibly from more than one mic.

I am trying to record some videogame play footage, whether it is using a Dazzle to record it off a console or Fraps/Camtasia Studio (if Fraps dosen't recognize the game) for PC games, and record my commentary on it as I am playing.

I know I could record the audio with a separate program, or even an altogether separate computer/device, but I have no idea how I would get a separate audio file that would have a different length than the video itself to sync-up correctly (its not like I would be able to hit record and stop on the video recorder and the audio recorder at the exact same millisecond).

Also, how would this work, if it can work, if I wanted to use more than one mic so two people could leave commentary?

I understand it would be best if I recorded the audio to a separate file, that way I can adjust volume levels so the game's audio isn't drowning out the commentary or is so low you can't hear the game at all, but I just am not sure how to do it. My biggest concern is getting all the audio tracks to sync up correctly, not the actual act of muxing them together (Or possibly even just leaving them as separate tracks that can be turned on or off in a mp4/mkv container file... can you set these files to allow playing more than one audio track at once?) which is why I would prefer being able to do them all at once within the same program, since that way all the audio files will be the same length and I would not have to worry about syncing them.

Typically if I need to use the Dazzle capture device I use VirtualDub in CaptureAVI mode with huffyuv, and Fraps/Camtasia for recording on-screen, then encode it with megui or virtualdub if im going to mp4 or avi respectively.

Are there any better programs I can use in this instance? Is what I want to do even possible with VirtualDub, Fraps, or Camtasia?

What would you recommend I do to be able to actually pull this off?

Also, how can I stop the game's audio from getting into the mics? I only want the mics to record voices, but I would still need to be able to hear the gameplay audio while playing.

[Ghitulescu]

Buy yourself an audio mixer....

[Skelsgard]

If you don't want to spend any money at all, I guees you could do a 2-step recording. In the first one you record the game and in the second one, your commentaries, then mix and sync the commentaries with the game audio and finally remux the audio with the video.
This can be done using an audio editor like Audacity (free) to mix and sync the audio, and VirtualDub to mux audio+video.

If you want to do that in a visual environment, then you can get a video editing software like Sony Vegas or free NLEs like LiVES (http://lives.sourceforge.net/) or ZS4 (http://www.zs4.net/).
In this case you'll be able to sync game audio and commentaries and game video all at once while seeing the results on the fly.

[Cyber Akuma]

Buy yourself an audio mixer....

There are two reasons why I can't just use a mixer:

1. I want at the very least the commentary and game audio to be separate.

2. This won't work when recording gameplay off the computer itself.

If you don't want to spend any money at all, I guees you could do a 2-step recording. In the first one you record the game and in the second one, your commentaries, then mix and sync the commentaries with the game audio and finally remux the audio with the video.

Actually, we are trying to avoid takes because we want to record commentary and reactions as they happen.

I don't mind buying extra hardware as long as the price is reasonable, but I forgot to mention that this is a laptop, so I won't be able to use any extra hardware unless it is USB or ExpressCard based.

[Ghitulescu]

There are two reasons why I can't just use a mixer:

1. I want at the very least the commentary and game audio to be separate.

2. This won't work when recording gameplay off the computer itself.



There's a third reason though :p, you probably don't know that there are mixers having more than 2 busses, usually they are coupled with so called multitrackers - they are used to record each instrument on its own track then perform the final mix as wanted.

There are also [digital] videorecorders that have 4 separate audio inputs.

[Cyber Akuma]

These multi-bus mixers sound very expensive, and clearly meant for musicians recording an entire orchestrated soundtrack or something...

And a video recorder wouldn't really help me, I am trying to get direct input from a composite or on-screen source.

[mariush]

Get a second sound card, plug it in your computer... use SoundForge or Audition to record from microphone from the second sound card (you can set the device in settings window) and the game will use the default (first) card so you'll record the game sound separately.

There are also quality sound cards (though a bit expensive) which can record from multiple sources at the same time, for example these:

http://www.newegg.com/Product/Product.aspx?Item=N82E16829121120&cm_re=m-audio-_-29-121-120-_-Product
http://www.newegg.com/Product/Product.aspx?Item=N82E16829121011&cm_re=m-audio-_-29-121-011-_-Product

So you can capture the game sound output digitally as you can route the signal from line out to line in digitally, and at the same time record the microphone..

[Cyber Akuma]

Get a second sound card

http://www.newegg.com/Product/Product.aspx?Item=N82E16829121120&cm_re=m-audio-_-29-121-120-_-Product
http://www.newegg.com/Product/Product.aspx?Item=N82E16829121011&cm_re=m-audio-_-29-121-011-_-Product

This is a laptop, I can't use those

[Ghitulescu]

There's an USB solution from Edirol, really cheap for a Roland, some 150€. Hopefully 6 channels suffice :p