USB Audio Input??? - Feature Requests - CHDK Forum
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USB Audio Input???

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Offline cybercom

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USB Audio Input???
« on: 30 / March / 2008, 22:08:42 »
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Although we haven't ported the TX-1 as yet, when we do (ever the optimist) one feature that would be absolutely brilliant would be the ability to record audio through the USB port when shooting video.

As with most of these smaller cameras, the audio is subject to all the problems of onboard microphones - handling- and wind-noise and distance from the source.

There are great USB Mixers available that would enable high quality, multi-mic mixing using wireless mics, shotgun mics etc. if the USB datalines could be accessed during recording.

Any ideas...??
« Last Edit: 30 / March / 2008, 22:11:40 by cybercom »
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Offline Sterling

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Re: USB Audio Input???
« Reply #1 on: 02 / April / 2008, 21:22:14 »
Brilliant suggestion!
I don't know why that never even occurred to me. That's one of the biggest complaints about the TX-1; the lack of an external mic jack for such a great camera.
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Offline Barney Fife

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Re: USB Audio Input???
« Reply #2 on: 03 / April / 2008, 01:32:02 »
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« Last Edit: 22 / April / 2008, 16:03:45 by Barney Fife »
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Offline jetzt

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Re: USB Audio Input???
« Reply #3 on: 03 / April / 2008, 09:20:42 »
And again someone should correct that, the first real HD cam was also done by a total newbe.
(Ok we have to say for fairness, that he had himself some money to invest and so it was much easyer to convince the other investors...)  :D
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Offline cybercom

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Re: USB Audio Input???
« Reply #4 on: 03 / April / 2008, 17:42:30 »
Barney Fife,

There are already many USB-interface mixers.

Usb Mixer - Compare Prices, Reviews and Buy at NexTag - Price - Review

They are not using the voltage lines 1 & 4, but rather the data lines - 2 & 3. The cameras can already upload and download images and they have onboard audio recording capabilities, so it is not a question of speed of the USB data lines really. USB 2 is about the same as IEEE 1394, aka Firewire, and that's used for DVCAM video all the time.

The A-to-D conversion you speak of is already taken care of by the mixer and all you have to do is simply (??) route the incoming bit stream to whatever buffers are normally used by the output of the ON BOARD A-to-D converters used by the ON BOARD analog microphones.

Something like:

Using CHDK, intercept the output of the on-board converters and replace it with the incoming data from the mixer through the USB Port. Basically a driver. The one difficulty might lie in synchronizing the clock, but since (at least my) cameras will already handle 44.1-kHz, 16-bit, stereo, there exists a standard interfacing.

Might have to buffer the input with the audio buffers and re-read the bytes (words?) to spit them out properly, but as long as they are recorded, frame accurate sync wouldn't be a concern as the tracks could always be slipped a frame or two in an editing program to compensate for any buffering delay.

I don't believe the audio is interleaved with the video, but that might be different depending on the camera involved.

Anyway, I think it could be done and it would add a great capability.

 
« Last Edit: 03 / April / 2008, 17:46:05 by cybercom »
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databoy

Re: USB Audio Input???
« Reply #5 on: 05 / April / 2008, 05:49:11 »
Regarding audio recording. The professional recording studios use computers to control the audio console. The actual processing is done by high quality A to D converters. The sound cards in Windows computers are too primitive to process high quality audio. They are designed for gaming. The audio amps and A to D converters are low quality. If you want to look at the audio recording aspect Google DAW - Digital Audio Workstation. There are plenty of professional sites which explain the recording processes.

If you want to record decent audio, on the cheap, do what the TV studios do. Use a high quality recorder and decent microphones. Record the audio through your camera as well as tape. You can use VirtualDub to synchronise the audio. If you want to spend the money try Sony Vegas Pro.

The Doom9 Forums have an active discussion on audio and video processing.

Doom9's Forum - Powered by vBulletin

It is probably the best place on the net to start.

Personally I think that people are trying to extract blood out of a stone by using the A to D chip in the camera. It would be better if someone can work out a way of synchronising the camera and the audio recorder using a PICAXE chip.   
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Offline cybercom

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Re: USB Audio Input???
« Reply #6 on: 06 / April / 2008, 00:26:19 »
databoy,

I think you missed something in my previous post. I'm not sure how an automated DAW relates to recording audio in the field.

The 44.1kHz, 16bit stereo format (CD quality standard) the TX-1 camera is capable of is more than sufficient for original capture of dialog and sfx. Using an external USB mixer to feed the camera would allow much higher quality and provide many additional advantages as well.

If you read my post, I'm not suggesting using the camera's A-to-D converters but rather bypassing them altogether.

I've worked as a professional location sound mixer for decades on features, documentaries, over 2500 commercials, etc, etc, etc. I've used ProTools, Sound Forge, Sonar and a number of other programs in  conjunction with my AVID and am pretty familiar with decent microphones as I own over 250 of them including Schoeps, Neumann, Sennheiser, RCA ribbon mics, Lectrosonics wireless, etc.

FWIW, there are numerous professional quality soundcards using balanced XLR, optical, S/PDIF or AES/EBU digital I/O that work just fine with Windows. But again this has nothing to do with my feature request.

While double-system recording, as you suggest is indeed a possibility, the ability to record directly into the camera eliminates a number of time consuming post production steps.

And, BTW, I don't know of any TV studios here in NYC that record to DAT or any kind of audio tape any longer. Everything is either single system video or digital capture. No one has the time to playback a tape in real time just to capture the audio. They'll still do it for video if they have to, but they really just want a file they can drag into the NLE.

Anyway, I was really just suggesting a feature request, not asking for an uninformed opinion of what I should do.
« Last Edit: 06 / April / 2008, 00:54:24 by cybercom »
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Offline Barney Fife

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Re: USB Audio Input???
« Reply #7 on: 06 / April / 2008, 05:28:43 »
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« Last Edit: 22 / April / 2008, 16:04:08 by Barney Fife »
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Offline cybercom

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Re: USB Audio Input???
« Reply #8 on: 06 / April / 2008, 11:08:39 »
I have no idea why this feature request is attracting such negative responses from people .

Nowhere do I mention anything about a "need for absolute quality" but repeatedly state that 44.1kHz, 16-bit stereo is just fine. Since this is a possible output from a USB mixer, there are no jet-engines to rowboats but rather a perfect match up.

Think for a minute instead of attacking me again.

Wouldn't it be great of you could get the output from your parabolic mic into the camera? You would get much better audio, free of camera location and wind- and handling noise. You could zoom in or out without losing any audio. When you downloaded to edit, all your audio would already be in perfect sync with the picture and at CD quality.

As far as the video quality goes, the TX-1 shoots 720P HiDef video that we have looked at on Avid Adrenaline HD systems and it compares extremely favorably with multi-thousand dollar cameras which are much larger and much more visible and cumbersome. The thought of a sub-$500.00 HD camera the size of a pack of cigarettes recording CD quality audio from a portable mixer output would have immense appeal to a large audience of independent filmmakers, news teams, documentarians & numerous others.

Please, no more postings about why YOU think this is a bad idea. That is not the purpose of a "feature request forum." If you cannot contribute something positive to perhaps move this idea into fruition, please refrain from contributing any more negativity.

Respectfully,
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Offline jetzt

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Re: USB Audio Input???
« Reply #9 on: 06 / April / 2008, 11:48:23 »
So for positive now:
It is interesting, I think you already mentioned usb-host to usb-slave by data and power lines ...

But wouln't it be much simpler to just put an additional microphone jack into some empty space and some electronics to always use the best micro?
Just if you could also live with hardware solutions, I think this woul really improve the quality.

Happy imaginin'
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