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Can someone explain KHz to me? I bought a recorder that can record in 44 KHz. But the standered for DV (which is what I will be using it for) is 48 KHz. Will it drift out of sync? And what exactly is KHz?

A very noob question, but still, I don't know.

"KHz" stands for "Kilohertz". 1 kilohertz is 1000 hertz. A hertz is a unit of frequency, and is interchangeable with "cycles per second".

When an audio signal is recorded, a snapshot of the audio (what frequencies make up the audio and what volume level the audio is) is taken, and if the sampling rate of an audio recording is "44.1 KHz" it means that a snapshot of the frequency of the sound is taken 44,100 times every second. The sampling rate ultimately determines how wide the frequency range of an audio recording is- if sampled at 44.1 KHz the recording will have frequencies up to 22,050 hertz (half the sampling rate) and if sampled at 48KHz the recording will have frequencies up to 24,000 KHz. So, the higher the sampling rate the higher the frequencies recorded! I don't know much about digital video, perhaps someone with more knowledge of that could answer your second to last question. Hope that helps!

Eli

questions like this can always best be answered by wikipedia:

http://en.wikipedia.org/wiki/Sample_rate

- Bram

Thanks OIDGNW. I was also wondering about changing sampling rate. Will that affect the length of the audio file? And if I record two different files with different sampling rates at the exact same time and same length will there be any difference?

Depending on what you use for playback, things may drift out of tune. If you are using a DAW (digital audio workstation), it may be able to handle recordings at multiple sample rates. Some will play back your audio files at the selected sample rate, which will alter pitch and length of playback time if the sample rates do not match. Some DAWs and samplers will simply not play back files at a different sample rate and they may require you to convert the file before it will load.

OK. Really what I was asking about was if I record with my MiniDV camera and a Small recorder that will record in 44 KHz and the camera will record in 48 KHz will they drift out of sync?

Ok, it looks like you are trying to do something that likely will drift. How do you plan on combining the two for playback? Presumably, you intend to combine the two different recordings at some point. In that case, my above reply applies. In addition, you are recording on two devices that do not have a single clock source. There will likely be some drift as a device that records at 44.1 could be running in the realm of 44101 or 44099. The same goes for your DV cam. You will likely be able to compensate on playback for short cuts, but you could start to drift by frames when you are editing the video.

Your best bet is to have a common sync source for the two devices. If that isn't possible, you will likely be able to compensate when you cut your clips together if they are relatively short.

OK, that's what I needed to know. I would be putting them together in editing and I do notice that they start to drift is the clip is over 10 minutes. Really dumb question, If I were record in say 16 KHz would it not drift? (My thinking is that 16 goes into 48, and maybe if I used Audacity to convert it....) :?: :?:

16 kHz is a bad idea, it will make your recordings sound like you had the mic under a pillow or anything. Also, it would not solve the drifting, it's only make it worse. The editing software simply reads all the samples and plays them back at the speed it wants to.
Compare with a good old analog tape, if you record onto it using a weak power source (near dead batteries, for example), the tape will go slow. Playing it back at the exact same speed you will not notice anything. But play it back on a proper tape deck, everything will have a higher pitch and speed. Making the tape run even slower when recording wouldn't fix this.

I would advise to check what your editing software is using, either 44.1 or 48, and convert the one recording that needs to be converted using Audacity.

All devices drift a bit (pro material a little, consumer material possibly a lot). In the pro video production world this is solved by using 1 sync source. I.e. the devices don't decide when to make a new "sample", they listen to a single eternal clock to which they synchronize. This could be called a world clock. The chances that your DV cam and recorder support this are very close to zero

If you're making relatively short takes (<10..30 minutes) I would say: don't worry too much about drift. Record the audio, record the video, use a good sampling-rate converter to convert the audio, line it up in your video editor.

A test should be very easy: switch on both, make some sharp, short sounds where you can see the movement/hit as well on the camera, keep recording, wait 10 minutes, make some sharp sounds. Line'm up, check the drift!

As nemoDaedalus mentiones: it's a bad idea to record at 16kHz. The higher the samplerate, the clearer the recording, the less "high frequency content" is lost. Some people swear by 96kHz and up, I myself can't hear the difference when it goes over 44.1

- Bram

Bram
All devices drift a bit (pro material a little, consumer material possibly a lot). In the pro video production world this is solved by using 1 sync source. I.e. the devices don't decide when to make a new "sample", they listen to a single eternal clock to which they synchronize. This could be called a world clock.

or "word clock"

Bram
A test should be very easy: switch on both, make some sharp, short sounds where you can see the movement/hit as well on the camera, keep recording, wait 10 minutes, make some sharp sounds. Line'm up, check the drift!

This is one reason why people use a slate when rolling takes for film, video, etc. Doing so gives a good point to align your audio with your video. You can see where the audio click should sound.

Bram
As nemoDaedalus mentiones: it's a bad idea to record at 16kHz. The higher the samplerate, the clearer the recording, the less "high frequency content" is lost. Some people swear by 96kHz and up, I myself can't hear the difference when it goes over 44.1

Absolutely! One could make an argument that you should go up, rather than down on your sample rate. Your best bet though, borrow a recorder that will record at 48kHz.

All right. Thanks so much guys! This thread really helped.

fractured
This is one reason why people use a slate when rolling takes for film, video, etc. Doing so gives a good point to align your audio with your video. You can see where the audio click should sound.

Yeah I do slate it. Its just easier to get better sound that way.

Thanks again :!: