Audio-Sample Rate on Camera

I'm using an External Recorder (PMD 661) for my audio. I came across a youtube video ( wish i could find it again) that said your sample rate on your camera must match your sample rate on your external Recorder to prevent audio drift.

Is this for real or was this guy also a noob also? very confused.
 
I don't know how cameras work but technically speaking that shouldn't be an issue. Sample rate is exactly that, the number of samples per second, so having different settings shouldn't be an issue, it only changes the frequency range and detail of said frequencies that are captured.

People who have experience with cameras - correct me if I'm wrong.
 
Check the camera for it's audio sample rate. Most camcorders record audio at 48kHz, I'm not sure about DSLRs.

You are ALWAYS going to get drift unless the camera and recorder are synchronized by a common clock. Since there are a multitude of camera/audio recorder combinations it is extremely difficult to know how much drift there will be, although two (2) to six (6) frames of drift for each ten (10) minutes seems to be the "norm;" however, there have been extreme cases approaching several seconds of drift after just five (5) minutes. This is why it's important to let your audio post person have the camera audio as well as the audio from the external recorder so s/he can check for drift.
 
I'm using an External Recorder (PMD 661) for my audio. I came across a youtube video ( wish i could find it again) that said your sample rate on your camera must match your sample rate on your external Recorder to prevent audio drift.
Under certain circumstances having different sample rates can cause drift but generally it shouldn't be a problem. However, it is best to stick to the same sample rate across all your devices, there are a number of things which can go wrong potentially so a good rule of thumb is to set all your devices to 48kHz and leave them at that setting for everything film/TV related.

Sample rate is exactly that, the number of samples per second, so having different settings shouldn't be an issue, it only changes the frequency range and detail of said frequencies that are captured.
A higher sample rate only increases the frequency range which can be captured, NOT the detail of that frequency range! A sample rate of 48kHz will extremely accurately capture frequencies up to about about 23kHz which is well beyond the range of human hearing and almost certainly beyond what your mic can capture and what your speakers can reproduce. A sample rate of 96kHz can theoretically capture audio frequencies up to 48kHz but with no more accuracy than a 48k sample rate.

G
 
Thanks guys my Recorder is set at 96KHZ but I can't seem ti figure out how to find the sample rate for my video camera gotta keep looking I guess.

Either or though, Sample rate is a fixable problem right? it's not a death sentence?
 
my Recorder is set at 96KHZ
No, as I said before, set it to 48kHz. You will gain nothing by setting it to 96kHz except doubling the size of your audio files and doubling the amount of CPU required to process them! Set all your equipment to 48kHz and only use 48kHz audio files in the timeline of your NLE. This is a habit well worth getting into as one day it's likely to bite you in the a$$ if you don't.

Sample rate is a fixable problem right? it's not a death sentence?
No it's not a death sentence, sample rates can be converted after the recording. It's better to avoid sample rate conversion (SRC) if there's a choice though.

I meant Audio Drift
Alcove, is correct. You will get drift over time between your recorder and your camera, irrespective of the relative sample rate settings between your camera and recorder.

G
 
Thanks a lot for the help, the problem is that, through out the filming process I have had it set on 96kHz so if I change it to 48 kHz Wont it be dramatically noticeable?
 
I have had it set on 96kHz so if I change it to 48 kHz Wont it be dramatically noticeable?
It won't be noticeable at all, let alone dramatically. There is NO quality difference (audible or even measurable) between 96kHz and 48kHz! When you're done shooting you should convert all your 96kHz material to 48kHz.

PCM 24bit/48kHz is how it should be set.

G
 
guess i can breath a sign of relief, gotta love the age we live in. Canon doesn't know the sample rate of the camera but i'll just set it at 48, thanks a lot man
 
Just got off the phone with them they had to do some research and they said it was set at 20-20,000 hertz so I don't know where to go with that but just thought I would share it.
 
20Hz-20,000Hz is the range of audio frequencies your camera is able to record. This information is not related to the sample frequency your camera is set to record at. The sample frequency/rate is the number of times per second the sound waves entering the camera/recorder's inputs are measured and stored.

G
 
I'm on my ipad so I can't see right at the second, but I'm fairly certain in the file information of the video files from your camera it will say the kHz. I do thinks its 48kHz, but I've (guiltily...) never cared enough to notice a lot.
 
A higher sample rate only increases the frequency range which can be captured, NOT the detail of that frequency range!
But the more room the better since higher sample rates give you more to work with in the higher frequencies (for editing purposes I mean here). For example, 48khz is studio standard, stick to 96 if you need to do heavy editing (time stretching, pitch changing etc) or work with sound effects. The extra frequencies recorded at the higher rates (i.e. extra detail) mean you can mangle the sounds more and not worry as much about losing the high-end clarity too much.

I've been working with sound for 10 years and I've educated myself very well. No need to try and correct me.
 
The extra frequencies recorded at the higher rates (i.e. extra detail) mean you can mangle the sounds more and not worry as much about losing the high-end clarity too much.
Unless you are using very specific equipment, there will be no "extra frequencies" recorded using a sample rate of 96kFS/s. The vast majority of mics do not respond to frequencies above 20kHz, which is well within the 23kHz or so limit of 48kFS/s, and also the analogue circuitry in many mic-pres, ADC's and recorders do not pass signals above about 20kHz. In this particular case, the specs of the recorder state 20Hz-20kHz, so again, there is probably nothing except static to record above the Nyquist point of even 44.1kFS/s, so 48kFS/s should provide ample frequency head room and 96kFS/s is pointless. There may (or may not) be some advantage to processing a drastic pitch-shift, say an octave or more, at 96kFS/s. In which case up-sample your 48kFS/s recording to 96kFS/s, apply the pitch-shift algorithm and then down-sample back to 48kFS/s. How often is this amount of pitch-shift going to be required by most indie filmmakers though, especially as in the vast majority of cases what they are recording is not SFX but production dialogue?

My advice stands, unless you have a specialist mic and other analogue front end equipment which can respond to audio frequencies above 24kHz and unless you intend to apply some drastic pitch-shifting, there is nothing to be gained from recording at 96kFS/s instead of 48kFS/s.

G
 
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