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Sample rate

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Sample rate

Postby shambles2 » Mon Oct 08, 2007 8:54 am

hi there anyone im a newby hence go the dum questions

im working on a a new project and am planning to mix everything in 24bit 48khz. from what i know the higher the bit rate the more head room u get right?
i will be recording sounds to and also using some samples from my sample library
here's my problem, what if my samples are in 44.1 16bits, how would i mix them in then? cause my project is running on 48khz/24bit
would it be advisable to convert(individually) the 44.1/16bit samples to 48khz/24bit? and then mix in all together?
if yes, what will it to to my 44.1/16bit samples when u convert them individually?will the samples drop quality or will it just give more head room to mix?

in a nut shell, is it ok to upsample an audio file which has been recorded in a lower sample rate?is it gonna make any difference or is it just gonna give more head room the the particular file?
sory for being long... as im pretty confuse
thanks alot for your time
cheerio
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Re: Sample rate

Postby James Perrett » Mon Oct 08, 2007 1:56 pm

If you are planning on releasing your project on CD or for download then there is little point working at 48kHz - that extra 4kHz really gains you very little in practice. It would make more sense to work at 44.1kHz. Most software should have no problem mixing 16 bit, 24 bit or 32 bit sources so you could just import your samples directly.

48kHz is only recommended if your main outlet is sound for video.

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Re: Sample rate

Postby Jack Ruston » Mon Oct 08, 2007 3:37 pm

You've misunderstood the concept of headroom as it pertains to word length and sample rate.

As you increase the word length from 16 bits to 24 bits you are able to record at a lower level while retaining the same signal to noise ratio (or a better signal to noise ratio). So effectively you can leave more headroom.

As you increase sample rate, you increase the maximum frequency that can be recorded which in turn moves the filters that must be in place close to that maximum frequency away from the audible spectrum. Sample rate is more akin to the 'resolution' on a digital photograph (ie pixels) than word length is.

As pointed out, 48k does not really give you a huge advantage over 44.1k most of the time. It rather depends on the quality of your converters.

If you DO choose to work at 48k you can simply upsample your 44.1k samples to match the 48k session. Be careful to ensure that this process is done so that samples dont come in playing back too fast. In the software I use, when I import files from another sample rate I can check a box which allows me to either convert them or run them at the wrong speed.

Best of luck

Jack
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Re: Sample rate

Postby Donal Whelan » Mon Oct 08, 2007 3:57 pm

A higher bit rate will give you more headroom - 24bit has 48dB more headroom than 16 bit (6dB per extra bit).

A higher sampling frequency will give you a higher frequency response, though there's very little difference between 44.1kHz and 48kHz. Many people record at the sampling frequency of the end medium, in the case of CD, 44.1kHz.

Most workstations will mix files of different bit rates without blinking, but will protest heartily at mixing files of different sample rate.

For your current project, I'd carry on working in 48kHz and sample rate convert at the end. Switch the bit rate from 16bit to 24bit for the mixdown. 16 bit files and samples will play fine and you'll get more headroom/resolution. Then try out different sample rate converters to get it to 44.1kHz at the mastering stage.

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Re: Sample rate

Postby Donal Whelan » Mon Oct 08, 2007 3:59 pm

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Re: Sample rate

Postby narcoman » Mon Oct 08, 2007 8:26 pm

Donal Whelan wrote:A higher bit rate will give you more headroom - 24bit has 48dB more headroom than 16 bit (6dB per extra bit).

A higher sampling frequency will give you a higher frequency response, though there's very little difference between 44.1kHz and 48kHz. Many people record at the sampling frequency of the end medium, in the case of CD, 44.1kHz.

Most workstations will mix files of different bit rates without blinking, but will protest heartily at mixing files of different sample rates.

For your current project I'd carry on working at 48kHz, then sample rate convert at the end. Switch the bit rate from 16bit to 24bit for the mixdown. 16 bit files and samples will play fine and you'll get more headroom/resolution. Then try out different sample rate converters to get it to 44.1kHz at the mastering stage.

:beamup:


as someone who works in this area you should know better - c'mon bro' don't perpetuate misinformation. It's important to get this stuff right !! Whinge over.....


It's bit DEPTH not rate. Bit rate is a very different thing. Bit depth refers to the available bits to describe each sample (the value if you like)

It does not give you any more headroom directly - you get a larger dynamic range and hence lower noise floor. You get more headroom by, as the previous poster said, not having to record all the way up to 24bits. You can quite happily sit at -20dbfs and still be recording around the 20bit mark with the next 4 bits to essentialy describe your "headroom", capturing the biggest impact transient information and leaving more than enough room for waveform calculations.

As said, no real advantage of recording at 48k over 44.1 but it depends on the project.
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