Correct bit rate for mastering project?

[Tidwells@aol.com]

This has been my "mastering technique" for years: I mix down my 24-bit audio to in DP to a stereo soundbite, then export port it and import it into a new DP "mastering" project. I place each audio track for the cd on a separate fader, then I can quickly mute/unmute different tracks and compare the volume levels and eq levels to get them sounding similar. Then I output them one at a time through a Masterworks Limiter on the master fader, where I dither from 24 bits down to 16 and record it back to a stereo track in DP (realtime). Then I export the soundbite and import into Toast to burn a master cd.

Question: Should my "mastering" project bitrate be set to 24 bit or 16 bit? I had assumed that since my final mastered mix is 16 bit, I should set the project to 16 bit. But last night I got to wondering if setting the project bitrate at 16 makes my 24-bit un-mastered soundbite get truncated, dropping the lowest 8 bits before it gets dithered in the Masterworks Limiter. Do I need to set the project bitrate at 24? If so, how do I convert the final mastered soundbite down to 16 bits after I've already dithered it to 16 bits in the Masterworks Limiter?

Doug

[Phil O]

I master in a similar fashion and set my project sample format to 16 bits (using iZotope Ozone for SRC and dither). The project's sample format does not affect playback, but material being recorded will be at the project's bit depth. So if you're mastering for CD, 16 bits is correct.

If you're concerned about your bits, there's a simple (free) bit meter from Stilwell:

http://www.stillwellaudio.com/plugins/bitter/

Works great and you can't beat the price.

Phil

[mhschmieder]

Phil, I may be misinterpreting your advice. Do you mean you apply mastering plug-ins at 16-bit sample rate, or that you are at 16-bits by the time you do stuff such as IIRC and DDP?

I highly deprecate mastering at 16-bits, in terms of the audio plug-in chain! I can tell the difference there, even more than at the mixing and tracking stage, as it is far easier to mess up the phase and/or intra-instrument balance at the mastering stage if not enough bit resolution is available.

[FMiguelez]

Question: Should my "mastering" project bitrate be set to 24 bit or 16 bit? I had assumed that since my final mastered mix is 16 bit, I should set the project to 16 bit. But last night I got to wondering if setting the project bitrate at 16 makes my 24-bit un-mastered soundbite get truncated, dropping the lowest 8 bits before it gets dithered in the Masterworks Limiter. Do I need to set the project bitrate at 24? If so, how do I convert the final mastered soundbite down to 16 bits after I've already dithered it to 16 bits in the Masterworks Limiter?

Doug

DP would only convert the 24 bit files down to 16 bits IFF that is set in the preferences with autoconversions on AND if DP is set to 16 bits.
If you leave it off, it won't do it.

Either way, I'd leave DP's audio engine set to operate at 32 or 24 bits.

If I may suggest a couple of things:
1.- You don't need to "export" your recorded or bounced files. It's an unnecesary step. You cqn simply copy the audio file from DP's folder to wherever you need it

2.- You could try bouncing (or recording in real time) your final mix to 32 bFP, so you always stay at DP's native resolution every step of the way until you master down to 24 and 16 bits.

[FMiguelez]

Sorry!
I forgot to mention that if you record in real time, and DP is set to 24 or 32 bFP, and you set your limiter to 16 bits, you would end up with a 24 or 32bFP representation of a 16 bit file, which would be confusing, a waste of space, and mostly a no-no. In this case, I would rather bounce to avoid this issue.

[kassonica]

Simple rule to follow, always leave the bitrate change as the last possible thing in mastering..

[mikehalloran]

Simple rule to follow, always leave the bitrate change as the last possible thing in mastering..

and that's when you apply dither.

[Phil O]

Phil, I may be misinterpreting your advice. Do you mean you apply mastering plug-ins at 16-bit sample rate, or that you are at 16-bits by the time you do stuff such as IIRC and DDP?

I bounce my mixes down to bwav 32bit FP. Those are kept at 32bit in the mastering project. With the mastering project's format set to 16 bit , when I'm ready for SRC I bounce down in real time. The Ozone pluggin takes care of SRC, dither, noise shaping, etc. and as soon as the tracks are bounced down they are already recorded at 16 bits (with appropriate names). So, no, no mastering is actually done at 16 bits. It's all at 32bit FP. Using this method, with an instance of Ozone on each track, I can bounce all my tracks simultaneously with a single pass. So say I have 12 songs to master. When I'm done with all the tweaking I set the output of each track to one of 12 stereo busses and record to 12 new stereo tacks (all at once). So all 12 get recorded (at 16 bits) in the time of the longest track. Then I just trim off the excess of the other tracks. Twelve tracks converted in 3.5 minutes - no problem. The biggest project I did like this had 163 songs and I did 24 songs per Mastering file.


Phil

[HCMarkus]

Question: Should my "mastering" project bitrate be set to 24 bit or 16 bit?

While I think everyone here understands what the OP means by "bit rate", I believe using this term as we have in this thread is not accurate. I feel the term "bit depth" would be more appropriate. I checked Wikipedia, finding this:

...the standard audio CD, is said to have a data rate of 44.1 kHz/16, meaning that the audio data was sampled 44,100 times per second and with a bit depth of 16. CD-DA is also stereo, using a left and right channel, so the amount of audio data per second is double that of mono, where only a single channel is used.

The bit rate of PCM audio data can be calculated with the following formula:

bit rate = sample rate x bit depth x channels

In other words, bit rate describes the number of bits flowing through a system in a given period of time. It embodies both bit depth AND sample rate, as well as number of channels.

[Shooshie]

The bit rate of PCM audio data can be calculated with the following formula:

bit rate = sample rate x bit depth x channels

In other words, bit rate describes the number of bits flowing through a system in a given period of time. It embodies both bit depth AND sample rate, as well as number of channels.

Worthy of note, and we should respect accuracy of terms. Bit rate used to be critical, because it was fairly easy to attempt to record or play more bits/second than our CPU busses or hard drives could handle. Go over the rate, and your Mac would flip out. At least, DP would, and it seems like it would take the Mac down with it. It would be pretty hard, if not impossible, to do that now, but it's easy to figure out if that's the case by using the formula. However, I don't think we could ever figure out what the CPU is doing, with all the plugins and such. Still, the bit rate is there to figure.

Bit depth is the appropriate term for the discussion.

Shoosh

[mhschmieder]

Phil, OK, I see what you mean now. I always produce 24-bit masters but I generate the 16-bit masters separately, and I try to stay in 32-bit land. That's why I was upset when RX Advanced stopped working for me as a mastering tool (long story, and not just due to having to save each plug-in bounce as a separate file vs. applying a full chain of plug-ins).

Another option is to use one of the two Sonnox encoders, and master to each target format (separate from the more generalized decision of 24-bits, 16-bits, etc.) independently. I think they're still on sale for a while longer; I bought them a couple of months ago and intend to work them into my mastering workflow as soon as I get to my next mastering task.

So yes, I think it's a good policy to target your end format, if you can keep to 32-bits for the interim data. Obviously you can do this in DP, so there is an advantage to finding a mastering workflow within DP for those who don't need the super-detailed audio editing features of a dedicated mastering app.

[Phil O]

Obviously you can do this in DP, so there is an advantage to finding a mastering workflow within DP for those who don't need the super-detailed audio editing features of a dedicated mastering app.

Yes, I failed to mention that I'm not a mastering engineer. There's a fellow in Newton that I usually send my clients to, but when it's not in the clients' budget, I do the mastering in house. So for a tight budget mastering job, DP fills all my needs.

Phil

[mhschmieder]

Phil, I have a feeling I know who this guy in Newton is that you refer to, and he's one of the best. A former housemate has used him on several projects, one of which also involved Peter Wolf (former J. Geils Band vocalist).

[Phil O]

I don't think there's a problem with mentioning his name. Jeff Lipton at Peerless Mastering. I highly recommend him.

Phil

[mhschmieder]

Yes, I know who he is, but have not met him personally. He comes highly recommended, and even though I now live on the west coast, I have considered using his services the next time I do something more pop/rock oriented, based on the amazing job he did on my friends' albums.