Bit depth

Hi,

In this thread, I would like to discuss the various bit depth settings in SONAR X1 and their exact roles. Ideally, I would like the topic to end up in a clear summary of how SONAR X1 handles the audio data and when dithering occurs or does not occur.

Before, here's a cool thread I've found, which is more particularly about dithering : http://forum.cakewalk.com/tm.aspx?m=1825218&mpage=1. It already partially answers my questions.

In SONAR X1 settings, you set bit depths in two main sections :
Audio > Driver Parameters , and File > Audio Data.

As for me, in the Driver Parameters section, the audio driver resolution field is grayed out. It's set to 24 bit and I cannot change it. However, I can check the 64 bit double precision box but I don't do it (I might be wrong but it looks like a marketing stuff to me)

In the Audio Data section, by default, Record is set to 16 bit, Render is set to 32 bit, and Import is set to Original.

Here are a few questions or remarks that come into my mind, without particular order.

1) What's the point of setting Render to 32 bit if the audio driver is set to 24 bit ? Does it mean that dithering (or truncating if dithering deactivated) occurs in real-time while playing a project within SONAR ? (32 -> 24)

2) In the user's manual, it's said that no audio interface is able to record in 32 or 64 bit and thus these values are not usable. However, I can set the Record bit depth to 32 bit or 64 bit. For instance, if I set the Record bit depth to 32 bit and record something, SONAR says the audio clip has a resolution of 32 bit, which seems odd, because indeed my audio interface does not support more than 24 bit. What happened inside SONAR then ?

3) What is the recommended bit depth for Record and why ?

4) What is the recommended bit depth for Render and why ?

5) Why the 64-bit double precision engine checkbox is close to the audio driver bit depth settings ? Isn't it supposed to be related to the Render bit depth in the Audio Data section ? What's the difference between not checking the 64-bit double engine box and setting Render to 64 bit ; and checking the 64-bit double engine box and setting Render to 32 bit ?

Thanks

My system:
Windows 7 32-bit
Audio : TC Konnekt 8 in ASIO mode

First of all, please note that 16bit/24bit resolutions used by audio interfaces refers to fixed point, and 32bit/64bit refers to floating point. Floating point math allows for much greater dynamic range (hundreds of dB in 32bit, thousands of dB in 64bit) without clipping, and no loss of resolution (or increase in noise) at even extremely low signal levels.

Sonar converts everything to floating point internally and does all of it's operations using floating point math, so if you store it (temporarily) in another format it will need to be converted back to floating point by Sonar.

When you convert from, say, 32bit floating point to 24bit fixed point you will lose some (extremely) low level information. In the real world, what's lost would never be audible - that is unless you are doing subsequent processing that could make it audible. For this reason, it's best to always stay in 32bit until converting for output to either your audio interface or your final output file.

As to 64bit double precision vs. 32bit single precision, although 32bit floating point generally offers enough mathematical precision to process audio without any audible artifacts, in certain cases (involving lots of operations  - for instance if you were mixing hundreds of tracks) inevitable mathematical "rounding" errors might propagate to the point of being audible.

Generally, if you're using the 64bit engine, you will save disk space/throughput and won't lose anything by storing stuff in 32bit - even if it gets converted back to 64bit by Sonar for further processing.

Oops double posing.....

24/44.1 is pretty standard.  If you have a great interface, play around with 48, 88.2 or 96 - see if you can hear any difference.  One thing to take into consideration when you go bigger - you'll hammer the CPU more with your VST's.  So, if you are tapping your hardware with current projects at 44.1 - moving to 96 will have a pretty big impact on overall performance.

As for dithering, I've tried quite a few and settled on PSP Xenon.  Best I've found for the $$.