Pro Tools 11 vs Pro Tools 11 HD w/ HDX or Native Headroom difference

[avidous]

I read in an old SOS article:

"Because Pro Tools LE systems use the computer host CPUs to undertake all the audio processing, the LE mixer employs 32‑bit floating‑point arithmetic. Without getting into all the maths behind this, it means that there is loads of internal headroom in the LE mixer. The HD mixer is a different ball game, as it has to use the TDM chips on the Pro Tools cards, and these chips don't support floating‑point arithmetic. So, to be safe, the Pro Tools designers use a 48‑bit mixer to provide the appropriate headroom."

So back in the day there was a difference in headroom between Pro Tools and Pro Tools HD due to the mixer being handled on a PCIe card.

Today there is still a difference in processing--Pro Tools is handled on the CPU whereas Pro Tools HD w/ HDX and Pro Tools HD w/ Native are handled on their respective cards.

Is there still a difference in headroom between regular and HD Pro Tools, assuming only one PCIe card is used?

Thanks!

[avidous]

Originally Posted by Darryl Ramm

This stuff has been flogged to death on DUC before. You can search for those old posts that explain modern Pro Tools headroom in detail.

You are reading an old article about old Pro Tools HD/TDM hardware which used 48 bit fixed point arithmetic. Modern Pro Tools/Pro Tools HD software uses a 64 bit floating point mixer whether running on the host processor or on the HDX DSP cards. Float file formats provide 32 bit floating point workflow into and out of Pro Tools and plugin processing is at 32 bit (or 64 bit float).

Are you asking questions or making statements?



Ah no, there is no pro Tools mixing handled on a HD native card, there is some low-latency monitoring mixing handled three, but that is quite different. The HD native mixer is inside your computer. HDX mixes on the HDX card DSPs.



There is no difference today in headroom between HD native and HDX, and there is never any difference in headroom depending on how many DSP cards are used (HD/TDM or HDX, that would make no sense).... there sure is a difference in DSP power/voice counts and IO connectivity depending on exactly what HD/TDM or HDX cards you are talking about and how many in a system.

In practice with these modern high-headroom DAWs, the issues occur at converter input and converter output, not during mixing/processing. You need to understand converter dynamic range, and analog distortion.

Ok cool. Thanks a lot for the response.

So just to make sure I understand completely, using non-HD Pro Tools on my machine without any PCIe card, I will have "over 1,000 dB of additional headroom", same as HDX? (source for HDX headroom: http://avid.force.com/pkb/articles/en_US/faq/en423351)

[Craig F]

yes but you still need to output through the fixed DAC of your interface and it's limited headroom

[avidous]

Originally Posted by Craig F

yes but you still need to output through the fixed DAC of your interface abd it's limited headroom

Can you elaborate? I'm not sure what you mean, sorry.

[musicman691]

Originally Posted by avidous

Can you elaborate? I'm not sure what you mean, sorry.

It means you are still limited by whatever digital to analog converters are in the hardware you have and the analog electronics they go to. It's analogous to having a pipe carrying water and you increase the diameter of the pipe. Sure the pipe will be carrying more water but if everything downstream isn't upsized you still won't get more water at the end of the pipe.

[Amack]

So, does everything inside ProTools 11 and 12 software (including plug-ins) run at either 32 or 64 bit floating point regardless or the bit depth specified for the session?

[Amack]

Great! - that makes a lot of sense. But, how do you know that? It seems like a rather important feature that Avid seemingly does not publicize. Also, do you have or know of a block diagram for ProTools? Please excuse me if these seem like stupid questions - ProTools is relatively new to me! Thanks!!

[Amack]

Darryl,

So, should the 11 and 12 Reference Guides be updated to reflect that, or am I somehow misinterpreting what they say? (See attached pages from the 11 Guide.)

Amack

Quote:
Originally Posted by Amack View Post
So, does everything inside ProTools 11 and 12 software (including plug-ins) run at either 32 or 64 bit floating point regardless or the bit depth specified for the session?
Yes.
__________________
Darryl

Originally Posted by Darryl Ramm

Yes.

[mesaone]

operational bit depth of the software mixer and plug-ins is independent of the bit depth of the files it works with. The pages you just shared are talking about the format for the audio files.

[Amack]

So, is my impression/experience that audio files are saved (when a session is saved) at 32 bit floating point regardless of the session's bit depth selection not correct?

Originally Posted by mesaone

operational bit depth of the software mixer and plug-ins is independent of the bit depth of the files it works with. The pages you just shared are talking about the format for the audio files.