sample bit depth and fidelity (SF13 pro)

James-Lo wrote on 8/18/2020, 2:17 PM

I'm trying to understand why my output sometimes sounds lo-fi compared with professional productions, and that led me to ask if my use of 44.1/16 in most circumstances could be a factor. In other software I use, samples are processed as 32 bit floats, so I thought I might compare the output of paragraphic EQ when operating on a 16 bit sound file vs a 32 bit float sound file. I recorded a minute of voice at 44.1/16, saved it as Microsoft WAV, then opened it in a second data window. I then converted the bit depth of the 2nd data window to 32 (IEEE float) using Process->Bit Depth->Bit-Depth Converter. I applied paragraphic EQ to both files, 100% wet, 200 hz -Inf low shelf. To see if there was a difference, I copied the data in the 2nd window to a 3rd data window (which inherited the 32 bit float bit depth), then mixed the 1st window (still 16 bit) into the 3rd window, inverted. I expected the 3rd file to contain the sample-by-sample round-off errors, but Tools->Statistics shows that the entire file is composed of zeros. But if I re-save the original data window, save the 2nd data window, then reload both of them, now the errors show. So it seems like SF13 is also processing samples in some common high-precision bit depth, and only reflecting the configured bit depth when the data is saved to file.

So my question is: is it possible that I'm losing fidelity because I keep adding round-off error every time I save to disk? It's true that I tend to record, then save. Then normalize and save. Then de-noise and save, etc. All on different days. Can I assume that saving as a SF project won't help unless I use 32 bit float bit depth?

Comments

Former user wrote on 8/18/2020, 2:36 PM

That's a busy, busy post, man. I find it very difficult to read.

Recordings can sound 'lo-fi' for a lot of different reasons. Recording at 16/44.1 doesn't help, especially if you do a lot of processing afterwards. A pro engineer up the road from me always records at 24-bit depth to give himself enough headroom for processing. Sometimes his masters are 44.1 s/r, sometimes 88.2 s/r, but the bit depth is always 24.

rraud wrote on 8/18/2020, 3:47 PM

"That's a busy, busy post, man. I find it very difficult to read"
 +1

Lossy formats (MP3, AAC, ect) can degrade quality rather quickly. A 44.1k or higher 16, 24 or 32 bit PCM file should still sound decent after many re-render cycles. Using the project file mode offers more options of going back and making changes. Plug-ins can certainly fork things up. If some is good, more is better is a common occurrence.

If you can post some before and after examples on Dropbox, GoogleDrive or or cloud sharing site, we may get a better comprehension of your issue.

James-Lo wrote on 8/18/2020, 4:23 PM

Sorry, I got lost in the details. Let me turn my question on its head: is it possible to measure how much higher fidelity 32 bit PCM is than 24 or 16, and if so, how would you do it? @rraud's answer suggests to me that if such a measurement is possible, the difference would be so small that you couldn't hear it even after 4 or 5 re-render cycles. (and so I'm barking up the wrong tree WRT improving the fidelity of my recordings)

rraud wrote on 8/18/2020, 5:21 PM

The bit depth has an affect on the dynamic range. For instance, if a file was recorded at a very low level, it could be normalized up with fewer artifacts (noise) than lower, 16 bits or (god forbid) 8 bits. The sample rate affects frequency response. (search Nyquist frequency).. It is not uncommon to record music and S/FX at 96kHz and higher. Dialog is pretty much always recorded at 48k even on mega budget block buster movies.

The new 32 floating bit point recorders from Sound Devices and Zoom offer almost unlimited headroom. However if record levels are properly set in the first place, there is no audible difference. Sound Forge proxies files to 32 floating bit point internally. For lossy file types, the proxy option must be enabled in settings.