More > JRiver Media Center 21 for Windows
PEQ Bug Causing Clipping (or at least causing JRiver to report Clipping)
mwillems:
--- Quote from: mattkhan on August 14, 2015, 04:20:34 pm ---I have done limited testing recently on this sort of thing (the effect of minimum vs linear vs composite filters on a signal) and the effect is really about deformation of the waveform rather than serious level changes.
--- End quote ---
It's definitely not just about the shape of the waveform, constructive interference can result in larger or smaller waveforms, and changing phase relationships can create constructive interference (or remove destructive interference). Given that most audio is mastered to ride 0dBFS, it doesn't take much boost to make things clip.
To use a fairly extreme case, if you have a 500Hz signal and a 1KHz signal that are 180 degrees out of phase and of equal amplitude in the recording (so comb filtering is being introduced) and a crossover filter introduces even minimal relative phase shift between them it will bring them out of total cancellation resulting in a signal that's significantly more energetic than it previously was at the comb dip points in time above the crossover (the comb dips will start to fill in). If "everything else" in the signal is at or near 0dBFS at those moments that will cause the signal to clip.
See also, someone getting close to 5dB of boost from a 48Hz high pass.: https://sound.stackexchange.com/questions/24981/why-is-my-cutting-equalizer-increasing-output-level
--- Quote ---Fundamentally, the filtering process changes the shape of the waveform, so although there may be less total energy in the signal, the peak amplitude may well increase.
--- End quote ---
I do agree that some additional testing would be worthwhile.
mattkhan:
The thread I referred to about jriver not handling certain filters correctly was this one - http://yabb.jriver.com/interact/index.php?topic=93578.msg646991#msg646991 - unfortunately the link is dead now, I imagine I could recreate the test case though if Hendrik wants one.
I suppose the problem is exacerbated by the fact she's not peak level normalise which, as mojave pointed out in another thread, adjusts the level for intersample peaks.
Ultimately I think this is one of those things where jriver lets the user shoot themselves in the foot. A nice, if somewhat niche, enhancement might be if audio analysis were DSP aware, i.e. you could assign a DSP profile to a track (or inherit it from a zone) and then audio analysis runs with that DSP applied and then can adjust levels automatically to keep the signal clean.
mwillems:
--- Quote from: mattkhan on August 15, 2015, 05:35:05 am ---I suppose the problem is exacerbated by the fact she's not peak level normalise which, as mojave pointed out in another thread, adjusts the level for intersample peaks.
--- End quote ---
I agree; volume leveling also solves a lot of these problems.
--- Quote from: mattkhan on August 15, 2015, 05:35:05 am ---Ultimately I think this is one of those things where jriver lets the user shoot themselves in the foot. A nice, if somewhat niche, enhancement might be if audio analysis were DSP aware, i.e. you could assign a DSP profile to a track (or inherit it from a zone) and then audio analysis runs with that DSP applied and then can adjust levels automatically to keep the signal clean.
--- End quote ---
You're right that you'd basically need to reanalyze all of your content to make that possible (It's hard to predict if a given combination of DSP would cause a track to clip in advance without doing analysis).
Honestly, I'm not sure a more sophisticated solution is really necessary as all any such solution would do is just turn down the volume a bit, which:
a) a user could easily do themselves on demand in a way that addresses their situation (either permanently in the DSP chain or on demand using the actual volume control).
b) If you enable volume leveling or adaptive volume with peak level normalize, you get a 90% solution as they both attenuate tracks a minimum of the amount of 1dB + whatever is needed to avoid intersample peaks, and volume leveling will often provide even more headroom.
c) And if things get out of hand clip protection will catch any oops's, by turning down the volume on demand.
Basically, it all comes down to turning down the volume some when using DSP. If I were facing this problem, I'd probably rather just dial in a permanent -2dB for all channels in PEQ rather than reanalyze 80,000 files ;D
mattkhan:
But I have all these spare cpu cycles!! :'(
I agree we can file that idea under technically feasible but not sensible :D
Navigation
[0] Message Index
[*] Previous page
Go to full version