The test runs in four consecutive phases with different pitch and time modifications, and so the x-axis is divided into four (uneven) quadrants: raising pitch, lowering pitch, slowing down, and speeding up. Obviously the relative heights may also vary from system to system, so this is still quite tentative. No units are shown because they are totally system-dependent - this is purely a comparative visualisation, we’re only interested in the relative heights. The y-axis is linear in time with zero at the bottom, so lower is better. The results for R2 and R3, as of the 3.0 release, look like this: This is a graph of processing cycle count (x-axis) against time taken per 512-frame cycle (y-axis). The stretcher is initialised with typical parameters for this activity (in code terms, OptionProcessRealTime | OptionPitchHighConsistency | OptionFormantPreserved) and it is primed with an initial pad before entering the cycle loop, as otherwise the first call would dominate results. To measure this, I set up a test case that simulates a typical sound processing callback, passing a music recording through a stretcher and emitting a fixed 512 sample frames from each processing cycle, while varying the time and pitch ratios and measuring how long each cycle takes to return. Rubber Band is often used in real-time situations where the worst-case time per processed block is what matters most. Sustained throughput is not the only measure. Still, as it turns out, there are a few things we can do. It would be nice to do better, but the R3 code was already quite heavily optimised before release - it is simply a fairly CPU-intensive method. Both are eminently usable in real-time on hardware from the last decade, but the headroom available for R2 can make a big difference. Measuring sustained throughput in frames-per-second for common fixed stretch factors, we find R2 to be typically about three times as fast as R3. The older one is still included, and I’ll call that R2.Īlthough the output of R3 typically sounds much better than R2, it uses a lot more CPU power to run. In version 3.0 we introduced a totally new, higher-quality processing engine, which I’ll refer to as the R3 engine. This release focuses primarily on performance improvements. We can use the following lines to extract the bits, by passing a frequency and a threshold.Today marks version 3.1 of the audio time-stretching and pitch-shifting library Rubber Band. Let us export the result and extract the bits contained in this wave. We can use audacity to extract that frequency, by using an high-pass filter and by amplifying the result. For sure there was a better way that we do not know.īy looking at the spectrogram (using sonic visualizer) we can see that there is some sequence hidden at frequency 18k. This is an example of how a challenge should not be solved. In this challenge an audio file is given and it is required to find the flag hidden in it.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |