Introduction
On IRC we had another huge test and brainstorming session about editing music files in order to make them loop them correctly in Danmakufu. But we have not yet found a solid and reliable method for making this happen but we got really close (before as well).
Now I know that few people succeeded in getting perfect or somewhat extremely well looping BGM files before. But mostly they fiddled around with audacity adding/removing silence until it somewhat loops correctly.
Related literature
According to Iryan et al. (2010), Danmakufu needs a silence section to round it up to an integer of a second. Meaning if a song lasts 1m and 34,5s, it requires 0,5s of silence to round it up to 1m 35s. How ever Blargel et al. (2010) claims that adding to any track a silence of 1 second is sufficient. But he also explains that he used silence in front of the BGM track.
Now if we for example examine Mitori's theme (Unknown et al, 2010): The Kappa Way as Said ~ One way Accelerator, we can note the music file immediately starts playing and has a tiny bit of silence at the end. (~0,027s). This music file loops like perfect in Danmakufu.
Research approach
For this research I took my Uwabami Breakers 3rd boss track, Lemuria, and cut away the song so only like 1-2seconds remain (for fast listening). Then I added the following amount of silences: +0,027s and +1,0s and added the amount of silence until the total length of the track becomes +1,128s, +0,768s, +0,512s. Which Iryan has proposed.
Results
adding regular +0,027s silence did not work and you could hear a clear choke + repeating of outro being mixed into the intro.
length of +1,0s silence gave a small noticeable silence in the track before it looped.
length of +1,128s gave even greater noticeable silence.
length of +0,768s gave a small choke of outro being mixed into the intro
length of +0,512s gave a noticeable choke of outro being mixed into intro (repeating)
Conclusion, discussion and further research
As we can see by this research, extending the silence around ~1,0s, and keeping in mind Iryan's theory, creates a better looping BGM. Personally I have concluded that adding silence untill it reaches X,768s has a better chance of looping than the other tests.
For further research the silence in the beginning has to be added and tested out.