[ecasound] Confusion about Fading Amplification
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From: Mark A. <li...@en...> - 2011-08-05 01:52:20
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* Note: I assume attachments are not kosher on this list, so I posted this question on StackOverflow as so you can see my resulting waveforms: http://stackoverflow.com/questions/6950482/how-do-multiple-amplitude-fades-work-on-ecasound ----- I want to fade a track in and out as specific time codes. For example, I would like to take an audio file, and: Start it at 100% Volume, Fade it to 20% at 2 seconds Fade it to 100% at 4 seconds Fade it to 20% at 6 seconds Fade it to 100% at 8 seconds Fade it to 20% at 10 seconds Fade it to 100% at 12 seconds Fade it to 0 at 14 seconds. I've been testing this with a constant tone generated by ecasound so that I can open the resulting file in Audacity and see the results visually. As far as I can tell, increasing the amplitude is relative, while decreasing it is not. It seems that if I fade the amplitude up that it affects the volume of the whole track and not just at the specific time I set the fade, which is where I'm getting lost. Note: I seem to have figured out the "why" as I was coming up with examples, but I'm still hoping you can explain if this is correct or if there is a "better" way. An example of what has me scratching my head ----------------------------- # generate the tone ecasound -i tone,sine,880,20 -o:tone.wav # Just the test to see that i can fade start it at 100 and fade it to 20. ecasound -a:1 -i tone.wav -ea:100 -kl2:1,100,20,2,1 -a:all -o:test_1.mp3 # Fade it out and in ecasound -a:1 -i tone.wav -ea:100 -kl2:1,100,20,2,1 -ea:100 -kl2:1,20,100,4,1 -a:all -o:test_2.mp3 # Fade it out and in with a peak of 500 ecasound -a:1 -i tone.wav -ea:100 -kl2:1,100,20,2,1 -ea:100 -kl2:1,20,500,4,1 -a:all -o:test_3.mp3 # Fade it out from 500, out, and then back to 500 ecasound -a:1 -i tone.wav -ea:100 -kl2:1,500,20,2,1 -ea:100 -kl2:1,20,500,4,1 -a:all -o:test_4.mp3 # Fade it out from 500, out to a low of 10, and then back to 500 ecasound -a:1 -i tone.wav -ea:100 -kl2:1,500,10,2,1 -ea:100 -kl2:1,10,500,4,1 -a:all -o:test_5.mp3 # Fade it out from 1000, out to a low of 10, and then back to 1000 ecasound -a:1 -i tone.wav -ea:100 -kl2:1,1000,10,2,1 -ea:100 -kl2:1,10,1000,4,1 -a:all -o:test_6.mp3 # The eventual result I'm looking for ecasound -a:1 -i tone.wav -ea:100 -kl2:1,500,20,2,1 -ea:100 -kl2:1,20,500,4,1 -ea:100 -kl2:1,500,20,6,1 -ea:100 -kl2:1,20,500,8,1 -ea:100 -kl2:1,500,20,10,1 -ea:100 -kl2:1,20,500,12,1 -ea:100 -kl2:1,500,0,14,4 -a:all -o:test_7.mp3 ------------------------------- The best I can tell from these results is that the amplitude of the whole track is relative to the difference between the low and the peak of all the fading effects. I'm not sure if this result is expected, but it's very confusing. Also, in the last result, the fades are no longer taking a full second each. In order to figure out why that may be, I took the final fade-to-zero off and the durations were back to normal. This does not seem like expected behavior. ------------------------------- # "Fixing" the fade durations ecasound -a:1 -i tone.wav -ea:100 -kl2:1,500,20,2,1 -ea:100 -kl2:1,20,500,4,1 -ea:100 -kl2:1,500,20,6,1 -ea:100 -kl2:1,20,500,8,1 -ea:100 -kl2:1,500,20,10,1 -ea:100 -kl2:1,20,500,12,1 -a:all -o:test_8.mp3 ------------------------------- As a side note, I've also tried changing the -ea values to the "current" amplitude with every line. It didn't make any difference (no matter what I set -ea to) I have the very latest installed from git (2.8.1+dev). I had these same issues with 2.7.0, which is why I upgraded and eventually found myself here. Am I doing this wrong? Thank you for your time. |