How do multiple amplitude fades work on ecasound?

I want to fade a track in and out at 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, it affects the relative volume of the whole track and not just at the specific time I set the fade, which is where I'm getting lost.

Example commands

# 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 Results

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 (second to last in the image), the fades are no longer taking a full second each. In order to figure out why 开发者_如何学Pythonthat 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?

---

-kl2

After a few hours of head scratching, I finally think I have it figured out. The "From" amplitude on every fade needs to be 100. If you are increasing the amplitude, the "To" amplitude is maximum / from * to.

So if you're trying to go from 20 to 100, it's 100 / 20 * 100 or 500. If you're trying to get to 120: 100 / 20 * 120 or 600. I assume this all makes perfect sense to someone, but I was perfectly stumped.

The working example (with a slightly higher bottom range in the middle to demonstrate):

ecasound -a:1 -i tone.wav \
         -ea:100 -kl2:1,100,20,2,1 \
         -ea:100 -kl2:1,100,500,4,1 \
         -ea:100 -kl2:1,100,40,6,1 \
         -ea:100 -kl2:1,100,250,8,1 \
         -ea:100 -kl2:1,100,20,10,1 \
         -ea:100 -kl2:1,100,500,12,1 \
         -ea:100 -kl2:1,100,0,14,1 \
         -a:all -o:test_7.mp3

And the output:

Keep in mind that these amplitudes are still relative. If you're going from 45% to 90%: 100 / 45 * 90 = 200, and then now if you drop to 20% of the current amplitude, it's actually 18% (.20 * 90), so going back to 100 would be 100 / 18 * 100 = 555.56

-klg

Just as I figured this out, and came here to post, I received a response from the ecasound mailing list. It's not a direct answer to the kl2 issue, but offers an alternative, easier-on-the-brain answer, which is the klg parameter.

-klg:fx-param,low-value,high-value,point_count,pos1,value1,...,posN,valueN Generic linear envelope. This controller source can be used to map custom envelopes to chain operator parameters. Number of envelope points is specified in 'point_count'. Each envelope point consists of a position and a matching value. Number of pairs must match 'point_count' (i.e. 'N==point_count'). The 'posX' parameters are given as seconds (from start of the stream). The envelope points are specified as float values in range '[0,1]'. Before envelope values are mapped to operator parameters, they are mapped to the target range of '[low-value,high-value]'. E.g. a value of '0' will set operator parameter to 'low-value' and a value of '1' will set it to 'high-value'. For the initial segment '[0,pos1]', the envelope will output value of 'value1' (e.g. 'low-value').

Here's the command to do what I need using klg instead of kl2:

ecasound -a:1 -i:tone.wav -ea:100 \
-klg:1,0,100,14,2,1,3,0.20,4,0.20,5,1,6,1,7,0.40,8,0.40,9,1,10,1,11,0.20,12,0.20,13,1,14,1,15,0 \
-o:test.mp3

The output is exactly the same as the 2nd track on the image.

This resulting command line is definitely a bit harder to read and hence debug, but may actually be easier to generate dynamically. Regardless, I now have 2 working options to resolve this problem.

And finally, here are my notes for how I figured out the coordinates of the klg command. The asterisks are the "points" which are listed in the klg parameter, the numbers at the top are seconds:

     0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2
     1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
1.0  --*     *-*     *-*     *-*   
 ~      \   /   \._./   \   /   \
0.2      *-*             *-*     \
0.0                              *----------

I hope this helps someone save at least the amount of hair that i've lost scratching my head.