Discontinuities when changing sound volume in VSE #24194

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Jacob F · 2010-10-08T18:21:55+02:00

Jacob F commented

2010-10-08 18:21:55 +02:00

%%%r32379; Linux

Here I attached a .blend that plays a sine wave and changes the volume using keyframes on the sound strip's volume value. You will notice the ticking when the volume is changing.

Looking at the outputted waveform in Audacity it is clear what is going on. Blender is getting the volume from the f-curve for each frame, making each frame have a constant volume. It needs to interpolate to the next frame.

I recently used the VSE to control volume in a fun anim (see http://blenderartists.org/forum/showthread.php?t=199241) and the ticking is quite noticeable. Surely in professional grade films it woudn't do.

This is probably more of a feature request since it's a change of functionality, but I thought I'd make it known anyhow.%%%

%%%r32379; Linux Here I attached a .blend that plays a sine wave and changes the volume using keyframes on the sound strip's volume value. You will notice the ticking when the volume is changing. Looking at the outputted waveform in Audacity it is clear what is going on. Blender is getting the volume from the f-curve for each frame, making each frame have a constant volume. It needs to interpolate to the next frame. I recently used the VSE to control volume in a fun anim (see http://blenderartists.org/forum/showthread.php?t=199241) and the ticking is quite noticeable. Surely in professional grade films it woudn't do. This is probably more of a feature request since it's a change of functionality, but I thought I'd make it known anyhow.%%%

Jacob F commented

2010-10-08 18:21:55 +02:00

Changed status to: 'Open'

Nathan Letwory commented

2010-10-09 00:16:01 +02:00

%%%Assigning to our sound guy.%%%

Joerg Mueller commented

2010-10-09 00:36:06 +02:00

%%%Actually I complained about that problem of the animation system myself. Talking to Joshua he said that this way is good enough, so assigning to him and let him decide what to do.%%%

Joshua Leung commented

2010-10-16 06:30:11 +02:00

%%%I see...

Joerg: So, uhm, what were the alternatives?%%%

%%%I see... Joerg: So, uhm, what were the alternatives?%%%

Joerg Mueller commented

2010-10-16 12:02:10 +02:00

%%%Well, we need some sort of subsampling for the frames. Calling the callback we currently have 44100 times a second will most likely be too inefficient. So there should at least be a mechanism to retrieve a value plus the next or the slope for linear interpolation. And we may should be sampling more often then fps times a second.%%%

Janne Karhu commented

2010-12-07 14:45:33 +01:00

%%%This is a valid problem indeed. For video checking the values once per frame works fine of course, but for audio this is definitely noticable. However this is not really a bug, since the code works as it's intended to. It's just that the original design is not really well equiped to handle this kind of things. I'll move this to the todo-list, so that this issue can be handled properly in the future with good design behind it.%%%