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Audio glitch on every volume keyframe

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I just came to Kdenlive (daily build for x86) to make my first video project. I use the "Volume (keyframable)" effect to envelop music track and an audio commentary track. Whenever the commentary begins, I lower the volume of the music clip and raise it afterwards.

I experience a glitch on every keyframe that is not the first or last keyframe in the clip and that is not 0% or 100% gain and that is not positioned over silence. The glitch has a duration of one frame (18fps=2666samples in my case) and appears as short volume change. When the keyframe is between 0% and 100% gain, the glitch has lower volume. When the keyframe is above 100%, the glitch has higher volume. It looks like that gain is applied twice at each keyframe.

My current workaround is to split the music clip at each keyframe, so there is never a keyframe inside a clip.

best regards

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The stable Kdenlive branch Applications/15.08 does not seem to have this issue; albeit I suspect it to be probably a MLT issue. I'm currently using the keyframable audio volume effect to reduce gain of the background music to allow voice over. While I don't get any glitches at the keyframes, I got slightly distorted audio wherever the background music and speaker voice were mixed. I ended up transcoding both audio sources to use the same sampling rate and format (wav, 48kHz, 32bit float). This then gave a satisfying audio result without distortions.

I'm currently using the most recent stable MLT build, 0.9.8.

I also had to work around a problem where in my project the second audio track would not mix with other audio tracks, no clue why. In fact, I cannot even add or remove tracks at this time, but this seems to be a Kdenlive bug.

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