Audio meter drop & overshoot issue

Me again. I've recently edited a video where I had to keyframe a pure sine tone (1000 Hz) so that it beeps on and off. While doing so I noticed two issues:

  1. When playing the pure sine tone without any modifications, the audio meter suddenly drops even though it's still playing.
  2. When keyframing the Level property of the tone, a massive overshoot occurs when the level is keyframed from -60.0 dB to 0.0 dB. This only seems to happen when the beep interval is rather short, 5 frames in my instance.

GIF:

The composite shot was set to 1280 x 720 with 30 fps and Square Pixels. No fog enabled, motion blur left at the standard values.

I don't know if this issue is truly a bug or rather an effect of digital audio? The tone was generated in Audacity with an Amplitude of 0.8 (peak amplitude at -2 dB). The file was exported as a WAV 32-bit float PCM. Maybe -2 dB are too loud in the first place?

My System specs:

  • OS: Windows 10 Version 1809 (OS Build 17763.615)
  • CPU: AMD FX-8320E
  • RAM: 8192MB (DDR3)
  • GPU: Sapphire (AMD Radeon) HD 7950 (Radeon Software version 19.6.2, BIOS version 015.025.000.099)
  • DirectX version: 12
  • HitFilm version: Pro 12.3.8815.7201

Regards,

Cronoxyd

Comments

  • edited July 18

    TMI update: I've hooked up an oscilloscope (Tektronix TDS 350) to my PC and took two samples:

    1000 Hz sine wave (w/o keyframing)

    1000 Hz sine wave (w/ keyframes, rising from -60 dB to 0 dB in 166.66 ms or 5 frames @ 30 fps)

    The image shows only two keyframes (@ -60 and 0 dB).

    Dunno if it helps in any way, it's at least somewhat interesting to look at. And sorry for the bad quality, I had to take these snapshots with my phone since my oscilloscope doesn't support image export.

    Regards,

    Cronoxyd

  • Okay last update, I promise 😅: I've recorded the HitFilm output in audacity and also generated a sine wave and then applied the Fade In and Fade Out effects in Audacity to check whether it is my sound chip playing tricks on me:

    But as you can see, the manually generated waveform (lower) is smooth and without overshoot.

    The HilFilm generated one is the upper one and it not only shows the overshoot (clipping at the 0,15 mark) but you can also "see" the frames in the wave (label track in the middle for reference).

    My guess is that this might be an issue in HitFilm because it seems that the audio generation is handled per frame and then discarded where it should be carried over into the next frame.

    Regards,

    Cronoxyd

  • Tag @cedricbonnier this looks like something. 

    @Cronoxyd do you have the media file to share, try it on another architecture to see if issue follows.

  • @Cronoxyd something odd happening there, I can recreate it as well using your file. I suggest logging a support ticket.

  • @Cronoxyd Please could you send this in a support ticket, and I will ask the Dev team to take a look.

  • @DibsMcCallum I've created a ticket.

  • Thank you, I have passed it onto the Devs to investigate. 

     

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