Duplicated audio does not sound the same #83997

New Issue

Hugo Schouppe · 2020-12-20T22:08:06+01:00

Hugo Schouppe commented

2020-12-20 22:08:06 +01:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.38

Blender Version
Broken: version:

2.92.0 Alpha, branch: master, commit date: 2020-12-19 06:25, hash: a5a302bd18
2.91.0
Worked: (newest version of Blender that worked as expected)

Short description of error
Duplicating the same audio strip several times in a timeline, gives a different sound.

Exact steps for others to reproduce the error

Download the attached blend-file with a sample audio strip.
Duplicate the audio strip a few times.
Render the output and import the mp4-file into Audacity or Blender to see the wave form. They look different.
Check the sound. The exported audio file from Blender sound different.

Rendering the audio only (menu Render > Render audio) and decreasing the accuracy will improve the audio.

test-audio.blend

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.38 **Blender Version** Broken: version: - 2.92.0 Alpha, branch: master, commit date: 2020-12-19 06:25, hash: `a5a302bd18` - 2.91.0 Worked: (newest version of Blender that worked as expected) **Short description of error** Duplicating the same audio strip several times in a timeline, gives a different sound. **Exact steps for others to reproduce the error** 1. Download the attached blend-file with a sample audio strip. 2. Duplicate the audio strip a few times. 3. Render the output and import the mp4-file into Audacity or Blender to see the wave form. They look different. 4. Check the sound. The exported audio file from Blender sound different. Rendering the audio only (menu Render > Render audio) and decreasing the accuracy will improve the audio. [test-audio.blend](https://archive.blender.org/developer/F9520125/test-audio.blend)

Hugo Schouppe commented

2020-12-20 22:08:06 +01:00

Added subscriber: @HUSCH

Robert Guetzkow commented

2020-12-21 15:08:22 +01:00

Added subscriber: @rjg

Robert Guetzkow commented

2020-12-21 15:08:22 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Robert Guetzkow commented

2020-12-21 15:08:22 +01:00

I've tested this only Linux and can't hear any different between the duplicated strips. That the waveform of the export to mp4 may not look exactly like the one from the original .wav file can be due to lossy encoding. Could you please provide a file with the audio duplicated where the strips sound differently? How often did you have to duplicate the audio strip until the issue occurred?

Robert Guetzkow commented

2020-12-21 15:19:13 +01:00

The problem could be the same as #83991.

Hugo Schouppe commented

2020-12-21 16:13:21 +01:00

I included the original sound-file (bounce.wav), a blend-file with the sound-strip + 2x duplicated. You can hear the difference between the swooshes (but not very clearly). I included also the wave-form of the render (of the three (identical?) soundstrips. You can clearly see that the waveform of all three has small differences. After rendering the audio only, in which case you can set the accuracy (low value = high accuracy), the differences disappear. I included also the Audacity-profile of this audio-only output..

Blendfile
test-audio1.blend1

Audacity profile of rendered (MP4) output

Audacity profile of render audio (AC) output

Sound
Bounce.wav

I included the original sound-file (bounce.wav), a blend-file with the sound-strip + 2x duplicated. You can hear the difference between the swooshes (but not very clearly). I included also the wave-form of the render (of the three (identical?) soundstrips. You can clearly see that the waveform of all three has small differences. After rendering the audio only, in which case you can set the accuracy (low value = high accuracy), the differences disappear. I included also the Audacity-profile of this audio-only output.. Blendfile [test-audio1.blend1](https://archive.blender.org/developer/F9521943/test-audio1.blend1) Audacity profile of rendered (MP4) output ![test-audio2-audacity.png](https://archive.blender.org/developer/F9521942/test-audio2-audacity.png) Audacity profile of render audio (AC) output ![test-audio1-audacity.png](https://archive.blender.org/developer/F9521941/test-audio1-audacity.png) Sound [Bounce.wav](https://archive.blender.org/developer/F9521940/Bounce.wav)

Robert Guetzkow commented

2020-12-21 16:17:51 +01:00

Changed status from 'Needs User Info' to: 'Needs Triage'

Robert Guetzkow commented

2020-12-21 16:17:51 +01:00

Thank you for the files, we will investigate.

Robert Guetzkow commented

2020-12-21 16:28:58 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Robert Guetzkow commented

2020-12-21 16:33:56 +01:00

After the export the audio is significantly different, before the export they all sound the same to me, but that might just be my ears not picking up subtle differences.

Hugo Schouppe commented

2020-12-21 16:45:46 +01:00

Yes, you're right. Before the export they sound indeed the same. Perhaps I wanted to hear the difference because I knew about the profiles. So, I did the test and recorded the sound (with volume set to 5) with a microphone. The waveform looks identical in Audacity. So, it's a problem of the render (to video). The render audio can do it right, if accuracy is set low.

tintwotin commented

2020-12-21 19:30:21 +01:00

Added subscribers: @neXyon, @tintwotin

tintwotin commented

2020-12-21 19:30:21 +01:00

It could be related to the fixed value of AUD_DEFAULT_BUFFER_SIZE. https://developer.blender.org/diffusion/B/browse/master/extern/audaspace/config/Audaspace.h.in$103
It seems to be the reading-buffer-size which is set too high and cause inaccuracy. Maybe this value should be lowered or exposed so users can set this value manually?

@neXyon Maybe you could have a look at this?

It could be related to the fixed value of AUD_DEFAULT_BUFFER_SIZE. https://developer.blender.org/diffusion/B/browse/master/extern/audaspace/config/Audaspace.h.in$103 It seems to be the reading-buffer-size which is set too high and cause inaccuracy. Maybe this value should be lowered or exposed so users can set this value manually? @neXyon Maybe you could have a look at this?

blender-admin commented

2020-12-24 10:39:28 +01:00

This issue was referenced by 83ad35cb9c

This issue was referenced by 83ad35cb9c41c7e7df5ff239e5c2232742f4d5b6

Joerg Mueller self-assigned this 2020-12-24 10:43:51 +01:00

Joerg Mueller commented

2020-12-24 10:43:51 +01:00

That one was a bit harder to find. Running down the wrong rabbit hole, I also found another inaccuracy! :D

@tintwotin While the behavior depends on the size of the mixdown buffer, this is not the precise cause for the bug. During audio rendering, users can actually choose the value manually.

That one was a bit harder to find. Running down the wrong rabbit hole, I also found another inaccuracy! :D @tintwotin While the behavior depends on the size of the mixdown buffer, this is not the precise cause for the bug. During audio rendering, users can actually choose the value manually.

Joerg Mueller commented

2020-12-24 10:44:44 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Joerg Mueller closed this issue

2020-12-24 10:44:44 +01:00

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Duplicated audio does not sound the same #83997