Render audio produces random clipping #79374

New Issue

Lord Odin · 2020-07-29T20:46:05+02:00

Lord Odin commented

2020-07-29 20:46:05 +02:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce RTX 2080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.75

Blender Version
Broken: version: 2.90.0 Alpha, branch: master, commit date: 2020-06-25 21:53, hash: 62aa103d48

Short description of error
I have a blend file with audio placed in the sequencer according to when items hitting the ground

What works:
Scrubbing / Playing in the viewport
Exporting as a video h264 mp4 with vorbis audio

What doesn't work:
Exporting as a video h264 mp4 with mp3 audio
Exporting as a video h264 mp4 with aac audio
Rendering audio mix down as vorbis
Rendering audio mix down as flac
Rendering audio mix down as mp3

When rendering the same scene multiple times, clipping appears randomly:

Blend File
sound_error.blend

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce RTX 2080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.75 **Blender Version** Broken: version: 2.90.0 Alpha, branch: master, commit date: 2020-06-25 21:53, hash: `62aa103d48` **Short description of error** I have a blend file with audio placed in the sequencer according to when items hitting the ground ![blender_HHgYZJcZBY.png](https://archive.blender.org/developer/F8729103/blender_HHgYZJcZBY.png) What works: Scrubbing / Playing in the viewport Exporting as a video h264 mp4 with vorbis audio What doesn't work: Exporting as a video h264 mp4 with mp3 audio Exporting as a video h264 mp4 with aac audio Rendering audio mix down as vorbis Rendering audio mix down as flac Rendering audio mix down as mp3 ![image.png](https://archive.blender.org/developer/F8729138/image.png) ![audacity_QQhPy9QIEv.png](https://archive.blender.org/developer/F8729109/audacity_QQhPy9QIEv.png) When rendering the same scene multiple times, clipping appears randomly: ![random clipping from same scene.PNG](https://archive.blender.org/developer/F8733143/random_clipping_from_same_scene.PNG) **Blend File** [sound_error.blend](https://archive.blender.org/developer/F8729148/sound_error.blend)

Lord Odin commented

2020-07-29 20:46:05 +02:00

Added subscriber: @derekbarker

ChristopherAnderssarian commented

2020-07-30 10:41:39 +02:00

Added subscribers: @neXyon, @ChristopherAnderssarian

ChristopherAnderssarian commented

2020-07-30 10:41:39 +02:00

I would hazard a guess that there is a some limiter on for the vorbis video encode.

In #54418#492826, @neXyon wrote:
When the number of channels is changed, the total power (not amplitude) is kept at the same level.
...merging stereo to mono, the power of the two stereo channels is added and not averaged. This approach is volume preserving and is also what OpenAL does, though Blender doesn't use OpenAL to do this in the sequencer.

@neXyon can clarify, but I think this is working as intended...

I would hazard a guess that there is a some limiter on for the vorbis video encode. > In #54418#492826, @neXyon wrote: > When the number of channels is changed, the total power (not amplitude) is kept at the same level. >...merging stereo to mono, the power of the two stereo channels is added and not averaged. This approach is volume preserving and is also what OpenAL does, though Blender doesn't use OpenAL to do this in the sequencer. @neXyon can clarify, but I think this is working as intended...

Lord Odin commented

2020-07-31 10:00:39 +02:00

This comment was removed by @derekbarker

*This comment was removed by @derekbarker*

Lord Odin commented

2020-07-31 10:07:50 +02:00

@neXyon can clarify, but I think this is working as intended...

Id have to disagree considering its the same sound on every frame in that blend but the clipping only happens randomly a few times.
Since the frames are so even and densely packed if it was something that was meant to happen you would figure it would happen every time not randomly.

> @neXyon can clarify, but I think this is working as intended... Id have to disagree considering its the same sound on every frame in that blend but the clipping only happens randomly a few times. Since the frames are so even and densely packed if it was something that was meant to happen you would figure it would happen every time not randomly. ![image.png](https://archive.blender.org/developer/F8732733/image.png)

ChristopherAnderssarian changed title from ~~Render audio produces horrible clipping~~ to Render audio produces random clipping

2020-07-31 13:33:26 +02:00

ChristopherAnderssarian commented

2020-07-31 13:33:33 +02:00

Ah, my mistake, I took the "horrible clipping" to mean that the audio was unusable.

Ah, my mistake, I took the *"horrible clipping"* to mean that the audio was unusable.

Lord Odin commented

2020-07-31 13:56:48 +02:00

Here is the audio if you didn't try exporting it your self
test.flac

Here is the audio if you didn't try exporting it your self [test.flac](https://archive.blender.org/developer/F8733210/test.flac)

Richard Antalik commented

2020-08-01 23:37:21 +02:00

Added subscriber: @iss

Richard Antalik commented

2020-08-01 23:37:21 +02:00

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

Richard Antalik commented

2020-08-01 23:37:21 +02:00

@derekbarker can you try this:

@derekbarker can you try this: ![Untitled.png](https://archive.blender.org/developer/F8736661/Untitled.png)

Lord Odin commented

2020-08-02 13:06:22 +02:00

In #79374#988991, @iss wrote:
@derekbarker can you try this:

32 accuracy seems to fix it. I was always upping the accuracy (Because bigger is better obviously)

Care to explain why less accuracy is better?

> In #79374#988991, @iss wrote: > @derekbarker can you try this: > ![Untitled.png](https://archive.blender.org/developer/F8736661/Untitled.png) 32 accuracy seems to fix it. I was always upping the accuracy (Because bigger is better obviously) Care to explain why less accuracy is better?

Richard Antalik commented

2020-08-02 19:36:52 +02:00

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

Richard Antalik closed this issue

2020-08-02 19:36:52 +02:00

Richard Antalik self-assigned this 2020-08-02 19:36:52 +02:00

Richard Antalik commented

2020-08-02 19:36:52 +02:00

In #79374#989215, @derekbarker wrote:

In #79374#988991, @iss wrote:
@derekbarker can you try this:

32 accuracy seems to fix it. I was always upping the accuracy (Because bigger is better obviously)

Care to explain why less accuracy is better?

It says so in tooltip :)

Well I am no 100% sure. I think accuracy is measured in audio samples, probably of project sample rate. it definitely helps to lower accuracy if you use fast animations like quick fades and such.

In this case it probably renders 1024 samples to buffer and "request updates" and Blender tells it that a strip should be already playing and we are xx samples late, so it starts playing not from beginning. This is based on rough knowledge of how audio system works, so info may be inaccurate.

However this works as designed, it is not perfect, but for vast majority of use cases, this works good enough.

> In #79374#989215, @derekbarker wrote: >> In #79374#988991, @iss wrote: >> @derekbarker can you try this: >> ![Untitled.png](https://archive.blender.org/developer/F8736661/Untitled.png) > > 32 accuracy seems to fix it. I was always upping the accuracy (Because bigger is better obviously) > > Care to explain why less accuracy is better? It says so in tooltip :) Well I am no 100% sure. I think accuracy is measured in audio samples, probably of project sample rate. it definitely helps to lower accuracy if you use fast animations like quick fades and such. In this case it probably renders 1024 samples to buffer and "request updates" and Blender tells it that a strip should be already playing and we are xx samples late, so it starts playing not from beginning. This is based on rough knowledge of how audio system works, so info may be inaccurate. However this works as designed, it is not perfect, but for vast majority of use cases, this works good enough.

blender-admin commented

2020-08-03 17:40:31 +02:00

This issue was referenced by f9aba4f6e1

This issue was referenced by f9aba4f6e190b9411ab3cd68e9c6d90cc68eb5c7

blender-admin commented

2020-08-03 17:40:31 +02:00

This issue was referenced by 3593dff147

This issue was referenced by 3593dff147ae2a13c07e6338cb0d6a71218596b1

Richard Antalik was unassigned by Joerg Mueller

2020-08-03 17:41:41 +02:00

Joerg Mueller self-assigned this 2020-08-03 17:41:41 +02:00

Joerg Mueller commented