Rear Channels Levels Wrong in AC3 5.1 Export #104190

New Issue

Walt Talley · 2023-01-27T21:55:55+01:00

Walt Talley commented

2023-01-27 21:55:55 +01:00

System Information
Operating system: Windows 10.0.19045 Build 19045
Graphics card: NVIDIA GeoForce RTX 3090

Blender Version
Broken: 3.3.1 b292cfe5a9
Worked: Don't Know

Short Description
When exporting to 5.1 surround sound, using AC3 it amplifies the rear channels compared to the front channels.
Happens same on both Video Exports or Render Audio.

Steps
#104190.blend
Open file and render audio. Speakers at +/-30° have amplitude of about 0.4, speakers at +/-110° have amplitude of about 0.9. Seems, that it should be other way around.

**System Information** Operating system: Windows 10.0.19045 Build 19045 Graphics card: NVIDIA GeoForce RTX 3090 **Blender Version** Broken: 3.3.1 b292cfe5a936 Worked: Don't Know Short Description When exporting to 5.1 surround sound, using AC3 it amplifies the rear channels compared to the front channels. Happens same on both Video Exports or Render Audio. ![Blender Audio Levels Issue.png](https://archive.blender.org/developer/F14204545/Blender_Audio_Levels_Issue.png) Steps [#104190.blend](https://archive.blender.org/developer/F14216472/T104190.blend) Open file and render audio. Speakers at +/-30° have amplitude of about 0.4, speakers at +/-110° have amplitude of about 0.9. Seems, that it should be other way around.

Walt Talley commented

2023-01-27 21:55:55 +01:00

Added subscriber: @walt.talley

Richard Antalik commented

2023-01-31 04:03:44 +01:00

Added subscriber: @iss

Richard Antalik commented

2023-01-31 04:03:44 +01:00

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

Richard Antalik commented

2023-01-31 04:03:44 +01:00

Please upload .blend file or provide pan levels for each strip.

Richard Antalik commented

2023-01-31 04:59:00 +01:00

Actually I think, I was able to reproduce this, will upload sample files

Richard Antalik commented

2023-01-31 05:09:03 +01:00

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

Richard Antalik commented

2023-01-31 05:09:37 +01:00

Added subscriber: @neXyon

Richard Antalik commented

2023-01-31 05:09:37 +01:00

@neXyon Can you check if this is correct?

Joerg Mueller commented

2023-02-01 10:55:34 +01:00

The sound file in your blend file is stereo. Stereo speakers are placed at +/-90° - so if you distribute the sound to +/-30° and +/-110° 5.1 speakers, then the 110 ones are clearly closer. You can even compute the amplitude: cos(110-90)^2 and cos(30-90)^2.

The screenshot in the report shows a 5.1 input file? Is that available somewhere?

The sound file in your blend file is stereo. Stereo speakers are placed at +/-90° - so if you distribute the sound to +/-30° and +/-110° 5.1 speakers, then the 110 ones are clearly closer. You can even compute the amplitude: cos(110-90)^2 and cos(30-90)^2. The screenshot in the report shows a 5.1 input file? Is that available somewhere?

Richard Antalik commented

2023-02-01 12:09:26 +01:00

In #104190#1482516, @neXyon wrote:
The sound file in your blend file is stereo. Stereo speakers are placed at +/-90°

I see. I assumed stereo speakers to be around +/-30° as well, as it's closer real world setups...

Would it be possible to map stereo speakers to front speakers in both playback and rendering? I would imagine this would represent actual hearing bit closer than current state. I haven't checked this in more detail though

The screenshot in the report shows a 5.1 input file? Is that available somewhere?

The file wasn't provided but amplitude ratio looked very similar, so I assumed this was same case.

> In #104190#1482516, @neXyon wrote: > The sound file in your blend file is stereo. Stereo speakers are placed at +/-90° I see. I assumed stereo speakers to be around +/-30° as well, as it's closer real world setups... Would it be possible to map stereo speakers to front speakers in both playback and rendering? I would imagine this would represent actual hearing bit closer than current state. I haven't checked this in more detail though > The screenshot in the report shows a 5.1 input file? Is that available somewhere? The file wasn't provided but amplitude ratio looked very similar, so I assumed this was same case.

Joerg Mueller commented

2023-02-01 17:37:06 +01:00

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

Joerg Mueller self-assigned this 2023-02-01 17:37:06 +01:00

Joerg Mueller commented

2023-02-01 17:37:06 +01:00

No this is not possible, for three main reasons: First, panning is linearly translated to the speaker angle by a factor of 90 °, i.e. -1 panning is full left, 1 is full right and anything in between or extrapolated gives you an expected panning. Second, I don't want to break the behavior when working with older files and backwards compatibility would be unnecessarily complex to implement. Third, the issue of remapping channels between different speaker setups is very difficult and there is no real standard. People actually have their speakers set up all over the place and the only way to get something accurate is using something like ambisonics. There is actually only one setup that is the pretty much the same for everyone: stereo headphones - and there we are pretty close to 90 degrees. ;)

We could let the user modify the speaker angles, but the UI would be quite complex there as well since at the very least you would have to specify speaker angles for all possible speaker counts. If the users really want full control, they should split their audio files into single channel files and manually pan them in Blender. That may sound tedious but is actually the most simple UI solution.

Now as for this bug, @walt.talley please provide a sample file with which this issue happens so that we can see if it's actually a bug and what is going on.

No this is not possible, for three main reasons: First, panning is linearly translated to the speaker angle by a factor of 90 °, i.e. -1 panning is full left, 1 is full right and anything in between or extrapolated gives you an expected panning. Second, I don't want to break the behavior when working with older files and backwards compatibility would be unnecessarily complex to implement. Third, the issue of remapping channels between different speaker setups is very difficult and there is no real standard. People actually have their speakers set up all over the place and the only way to get something accurate is using something like ambisonics. There is actually only one setup that is the pretty much the same for everyone: stereo headphones - and there we are pretty close to 90 degrees. ;) We could let the user modify the speaker angles, but the UI would be quite complex there as well since at the very least you would have to specify speaker angles for all possible speaker counts. If the users really want full control, they should split their audio files into single channel files and manually pan them in Blender. That may sound tedious but is actually the most simple UI solution. Now as for this bug, @walt.talley please provide a sample file with which this issue happens so that we can see if it's actually a bug and what is going on.

Bastien Montagne added this to the Module: Core project 2023-02-09 15:43:53 +01:00

Bastien Montagne removed this from the Module: Core project 2023-02-09 18:20:29 +01:00

Philipp Oeser removed the

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Rear Channels Levels Wrong in AC3 5.1 Export #104190