This IS the Avid L2: 9/22/24

Wednesday, September 25, 2024

Re: [Avid-L2] 5.1 Fold Down to Stereo Math Quiz for today?

LtRt is, I believe, designed to be un-matrixed back to surround (i.e. Dolby ProLogic II encoding/decoding) - from back in the day when surround was hidden in the stereo mix (roughly: anything mono -> C, anything stereo -> LR anything 90° different -> LsRs).

I don't *think* anything is relying on PLII any more - any downmixed stereo is likely to be LoRo.

Isn't most stereo in Atmos/5.1 broadcast chain now derived from the LoRo downmix done by the receiver?

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Tuesday, September 24, 2024

Re: [Avid-L2] 5.1 Fold Down to Stereo Math Quiz for today?

Wild guess is that it is not time shifted back aka 'un'

Perhaps to have a richer sound on MS situations. (Where in downmix to mono you loose an entire mic with ambient, never understood why correlation meters don't go berserk on that.)

Bouke / edit 'B

videotoolshed.com
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On 24 Sep 2024, at 21:36, John Moore <bigfish@pacbell.net> wrote:

[Edited Message Follows]

Nice article. It's interesting that one of the choices involves a 90 degree phase shift to avoid undesirable signal cancellation. I understand a 180 degree phase shift is reversing the polarity of the signal. I can envision what a perfect sine wave shifted 90 degrees looks like compared to the original sine wave but a complex audio waveform with several sinusoidal esk waveforms is harder to picture. Is the particular signal being time shifted relative to the other signal and then later un timeshifted?

Here's part of the article:

Stereo downmix settings:

All the stereo downmix options except Direct Render are created by first creating a 5.1 downmix
from the 7.1 render of .atmos content, and then downmixing from 5.1 to 2.0 in the same manner as 2.0
consumer products. The choice of the 5.1 downmix method above affects the subsequent 5.1 to 2.0 downmix.

Lo/Ro - default: Downmixes from 5.1 to Stereo using the coefficients:
Lo = L + (–3 dB × C) + (–3 dB × Ls)
Ro = R + (–3 dB × C) + (–3 dB × Rs)

Lt/Rt (Pro Logic II): Downmixes from 5.1 to Stereo using the coefficients:
Lt = L + (–3 dB × C) – (–1.2 dB × Ls) – (–6.2 dB × Rs)
Rt = R + (–3 dB × C) + (–6.2 dB × Ls) + (–1.2 dB × Rs)

Lt/Rt (Pro Logic II) w/Phase 90: Downmixes from 5.1 to Stereo using the coefficients:
Lt = L + (–3 dB × C) – (–1.2 dB × Ls) – (–6.2 dB × Rs)
Rt = R + (–3 dB × C) + (–6.2 dB × Ls) + (–1.2 dB × Rs)
Applies a 90 degree phase shift to Ls/Rs prior to feeding the downmix which reduces undesirable signal cancellation,
improves imaging, and enables proper matrix decoding. It is strongly recommended to use the 90-degree phase shift for
any Lt/Rt downmixes.

Re: [Avid-L2] 5.1 Fold Down to Stereo Math Quiz for today?

[Edited Message Follows]

Nice article. It's interesting that one of the choices involves a 90 degree phase shift to avoid undesirable signal cancellation. I understand a 180 degree phase shift is reversing the polarity of the signal. I can envision what a perfect sine wave shifted 90 degrees looks like compared to the original sine wave but a complex audio waveform with several sinusoidal esk waveforms is harder to picture. Is the particular signal being time shifted relative to the other signal and then later un timeshifted?

Here's part of the article:

Stereo downmix settings:

All the stereo downmix options except Direct Render are created by first creating a 5.1 downmix

from the 7.1 render of .atmos content, and then downmixing from 5.1 to 2.0 in the same manner as 2.0

consumer products. The choice of the 5.1 downmix method above affects the subsequent 5.1 to 2.0 downmix.

Lo/Ro - default: Downmixes from 5.1 to Stereo using the coefficients:

Lo = L + (–3 dB × C) + (–3 dB × Ls)

Ro = R + (–3 dB × C) + (–3 dB × Rs)

Lt/Rt (Pro Logic II): Downmixes from 5.1 to Stereo using the coefficients:

Lt = L + (–3 dB × C) – (–1.2 dB × Ls) – (–6.2 dB × Rs)

Rt = R + (–3 dB × C) + (–6.2 dB × Ls) + (–1.2 dB × Rs)

Lt/Rt (Pro Logic II) w/Phase 90: Downmixes from 5.1 to Stereo using the coefficients:

Lt = L + (–3 dB × C) – (–1.2 dB × Ls) – (–6.2 dB × Rs)

Rt = R + (–3 dB × C) + (–6.2 dB × Ls) + (–1.2 dB × Rs)

Applies a 90 degree phase shift to Ls/Rs prior to feeding the downmix which reduces undesirable signal cancellation,

improves imaging, and enables proper matrix decoding. It is strongly recommended to use the 90-degree phase shift for

any Lt/Rt downmixes.

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Re: [Avid-L2] 5.1 Fold Down to Stereo Math Quiz for today?

Interesting article. It's interesting that one of the choices involves a 90 degree phase shift to avoid undesirable signal cancellation. I understand a 180 degree phase shift is reversing the polarity of the signal. I can envision what a perfect sine wave shifted 90 degrees looks like compared to the original sine wave but a complex audio waveform with several sinusoidal esk waveforms is harder to picture. Is the particular signal being time shifted relative to the other signal and then later un timeshifted?

Here's part of the article:

Stereo downmix settings:

All the stereo downmix options except Direct Render are created by first creating a 5.1 downmix

from the 7.1 render of .atmos content, and then downmixing from 5.1 to 2.0 in the same manner as 2.0

consumer products. The choice of the 5.1 downmix method above affects the subsequent 5.1 to 2.0 downmix.

Lo/Ro - default: Downmixes from 5.1 to Stereo using the coefficients:

Lo = L + (–3 dB × C) + (–3 dB × Ls)

Ro = R + (–3 dB × C) + (–3 dB × Rs)

Lt/Rt (Pro Logic II): Downmixes from 5.1 to Stereo using the coefficients:

Lt = L + (–3 dB × C) – (–1.2 dB × Ls) – (–6.2 dB × Rs)

Rt = R + (–3 dB × C) + (–6.2 dB × Ls) + (–1.2 dB × Rs)

Lt/Rt (Pro Logic II) w/Phase 90: Downmixes from 5.1 to Stereo using the coefficients:

Lt = L + (–3 dB × C) – (–1.2 dB × Ls) – (–6.2 dB × Rs)

Rt = R + (–3 dB × C) + (–6.2 dB × Ls) + (–1.2 dB × Rs)

Applies a 90 degree phase shift to Ls/Rs prior to feeding the downmix which reduces undesirable signal cancellation,

improves imaging, and enables proper matrix decoding. It is strongly recommended to use the 90-degree phase shift for

any Lt/Rt downmixes.

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Monday, September 23, 2024

Re: [Avid-L2] What is the purpose of Boris Title Studio Stand Alone App/Program?

Well this thread from 2019 seemed promising but I still don't see an export function added 5 years later:

https://forum.borisfx.com/t/exporting-files-from-title-studio/6877/13

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[Avid-L2] What is the purpose of Boris Title Studio Stand Alone App/Program?

I'm trying to find a way to export either from BCC Title Studio in Avid or the Stand Alone Boris Title Studio anything. I can save a project but how do I export a file out of Boris Title Studio. My goal is to take the text I've created in Avid BCC Title Studio and export it as a keyable element I can bring into photo shop. I must be missing something obvious in the interface. What's the point of a stand alone version of the app if you can't export what you create. I must be missing the obvious.

John Moore Barking Trout Productions Studio City, CA bigfish@pacbell.net

Re: [Avid-L2] 5.1 Fold Down to Stereo Math Quiz for today?

https://professionalsupport.dolby.com/s/article/How-do-the-5-1-and-Stereo-downmix-settings-work?language=en_US

BUT, go back to the sound mixer and tell him you don't like his mix.

6 dB is A LOT, it might also be a mistake instead of a choice.

Bouke / edit 'B

videotoolshed.com
Van Oldenbarneveltstraat 33
6512 AS Nijmegen, the Netherlands
+31 6 21817248
If you want to send me large files, please use:
https://videotoolshed.wetransfer.com/

On 23 Sep 2024, at 20:56, John Moore <bigfish@pacbell.net> wrote:

I have complete mix stems for our 2.0 and 5.1 mix. There is a short nat sound section that I think should be a bit louder, +6db to be exact. Listening to the 2.0 mix I added the necessary audio keyframes to the left and right mix stems to ramp up the +6db in the short nat sound section and ramping back to 0db after the ramp up. This sounds the way I would like it to have been mixed.

My question is for the 5.1 mix stems can I apply the same +6db keyframe ramp up to the L,R,Ls,Rs & Center stems and have that effect the surround mix the same way. Also the center channel has the Nat Sound in it. It is my understanding, correct me if I'm wrong, that in ProTools they mix 5.1 and then fold down to the 2.0 stereo mix. I'm not clear on what the gain structure math is for the 5.1 to 2.0 fold down but I assume there is a formular as to how the various tracks are multed together to achieve the 2.0 mix.

My log math is so long gone but I'm thinking I should apply the 6db lift to all those stems.

John Moore Barking Trout Productions Studio City, CA bigfish@pacbell.net

[Avid-L2] 5.1 Fold Down to Stereo Math Quiz for today?

I have complete mix stems for our 2.0 and 5.1 mix. There is a short nat sound section that I think should be a bit louder, +6db to be exact. Listening to the 2.0 mix I added the necessary audio keyframes to the left and right mix stems to ramp up the +6db in the short nat sound section and ramping back to 0db after the ramp up. This sounds the way I would like it to have been mixed.

My question is for the 5.1 mix stems can I apply the same +6db keyframe ramp up to the L,R,Ls,Rs & Center stems and have that effect the surround mix the same way. Also the center channel has the Nat Sound in it. It is my understanding, correct me if I'm wrong, that in ProTools they mix 5.1 and then fold down to the 2.0 stereo mix. I'm not clear on what the gain structure math is for the 5.1 to 2.0 fold down but I assume there is a formular as to how the various tracks are multed together to achieve the 2.0 mix.

My log math is so long gone but I'm thinking I should apply the 6db lift to all those stems.

John Moore Barking Trout Productions Studio City, CA bigfish@pacbell.net