Downmix Feature

[AP]

Hi all,
We have been busy working on some fixes and improvements! The DSD 4.0 downmix in the original firmware wasn't probably very useful for many. Also, there was a little bug in the mixing algorithm and some customers pointed out that the Center/LFE channel mapping in the second stereo pair was incorrect (more on this in another thread).

Therefore, we have reworked the downmix from scratch:

• * It works with all audio formats
  * User configurable speaker presence
  * Added Center and LFE channels swap
  * Bit-transparent Downmix bypass mode

How it works. When Downmix is enabled, the Center, LFE and SRB channels can be turned ON or OFF. When the channel is ON, nothing happens and the signal goes through as normal. When OFF, the Center and/or LFE channels are mixed with the front stereo and SRB channels are mixed with SR.

As a result, the 7.1 configuration can be mixed down to 4.0 through the following configs: 6.1, 6.0, 5.1. 5.0 & 4.1.

Also, less common speaker configuration can be achieved from 3.1 down to 2.0 (through 3.0 & 2.1).

Algorithmically the downmix can be described as below:

[center]FL[sub]mix[/sub] = 0.5FL+0.25C+0.25LFE
FR[sub]mix[/sub] = 0.5FR+0.25C+0.25LFE
SRL[sub]mix[/sub]=0.5SRL+0.5SRBL
SRR[sub]mix[/sub]=0.5SRR+0.5SRBR[/center]

And finally, the Center and LFE have been remapped, so the Center is in the left channel of the second stereo pair and the LFE is is the right channel with the option to swap them to the previous configuration.

Menu screen:
[img]http://audiopraise.com/img/VanityPRO_Speakers_screen_small.jpg[/img]

Please feel free to comment here. Also, if anyone would like to try the downmix in beta firmware release, please PM or email me.

Best Regards,
Pavel

[Karl W.]

Great news. I'll send you an email. I'd love to try.

[shamov575]

I would be interested in seeing a 5.1 to 7.1 upmix option, where the surround channels are played through both the surround and back speakers. In a 7.1 configuration, the surround speakers are not placed far enough back. You're left at the very edge of the sound bubble which isn't great. Likewise, by remapping surround l/r to surround back l/r, the angles are off again and it's not quite what it should be. I remember seeing a formula for 5.1 to 7.1 conversion somewhere but I cannot find it anymore. To me, it seems like this option should be fairly easy to add if you agree it is useful enough. To be clear I do not currently own the VanityPRO, however this feature may finally push me over the edge as it would make my speaker layout compatible.

[AP]

Hi shamov575,
Thank you for your suggestion. If I understand correctly, to convert 5.1 mix to 7.1 you only replicate the Surround stereo to Surround Back stereo and have the same signal played via both pairs. That is certainly doable, I would only question if there is any level variation, because if you just replicate the signal it would come out twice as loud. If there is a suggested formula for this 5.1->7.1 upmix, let's try to find it, because it should not be difficult to implement it.
Regards,
Pavel

[OnaIp]

Can you please have an option to drop the LFE channel completely? The consumer AV receiver market provides the option to bleed the LFE channel into the mains when lacking a subwoofer, but in the professional market, the LFE channel is discarded completely. TV/film has been doing that for decades, per Dolby:

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

Stereo downmix options are endless, but if I had to choose one, I'd go with the ITU recommendation: [url=https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.775-4-202212-I!!PDF-E.pdf]https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.775-4-202212-I!!PDF-E.pdf[/url]

Cheers!

[AP]

Hi OnaIP,
Thank you for your suggestion. Removing the LFE channel as a menu option is of course very easy. With the current downmix implementation if you just leave the LFE channel ON then no downmix of the LFE channel into the front stereo occurs. Then, if there is no sub and nothing is connected to the LFE channel, it effectively discards the LFE channel. Or maybe I just don't understand the specific application .
Regards,
Pavel

OnaIp Wrote:
-------------------------------------------------------
> Can you please have an option to drop the LFE
> channel completely? The consumer AV receiver
> market provides the option to bleed the LFE
> channel into the mains when lacking a subwoofer,
> but in the professional market, the LFE channel is
> discarded completely.

[OnaIp]

There is a subwoofer connected. In my use case, the idea is to be able to easily compare (such as a one-button toggle) surround vs stereo mixes somewhere in the monitoring system, and now that I've thought about it some more, I probably wouldn't use the VanityPRO for this feature. It makes more sense to have this feature on a surround monitor controller. It could come in handy as a workaround for certain incomplete implementations of surround monitoring, but I wouldn't ask you to make it a top priority feature ask Thanks for making me dwell on it for clarity!

[AP]

Hi OnaIp,
Thanks for elaborating! If you have any other idea for a new feature or functionality, don't hesitate to share with us.
Best Regards,
Pavel

[bas303]

Hi Pavel,

Love the downmix support as found in V5.

There are two use cases when implemented that would make it even better for me especially when dealing with 2 channel content:

An option to have channel L+R be muxed and sent to the LFE channel. Currently one often has to choose to connect sub either to dedicated LFE channel for HT content or to piggyback on L+R outputs to provide sub bass for stereo content.

Option to have left and right channels be output bit perfectly (so no headroom correction) when 2 channel content is received while having the multi channel content be downmixed as set up for example when not having an center speaker.

cheers,

Bas

[AP]

Hi Bas,
Thanks for the suggestion. This should not be difficult to do. We might add it in the next software release.
Best Regards,
Pavel