LFE and the DD Downmix to (original DS)

[kfbkfb]

The Dolby Labs standard for creating a Dolby Surround encoded version
from Dolby Digital 5.1 channel content leaves out the LFE channel (I've
never understood the reason for this).

My Sony Blu-ray/SACD player will create a DS encoded output from
MCH SACD, DTS and DD, but still leaves out the LFE channel content.

Anyone know of a downmix process (inside a Blu-ray player) that
adds the LFE content to the Matrix encoded output (could be
DynaQuad with the LFE content added to Lt and Rt so it would
be decoded by a Dolby Surround decoder yet not be an "official"
Dolby Surround encode)?


Kirk Bayne

 

[par4ken]

I think the main reason that it's not done is there is no real reason for it. Most of the bass would be carried in the main channels already. Adding more bass would be overkill, the LFE channels use is more system dependant. As I understand it bass management directs the LFE channel to the proper speakers or sub and controls the level as well. With no sub and small speakers it wouldn't be used at all.
When I mix-down a 5.1 source for Quad playback I put the Cf into the front channels at -3 Db. I usually put the LFE in the rears at -3 Db or into all four channels at -6 Db. For Quad titles that were put out as 5.1, I simply discard the Cf and LFE channels as they are not need an are merely derived from the original four channels anyway.

 

[kfbkfb]

I'm probably in a small minority, still using DS, I think the LFE
content shouldn't be discarded, just placed in CF.


Kirk Bayne

 

[Wunlow]

Some of the answer comes from the original use of the .1 channel in 5.1 cinema uses and it's translation to consumer 5.1.

When the 5.1 system was devised, the five primary channels were always meant to all be full range with a low end equaling the LFE channel.

So why even include a separate LFE channel?

The reason was ultra low "Sensurround" type of effects that were dedicated to explosions and other Low Frequency Effects variety that can be very loud and very dynamic.

This type of potentially system threatening bass was not considered essential and is potentially dangerous for lower end systems. So from day #1, all consumer 5.1 mixes have been done knowing the LFE will be discarded in a stereo or Dolby Surround mix-down. Professional mixers know this and should be mixing accordingly.

In short: If ultra low end LFE is essential, a discrete 5.1 system is required due to the reasons above.