LFE DCPs 125 Hz

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  • Create Date 2022-01-05
  • Last Updated 2022-01-06

LFE DCPs 125 Hz

This file is being revised and is not downloadable in the current state – more later....cjf

This 8 Gig file expands into 42 DCPs, each one 10 seconds long, each one testing the different pairs of a 5.1 cinema audio system. (There are 7 DCPs with only one channel.) The signal is an extremely band limited but otherwise standard pink noise.

The front speakers are at -20, the surrounds are 3dB above that, and the LFE are at -30.

There are already .wav files of these pairs on the Media Server.

After some general testing, these files could go there too, delivered by someone who has the bandwidth and speed. (Unfortunately, there seems to be no way to rsync into the MediaServer or I would do that.)

The passcode will be given to those SMPTE Committee members who can do some tests

Process:

3 x 10 second pieces of bandwidth limited Pink Noise were created by an adroit committee member. The 3 are named '125', 60-120 and 120-240. The slopes of 125 look like this. The others are identical except for the 'roll off' frequencies.

With Audacity's Invert command, each has a twin made 180° out of phase. These six files were placed on an Ubuntu 20.04 server, along with a set of slides (universal to all sets) that show the position of the speakers in play, and a subtitle file that places the name of the 'tone' in play onscreen.

DCP-O-Matic (through Carl Harrington) made adjustments to the command line options so that these files can be placed in assigned channels, alone or in pairs (or groups). There is also a command that adjusts the level of the signal.

Thus, the following command will create a DCP directory named "LFE_180_LftSurr_0_R0"that creates an .xml for the  the 180° signal in the LFE channel with a 10 dB decrease from the original .wav file, and create a tone 3 dB hotter into the Left Surround, and also place an appropriately named slide onscreen for 10 seconds along with the subtitle file (which is made to put the name of the wav file in the gap in the center of the slide). (A 2nd command will create the actual DCP. )

sudo dcpomatic2_create -n LFE_180_LftSurr_0_R0 -o 125_DCPs/LFE_180_LftSurr_0_R0 --container-ratio 239 -f 24 -c TST --channel Lfe --gain -10 in-125/125_180deg_-20.wav --channel Ls --gain  in-125/125_0deg_-20.wav --still-length 10 in-125/lfe-sl/LFE_180_LftSurr_0.tiff in-125/p125.xml

These commands are created with an excel file that Concatenates all the various parts with pull downs to change the originating and created files and directories. That excel file is a work in progress, the most recent being here: LFE Project Excel Worksheet

Instructions for creating a Debian/Unbuntu Server for this purpose:

Work In Progress

– drawinΩand further instructions being prepared.

– Download pages for the other two files will be posted soon.

If someone can help secure the site so that others may. be allowed to create/process files, then further instructions for use of this server will be made.

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