8mm Forum: Real time Audio restoration for film projection

This is topic Real time Audio restoration for film projection in forum 16mm Forum at 8mm Forum.

To visit this topic, use this URL:
https://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=5;t=000503

Posted by Vangelis Lympouridis (Member # 1753) on November 05, 2009, 07:05 AM:

Hello,

I spent some time lately to work on how to treat/restore the sound from the projector in real time.
Of course one can use expensive pro audio hardware for that but who can afford it? Not me at least, so I tried with some mastering software with optimized algorithms for real time processing.
I tried a few layouts but my general concept was the following:
First use an EQ to cut of nasty low and high frequencies and remove some of the hiss.
I then used a compressor and a limiter to emphasize mainly the dialogues (mid) frequencies and finally a clipper to avoid any distortion from the process. Another problem that is treated in this way are the big dynamic differences that often a film has. To give an example you set the volume of the projector to enjoy a film based on the dialogues and suddenly a car or the music or something else kicks in that is really disturbing loud!.. That has to do mainly with the production and the sound engineering of the film, and if that was bad cannot be undone anyway, but things certainly improved a lot after some digital post processing.
The final step was to use a noise removal software that can take out the noise/hiss before sending the signal to the amplifier-speakers. This seems to work great, and even that without any other processing offers much less hiss.
I was a bit worried in case the process "digitizes" the sound chromatics destroying the film aesthetic, but no. I suppose that all film qualities are still there but much cleaner and enjoyable. I was wondering if anyone else tried something similar so to exchange some ideas.
I used MaxMsp and VST audio plugins T-RackS 3 Deluxe mastering suite and SoundSoap2 but there are many other alternatives.
I can provide more pictures and sound samples and more info if you want.
Also, there are no generic settings. Each film has to be treated in its own way but experience from the process is being added.
Finally the latency of the whole processing was really small I would guess less than 100ms so not noticeable at all..
Happy screenings
Vangelis

Posted by Bill Brandenstein (Member # 892) on November 05, 2009, 10:40 PM:

With all due respect for you coming up with a rather ingenious process, I'm not sure I get why this is a good idea. Projectors of reasonable quality have decent sound; killing high treble and low bass no doubt has to remove some of the content of the sound, at least in some cases, and bringing out speech by boosting up the midrange certainly has to make everything else seem worse. And 100ms is more than 2 frames late, which to some people would be unnoticed but to me annoying. I've never sound an 8 or 16mm film to have too wide of a dynamic range, usually quite the contrary.

Forgive me for raining on your parade. However, respectable equipment and good quality films (neither of which need be expensive) should sound reasonably clear and good without major processing.

Rebuttals, please.

Posted by Joe McAllister (Member # 825) on November 06, 2009, 02:33 AM:

My own solution to improving 16mm sound at the moment is to pass the signal from the projectors LS output through a graphic equalizer into a decent amp and speakers. I have also had great results using an old valve amp (leak) with a pre amp that has some settings designed for 78rpm record characteristics which seem to suit 16mm frequency and dynamic range very well.
I would love to find a decompression unit ( I think they were called DX'ers) and some Phillips active speakers which apparently "listened" to themselves and adjusted their response to accomodate the acoustics of the room they were playing in.

Posted by Vangelis Lympouridis (Member # 1753) on November 06, 2009, 09:40 AM:

Hello Joe,

Thats a very interesting concept! To be honest with you I ve never heard of decompression before but it seems like a very interesting technique. Please let me know more, especially if you manage to find and try a unit. Can I please ask you how you are using your equalizer? I bet you are treating your films also independently but I was wondering if you apply any generic approach relative to the 16mm film sound spectrum and dynamics.
I was wondering also whether optical sounds ages with the film too and what that practically means for its transformation...
It is interesting this observation with the 78rpm...I will try to find some more about that.
All best regards
Vangelis

P.S> Bill, if you don't have something to compare everything seems ok !...By the way I love American expressions! They are so funny ! ehehehehe "....raining on my parade ! " cooool :-)

Posted by Antonis Galanakis (Member # 1455) on November 06, 2009, 12:10 PM:

Thumbs up Vangeli !

Posted by David Michael Leugers (Member # 166) on November 07, 2009, 06:30 PM:

Pretty cool! I must say though, that I am always impressed with the sound quality from good 16mm prints when played through a good projector. The sound quality from a well maintained JAN played back through a pair of JAN speakers is pretty awesome. Don't know that fiddling with the sound is really needed, especially for my ears. Late model B+H, Kalart Victor, Elmo, EIKI and others have excellent sound.

Posted by Vangelis Lympouridis (Member # 1753) on November 07, 2009, 11:33 PM:

Hello,

I am sure that all projectors are not the same. I only have my projector and nothing to compare it to, so I am more interested as a study to see what I can find while trying to improve my projector's sound.
Playing a bit around I ve noticed that there is a strong hum noise always present.
I used a 50hz hum removal tool to filter it and it worked great.
I ve uploaded a sound which you can listen to online. There is the original sound and then the filtered one, later I just bypassing the filter to focus on the difference. The sound level is higher than normal but notice the difference at the sound when the hum is filtered leaving pure white noise

sound file

I think it is the transformer generating his hum. Do you know if it is common to most projectors ?
Using a sub woofer really makes this problem audible!
V~

Posted by Jeff Taylor (Member # 442) on November 21, 2009, 03:40 PM:

I only have 16mm, so this obviously doesn't apply to 8mm. I take the mono audio from my Eiki xenons into a stereo equalizer which basically acts as a crossover separating everything under 500-600 cycles from the rest of the signal. Under 5-600 goes to a dbx subharmonic synthesizer which creates a real bass "feel" (you can honestly feel your pants legs move on a film with a good track). That goes to one channel of a QSM 900 watt amp, while the higher frequencies go to the other channel. The bass side goes to a Yamaha 18" subwoofer cabinet, while the "stage" channel goes to a 12"/horn Yamaha box. Honestly I'm very happy with the results which are the result of 50 years (God, am I that old??????????) of 16mm tinkering.

UBB.classic^TM 6.3.1.2