Film-Tech Forum ARCHIVE: CP750 remote control

This is topic CP750 remote control in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Wim Nagtegaal (Member # 11023) on 10-02-2019, 09:40 AM:

We would like to control the volume from the theater to make fine adjustments to the trailer volume. After searching on the internet there has been an Android app to do that from Roman Braun. The app seems to have disappeared from the Playstore and the apk download sites. Already tried a message to Mr. Braun but no answer. Does anybody know more about this or does he have the apk available? We would like to use an old Android phone so the software being 'aged' should not be a problem. I've done some testing with a Windows PC and that seems to work with the described commands, but we would like to use a smartphone which is more compact than a laptop.

Posted by Marcel Birgelen (Member # 6801) on 10-02-2019, 10:40 AM:

Download a copy of Android Studio and do-it-yourself? [Smile]

As long as it only needs to work within the same network and doesn't need to traverse NAT, etc. it's still a pretty trivial thing to build, as long as the only thing you want to control is the fader setting.

Keep in mind that opening up your CP750 from any odd network will involve some security risks.

Posted by Wim Nagtegaal (Member # 11023) on 10-02-2019, 10:46 AM:

Already thought of that, but if somebody else has done it, why reinvent the wheel [Wink]

.
Also thought about security, the idea is to connect an AP to the cinema network and not show the network name (SSID). Then connect only an old Android phone to the WiFi network which can only be used as remote control. Switch off the AP when the equipment is not in use.

Posted by Scott Norwood (Member # 30) on 10-02-2019, 02:53 PM:

Hiding your SSID doesn't really do much for security.

Why not just get the CP750 remote fader box (cat. 868)?

If your cinema has automation equipment, there might be a way to use a remote interface to the automation system to control the CP750.

Posted by Marcel Birgelen (Member # 6801) on 10-02-2019, 04:47 PM:

Hiding your SSID is indeed not a real security measure. Applying a WPA2 key with sufficient strength and something like a MAC filter will probably shield most of it though. Still, I don't really like to expose a control network directly via wireless, it's usually a firewall with VPN I want to put in front of it.

I guess the APK was pulled, because it was targeted at a rather old Android API level. Maybe some archive still has it, but you need to watch out for those bad archives that push crapware down your throat.

Posted by Steve Guttag (Member # 268) on 10-02-2019, 11:26 PM:

There needs to be a bit of a reality check here. Hiding the SSID will stop 99% of the lookie-loos that are merely sniffing for an available WiFi network. Putting a suitable password on it will knock out most of that last 1% to the point of just what are you worried about on the projection network.

I'll admit, I take it a step further, the Wifi network isn't even on the same subnet as the projection network and you have to pass through my firewall and know the specific IP addresses (again, not even on the same subnet as Wifi) and even then only specific ports needed for the manger to get to the devices they want to control. So you'd need to know where the CP750s are on a different range before connecting up to the Wifi that doesn't call attention to itself and is password protected and, if need be, also MAC filtered.

I would say it also depends where you are in the world as to how heavy you need to protect yourself.

As more stuff gets web-ui based however, the desire for a WiFi connection has been increasing dramatically.

Posted by Marcel Birgelen (Member # 6801) on 10-03-2019, 12:46 AM:

The problem with putting your "control network" in the same subnet as where you put the access point is that it will carry all the broadcast traffic on that network to the outside, so there will always be plenty traffic to snoop. Combine this with not-so-strong WPA2 keys and other vulnerabilities and your network may be more open than you think.

A cinema may not be such a juicy target, but still no excuse for sloppy security. Cyber-attacks in many forms are a fact of life now, whether it's just a bunch of script kiddies poking some "fun" with their latest set of toys or something more sophisticated.

Posted by Wim Nagtegaal (Member # 11023) on 10-03-2019, 03:30 AM:

Ok, I understand the security implications for the WiFi, but no SSID, MAC filter and switch the AP off when the theater is not in use should do, we think. Long passwords are already in place and maybe we can add a firewall.

But the main question: does anybody has the apk for that old app??

Posted by Steve Guttag (Member # 268) on 10-03-2019, 05:32 AM:

I know there are sites that claim to still have it. I downloaded it a LONG time ago when it was still available from the play store and it still works on my S8.

Posted by Wim Nagtegaal (Member # 11023) on 10-03-2019, 06:46 AM:

Tried a lot of them but they all hang or redirect to the Playstore.

Posted by Steve Moore (Member # 4753) on 10-03-2019, 07:47 AM:

I still have a working version of the APK myself, from when I recently upgraded my phone and could no longer find it and managed to extract it from my old phone. If interested I could try upload it to somewhere like a google drive and send a link perhaps?

Posted by Wim Nagtegaal (Member # 11023) on 10-03-2019, 08:04 AM:

That would be great!! Please send me a DM (if possible) then I can send you my email address and mail it to me in a zip file (should not be that large).

Posted by Scott Norwood (Member # 30) on 10-03-2019, 12:24 PM:

If I read Steve's post correctly, he has the cinema network on the opposite side of a firewall on the wireless network. That would separate the broadcast traffic.

If a theatre uses the standard Dolby-style IP numbering convention, it wouldn't be too hard to guess the IP addresses of the projector, processor, automation, etc.

That said, I agree that Steve's approach is probably good enough for most, since it's just designed to keep people from wrecking havoc with screenings, which does not exactly require military-grade security.

Posted by Marcel Birgelen (Member # 6801) on 10-03-2019, 06:08 PM:

quote: Scott Norwood
If I read Steve's post correctly, he has the cinema network on the opposite side of a firewall on the wireless network. That would separate the broadcast traffic.

That's correct. Also, the firewall should avoid you being able to scan for any equipment on that network.

Some cinema stuff is surprisingly fragile, like the CP650's network interface. It's pretty easy to wreak havoc on such a device by just sending arbitrary traffic to its control TCP port for example. At the very least, it's easy to block legitimate macro calls from getting thru.

quote: Scott Norwood
If a theatre uses the standard Dolby-style IP numbering convention, it wouldn't be too hard to guess the IP addresses of the projector, processor, automation, etc.

Just listening to broadcast traffic is sufficient to see eventually practically all active speakers on an Ethernet network. You don't even need to actively scan it. That's why it's actually a good idea to use a separate subnet for mobile networks in many cases.

quote: Wim Nagtegaal
That would be great!! Please send me a DM (if possible) then I can send you my email address and mail it to me in a zip file (should not be that large).

If the original author responds, maybe ask him if he would be willing to share the APK with the rest of the world?

Maybe we can motivate Brad to put it up in the warehouse section of this site, that way, the tool, which is still useful, can live on, even if he doesn't officially support it anymore.

Posted by Wim Nagtegaal (Member # 11023) on 10-04-2019, 03:08 AM:

quote: Marcel Birgelen
If the original author responds, maybe ask him if he would be willing to share the APK with the rest of the world?

When he responds, I'll ask him.

Posted by Steve Moore (Member # 4753) on 10-04-2019, 04:14 AM:

I have shared it with Wim now, so if it does work for him, I can share the file if people want it and if Brad is willing, yes he could go for it. Of course with it being and extracted APK an android phone will prompt that it may not be trustworthy; so I don't want to be responsible if it breaks people phones! [Smile]

Anyway, we can see if it works initially for Wim first.

Posted by Marlon Martins (Member # 8823) on 10-05-2019, 03:09 PM:

if anyone can share the app, i would be thankful.

i bought a while ago, but after a phone format, it was removed from playstore. As it was originally a paid app, there was no mirror in any site like apkmirror

i found a while ago a french app that said to control cp750, but i only got errors and crashes.

it was really nice control the volume on the phone from the seat [Frown]

Posted by Steve Moore (Member # 4753) on 10-05-2019, 03:43 PM:

Well here it goes... https://drive.google.com/open?id=1SfBb1Oco_2zd84nsyNm1GqgbJT3Ibkoj

I don't know if this breaks rules, either here or copyright. The original author didn't charge for this app, but of course it still remains his property, I guess as he developed it. If it "cocks up" your phone, then I take no responsibility for that.

I never heard back from Wim as to if the link worked for him
Note, this was extracted from my old HTC phone to create the APK, so I could move it to my new one (after the app disappeared from google play) So I don't know how well it works across other brands of phone, but myself and someone else has used this extracted file successfully.

You would have to download it to your phone and then install it; you may well have to unblock a setting on your phone (I did) and all phones differ slightly to install an app downloaded from the internet, rather than google play.

Posted by Wim Nagtegaal (Member # 11023) on 10-05-2019, 05:45 PM:

I was able to install it on an old Samsung phone with Android 4. First checked it with a CP750 emulator and that worked and tonight I checked it with a real CP750 and a quick test showed that it worked. So I'm happy with it!
BTW still no response from the author.

Posted by Marcel Birgelen (Member # 6801) on 10-09-2019, 03:02 AM:

quote: Steve Moore
I don't know if this breaks rules, either here or copyright. The original author didn't charge for this app, but of course it still remains his property, I guess as he developed it. If it "cocks up" your phone, then I take no responsibility for that.

Might sound a bit harsh, but publishing his app without his consent is already copyright infringement, even if he offered it for free. The whole idea is that the owner of the copyright (usually the author), is in full control of whatever may happen with his/her original work.

That's also why I think copyright needs a big international reform. I do get why copyright is important for creators of new, original work, but the way it currently works, causes a lot of stuff to be locked up in some kind of limbo, where the owners of that copyright don't give a flying **** about their assets, but other's still can't have it, essentially locking it away.

Posted by Jesse Crooks (Member # 9389) on 10-14-2019, 01:53 PM:

While it’s not the most elegant solution, in a few situations I’ve used TeamViewer on my phone to control our office computer that has a VNC connection to the server, and used the server to adjust the volume. Not ideal for regular use, but it will do the job without a dedicated booth WiFi network or an Android device.

For my one theater that has a booth WiFi network I set up a 2-in-1 laptop/tablet so the projectionists have a dedicated device to control the servers and projectors, but you have to control the CP750s through the servers. Fine for adjusting the volume, but you’d have to play cues to do anything else.