Android Tutorial MJPEG / CCTV Server

A few days ago I've helped a developer with implementing a MJPEG client: https://www.b4x.com/android/forum/threads/73702/#content
It was a good experience as while implementing it I've become familiar with the MJPEG protocol.
MJPEG is quite simple. Each frames look like:

--myboundary
Content-Type:image/jpeg
Content-Length:xxx

<image data>

Note that the end of lines are made of Chr(13) & Chr(10) and not the standard Chr(10) which is the value of CRLF in B4A, B4i and B4J (this is the natural end of line character on those platforms).

This example turns the device into a CCTV camera. You can connect to it with any browser (including mobile browsers) and see the video stream. You can also access it over the internet if the router is configured to allow it.

The nice thing about this example is that it supports multiple clients.

Each connection is managed by a different instance of the "client" class. This makes it simple to support multiple and concurrent clients. AsyncStreams is responsible for the concurrency.

Note that the image sent as-is. The orientation might be wrong.


The frame rate is currently set to 6 frames per second. You can change it by modifying IntervalMS. Set it to 50 (1000 / 50 = 20 fps) and it will look much better.

Test it by running the app on the device and then enter the device ip address in the browser followed by the port (51042).

B4i example is available here: https://www.b4x.com/android/forum/threads/mjpeg-cctv-server.73821/

 

[Erel]

This is how the layout should look:

Delete the layout file and create a new one.

 

[Mikel Huerta]

This is how the layout should look:

Delete the layout file and create a new one.

Awesome !
Thanks You a lot for teach me howto.
It runs very well, great job.

btw, this is not a true video stream right ? is a high speed static pictures refreshing ?
I down the interval time to 5 and runs nearly to realtime.

 

[Erel]

Each frame is encoded separately. This limits the frame rate.

 

[FrankDev]

hi

Can you see the stream with the webview?
I have tested it but no display synonymous no error message

With
Ip address: 51041

 

[Erel]

Where is the server running and where is the client running? On the same device?

 

[FrankDev]

no .. cctv is running on a Smartphone
webview on a Amazon fire TV.
on my PC, I can see the stream of Firefox or chrome.
all devices are on the same wireless network

 

[Erel]

Start with the device default browser. Does it work?

I'm not sure that all versions of Android have built-in support for MJPEG decoding.
Alternative option: [B4X] [class] MJPEG decoder

 

[FrankDev]

hi


I think the Fire TV has no standard browser.
Is MJPEG decoding a thing of the operating system? I thought this might be dependent on the functionality of the webview.

Thanks for the information

 

[Erel]

Is MJPEG decoding a thing of the operating system?

It doesn't depend on anything. It decodes the stream and returns a stream of bitmaps that you show with ImageView.

 

[jchal]

i have tested the app and it works as far you do a portforword in the router, does anybody has an i dea how this will work over 3g? or 4 g? i canot figure out how can i do a portforward in the mobile phone

 

[Erel]

does anybody has an i dea how this will work over 3g?

It will not work over the cellular network as incoming connections are not allowed.

 

[moster67]

It should work with a VPN though - however to enforce the user to set up a VPN is not perhaps the best idea...

 

[maleche]

Anyway to use this method to send GPS lat/lon from one client (cell phone) to a server cell phone to pass information? I want to make an app that consolidates our Emergency Response and Search and Rescue team's positions and emergency recourses locations.
Basically, each Emergency Response member's Lat/Lon is transmitted via cellular to a 'master' cell phone which plots everyone's position every 5 minutes.
This would really help out!
best,

 

[Erel]

This is a specific example that implements the MJPEG protocol. You cannot use it to send any other data. However it is very simple to send GPS location.

Please start a new thread in the questions forum.

 

[chaiwatt]

Hi, Can I use in version 5.5?, purchased since long time ago and not update yet.

 

[lemonisdead]

Can I use in version 5.5?, purchased since long time ago and not update yet

If I recall it correctly, it was working with #5.5 but I would suggest you to update to #7.8 because they are lot of improvements and some libraries do require it now (just an advise)

 

[chaiwatt]

If I recall it correctly, it was working with #5.5 but I would suggest you to update to #7.8 because they are lot of improvements and some libraries do require it now (just an advise)

@lemonisdead, Thanks.

 

[Erel]

Example was updated. targetSdkVersion was set to 26.

 

[hatzisn]

Hi Erel,

I tried your example but it won't compile. I get this error:

B4A Version: 7.80
Parsing code.    (0.01s)
Compiling code.    Error
Object reference not set to an instance of an object.

My android.jar is set to android 27.

I don't see any red curled lines in the modules nor any error messages in the logs tab.

Any suggestions?

Thanks in advance...

 

[Erel]

This means that there is an error in the manifest editor. The actual error message is missing (it is a bug in B4A v7.80). For further discussion start a new thread.