New Camera Class

[TheDominis]

BETA

I've heavily modified some camera code. There is slightly different functionality in smash_camera.cpp in GetJpegImageBlocking. It blocks with different functionality. It will not always succeed. You can change the functionality by copying the original method from PCVideoServer.cpp. Also, for now, you must manually set the IP to the computer to want to receive video from. You must do this in the method VideoServerHelper on line 65 in smash_video_server.cpp.

Required Code:

#include "smash_camera.h"

smash::AxisCamera& camera = smash::AxisCamera::getInstance();
camera.writeResolution(smash::k160x120);
camera.writeBrightness(0);

The Dashboard will fill a drop down box with all available IP addresses that are IPv4. This will automatically detect the data and start the server. If you want to stop the server, close the program. There is a timeout period of 250ms and the server status will be "waiting". The dashboard supports any Jpeg size. However, it seems to be slightly buggy on 320x240 and very buggy on 640x480. I'll be working on this.

I didn't try to 2Go PC, but I got 20+ FPS on 160x120.

I'll upload dashboard later.... must go!

[slavik262]

I'm sorry if I'm not getting this, but what does this do? Does it give an increased framerate or is it just designed to let the user customize what IP they want to use to receive video data?

Does this run on a LabVIEW dashboard, or some custom implementation of your own?

[TheDominis]

I didn't know that the zip limit was greater than the rar format. It failed for that reason.

The Dashboard frame rates at 160x120 were 20+ on the laptop I tested it on (not the 2Go computer). The other formats were less, but I think that was due to an error in the dashboard.

You will need 3.5 .NET Framework for this to work. Perhaps even SP1 for 3.5 .NET.

[slavik262]

You still didn't really answer my question. Is this just a custom video dashboard? What advantages does this have over the standard code?

[TheDominis]

Originally Posted by slavik262

You still didn't really answer my question. Is this just a custom video dashboard? What advantages does this have over the standard code?

Opposed to the stock camera server, my server gets 20+ FPS at 160x120. Other image sizes are slightly buggy, but I'll fix that soon. Adding more features later.

[slavik262]

Awesome! Without pouring through the code, how did you manage to do this?

[TheDominis]

Originally Posted by slavik262

Awesome! Without pouring through the code, how did you manage to do this?

Server

Step 1. Acquire Image
Step 2. Calculate how many packets will be required to send the image
Step 3. Send packet(s) via UDP (1032 byes), populate any outdated data
Step 4. Repeat 1 - 3

Receiver

Step 1. Acquire a 1032 byte packet
Step 2. Translate the packet into usable information (i.e Big Endian to Little Endian)
Step 3. Populate "Status" with new information
Step 4. If the image is finished, present it
Step 5. Repeat 1 - 4

This is, of course, a simplified overview.

[slavik262]

So you segment the image into several packets and send it over UDP instead of TCP? I assume you have error-checking built in? I'll have to check it out.

[TheDominis]

Originally Posted by slavik262

So you segment the image into several packets and send it over UDP instead of TCP? I assume you have error-checking built in? I'll have to check it out.

I carry very little about errors. I throw them out and wait for a new image.

[Tom Line]

I'm curious - how does this affect the total bandwidth used by a single Crio and dashboard.

In other words, have you increased 20-fold (or is it 20^2 for an image) the number of packets that are going to be sent to increase your framerate by 20 times?

For some reason I thought the communication protocalls were sancrosanct - that is I thought we weren't allowed to touch them because of bandwidth concerns. I had thought that was why they limited the dashboard to a 1 hz update, though I might be wrong: you know what they say about assuming.

[TheDominis]

Originally Posted by Tom Line

I'm curious - how does this affect the total bandwidth used by a single Crio and dashboard.

In other words, have you increased 20-fold (or is it 20^2 for an image) the number of packets that are going to be sent to increase your framerate by 20 times?

For some reason I thought the communication protocalls were sancrosanct - that is I thought we weren't allowed to touch them because of bandwidth concerns. I had thought that was why they limited the dashboard to a 1 hz update, though I might be wrong: you know what they say about assuming.

I'm not sure either. The TCP stream tries to send an image pretty fast, but fails. Also it implicitly fragments, but I do not know how this affects socket I/O. I know that I use ~1MB/s for 640x480@30Hz with Jpegs drawn on the computer, but they are much larger than the camera's Jpegs at no compression. I'll post bandwidth usage for each image size tomorrow.

[TheDominis]

The source code can be found by using svn.

svn checkout http://frc-video-collab.googlecode.com/svn/trunk/ frc-video-collab-read-only

The C++ code will be updated tomorrow morning at around 10:30 EST.

[slavik262]

The GDC got back to us, and their answer is, in a word, no:

http://forums.usfirst.org/showthread.php?t=14284

We'll have to see what this update brings before moving forward.

[jhersh]

It looks like what they really said is no to UDP... can you make it work over TCP?

[slavik262]

Originally Posted by jhersh

It looks like what they really said is no to UDP... can you make it work over TCP?

Sure, but we think that a lot of the slowness was caused by TCP. For example, if a frame of the video being transmitted gets screwed up, it's not that big of a deal using UDP, especially if you have a high framerate. You can just drop the frame and wait for the next one (no big deal if you're getting a good 20 of them every second - the user will barely notice). If we use TCP and the same thing happens to a packet, the receive() function stops the entire program execution, sends a request to resend the packet, and waits for the packet to get sent again, all for just one frame (or even just one part of a frame). You're making the entire system, which could be better spending its time just displaying the next frame(s), wait on just one frame instead of moving on.

We're also aware that some of the latency is being caused by the Classmate not being enough to keep up with the cRIO, but TCP doesn't help in this respect.