GeezerVison

The World Wide Web, restored to 800 pixels of glory.

GeezerVison is showing github.com — bug in parseCaps · Issue #224 · processing/processing-video

bug in parseCaps #224

New issue

Copy link

New issue

Copy link

Open

bug in parseCaps#224

Copy link

Description

clankill3r

opened

on Feb 13, 2024

Issue body actions

I need to get the resolution of the webcam. In the source we have the following:

  // This is a temporary addition until it's decided how to bring back resolution/framerate caps to the official API.
  // The old way of doing things is still listed in the video tutorial:
  // https://processing.org/tutorials/video
  static public String[] getCapabilities(String device) {
    for (int i=0; i < devices.size(); i++) {
      String deviceName = assignDisplayName(devices.get(i), i);
      if (devices.get(i).getDisplayName().equals(device) || devices.get(i).getName().equals(device) || deviceName.equals(device)) {
        return parseCaps(devices.get(i));
      }
    }
    return new String[]{};
  }

The above calls parseCaps which has the following part (this is a piece of it):

      if (0 < indexWidth && 0 < indexHeight && 0 < indexFramerate) {
        stringWidth = cap.substring(indexWidth, cap.indexOf(',', indexWidth));
        stringHeight = cap.substring(indexHeight, cap.indexOf(", format", indexHeight));
        stringFramerate = cap.substring(indexFramerate, cap.indexOf(']', indexFramerate));
      }

An example of the String cap is " video/x-raw, format=(string)YUY2, width=(int)1280, height=(int)720, framerate=(fraction)10/1, pixel-aspect-ratio=(fraction)1/1".

The problem with the above code is that stringHeight = cap.substring(indexHeight, cap.indexOf(", format", indexHeight)); assumes a certain order of the elements being listed. The assumption being made is wrong resulting in the following error:

java.lang.StringIndexOutOfBoundsException: begin 52, end -1, length 127
        at java.base/java.lang.String.checkBoundsBeginEnd(String.java:4606)
        at java.base/java.lang.String.substring(String.java:2709)
        at processing.video.Capture.parseCaps(Capture.java:791)
        at processing.video.Capture.getCapabilities(Capture.java:768)
        at room_activity.Room_Activity.setup(Room_Activity.java:95)
        at processing.core.PApplet.handleDraw(PApplet.java:2051)
        at processing.opengl.PSurfaceJOGL$DrawListener.display(PSurfaceJOGL.java:840)
        at jogamp.opengl.GLDrawableHelper.displayImpl(GLDrawableHelper.java:692)
        at jogamp.opengl.GLDrawableHelper.display(GLDrawableHelper.java:674)
        at jogamp.opengl.GLAutoDrawableBase$2.run(GLAutoDrawableBase.java:443)
        at jogamp.opengl.GLDrawableHelper.invokeGLImpl(GLDrawableHelper.java:1293)
        at jogamp.opengl.GLDrawableHelper.invokeGL(GLDrawableHelper.java:1147)
        at com.jogamp.newt.opengl.GLWindow.display(GLWindow.java:797)
        at com.jogamp.opengl.util.AWTAnimatorImpl.display(AWTAnimatorImpl.java:81)
        at com.jogamp.opengl.util.AnimatorBase.display(AnimatorBase.java:471)
        at com.jogamp.opengl.util.FPSAnimator$MainTask.run(FPSAnimator.java:245)
        at java.base/java.util.TimerThread.mainLoop(Timer.java:566)
        at java.base/java.util.TimerThread.run(Timer.java:516)

Activity

glvjr commented on May 4, 2026

glvjr

on May 4, 2026

More actions

Hello,

This was used to read the camera capability data from Processing Video’s internal device list:

import processing.video.*;

import java.lang.reflect.*;
import java.util.*;

void setup() 
  {
  try 
    {
    String[] cameras = Capture.list();
    printArray(cameras);
    println();
    
    // This failed:
    // println(Capture.getCapabilities(cameras[0]));
    // Related issue:
    // https://github.com/processing/processing-video/issues/224

    Field f = Capture.class.getDeclaredField("devices");
    f.setAccessible(true);
    
    List devices = (List) f.get(null);

    Object dev = devices.get(0);
    Method m = dev.getClass().getMethod("getCaps");

    println("Camera 0: " + cameras[0]);
    println();

    String modes = String.valueOf(m.invoke(dev));
   
    String formattedModes = modes.replace(";", ";\n");
    println(formattedModes);
    }
  catch (Exception e) 
    {
    e.printStackTrace();
    }
  }

/*
Capture.getCapabilities(cameras[0]) failed with:

java.lang.StringIndexOutOfBoundsException: begin 49, end -1, length 133
  at java.base/java.lang.String.checkBoundsBeginEnd(String.java:4606)
  at java.base/java.lang.String.substring(String.java:2709)
  at processing.video.Capture.parseCaps(Unknown Source)
  at processing.video.Capture.getCapabilities(Unknown Source)
  at sketch_260503a.setup(sketch_260503a.java:38)
  at processing.core.PApplet.handleDraw(PApplet.java:2055)
  at processing.awt.PSurfaceAWT$9.callDraw(PSurfaceAWT.java:1388)
  at processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:356)
*/

It was a long list so test was for one camera only.

My research started here:
https://discourse.processing.org/t/capture-list-showing-duplicate-cameras/47153

Developed through research, testing, and input from various AI tools.

Metadata

Assignees

No one assigned

Labels

No labels

Type

No type

Projects

No projects

Milestone

No milestone

Relationships

None yet

Development

No branches or pull requests

Issue actions

You are visitor 01402503 — GeezerVison does not store the pages you look up.
Best viewed with Netscape Navigator 4.7 or Internet Explorer 6 at 800×600. No cookies required.