Zagura’s blog

July 12, 2010

How to check packet loss for VOIP purposes

Filed under: English, Linux, voip — puthre @ 9:52 am

Yesterday I had some problems with the VOIP connection. I heard my party very well but he could barely hear me.
Normal run of mtr to the other host showed no packet loss but I was able to pinpoint the packet loss to the other party with
mtr -n -s 200 -i 0.02 [ip-address]
(you need to be root)
which sends 50 packets/seconds 200 bytes/packet which pretty much emulates the rtp stream.

March 19, 2010

SPL-C ERROR - Please use the proper driver on Samsung CLP-310N printer

Filed under: English, Linux — puthre @ 12:10 am

If you get this error written on the test page when using Ubuntu or any other Linux distribution, you should install the Samsung Unified Driver. I’ve followed the tutorial on http://ubuntuforums.org/showthread.php?t=341621 point II.c and then I’ve added the network printer as lpd:///PASSTHRU with Make and Model “Samsung CLP-310 Series (SPL-C)” (NOT Samsung CLP-310 Foomatic/foo2qpdl)

March 10, 2010

How to programmatically dump the threads list of a running java process in bash

Filed under: English, Java, Linux, Programming — puthre @ 4:43 pm

It seems that jdb cannot accept commands from command line, so we must use expect.
I created the following expect script dumpthreads
You can use it like:
dumpthreads java_process_pid

#!/usr/bin/expect
set pid [lindex $argv 0];
spawn jdb -connect sun.jvm.hotspot.jdi.SAPIDAttachingConnector:pid=$pid;
expect “>”;
send “threads\n”;
expect “>”;
send “quit\n”;

January 27, 2010

Midnight commander does not save the settings in Ubuntu

Filed under: English, Linux — puthre @ 2:34 pm

Today I encountered a strange problem with Midnight Commander 4.6.2 in Ubuntu. I wanted to change the default Ubuntu setting to use the internal edit. I actually like the mc internal editor and I want to use it. The problem was that the setting was not saved when I chosed “Save setup” even if a message “Setup saved to ~/.mc/ini” appeared. There was no ~/.mc folder. After I did
mkdir ~/.mc
everything worked as expected.
This seems to be a bug in mc.

January 13, 2010

Emtec S800 board picture

Filed under: English, Linux — puthre @ 11:39 am

Here is a picture of the internal board of my newly aquired Emtec S800 PVR. It works on Linux but Emtec was not so kind to provide the sources of the PVR application (there are some sources of an alternative OEM - Ellion available on the net). I needed to open the box to put a resistor at the internal fan because it was too noisy.
dsc_0806.JPG

October 13, 2009

How to convert DVD iso to avi using mplayer

Filed under: English, Linux — puthre @ 9:43 pm

Here is a python script to convert an .iso of a DVD to avi and to encode it using mpeg4. It is a slightly modified version of the script found at http://lists.mplayerhq.hu/pipermail/mplayer-users/2003-April/032226.html to work with newer versions of mplayer/mencoder.

Later edit:
It seems that mplayer/mencoder know to play/convert .iso files directly so we can do:
mencoder in.iso -o /dev/null -ovc xvid -xvidencopts pass=1:bitrate=800:threads=2 -oac copy
mencoder in.iso -o out.mpeg -ovc xvid -xvidencopts pass=2:bitrate=800:threads=2 -oac copy

June 16, 2009

How to convince the SmartGWT ListGrid to automatically fetch from the server only the data it displays

Filed under: English, Java, Programming, Web — puthre @ 7:29 pm

Since I was looking all over the net how to do this and I only found pieces of information, here is an example:

PLAIN TEXT
JAVA:
  1. public class OperationsGrid extends ListGrid{
  2.     OperationsGrid(){
  3.         super();
  4.         TreeGridField accNoField = new TreeGridField("accountNo", 150);
  5.         TreeGridField commentField = new TreeGridField("comment",  150);
  6.  
  7.         setFields(accNoField,commentField);
  8.         setHeight100();
  9.         setWidth100();
  10.         setAutoFetchData(true);
  11.         setAlternateRecordStyles(true);
  12.         setDataSource(OperationsDS.getInstance());
  13.         setShowFilterEditor(true);
  14.     }
  15. }

PLAIN TEXT
JAVA:
  1. public class OperationsDS extends DataSource{
  2.     static OperationsDS instance = null;
  3.      static OperationsDS getInstance(){
  4.         if(instance == null){
  5.             instance = new OperationsDS();
  6.         }
  7.          return instance;
  8.     }
  9.  
  10.     OperationsDS(){
  11.  
  12.         setDataURL(xpath);
  13.         DataSourceTextField noField = new DataSourceTextField("accountNo", "Account Number", 128);
  14.         DataSourceTextField commentField = new DataSourceTextField("comment", "Comment", 128);
  15.  
  16.         noField.setRequired(true);
  17.         noField.setPrimaryKey(true);
  18.  
  19.         setFields(noField,commentField);
  20.         setDataFormat(DSDataFormat.JSON);
  21.         setRecordXPath("response/result");
  22.         setClientOnly(false);
  23.     }
  24.      @Override
  25.      protected Object transformRequest(DSRequest dsRequest){
  26.          String url = null;
  27.  
  28.          if(dsRequest.getOperationType().equals(DSOperationType.FETCH)){
  29.              dsRequest.setActionURL(getDataURL()+"&start="+dsRequest.getStartRow()+"&end="+dsRequest.getEndRow());
  30.          }
  31.          return super.transformRequest(dsRequest);
  32.      }
  33.      @Override
  34.     protected void transformResponse(DSResponse response, DSRequest request,
  35.             Object data) {
  36.         DSOperationType operationType = request.getOperationType();
  37.  
  38.         if (operationType == DSOperationType.FETCH) {
  39.             JSONArray info = XMLTools.selectObjects(data, "/response/resultInfo/numTotalRows");
  40.             Integer total = (int)Math.round(info.get(0).isNumber().doubleValue());
  41.  
  42.             info = XMLTools.selectObjects(data, "/response/resultInfo/startRow");
  43.             Integer start = (int)Math.round(info.get(0).isNumber().doubleValue());
  44.  
  45.             info = XMLTools.selectObjects(data, "/response/resultInfo/endRow");
  46.             Integer end = (int)Math.round(info.get(0).isNumber().doubleValue());
  47.  
  48.             if(total != null)
  49.                 response.setTotalRows(total);
  50.             if(start != null)
  51.                 response.setStartRow(start);
  52.             if(end != null)
  53.                 response.setEndRow(end);
  54.         } else {
  55.             super.transformResponse(response, request, data);
  56.         }
  57.  
  58.     }
  59. }

In this example the server outputs in JSON format and returns the the current start row, current end row and total number of rows in response/resultInfo.
Basically you need to override transformRequest and transformResponse. In transformRequest you should add the start and end row to the requestURL and in transformResponse you should set the startRow, endRow, and totalRows, provided that you receive this information from your server. Also don't forget to setAutoFetchData(true) on the grid.

Hope this helps somebody.

June 5, 2009

MySQL Java SQLException error codes enum

Filed under: English, Java, Programming — puthre @ 4:02 pm

Because I had this problem and I could not find a list of MySQL error codes on the Internet, I've decided to implement my own MySQL error codes enum. It is based on MySQL 5.1.35 sources, include/mysqld_ername.h file.
Now I can do something like this:

PLAIN TEXT
JAVA:
  1. catch (SQLException e) {
  2.                         if(e.getErrorCode() == MySQLExceptionCode.ER_DUP_ENTRY.getErrorCode()){
  3.                                  r = Result.DUPLICATE_ACCOUNT_NO;
  4.                         } else
  5.                                  r = Result.DATABASE_ERROR;
  6. }

You can find the java file here.

May 15, 2009

Download completed. You can now disconnect from the Internet.

Filed under: English, Fun — puthre @ 5:15 pm

screenshot.jpg

January 28, 2009

Midnight Commander Returns

Filed under: English, Linux — puthre @ 11:23 pm

The development for Midnight Commander seems to be revived. There is a new site that supports it's development at http://www.midnight-commander.org They are keeping the sources on a git repository and they accept patches.

This is good news for me, as I have some old issues with Midnight Commander and this might stimulate me to fix them :)

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