pollux khafra - Developer IT

How to create pulsating value from 0..1..0..1..0 etc for a given duration?

- by pollux

Hi I'm working on some code where I have a Time object with a member time. Time.time gives me the time since my application started in seconds (float value). Now I want to create a pulsating value between 0 and 1 and then from 1 to 0 again, which continues doing thins untill the application stops. I was thinking to use sin() but don't know what to pass to it as paramters to create this pulsing value. How would I create this pulsating value? Kind regards, Pollux

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How to get the number of loop when using an iterator, in C++?

- by pollux

Dear reader, I'm working on a aplication where I draw a couple of images, like this: void TimeSlice::draw(float fX, float fY) { list<TimeSliceLevel*>::iterator it = levels.begin(); float level_x = x; float level_y = y; while(it != levels.end()) { (*it)->draw(level_x,level_y); level_y += (*it)->height; ++it; } } Though this is a bit incorrect. I need to position the TimeSliceLevel* on a X.. When I've got a for(int i = 0; i < slices.size(); ++i) loop, I can use x = i * width. Though I'm using an iterator as I've been told many times that's good programming : and I'm wondering if the iterator has a "index" number of something which I can use to calculate the new X position? (So it's more a question about using iterators) Kind regards, Pollux

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C++ JSON parser

- by pollux

Dear reader, I'm working on a twitter client which uses the twitter streaming json api. Twitter advices JSON as XML version is deprecated. I'm looking for a good JSON parser which can parse the json data below. I'm receiving this JSON which I want to be able to read/parse using a JSON parser. { "in_reply_to_status_id": null, "text": "Home-plate umpire Crawford gets stung http://tinyurl.com/27ujc86", "favorited": false, "coordinates": null, "in_reply_to_user_id": null, "source": "<a href=\"http://apiwiki.twitter.com/\" rel=\"nofollow\">API</a>", "geo": null, "created_at": "Fri Jun 18 15:12:06 +0000 2010", "place": null, "user": { "profile_text_color": "333333", "screen_name": "HostingViral", "time_zone": "Pacific Time (US & Canada)", "url": "http://bit.ly/1Way7P", "profile_link_color": "228235", "profile_background_image_url": "http://s.twimg.com/a/1276654401/images/themes/theme14/bg.gif", "description": "Full time Internet Marketer - Helping other reach their Goals\r\nhttp://wavemarker.com", "statuses_count": 1944, "profile_sidebar_fill_color": "c7b7c7", "profile_background_tile": true, "contributors_enabled": false, "lang": "en", "notifications": null, "created_at": "Wed Dec 30 07:50:52 +0000 2009", "profile_sidebar_border_color": "120412", "following": null, "geo_enabled": false, "followers_count": 2485, "protected": false, "friends_count": 2495, "location": "Working at Home", "name": "Johnathan Thomas", "verified": false, "profile_background_color": "131516", "profile_image_url": "http://a1.twimg.com/profile_images/600114776/nessykalvo421_normal.jpg", "id": 100439873, "utc_offset": -28800, "favourites_count": 0 }, "in_reply_to_screen_name": null, "id": 16477056501, "contributors": null, "truncated": false } *This is the raw string (above it beautified) * {"in_reply_to_status_id":null,"text":"Home-plate umpire Crawford gets stung http://tinyurl.com/27ujc86","favorited":false,"coordinates":null,"in_reply_to_user_id":null,"source":"<a href=\"http://apiwiki.twitter.com/\" rel=\"nofollow\">API</a>","geo":null,"created_at":"Fri Jun 18 15:12:06 +0000 2010","place":null,"user":{"profile_text_color":"333333","screen_name":"HostingViral","time_zone":"Pacific Time (US & Canada)","url":"http://bit.ly/1Way7P","profile_link_color":"228235","profile_background_image_url":"http://s.twimg.com/a/1276654401/images/themes/theme14/bg.gif","description":"Full time Internet Marketer - Helping other reach their Goals\r\nhttp://wavemarker.com","statuses_count":1944,"profile_sidebar_fill_color":"c7b7c7","profile_background_tile":true,"contributors_enabled":false,"lang":"en","notifications":null,"created_at":"Wed Dec 30 07:50:52 +0000 2009","profile_sidebar_border_color":"120412","following":null,"geo_enabled":false,"followers_count":2485,"protected":false,"friends_count":2495,"location":"Working at Home","name":"Johnathan Thomas","verified":false,"profile_background_color":"131516","profile_image_url":"http://a1.twimg.com/profile_images/600114776/nessykalvo421_normal.jpg","id":100439873,"utc_offset":-28800,"favourites_count":0},"in_reply_to_screen_name":null,"id":16477056501,"contributors":null,"truncated":false} I've tried multiple JSON parsers from json.org though I've tried 4 now and can't find one which can parse above json. Kind regards, Pollux

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Serving a video and audio upload and streaming intense site

- by Pollux Khafra

I'm about to launch a new site that allows user to both upload/stream audio and video and I don't know anything about the server side of things. My original plan was to just use a dedicated server through Hostgator but from what I'm reading, Cloud hosting or Load balanced clustered is the best way to go for what Im trying to do. All the articles seem to have an agenda to sell you on an affiliate web host so how do I really need to do this?

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How to print a var inside a script

- by Pollux Khafra

Alright I'm trying to use a jplayer script to trigger the player in my template. I need to pass a value to the "mp3" option but I don't get how I get $music to print. $(document).ready(function(){ $("#jquery_jplayer_1").jPlayer({ ready: function () { $(this).jPlayer("setMedia", { var music = $(".album-playlist li").first().find("input").val(); mp3: $music, }).jPlayer(""); }, swfPath: "http://mysite.com/wp-content/themes/beta/libs", supplied: "mp3" }); });

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Blob ID matching over multiple frames in C++ (image analysis)

- by pollux

Dear reader, I'm working on a blob matching and tracking library in C++. Currently I'm using openCV to detect blobs and try to match blobs in a new frame by checking the position, velocity and size of the blob. This works quite okay and I'm receiving a high blob match rate (95% or higher). Sometimes blobs fall out of the image or new blobs appear. Now I need to give matched blobs the same ID as they had before. I'm wondering if there are typical or commonly used techniques for doing this. Or even some keywords I can use to google on. Thanks

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c++ Sorting a vector based on values of other vector, or what's faster?

- by pollux

Hi, There are a couple of other posts about sorting a vector A based on values in another vector B. Most of the other answers tell to create a struct or a class to combine the values into one object and use std::sort. Though I'm curious about the performance of such solutions as I need to optimize code which implements bubble sort to sort these two vectors. I'm thinking to use a vector<pair<int,int>> and sort that. I'm working on a blob-tracking application (image analysis) where I try to match previously tracked blobs against newly detected blobs in video frames where I check each of the frames against a couple of previously tracked frames and of course the blobs I found in previous frames. I'm doing this at 60 times per second (speed of my webcam). Any advice on optimizing this is appreciated. The code I'm trying to optimize can be shown here: http://code.google.com/p/projectknave/source/browse/trunk/knaveAddons/ofxBlobTracker/ofCvBlobTracker.cpp?spec=svn313&r=313 Thanks

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