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• Web services or shared database for (game) server communication?

  - by jaaronfarr

  We have 2 server clusters: the first is made up of typical web applications backed by SQL databases. The second are highly optimized multiplayer game servers which keep all data in memory. Both clusters communicate with clients via HTTP (Ajax with JSON). There are a few cases in which we need to share data between the two server types, for example, reporting back and storing the results of a game (should ultimately end up in the database). We're considering several approaches for inter-server communication: Just share the MySQL databases between clusters (introduce SQL to the game servers) Sharing data in a distributed key-value store like Memcache, Redis, etc. Use an RPC technology like Google ProtoBufs or Apache Thrift Using RESTful web services (the game server would POST back to the web servers, for example) At the moment, we're leaning towards web services or just sharing the database. Sharing the database seems easy, but we're concerned this adds extra memory and a new dependency into the game servers. Web services provide good separation of concerns and fit with the existing Ajax we use, but add complexity, overhead and many more ways for communication to fail. Are there any other good reasons not to use one or the other approach? Which would be easier to scale?

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• Revision Control System Recommendations

  - by Jordan Arsenault

  I've reached a point in my independent development work where I would like to start using Subversion techniques. Up to now, I've been simply making backups by exporting my current database, and zipping them together with my PHP project files. I've read some articles online and watched a video with Linus Torvalds - the general verdict seems to be that Git is in and old CVS techniques are out. I'm not currently operating under Linux, I do all PHP work out of Windows - Eclipse. Due to the fact that Eclipse runs on JVM, jumping into Linux - Eclipse will be more or less transparent - file system aside. What I would like to accomplish is being able to keep a constant revision history - But I want this to be almost entirely transparent. Also, I work in an MVC framework, and I would like to be able to release my views to Designers, and have them work from within the revision control system too. Will Egit accomplish what I need? Or is it too much overhead for a one-man workforce? What do you recommend I use so that I can keep a revision history? I also require the service to be free! Thank you all - StackOverflow ftw!

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• Creating serializeable unique compile-time identifiers for arbitrary UDT's.

  - by Endiannes

  I would like a generic way to create unique compile-time identifiers for any C++ user defined types. for example: unique_id<my_type>::value == 0 // true unique_id<other_type>::value == 1 // true I've managed to implement something like this using preprocessor meta programming, the problem is, serialization is not consistent. For instance if the class template unique_id is instantiated with other_type first, then any serialization in previous revisions of my program will be invalidated. I've searched for solutions to this problem, and found several ways to implement this with non-consistent serialization if the unique values are compile-time constants. If RTTI or similar methods, like boost::sp_typeinfo are used, then the unique values are obviously not compile-time constants and extra overhead is present. An ad-hoc solution to this problem would be, instantiating all of the unique_id's in a separate header in the correct order, but this causes additional maintenance and boilerplate code, which is not different than using an enum unique_id{my_type, other_type};. A good solution to this problem would be using user-defined literals, unfortunately, as far as I know, no compiler supports them at this moment. The syntax would be 'my_type'_id; 'other_type'_id; with udl's. I'm hoping somebody knows a trick that allows implementing serialize-able unique identifiers in C++ with the current standard (C++03/C++0x), I would be happy if it works with the latest stable MSVC and GNU-G++ compilers, although I expect if there is a solution, it's not portable.

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• Most efficient way of checking if Date object and Calendar object are in the same month

  - by Indigenuity

  I am working on a project that will run many thousands of comparisons between dates to see if they are in the same month, and I am wondering what the most efficient way of doing it would be. This isn't exactly what my code looks like, but here's the gist: List<Date> dates = getABunchOfDates(); Calendar month = Calendar.getInstance(); for(int i = 0; i < numMonths; i++) { for(Date date : dates) { if(sameMonth(month, date) .. doSomething } month.add(Calendar.MONTH, -1); } Creating a new Calendar object for every date seems like a pretty hefty overhead when this comparison will happen thousands of times, soI kind of want to cheat a bit and use the deprecated method Date.getMonth() and Date.getYear() public static boolean sameMonth(Calendar month, Date date) { return month.get(Calendar.YEAR) == date.getYear() && month.get(Calendar.MONTH) == date.getMonth(); } I'm pretty close to just using this method, since it seems to be the fastest, but is there a faster way? And is this a foolish way, since the Date methods are deprecated? Note: This project will always run with Java 7

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• Identifying a class which is extending an abstract class

  - by Simon A. Eugster

  Good Evening, I'm doing a major refactoring of http://wiki2xhtml.sourceforge.net/ to finally get better overview and maintainability. (I started the project when I decided to start programming, so – you get it, right? ;)) At the moment I wonder how to solve the problem I'll describe now: Every file will be put through several parsers (like one for links, one for tables, one for images, etc.): public class WikiLinks extends WikiTask { ... } public class WikiTables extends WikiTask { ... } The files will then be parsed about this way: public void parse() { if (!parse) return; WikiTask task = new WikiLinks(); do { task.parse(this); } while ((task = task.nextTask()) != null); } Sometimes I may want to use no parser at all (for files that only need to be copied), or only a chosen one (e.g. for testing purposes). So before running task.parse() I need to check whether this certain parser is actually necessary/desired. (Perhaps via Blacklist or Whitelist.) What would you suggest for comparing? An ID for each WikiTask (how to do?)? Comparing the task Object itself against a new instance of a WikiTask (overhead)?

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• VB6 Game Development : Don't ask me why :-)

  - by CVS-2600Hertz-wordpress-com

  Hi All, I am developing a game in VB6 (plz don't ask me why :) ). The storyboard is ready and a rough implementation is underway. I am following a "pure-software-rendering" approach. (i.e. no DirectX, no openGL etc.) Amongst many others, the following "serious" problems exist: 2D alpha transparency reqd. to implement overlays. Parallax implementation to give depth-of-field illusion. Capturing mouse-scroll events globally (as in FPS-es; mapping them to changing weapon). Async sound play with absolute "zero-lag". Any ideas anyone. Please suggest any well documented library/ocx or sample-code. Plz do provide solutions with max performance and with as little overhead as possible. Also, anyone who has developed any games, and would be open to sharing her/his code would be highly appreciated. (any well-acknowledged VB games whose source-code i can study??) Thank You

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• Setup for games animation: How do I know JFrame is finished setting itself up?

  - by Jokkel

  I'm using javax.swing.JFrame to draw game animations using double buffer strategy. First, I set up the frame. JFrame frame = new JFrame(); frame.setVisible(true); Now, I draw an object (let it be a circle, doesn't matter) like this. frame.createBufferStrategy(2); bufferStrategy = frame.getBufferStrategy(); Graphics g = bufferStrategy.getDrawGraphics(); circle.draw(g); bufferStrategy.show(); The problem is that the frame is not always fully set-up when the drawing takes place. Seems like JFrame needs up to three steps in resizing itself, until it reaches it's final size. That makes the drawing slide out of frame or hinders it to appear completely from time to time. I already managed to delay things using SwingUtilities.invokeLater(). While this improved the result, there are still times when the drawing slides away / looks prematurely draw. Any idea / strategy? Thanks in advance. EDIT: Ok thanks so far. I didn't mention that I write a little Pong game in the first place. Sorry for the confusion What I actually looked for was the right setup for accelerated game animations done in Java. While reading through the suggestions I found my question answered (though indirectly) here and this example made things clear for me. A resume for this might be that for animating game graphics in Java, the first step is to get rid of the GUI logic overhead.

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• Aliasing `T*` with `char*` is allowed. Is it also allowed the other way around?

  - by StackedCrooked

  Note: This question has been renamed and reduced to make it more focused and readable. Most of the comments refer to the old text. According to the standard objects of different type may not share the same memory location. So this would not be legal: int i = 0; short * s = reinterpret_cast<short*>(&i); // BAD! The standard however allows an exception to this rule: any object may be accessed through a pointer to char or unsigned char: int i = 0; char * c = reinterpret_cast<char*>(&i); // OK However, it is not clear to me if this is also allowed the other way around. For example: char * c = read_socket(...); unsigned * u = reinterpret_cast<unsigned*>(c); // huh? Summary of the answers The answer is NO for two reasons: You an only access an existing object as char*. There is no object in my sample code, only a byte buffer. The pointer address may not have the right alignment for the target object. In that case dereferencing it would result in undefined behavior. On the Intel and AMD platforms it will result performance overhead. On ARM it will trigger a CPU trap and your program will be terminated! This is a simplified explanation. For more detailed information see answers by @Luc Danton, @Cheers and hth. - Alf and @David Rodríguez.

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• Random begining index iterator for HashSet

  - by funktku

  I use HashSet for add(); remove(); clear(); iterator(); methods. So far everything worked like a charm. However, now I need to fulfill a different requirement. I'd like to be able to start iterating from a certain index. For example, I'd like the following two programs to have same output. Program 1 Iterator it=map.iterator(); for(int i=0;i<100;i++) { it.next(); } while (it.hasNext()) { doSomethingWith(it.next()); } Program 2 Iterator it=map.iterator(100); while (it.hasNext()) { doSomethingWith(it.next()); } The reason I don't want to use the Program 1 is that it creates un-neccesary overhead. From my researchs, I couldn't not find a practical way of creating an iterator with begining index. So, my question is, what would be a good way to achieve my goal while minimizing the overheads? Thank you.

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• How do I introspect on a SQL Server?

  - by MetaHyperBolic

  I have a server with a vendor application which is heavily database-reliant. I need to make some minor changes to the data in a few tables in the database in an automated fashion. Just INSERTs and UPDATEs, nothing fancy. Vendors being vendors, I can never be quite sure when they change the schema of a database during upgrade. To that end, how do I ask the SQL server, in some scriptable fashion, "Hey, does this table still exist? Yeah, cool, okay, but does it have this column? What's the data type and size on that? Is it nullable? Could you give me a list of tables? In this table, could you give me a list of columns? Any primary keys there?" I do not need to do this for the whole schema, only part of it, just a quick check of the database before I launch into things. We have Microsoft SQL Server 2005 on it currently, but it might easily move to Microsoft SQL Server 2008. I am probably not using the correct terminology when searching. I do know that ORM is not only too much overhead for this sort of thing, but also that I have no chance of pitching it to my coworkers.

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• Vector Usage in MPI(C++)

  - by lsk1985

  I am new to MPI programming,stiil learning , i was successful till creating the Derived data-types by defining the structures . Now i want to include Vector in my structure and want to send the data across the Process. for ex: struct Structure{ //Constructor Structure(): X(nodes),mass(nodes),ac(nodes) { //code to calculate the mass and accelerations } //Destructor Structure() {} //Variables double radius; double volume; vector<double> mass; vector<double> area; //and some other variables //Methods to calculate some physical properties Now using MPI i want to sent the data in the structure across the processes. Is it possible for me to create the MPI_type_struct vectors included and send the data? I tried reading through forums, but i am not able to get the clear picture from the responses given there. Hope i would be able to get a clear idea or approach to send the data PS: i can send the data individually , but its an overhead of sending the data using may MPI_Send/Recieve if we consider the domain very large(say 10000*10000)

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• How to properly cast a global memory array using the uint4 vector in CUDA to increase memory throughput?

  - by charis

  There are generally two techniques to increase the memory throughput of the global memory on a CUDA kernel; memory accesses coalescence and accessing words of at least 4 bytes. With the first technique accesses to the same memory segment by threads of the same half-warp are coalesced to fewer transactions while be accessing words of at least 4 bytes this memory segment is effectively increased from 32 bytes to 128. To access 16-byte instead of 1-byte words when there are unsigned chars stored in the global memory, the uint4 vector is commonly used by casting the memory array to uint4: uint4 *text4 = ( uint4 * ) d_text; var = text4[i]; In order to extract the 16 chars from var, i am currently using bitwise operations. For example: s_array[j * 16 + 0] = var.x & 0x000000FF; s_array[j * 16 + 1] = (var.x >> 8) & 0x000000FF; s_array[j * 16 + 2] = (var.x >> 16) & 0x000000FF; s_array[j * 16 + 3] = (var.x >> 24) & 0x000000FF; My question is, is it possible to recast var (or for that matter *text4) to unsigned char in order to avoid the additional overhead of the bitwise operations?

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• What type of data store should I use for my ios app?

  - by mwiederrecht

  I am pretty new to ios and using servers so forgive me. I am building an ios app for research. I need to monitor things that the user does and then push it up to a server for analysis (yes, with user and IRB permission). On the client's side I need to keep quite a bit of data that won't really change except in the case of pulling an updated version from the server, and then a minimal amount of user-specific data. Most of the data I will collect needs to be pushed to a server for analysis and then can be deleted from the client side. I am struggling to figure out what kind of data store I need to use, especially since I am not quite sure how the pushing and pulling from the server process works yet. Does it make sense to use Core Data? XML? SQLite? I like the Core Data idea, but I am not sure what kind of problems I will run into when I need to send large amounts of data to it and from it from the server. I imagine I might need to send data in a different form than it is probably stored in on either end - so what kind of overhead am I likely to run into in the process of converting that data? Is there a good format to save stuff in that would work well for me on both ends AND for sending the data? As you can probably tell, I could use some advice. Thanks!

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• Extract information from a Func<bool, T> or alike lambda

  - by Syska

  I''m trying to build a generic cache layer. ICacheRepository Say I have the following: public class Person { public int PersonId { get; set; } public string Firstname { get; set; } public string Lastname { get; set; } public DateTime Added { get; set; } } And I have something like this: list.Where(x => x.Firstname == "Syska"); Here I want to extract the above information, to see if the query supplied the "PersonId" which it did not, so I dont want to cache it. But lets say I run a query like this: list.Where(x => x.PersonId == 10); Since PersonId is my key ... I want to cache it. with the key like "Person_10" and I later can fetch it from the cache. I know its possible to extract the information with Expression<Func<>> but there seems to be a big overhead of doing this (when running compile and extract the Constant values etc. and a bunch of cache to be sure to parse right) Are there a framework for this? Or some smart/golden way of doing this ?

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• fluent nhibernate - storing and retrieving three classes in/from one table

  - by Will I Am

  Noob question. I have this situation where I have these objects: class Address { string Street; string City; ... } class User { string UserID; Address BillingAddress; Address MailingAddress; ... } What is the proper way of storing this data using (fluent) nHibernate? I could use a separate Address table and create a reference, but they are 1:1 relationships so I don't really want to incur the overhead of a join. Ideally I would store this as a single flat record. So, my question is, what is the proper way of storing an instance of class 'User' in such a way that it stores its contents and also the two addresses as a single record? My knowledge is failing me on how I can store this information in such a way that the two Address records get different column names (e.g. BillingAddress_Street and MailingAddress_Street, for example), and also how to read a record back into a User instance.

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• Maximum length of a std::basic_string<_CharT> string

  - by themoondothshine

  Hey all, I was wondering how one can fix an upper limit for the length of a string (in C++) for a given platform. I scrutinized a lot of libraries, and most of them define it arbitrarily. The GNU C++ STL (the one with experimental C++0x features) has quite a definition: size_t npos = size_t(-1); /*!< The maximum value that can be stored in a variable of type size_t */ size_t _S_max_len = ((npos - sizeof(_Rep_base))/sizeof(_CharT) - 1) / 4; /*!< Where _CharT is a template parameter; _Rep_base is a structure which encapsulates the allocated memory */ Here's how I understand the formula: The size_t type must hold the count of units allocated to the string (where each unit is of type _CharT) Theoretically, the maximum value that a variable of type size_t can take on is the total number of units of 1 byte (ie, of type char) that may be allocated The previous value minus the overhead required to keep track of the allocated memory (_Rep_base) is therefore the maximum number of units in a string. Divide this value by sizeof(_CharT) as _CharT may require more than a byte Subtract 1 from the previous value to account for a terminating character Finally, that leave the division by 4. I have absolutely no idea why! I looked at a lot of places for an explanation, but couldn't find a satisfactory one anywhere (that's why I've been trying to make up something for it! Please correct me if I'm wrong!!).

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• memcached: which is faster, doing an add (and checking result), or doing a get (and set when returni

  - by Mike Sherov

  The title of this question isn't so clear, but the code and question is straightforward. Let's say I want to show my users an ad once per day. To accomplish this, every time they visit a page on my site, I check to see if a certain memcache key has any data stored on it. If so, don't show an ad. If not, store the value '1' in that key with an expiration of 86400. I can do this 2 ways: //version a $key='OPD_'.date('Ymd').'_'.$type.'_'.$user; if($memcache->get($key)===false){ $memcache->set($key,'1',false,$expire); //show ad } //version b $key='OPD_'.date('Ymd').'_'.$type.'_'.$user; if($memcache->add($key,'1',false,$expire)){ //show ad } Now, it might seem obvious that b is better, it always makes 1 memcache call. However, what is the overhead of "add" vs. "get"? These aren't the real comparisons... and I just made up these numbers, but let's say 1 add ~= 1 set ~= 5 get in terms of effort, and the average user views 5 pages a day: a: (5 get * 1 effort) + (1 set * 5 effort) = 10 units of effort b: (5 add * 5 effort) = 25 units of effort Would it make sense to always do the add call? Is this an unnecessary micro-optimization?

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• How to store and synchronize a big list of strings

  - by Joel

  I have a large database table in SQLExpress on Windows, with a particular field of interest 'code'. I have an Apache web server with MySQL on Linux. The web application on the Linux box needs access to the list of all codes. The only thing it will use the list for is checking for the existence of a given code. Having the Linux server call out to the Windows server is impractical as the Windows server is behind a NAT'ed office internet connection, and it may not always be accessible. I have set it so the Windows server will push the list of codes to the web server by means of a simple HTTP POST request. However, at this point I have not implemented the storage of the codes on the Linux box. Should I store them in a MySQL table with a single field 'code'? Then I get fast indexed lookups O(1), however I think synchronization will be an issue - given an updated list of codes, pushed from the Windows box, how would I optimally synchronize the list with the database? TRUNCATE, followed by INSERT? Should I instead store them in a flat file? Then I have O(n) look up time rather than O(1). Additionally an extra constant-time overhead too, as I will be processing the file in Ruby. However, synchronization is easy - simply replace the file.

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• nothrow or exception ?

  - by Muggen

  I am a student and I have small knowledge on C++, which I try to expand. This is more of a philosophical question.. I am not trying to implement something. Since #include <new> //... T * t = new (std::nothrow) T(); if(t) { //... } //... Will hide the Exception, and since dealing with Exceptions is heavier compared to a simple if(t), why isn't the normal new T() not considered less good practice, considering we will have to use try-catch() to check if a simple allocation succeeded (and if we don't, just watch the program die)?? What are the benefits (if any) of the normal new allocation compared to using a nothrow new? Exception's overhead in that case is insignificant ? Also, Assume that an allocation fails (eg. no memory exists in the system). Is there anything the program can do in that situation, or just fail gracefully. There is no way to find free memory on the heap, when all is reserved, is there? Incase an allocation fails, and an std::bad_alloc is thrown, how can we assume that since there is not enough memory to allocate an object (Eg. a new int), there will be enough memory to store an exception ?? Thanks for your time. I hope the question is in line with the rules.

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• MySql: Is it reasonable to use 'view' or I would better denormalize my DB?

  - by Budda

  There is 'team_sector' table with following fields: Id, team_id, sect_id, size, level It contains few records for each 'team' entity (referenced with 'team_id' field). Each record represent sector of team's stadium (totally 8 sectors). Now it is necessary to implement few searches: by overall stadium size (SUM(size)); the best quality (SUM(level)/COUNT(*)). I could create query something like this: SELECT TS.team_id, SUM(TS.size) as OverallSize, SUM(TS.Level)/COUNT(TS.Id) AS QualityLevel FROM team_sector GROUP BY team_id ORDER BY OverallSize DESC / ORDER BY QualityLevel DESC But my concern here is that calculation for each team will be done each time on query performed. It is not too big overhead (at least now), but I would like to avoid performance issues later. I see 2 options here. The 1st one is to create 2 additional fields in 'team' table (for example) and store there OverallSize and QualityLevel fields. If information if 'sector' table is changed - update those table too (probably would be good to do that with triggers, as sector table doesn't change too often). The 2nd option is to create a view that will provide required data. The 2nd option seems much easier for me, but I don't have a lot of experience/knowledge of work with views. Q1: What is the best option from your perspective here and why? Probably you could suggest other options? Q2: Can I create view in such way that it will do calculations rarely (at least once per day)? If yes - how? Q3: Is it reasonable to use triggers for such purpose (1st option). P.S. MySql 5.1 is used, overall number of teams is around 1-2 thousand, overall number of records in sector table - overall 6-8 thousand. I understand, those numbers are pretty small, but I would like to implement the best practice here.

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• Linq based generic alternate to Predicate<T>?

  - by Eric

  I have an interface called ICatalog as shown below where each ICatalog has a name and a method that will return items based on a Predicate<Item> function. public interface ICatalog { string Name { get; } IEnumerable<IFamily> GetItems(Predicate<Item> predicate); } A specific implementation of a catalog may be linked to catalogs in various format such as XML, or a SQL database. With an XML catalog I end up deserializing the entire XML file into memory, so testing each item with the predicate function does does not add a whole lot more overhead as it's already in memory. Yet with the SQL implementation I'd rather not retrieve the entire contents of the database into memory, and then filter the items with the predicate function. Instead I'd want to find a way to somehow pass the predicate to the SQL server, or somehow convert it to a SQL query. This seems like a problem that can be solved with Linq, but I'm pretty new to it. Should my interface return IQueryable instead?

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• how to pass instance variables between handlers (routes) in sinatra (without flash, sessions, class variable or db)?

  - by jj_

  Say you have: get '/' do haml :index end get '/form' do haml :form end post '/form' do @message = params[:message] redirect to ('/') --- how to pass @message here? end I'd like the @message instance variable to be available (passed to) in "/" action as well, so I can show it in haml view. How can I do that without using session, flash, a @@class_variable, or db persistence ? I'd simply like to pass values as if I was working with passing values between methods. I don't want to use session cookies because user could have them turned off, I don't like it being a class variable which is exposed to all code, and I don't need to overhead of a db. Thanks edit: This is another question explaining a very easy way to deal with this in rails Passing parameters in rails redirect_to This is some more info i gathered around from forums. The following works for rails, i've tried it in Sinatra but no luck, but please try it, maybe I did something wrong, I don't know, and if this code help someone come up with a new idea, please share it If you are redirecting to action2 at the end of action1, just append the value to the end of the redirect: my_var = <some logic> redirect_to :action => 'action2', :my_var => my_var on the same thread another user proposes the folowing: def action1 redirect_to :action => 'action2', :value => params[:current_varaible] end def action2 puts params[:value].inspect end source: http://www.ruby-forum.com/topic/134953 Can something like this work in Sinatra? Thanks

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• Multi-Role Domain Controllers for Small Offices (< 50 clients)

  - by kce

  Warning: I'm a Linux/*NIX admin so this is all new to me. I understand that it's not considered a good idea to have only a single domain controller, and that it is also probably a good idea for a domain controller to only do AD/DHCP/DNS (Here). We have two offices, location A with 30 users and location B with 10 users. Our two offices are separated by a WAN that is not particularly robust so I have be instructed that we need to have standalone services in each office. This means that according to "best practices" we will need to build a domain controller and a separate file server in each office. Again, I am not knowledgeable in the ways of Windows but this seems a little unnecessary for an organization of 40 users. People have commented that I could "get away with" running file services on the domain controller as long as the "load is light". That just seems to generate more questions than it answers. What constitutes light load? What are the potential consequences of mixing these roles? Ideally I would prefer to only have one physical machine at each location. The one in location A (the location with IT staff) can act as the primary domain controller and the one in the smaller office can act as the backup domain controller. If either domain controller fails we can still use the other one for authentication (albeit with some latency) and if the WAN connection fails each office still has access to their respective "local" domain controller. If the file services are ALSO run on each server (and synchronized with something like DFS), a similar arrangement in terms of redundancy can be had without having to purchase, build and install two additional separate servers. It's not that I'm adverse to that (well, any more adverse than I am to whole thing to begin with) but to my simple mind it just seems, well a bit overkill. I can definitely see the benefits of functional separation when we're talking larger organizations, but I need to consider the additional overhead too. None of this excludes having a DRP setup for the domain controller/s. I assume you can lose two domain controllers just as easily as one.

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• Configuring gmail for use on mailing lists

  - by reemrevnivek

  This is really two questions in one. First, are nettiquette guidelines still accurate in their restrictions on ASCII vs. HTML, posting style, and line length? (Here's a recent metafilter discussion of the topic.) Second, If they are not, should these guidelines be respected? If they are (or if they should still be respected), how can modern mail programs be configured to work properly with them? Most mailing list etiquette statements appear to have been written by sysadmins who loved their command lines, and refuse to change anything. Many still reference rfc1855, written in 1995. Just reading that paginated TXT should give you an idea of the climate at the time. Here's a short, fairly random list of mailing list etiquette statements with some extracted formatting guidelines: Mozilla - HTML discouraged, interleaved posting. FreeBSD - No HTML, don't top post, line length at 75 characters. Fedora - No HTML, bottom-post. You get the idea. You've all seen etiquette statements before. So, assuming that the rules should be obeyed (Usually a good idea), what can be done to allow me to still use a modern mail program, and exchange mail with friends who use the same programs? We like to format our mail. Bold headings, code snippets (sometimes syntax highlighted, if the copy-paste pulls RTF text as from XCOde and Eclipse), free line breaks determined by your browser width, and the (very) occasional image make the message easier to read. Threaded conversations are a wonderful thing. Broadband connections are, I'm sure, the rule for most of the users of SU and of developer mailing lists, disk space is cheap, and so the overhead of HTML is laughable. However, I don't want to post a question to a mailing list and have the guru who can answer my question automatically delete it, or come off as uncaring. Until I hear otherwise, I'll continue to respect the rules as best I can. For a common example of the problem, Gmail, by default, sends HTML formatted messages with bottom-posted quotes (which are folded in, just read the last message immediately above), and uses the frame width to wrap lines, rather than a character count. ASCII can be selected, and quotes can be moved and reversed, but line wraps of quotes don't work, line breaks are tedious to add (and more tedious to read, if they're super small in comparison to the width of the frame). Is there a forwarding, free mail program which can help with this exercise? Should an "RFC1855 mode" lab be written? Or do I have to go to the command line for my mailing lists, and gmail for my other mail?

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• Encoding multiple video streams with a single avconv invocation

  - by automatthias

  I played with avconv on Ubuntu and I'm now able to e.g. record the desktop with sound from a soundcard. One thing I wanted to do was recording two video inputs at the same time, for instance the desktop and from the webcam. I thought about doing something like this: avconv \ -f alsa \ -i default \ -acodec flac \ -f video4linux2 \ -r 6 \ -i /dev/video0 \ -f x11grab \ -i :0.0 \ out.mkv My thinking was that if you define multiple video inputs, and the .mkv format can handle multiple video streams, avconv will encode 2 video streams and 1 audio stream into one file. But this isn't what happens: avconv version 0.8.4-6:0.8.4-0ubuntu0.12.10.1, Copyright (c) 2000-2012 the Libav developers built on Nov 6 2012 16:51:11 with gcc 4.7.2 [alsa @ 0x1091bc0] capture with some ALSA plugins, especially dsnoop, may hang. [alsa @ 0x1091bc0] Estimating duration from bitrate, this may be inaccurate Input #0, alsa, from 'default': Duration: N/A, start: 1354364317.020350, bitrate: N/A Stream #0.0: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s [video4linux2 @ 0x10923e0] Estimating duration from bitrate, this may be inaccurate Input #1, video4linux2, from '/dev/video0': Duration: N/A, start: 100607.724745, bitrate: 29491 kb/s Stream #1.0: Video: rawvideo, yuyv422, 640x480, 29491 kb/s, 6 tbr, 1000k tbn, 6 tbc [x11grab @ 0x107b2a0] device: :0.0+83,87 -> display: :0.0 x: 83 y: 87 width: 854 height: 480 [x11grab @ 0x107b2a0] shared memory extension found [x11grab @ 0x107b2a0] Estimating duration from bitrate, this may be inaccurate Input #2, x11grab, from ':0.0+83,87': Duration: N/A, start: 1354364318.488382, bitrate: 196761 kb/s Stream #2.0: Video: rawvideo, bgra, 854x480, 196761 kb/s, 15 tbr, 1000k tbn, 15 tbc Incompatible pixel format 'bgra' for codec 'mpeg4', auto-selecting format 'yuv420p' [buffer @ 0x107fcc0] w:854 h:480 pixfmt:bgra [avsink @ 0x10bdf00] auto-inserting filter 'auto-inserted scaler 0' between the filter 'src' and the filter 'out' [scale @ 0x10dc680] w:854 h:480 fmt:bgra -> w:854 h:480 fmt:yuv420p flags:0x4 Output #0, matroska, to '.../out.mkv': Metadata: encoder : Lavf53.21.0 Stream #0.0: Video: mpeg4, yuv420p, 854x480, q=2-31, 4000 kb/s, 1k tbn, 15 tbc Stream #0.1: Audio: libvorbis, 48000 Hz, 2 channels, s16 Stream mapping: Stream #2:0 -> #0:0 (rawvideo -> mpeg4) Stream #0:0 -> #0:1 (pcm_s16le -> libvorbis) Press ctrl-c to stop encoding [mpeg4 @ 0x10bd800] rc buffer underflow ^Cframe= 160 fps= 15 q=2.0 Lsize= 3414kB time=10.66 bitrate=2623.0kbits/s video:3273kB audio:131kB global headers:4kB muxing overhead 0.165600% Received signal 2: terminating. I'm not sure if it's the question of mapping (some -map options to add?) or that avconv just can't encode more than 1 video stream at one time. So is it an actual avconv limitation, or a limitation of the available containers, or me simply not finding the right combination of command line options?

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