Both has bindings for C, both can play various formats.
Which one is more superior? in terms of simplicity, performance, overhead and memory footprint.
Also which one is better at handling multiple streams?
I have not programmed with either of those, but I believe that OpenAL has been designed to render and output multiple-channel audio for games, with real-time performance as a requirement.
libSoX is more for input and output from audio files, as well as for format conversions. There are lots of plugins but AFAIK it has not been designed for real-time audio output. It seems significantly simpler to use, though.
You might also want to have a look at libsndfile.
What exactly is it that you want to do?
While I have never used OpenAL, I've heard a lot of bad things about it that make it sound unprofessional and basically a dead end. From Wikipedia:
OpenAL was originally developed by Loki Software in order to help them in their business of porting Windows games to Linux. After the demise of Loki, the project was maintained for a time by the free software/open source community, and implemented on NVIDIA nForce sound cards and motherboards. It is now hosted (and largely developed) by Creative Technology with on-going support from Apple, Blue Ripple Sound, and free software/open source enthusiasts.
While the OpenAL charter says that there will be an "Architecture Review Board" (ARB) modeled on the OpenGL ARB, no such organization has ever been formed and the OpenAL specification is generally handled and discussed via email on its public mailing list.
Since 1.1, the implementation by Creative has turned proprietary, with the last releases in free licenses still accessible through the project's subversion. However, OpenAL Soft is a widespread Open Source alternative.
There was also an issue with it messing up the state of the calling application; I believe just linking it caused some global constructors to run before the invocation of main in a way that altered the program's initial environment, and broke some programs (MPlayer perhaps?). It's unclear to me whether this issue was ever fixed, but it screams bad library and I would be skeptical of ever trusting a library historically contained such abuses.
Related
I'm looking for a simple-ish library for outputting audio. I'd like it to meet these criteria:
Licensed under LPGL/zlib/MIT or something similar – i'm going to use it in an indie commercial application and i don't have the money for a license.
Written in C, but C++ is fine.
Cross-platform (Windows, Linux, maybe OSX)
Able to read from some sort of audio file (i'd prefer WAV or OGG but i will gladly use less popular formats if need be) in memory (i've seen the use of a memfile struct and user-defined I/O callbacks). I need the file to be in memory because i put all my resources into a .zip archive, and i use another library to load those archived files into memory.
Supports playing multiple sounds at the same time, having a max of 8 or so is ok.
I'd really like to either have the source code or a static library (MinGW/GCC lib???.a), but if nothing else is available i will use a shared library.
I must have come accross two dozen different audio libraries in my search, all of which haven't quite met these criteria...
I would recommend PortAudio + libsndfile. Very popular combo, meets your requirements. Used by many other software applications including audacity.
Some of the candidates that immediately spring to my mind are:
SDL (there is a tutorial that demonstrates how to play a .wav format sound)
libav
ffmpeg
libao
OpenAL Soft
Jack Audio
You may have already looked at these and eliminated them, though. Can you give some more detail about the libraries that you have eliminated from consideration and why? This will help narrow down our recommendations.
You might want to look into SDL and SDL_mixer. Here is a good tutorial.
I've used SDL_mixer and it makes it easy to play background sounds or music and play multiple simultaneous sounds without having a need to write your own sound sample mixer.
I ended up using PortAudio (very low-level, flexible license) and wrote a mixer myself. See this topic i made on the C++ forums for some other people's tips on writing a custom mixer. It's not hard at all, really; i'm surprised that there are so many mixer libraries out there. For a breakdown of the WAV format (ready-to-stream raw audio data with a 44-byte header) see this.
This may sound noobish, especially as I'm ( as you may have guessed ) trying to write an Operating System. At the moment I'm stuck on trying to make a file system.
What I want is a similar file system as Linux Ubuntu which is EXT4 ( at least mine is ). I want to try and also either write it in C.
Any idea's on how I can go about this? And/or any tutorials that you might have found that may help me ( I have tried searching with no luck ) :L
Thanks in advance!
Jamie.
Really smart and experienced people who have studied this problem extensively have made bugs that ate users' data. The difference between a bug in the computation layer (e.g. a kernel crash) and a bug in the storage layer is that silently eating users' data is very bad - much worse than giving wrong answers in spreadsheets (excel is buggy yet popular) or intermittently sigfaulting while preserving data on disk (this is easily mitigated by frequent autosave).
Start by studying simpler designs, like the minix filesystems from the old operating systems book [1] (the same one Linus Torvalds started with, twenty years ago).
Like others said, ext2 without journaling, extents or ACLs is a better starting point than ext4. The source code for it is in the Linux kernel and in the e2fsprogs userspace tools package[2]. The format is well documented.
As for tutorials, consider who makes them and why they spend effort on this task. Tutorials are generally made by stakeholders in platforms to bring in new people to develop using that platform, to use the network effect to grow the platform and profit from being already-established actors in a larger ecosystem.
Do you see a business model in growing the number of people who implement their own incompatible buggy[3] file systems? Only if you sell software engineering degrees. So Microsoft only writes tutorials on how to use NTFS, not on how to implement it. Same for Sun and ZFS, Red Hat and Google with EXT2/3/4, SGI with XFS, IBM with JFS, Oracle with BTRFS, etc.
If you want education instead of training, you need to read books and study smart peoples' code they use in production, not look for tutorials.
http://en.wikipedia.org/wiki/Operating_Systems:_Design_and_Implementation
http://e2fsprogs.sourceforge.net/
How much use, in how many different use pattern with it see? Consider bugs discovered in production FSs after years of use on millions of computers. It is unlikely your code will be less buggy, even if you're as smart as Matthew Dillon.
Try looking at an existing implementation, like the one in Linux.
a previous relevant question from me is here Reverse Engineering old paint programs
I have set up my base of operations here: http://animatorpro.org
wiki coming soon.
Okay, so now I have a 300,000 line legacy MSDOS codebase. It's sort of a "be careful what you wish for" situation. I am not an experienced C programmer. I'm not entirely inexperienced either, but for all intents and purposes I'm a noob to the language and in particular the intricacies of its libraries. I am especially ignorant of the vagaries of the differences between C programs written specifically for MSDOS and programs that are cross platform. However I have been studying this code base for over a year now, and this is what I know about Animator Pro:
Compilers and tools used:
Watcom C compiler
tcmake (make program from Turbo C)
386asm, a specialised assembler for the Phar Lap dos extender
and of course, the Phar Lap dos extender itself.
a selection of obscure dos utilities
Much of the compilation seems to be driven by batch files. Though I have obtained copies of all these tools, I have not yet succeeded at compiling it. (though I have compiled its older brother, autodesk animator original.
It's got a plugin system that replicates DLL before DLL's were available, based on REX. The plugin system handles:
Video Drivers (with a plethora of included VESA drivers)
Input drivers (including wacom tablets, and keyboards)
Drawing Tools
Inks (Like photoshop's filters, or blending modes)
Scripting Addons (essentially compiled scripts)
File formats
It's got its own script interpreter named POCO, based on the C language- The scripting language has enough power to do virtually all the things the plugin system can do- Just slower.
Given this information, this is my development plan. Please criticise this. The source code is available in the link above, so you can easily, if you are so inclined, assess the situation yourself.
Compile with its original tools.
Switch to using DJGPP, and make the necessary changes to get it to compile with that, plus the original assembler.
Include the Allegro.cc "Game" library, and switch over as much functionality to that library as possible- Perhaps by simply writing new video and input drivers that use the Allegro API. I'm thinking allegro rather than SDL because: there is a DOS version of Allegro, and fascinatingly, one of its core functions is the ability to play Animator Pro's native format FLIC.
Hopefully after 3, I will have eliminated most or all of the Assembler in the project. I say hopefully, because it's in an obscure dialect that doesn't assemble in any modern free assembler without significant modification. I have tried them all. Whatever is left gets converted to assemble in NASM, or to C code if I can define the assembler's actual function.
Switch the dos extender from Phar Lap to HX Dos http://www.japheth.de/HX.html, Which promises to replicate as much of the WIN32 api as possible. Then make all the necessary code changes for that to work.
Switch to the win32 version of Allegro.cc, assuming that the win32 version can run on top of HXDos. Make any further necessary changes
Modify the plugin system to use some kind of standard cross platform plugin library. What this would be, I have no idea. Maybe you can offer some suggestions? I talked to the developer who originally wrote the plugin system, and he said some of the things it does aren't possible on modern OS's because of segmentation restrictions. I'm not sure what this means, but I'm guessing it means all the plugins will need to be rewritten almost from scratch.
Magically, I got all the above done, and we can try and make it run in windows, osx, and linux, whilst dealing with other cross platform niggles like long file names, and things I haven't thought of.
Anyone got a problem with any of this? Is allegro a good choice? if not, why? what would you do about this plugin system? What would you do different? Is this whole thing foolish, and should I just rewrite it from scratch, using the original as inpiration? (it would apparently take the original developer "About a month" to do that)
One thing I haven't covered above is the text/font system. Not sure what to do about that, but Animator Pro has its own custom font format, but also is able to use Postscript Type 1 fonts, and some other formats.
My biggest concern with your plan, in a nutshell: Your approach seems to be to attempt to keep the whole enormous thing working at all times, tweaking the environment ever-further away from DOS. During each tweak to the environment, that means you will have approximately a billion subtle assumptions that might have broken at once, none of which you necessarily understand yet. Untangling them all at once will be incredibly painful.
If I were doing the port, my approach would be to disable as much code as possible to get SOMETHING running in a modern environment, and bring the parts back online, one piece at a time. Write a simple test harness program that loads a display driver and draws some stuff, and compile it for DOS to make sure you understand the interface. Then write some C code that implements the same interface, but with Allegro (or SDL or SFML), and make that program work under Windows or Linux. When the output differs, you have a simple test case to work from.
Your entire job on this port is swapping out implementations of various interfaces and functions with completely new ones. This is a job that unit testing excels at. Don't write any new code without a test of some kind that runs on the old code under DOS! Make your potential problems as small and simple as you possibly can. Port assembly code instead of rewriting it only if you're reasonably confident that it will actually make your job easier (ie, algorithmic stuff that compiles fine with few tweaks under NASM). Don't bite off a bigger piece than you can comfortably fit in your brain at once.
I, for one, look forward to seeing your progress! I think what you're attempting to do is great. Thanks for doing it.
Hmmm - I might approach it by writing an OpenGL video "driver" for it. and todays machines are fast enough with tons of ram that you could do all the pixel specific algorithms on main CPU into a back buffer and it would work. As the "generic" VGA driver just mapped the video buffer to a pointer this would be a place to start. There was a zoom mode in the UI so you can look at the pixels on a high res display.
It is often very difficult to take an existing non-trivial code base that wasn't written with portability in mind - you mention a few - and then try to make it portable. There will be a lot of problems on the way. It is probably a better idea to start from scratch and rewrite the code using the existing code as reference only. If you start from scratch you can leverage existing portable UI solution in your new project like Qt.
I'm looking to implement 'branch and bound' over a cluster (like Amazon's say), as I want it to be horizontally scalable, not limited to a single CPU. There's a paper "Task Pool Teams: A Hybrid Programming Environment for Irregular Algorithms on SMP Clusters" by Judith Hippold and Gudula Runger. It's basically a bottom-up, task-stealing framework like Intel's TBB, except for ad-hoc networks instead of shared memory. If this library was available I'd use it (replacing the local, threaded part with TBB). Unfortunately they don't seem to have made it available for download anywhere that I could find, so I wonder are there other implementations, or similar libraries out there?
It doesn't look like Microsoft's Task Parallel Library has the equivalent, either, to steal from.
(I tried to make a tag 'taskpool' after 'threadpool', the most-used variant (before 'thread-pool') but, didn't have enough points. Anyone heavy enough think it's worth adding?)
edit:
I haven't tried it yet, but it PEBBL (under here: software.sandia.gov/trac/acro/wiki/Packages) claims to scale really high. The paper that the answerer mentions from the Wiley book 'Parallel Branch-and-Bound Algorithms', Crainic, Le Cun and Roucairol, 2006, from "Parallel Combinatorial Optimization", 2006 edited by El-Ghazali Talbi was where I found it, and there are other libraries listed; some may be better, I reserve the right to update this :). Funny that Google didn't find these libs, either my Googling was weak or Google itself fails to be magic sometimes.
When you say "over a cluster" it sounds like you mean distributed memory, and parallelizing branch and bound is a notoriously difficult problem for distributed memory - at least in a way that guarantees scalability. The seminal paper on this topic is available here, and there's an excerpt from a Wiley book on the topic here.
Shared memory branch is bound is an easier problem because you can implement a global task queue. A good high level description of how to do both shared memory and message passing implementations is available here. If nothing else, the references section is worth purusing for ideas and existing implementations.
One thing you might consider is investigating shared message queues like RabbitMQ. It is a AMQP server (a messaging protocol developed so distributed applications can send messages to each other).
you basically need some kind of distributed synchronization/queue
I suggest looking into armci as a low-level distributed memory interface with synchronization and build on top of that.
Alternative is to allocate mpi process as Master to distribute work allocation.
http://www.cs.utk.edu/~dongarra/ccgsc2008/talks/Talk10-Lusk.pdf
Once upon a time, a team of guys sat down and wrote an application in C, running on VMS on a VAX. It was a rather important undertaking and runs a reasonably important back-end operation at LargeCo. This whole shebang works so well that twenty-five years later it's still chugging along and doing it's thing.
Time passes and people retire and it so happens that the Last Man Standing has turned over the keys to a new generation who - we might imagine - are less than thrilled to find themselves caretakers of a system old enough to be their younger brother. Yet, as underwhelmed as they are by the idea of dealing with Ultra Legacy Systems, they can't justify the cost of replacing the venerable application.
LMS discovered that I habla unix and put this question to me. And since I habla unix but don't speak the C I shall summarize and put it to you. Long Story Short:
LMS wants to port LegacyApp, written in C. from VMS to unix. Resources? Any books he can read? People he can talk to?
The first question I'd need to ask is why, and I'd be leading the conversation in the direction of "Do you really need to port it off of VMS". There are a number of things worth mentioning about VMS:
-> VMS is still actively developed and maintained by HP. They just release V8.4 for Field Test last week (see http://h71000.www7.hp.com/openvmsft/).
-> VMS is available on new hardware; specifically HP's Integrity servers based on the Itanium processor.
-> VMS is also available on virtual platforms via the Charon Emulation products.
-> Popular estimates are that there are about 300,000 VMS systems still in active use today. LMS may be the last man at LargeCo, but he's far from the last man standing worldwide.
-> Lots of information out there, see openvms.org for example, to see lots of current information on VMS, all from current users.
OK - you still want to port off of VMS. How do you do it? Well, it depends on lots of stuff.
-> As others have said, how standard is the code? Chances are, not very. The more VMS-isms, the more difficult the job. 'nuff said.
-> What is the database? If it's Oracle, probably not too tough to move to Oracle on some other platform. If it's some sort of custom DB based on RMS index files, then you've got more work to do, you'll need to re-create that pseudo DB, or, understand it enough to replace it with some relational DB.
-> Besides C, what else is used to create the application? What's on the front end? DECforms? FMS? Is there a transaction engine, e.g. ACMS? RTR? These things will have a huge impact on the feasibility and effort required to port to UNIX.
-> What other products are involved? Are there any 3rd party libraries being used? Are there 3rd party products in use that are critical to the application or functionality?
-> Is this system clustered? If so why? You'll need to meet those same goals with the UNIX box.
-> There are companies out there that will help you do it, and claim to have tools to make it easier, but my experience is that these companies tend to be selling you more services than products (i.e. you need to hire them to use the tools. It'll be expensive).
The book UNIX for OpenVMS Users will give the VMS novice some help in understanding VMS, but, as the title says, the book is really intended for the opposite purpose.
Everything written on VMS uses lots of VMS specific stuff it was just so convenient.
There are a few companies that sell compatibility libs to make the port easier - they wont be cheap though, VMS tended to be used where reliability mattered more than cost.
The other option is to run openVMS on some modern hardware, possibly in a VM.
I am sure Brian has made his decision by now, but for my sins of working for many years in DEC OpenVMS language support (yes, some people had this dubious honour) the real question I would have asked a customer such as Brian is: is it a real-time application or not? If it is the former, then it would be heavily dependent on many VMS system services which would rule out a 'port' and indicate a re-write. If it were the latter then the frequency of VMS system services should (possibly) be limited and make a port viable.
The acid test for me, would be to SEARCH *.c "SYS$", "LIB$" i.e. to search all of the C source files for "SYS$" and "LIB$" tags which prefix VMS system services. If the count for these are in the 10s then a port is probably likely, between 10 and 100 makes it possibly likely, but over a 100 makes a successful port highly unlikely.
Hope this helps
You have several choices.
Get the OpenVMS source, and continue to maintain Open VMS as if it were a Linux distribution. Some folks don't mind keeping up with Linux distributions and OpenVMS distributions. It can be done.
Try to recompile the VMS C into Linux. This can be trivial if the C used only standard libraries. This can be very, very difficult if the C used a lot of VMS libraries.
Once you have facts at your fingertips, you can reevaluate this course of action. Since you didn't list a bunch of VMS library methods this program uses, it's impossible to tell how entangled it is with the OS.
This may be trivial or impossible. It's difficult to tell without analysis of the source.
Write bridge libraries from VMS to Linux. If your program only does a few VMS things, this isn't very difficult. If your program does extensive VMS things, this is craziness.
The bridge -- in the long run -- is a terrible idea. Managers love it, however.
An alternative is to replace the VMS library calls with proper, portable Linux calls rather than write bridges. This is better in the long run, because it excises the non-portable features of the program.
Rewrite it from scratch in Python. That is usually simpler than trying to port the C code. It will be shorter, cleaner, simpler, and portable.
If you're willing to keep running VMS in a VM, you can look into CHARON-VAX ( http://www.charon-vax.com/ ). As previously mentioned, the ease of porting really depends a lot on how much of the VMS extensions were used; searching the source code for $ characters embedded in strings (usually with a 3-character leading substring, such as lib$gettime or dsc$descriptor or sys$foobar etc) will give you at least a basic idea of what VMS system functions are called and how likely they are to be portable, if the name is reasonably obvious.
If it ain't broke, don't fix it! Why port it or migrate the app if you don't have to? Why not run it on a current install of OpenVMS running on an HP Itanium server; that is assuming you wish to upgrade the hardware, which may not even be necessary if your VAX hardware is still running strong.
To learn C, you might as well drag it from the horse's mouth: "The C Programming Language" by its inventors, Kernighan and Ritchie.
I can recommend "The UNIX programming environment" by (again) Brian Kernighan; a more authoritative source you'll hardly find, and it teaches you both Unix/C idioms and a bit of C programming at the same time.
For more depth and detail on C, I heartily enjoyed a book by Peter van der Linden: "Expert C Programming - Deep C Secrets".
You'll also want to wrestle LMS for a library documentation of VMS-specific C functions with (of course) special emphasis on those actually used in the app. That's where your porting effort will be.
The job could be easy or difficult, depending on how much machine-specific cleverness and bit-twiddling is done, and how many VMS-specific system calls are used. It would be very good if word size was equal (in other words, if your VMS box has a word size of 32 bits, don't run the code on a 64 bit version of Unix!)
Brian, I'm not sure if LMS specified/cared to port C-code or the WHOLE process. As too often people think of languages out of scope of systems.
If there're was a process built on VMS, most likely it used at least scheduling/batch facilities, which are often scripted in DCL (rather simple and clear language, unlike shell or perl scripting).
So the cost of porting the whole process may be higher than originally perceived by your LMS. Add here the reliability aspect, given your crunches with C, which is nothing impossible, of course, with enthusiasm and determination.
If you want simply give the C-code a try, as previously posted, search it for the "$" hits. Or just cc it with all headers present, the basics of compile-link command should be enough.
Alternatively, this looks like a consultant's call, as indeed such jobs were abundant at the "exodus" time. All said VMS remains quite a robust platform (24x7 is a norm!), unless the harware dies, then there're still tons of "exodus" spares. GOOD LUCK!
About a year and a half later, maybe you've already figured out what to do. My organization has recently decided to stick with OpenVMS instead of switching to Linux even though the old guard recently left. We just couldn't argue with what we felt was a very stable and reliable system. We are currently switching from Alpha servers to Integrity servers for end of life reasons. HP has been very helpful with our transition.
For that matter, there may be Linux vendors out there who can help with the transition. Ask your new hardware vendor if they have any recommendations.
Depending on what languages you already know, C is not that hard to learn. I taught myself C in the course of learning C++ after finally prying myself loose from Pascal.
(VAX Pascal, plus Rdb/VMS, plus DCL formed a combination that was hard to beat.)
If the software is typical C, you'll spend more time learning the library functions than learning the language.
It's pretty lightweight stuff, but I went through the online tutorials for C++ that Microsoft makes available in conjunction with the express edition of Visual Studio for C++.
Here's the beginner's tutorial:
http://msdn.microsoft.com/en-us/beginner/cc305129.aspx
It's probably worth making the effort to ask why LMS wants to port the application to Unix. The answer may seem obvious, but properly exploring the reasons has its benefits. I would assume:
OpenVMS is an "ultra legacy platform", and for that reason alone is something that is not worth running an application on anymore;
It's tough to find anyone who is willing to maintain an application that runs on OpenVMS these days;
The hardware on-which OpenVMS runs is threatening to become moribund.
We have a similar challenge, but in our case the application in question not only runs on OpenVMS but is also written in COBOL. I would have to say that your situation is rosy in comparison given that your application is written in a cross-platform language.
In any case, I think if you're about to make a big decision like moving from OpenVMS to Unix it would be prudent to do a little due diligence. In your case, try to assess just how portable the code is--only then will you know what the scale of the effort is (worst case could quite easily be a multiple of best case). In C, code portability is mostly a function of the dependencies--are they "standard" or are they VMS-specific?
Our enquiries revealed that HP would be supporting OpenVMS on Itanium until at least 2022. There isn't necessarily a need to rush to another platform--perhaps you could keep things on OpenVMS whilst embarking on an effort to prepare the application for porting (make it less dependent on OpenVMS specifics).
VMS has a surprisingly healthy community and if it's the lack of Unix that's the issue, then maybe GNV could help bridge the gap?
Well u have a few options. if this code needs to be ported rather quickly, i would write a bridge library to emulate the vms libs. whener you get it back up and running on a *nix, then go through replacing the vms library calls with native/portable calls for *nix.
Also if there is a lot of optimizations in the code ie inline assembly and bit twiddling. then you will have to rewrite thi code, which will take an understanding of the VAX arch. also. be sure to check word size differences and endian differences