I have seen a few examples of libmad usage and I can't locate in the code where the programmer tells libmad which file to decode, I expect to be some sort of function and the file name being one of its parameters.
It would be nice if you could provide some exapmle code
I am using Windows
Any answer with good intentions is appreciated
Related
is there any "good" way to distinguish between movie file and image file?
I would like to know what exactly my "std::wstring filePath" is - a movie, or an image.
Therefore, I could go further with strong assurance I am working with known file type.
In other words, I have two classes MyImage and MyMovie both need path to file in their constructors. I would like to verify path to file somehow before creating one of those classes.
bool isMovie(const std::wstring & filePath);
bool isImage(const std::wstring & filePath);
Of course I thought about file extensions, but I'm not sure that it is good and not prone to errors solution. So is it good to use file extension or any other feasible solution is possible.?
Thanks in advance
You can use libmagic to detect what kind of file it is. You pass the file path in and it'll give you a textual description or MIME type for the file.
Usually files have special so called magic bytes. I you have a control over the specification I would use this. If you try opening zip, gif, or other binary stuff you can usually find some distinctive strings there.
There is a unix tool utility called file that provides such functionality, so probably some sort of standard exists.
SQLite 3 provides a nice example. Look at 1.2.1 and 1.2.5. So not only the info that it is a SQLite 3 DB is given, but also additional application id, so other tools can recognize which application's DB it is.
I personally used few first bytes of a file to code type and version info for my files when I was playing with binary stuff.
have you ever worked with JPEG2000 and/or GML?.
I'm reading documentation about GMLJP2 but I don't find any libraries that implement this. I mean, as far as I know it should be possible to have a GML file within a jp2 file (that is, a single file with both of the thigs).
Also, it's difficult to get a viewer that integrates GML and JPEG2000.
Any information regarding how to work with GML or JPEG200 is wellcome ;-)
Many thanks!
PD: I want to work with C or C++ but it doesn't matter the language yet
"Also, it's difficult to get a viewer that integrates GML and JPEG2000."
As I understand GML is just a block of metadata in XML inserted into JPEG2000 file. Any decent decoder should be able to extract it.
I wrote a JP2 metadata editor and included basic GML support.
You can download it here:
http://j2k-codec.com/mde.html
See the "gml.jp2" file for an example.
Hope it will be helpful.
I often find myself needing to write functions to load/save from/to ASCII (or similar) text files; such as config files or data. I can and have done so many times but never feel like I do it well. ie the results are not very tolerant of minor changes to the file format.
Can anyone point me to a good guide to writing robust text file io or even better some libraries to make it easier?
Off the top of my head, there's:
Glib's key-value file parser
YAML
Both of these are pretty standard under linux.
YAML is a really good choice. Here we use yaml-cpp
my2c
I Have used a utility written by Mark Russinovich, it is used to validate the file signature.
Any one have ideas how this can be done, i know it is not a simple code, but just i need some hints, APIs, steps, A guide map, Just to go in the correct direction.
I read too much a bout the cryptAPIs, then I read too much about the certAPIs, but i cannot get any thing useful to simply link a given file with the (unknown to me) data stored in the windows.
if any can help me in this issue please help, thanks a lot.
You should read about Authenticode.
I've always been curious about audio conversion software, but I have never seen a proper explanation from a beginners point of view as to how to write a simple program that converts for example, a mp3 file to a wav. I'm not asking about any of the complex algorithms involved, just a small example using a simple library. Searching on SO, I came up with several names including:
Lame
The Synthesis Toolkit
OpenAL
DirectSound
But I'm unable to find a straightforward example of any of these libraries. Usually I don't mind wading through tons of code, but here I have absolutely no knowledge about the subject and so I always feel like I'm shooting in the dark.
Anyone here have a simple example / tutorial on converting a sound file using any of these libraries? My question is specifically directed towards C/C++ because those are the two languages I'm currently learning and so I'd like to continue to focus on them.
Edit: One thing I forgot to mention: I'm on a *NIX system.
Thanks everyone for the responses! I sort of cobbled them together to successfully make a small utility that converts a AIFF/WAV/etc file to an mp3 file. There seems to be some interest in this question, so here it what I did, step by step:
Step 1:
Download and install the libsndfile library as suggested by James Morris. This library is very easy to use – its only shortcoming is it won't work with mp3 files.
Step 2:
Look inside the 'examples' folder that comes with libsndfile and find generate.c. This gives a nice working example of converting any non-mp3 file to various file formats. It also gives a glimpse of the power behind libsndfile.
Step 3:
Borrowing code from generate.c, I created a c file that just converts an audio file to a .wav file. Here is my code: http://pastie.org/719546
Step 4:
Download and install the LAME encoder. This will install both the libmp3lame library and the lame command-line utility.
Step 5:
Now you can peruse LAME's API or just fork & exec a process to lame to convert your wav file to an mp3 file.
Step 6: Bring out the champagne and caviar!
If there is a better way (I'm sure there is) to do this, please let me know. I personally have never seen a step-by-step roadmap like this so I thought I'd put it out there.
For converting between various formats (except MP3) check libsndfile http://mega-nerd.com/libsndfile/
Libsndfile is a library designed to
allow the reading and writing of many
different sampled sound file formats
(such as MS Windows WAV and the
Apple/SGI AIFF format) through one
standard library interface.
During read and write operations,
formats are seamlessly converted
between the format the application
program has requested or supplied and
the file's data format. The
application programmer can remain
blissfully unaware of issues such as
file endian-ness and data format
It is also simple to use, with the API following the style of the Standard C library function names:
http://mega-nerd.com/libsndfile/api.html
And examples are included in the source distribution.
For actual audio output, another library will be needed, SDL as already mentioned might be a good place to start. While SDL can also read/write audio files, libsndfile is far superior.
If your curious about DSP and computers, take a look at the Synthesis Toolkit. It's sweet. It's designed for learning. The examples and tutorials they have on their website are straightforward and thorough. Keep in mind, the guys who wrote it, wrote it so they could create acoustic models of real instruments. As a result, they've included some instruments that are just plain wacky, but fun. It will give you a core understanding of processing PCM sound. And you'll probably be able to hack together some fun little noisemakers while your at it.
https://ccrma.stanford.edu/software/stk/
Check libmad http://mad.sourceforge.net " "M"peg "A"udio "D"ecoder library", should provide a good example.
Also for an easy cross-platform audio handling, check SDL http://www.libsdl.org/.
Hope that helps.