DISCLAIMER

Even though you can already generate AVI files, this library has not reached a final version yet and is still a work in progress. You've been warned... ;)

SYNOPSIS

libgwavi is a fork of libkohn-avi. It is a tiny C library aimed at creating AVI files.

Original credits go to Michael Kohn, who released his library under the LGPL license. He, however, allowed me to release my forked version under the less restrictive 3-clause BSD license so... Thanks to him!

Anyway, why the fork you might ask? I used it in an application that needed the library to be reliable. So here is what has already changed from libkohn-avi:

• added library documentation

• removed dead code

• improved error checking

• added unit tests

BUILD

This library has no dependencies, you only need the standard C library. To generate libgwavi.so, just type the following from the root's directory:

make

To generate the documentation of the library functions, type the following:

make doc

The code includes a demo application that uses libgwavi. You can build it using this command:

make examples

HOW TO USE IT

For a complete example, have a look at the demo application in the examples folder.

If you are in a hurry, here is a small explanation on how to use it.

First, you need to include the header file.

#include "gwavi.h"

There is basically four main function that you will need to use:

• gwavi_open()

• gwavi_add_frame()

• gwavi_add_audio()

• gwavi_close()

Please, note that error checking has been voluntarily omitted in the examples below for the sake of the clarification.

So first, you should declare a gwavi_t structure and initialize it. You can optionally declare a gwavi_audio_t structure if you need to add an audio channel to your AVI file.

To declare a gwavi_audio_t, firstly, you can see it's a structure constructed of channels, bits and samples_per_second. To get these info, you can save the audio first, and then, open it using VLC media player.

After that, Tools -> Codec Infomation -> Codec

• For channels, if VLC says "Mono", write 1; if it says "Stereo", write 2.
• For bits, write as same as "Bits per sample".
• For samples_per_second, write as same as "Sample rate".

By default, this program accepts audios whose codec in VLC shows araw only. For example, whose file extension is wav.

Note! You may need to declare this BEFORE running gwavi_open().

For example:

struct gwavi_t *gwavi;
struct gwavi_audio_t audio = {
        .channels = 2,
        .bits = 16,
        .samples_per_second = 44100
};

gwavi = gwavi_open("foo.avi",
                   1920,
                   1080,
                   "MJPG",
                   30,
                   &audio);

Note that the audio channel is optional and that you can pass NULL as the last argument of gwavi_open() if you don't need it.

Then you add your video frames:

gwavi_add_frame(gwavi, buffer, buffer_length);

You can also add audio with gwavi_add_audio().

And at the end, you can close the output file and free the allocated memory by calling the gwavi_close() function.

gwavi_close(gwavi);

DOCUMENTATION

The library documentation can be generated with make doc if you have doxygen installed. Otherwise, you can just visit http://doc.gw-computing.net/libgwavi.