This function writes frames from a video file into the output directory with various adjustable parameters. Also allow the possibility to save the in-between frames.
Be sure to have OpenCV and all its dependencies installed on your computer, and OpenCV libraries and headers reachable from $LD_LIBRARY_PATH and $INCLUDE_PATH. Update Makefile's ARGS and DIR_ARGS to your video and video directory test files in order to be able to run the tests.
You can now run make to build the executable, and make run to test it.
You can change several options according to your objective, the options are listed bellow.
No command line argument parser have been implemented yet, so the only way to change the argument is to change them directly in the code of extractFrames.cpp, and then run make run or make && extractFrames <path to vid or dir>.
The Python script does a bit less than the the C++ executable and is way slower, but could be used as a template for another project so I decided it is best to let it here. It is strongly advised to use the C++ tool instead.
Here is the exctractFrames function prototype with all it's default values.
int exctractFrames(const char *in_path, const char *out_dir,
unsigned int skip_frames = 1,
double skip_seconds = 0,
unsigned int start_at_frame = 0,
unsigned int stop_at_frame = 0,
unsigned int display_interval = 1,
bool save_in_between_frames = true,
bool stock_in_between_frames = true,
bool remove_identic_frames = false,
bool compute_difference = false,
unsigned int min_mean_counted = 20,
double diff_threshhold = 0.20,
bool verbose = true,
double pic_save_proba = 1,
double file_proportion = 1,
double timeout = 0, //In seconds
bool (*first_frame_func)(const Mat &) = NULL,
bool (*second_frame_func)(const Mat &) = NULL,
bool (*compare_frame_func)(const Mat &, const Mat &) = NULL);- in_path The path to a video file or a directory containing video files.
- out_dir The path to the output directory. If it doesn't exist, a new directory will be created.
- skip_frames The interval between each pair of frames that have to be compared and saved. For example, a skip_frames of 5 will compare and save frames 1-5, 6-11, 12-17...
- skip_seconds Same as skip_frames, but the unit is in seconds instead. If both skip_frames and skip_seconds are > 0, the priority is given to skip_seconds.
- start_at_frame The starting frame index.
- stop_at_frame The stoping frame index.
- display_interval The interval for information display. This is not by frame, but by loop. Each 'skip_frame' frames count for 1 loop. For example, having 'skip_frame' to 5 and display_interval to 3 will result in display at frames 1-5, 18-23...
- save_in_between_frames Whether or not in-between frames have to be saved.
- stock_in_between_frames Whether or not in-between frames have to be stocked in memory or saved later while relooping the video. It speeds up the function, but if too many frames are stored into the memory you might want to set this to false.
- remove_identic_frames Whether or not identic frames has to be removed or not. It is calculated for every successive frames so it slowers a bit the function.
- compute_difference Whether or not the difference between each pair of frames has to be calculated, in order to save only pictures that aren't very different. This slowers a lot the function.
- min_mean_counted The number of differences that have to be computed in order to have a meaningful mean.
- diff_threshhold The threshold idicating when frames are considered to too different (values are around 0~2).
- verbose Whether or not informations has to be displayed on the screen.
- pic_save_proba The probability to save a pair of frames or not (unselected pair won't compute difference or user-specified test functions)
- file_proportion The probability compute a found video or not (if too many videos are in the same directory).
- timeout A timeout in seconds. Note the if 'stock_in_between_frames' is set to 0, the last video's in-between frames might not be all saved.
- first_frame_func A user-specified function to test a property on the first frame. If this property if not verified, the pair of frames won't be saved.
- second_frame_func A user-specified function to test a property on the second frame. If this property if not verified, the pair of frames won't be saved.
- compare_frame_func A user-specified function to test a property on the pair of frames. If this property if not verified, the pair of frames won't be saved.