Install ffmpeg on Mac OSX
        1. brew unistall ffmpeg
        2. brew install ffmpeg
	Install ffmpeg on Ubuntu
	sudo apt-get install ffmpeg

        Draw text on video with ffmpeg
        check github/youtubescript/ file
	Watermark on video with ffmpeg
	ffmpeg -i test.mp4 -i watermark.png -filter_complex "overlay=10:10" test1.mp4
        Extract frames from a movie 
        This example extracts the first 2 seconds of a movie in video21.wmv into individual image files. The files will be called img-0001.png, img-0002.png, img-0003.png, etc. It is best to do this in a separate directory. 
        ffmpeg -i video21.wmv -r 30 -t 2 -f image2 img-%04d.png

        For wmv files it's sometimes necessary to specify the frame rate, in this case 30 (-r 30). The parameter '-f image2' means the input movie is in "image2" format; normally it's not necessary to specify it, but if it's not automatically detected, or if the extension is wrong, it may be needed.

        Combine individual frames into a movie 
        Create an MP4 movie from JPEG files with filenames 001.jpg, 002.jpg, etc. This example creates an mp4 with 10 frames per second and 1800 kbps. 
        ffmpeg -r 10 -b 1800 -i %03d.jpg test.mp4 
        The %3d is 'C' language notation for a 3-digit integer. Don't put a percent sign or a 'd' in the filename.

        This example creates an mpeg at the default rate (25 fps, 200 kbps). 
        ffmpeg -i %03d.jpg test.mpeg 
        Sometimes you have to set the bitrate to get a good quality movie. 
        ffmpeg -b 4000 -i frame-%5d.jpg test.mpeg

        Changing image file format 
        Sometimes you want to convert the files into JPEGs first. This script will do the conversion and change the extension of each file from .png to .jpg. 
        for f in *png ; do convert -quality 100 $f `basename $f png`jpg; done 

        Find what file formats are supported 

        ffmpeg -formats

        Get help 

        ffmpeg -h

        Convert movie from WMV to mp4 format
        Ffmpeg determines what file format you want by the extension. If your input file doesn't have the right extension, bad things will happen. 
        ffmpeg -i video04.wmv -f mp4 -strict -2 -t 5 a.mp4 
        ffmpeg -i output2.avi -strict -2 test.mp4

        Resize a movie 
        Resize a movie input.avi to 640 x 480 pixels. An AVI file titled output.avi is produced. 
        ffmpeg -i input.avi -vf scale=640:480 output.avi

        Crop a movie 

        ffmpeg -i input.avi -vf crop=100:110:200:80 output.avi 
        ffmpeg -i input.avi -vf crop=in_w:in_h/2:in_w:in_h/2 output.avi 

        The parameters are x:y:width:height in pixels. The first command tries to create a 200x80 image, but ffmpeg will change this to the correct movie aspect ratio. The second command saves only the bottom half of your movie.

        Cut a section from a movie 
        Cut a section out of the movie, saving only the five seconds between 70 and 75. 

        ffmpeg -i input.avi -ss 00:01:10 -t 00:00:05 -c:v copy -c:a copy output.avi 

        The -c:v copy -c:a copy option makes it faster by copying the video and audio instead of decoding and re-encoding them. You could also use -vf trim=70:75, but this doesn't re-set the time stamp, so viewers will just see a black screen for the first 70 seconds. Supposedly the setpts filter can fix this, but I couldn't get it to work.

        Retrieving metadata from a movie 
        Reads metadata and prints it on the screen. As with all ffmpeg commands, there are many options (man ffprobe). ExifTool gives a lot more information. 
        ffprobe DSC_6881.MOV Metadata:
        major_brand : qt 
        minor_version : 537331968
        compatible_brands: qt niko
        creation_time : 2015-06-09 01:10:21
        Duration: 00:01:41.35, start: 0.000000, bitrate: 18896 kb/s
        Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt470bg/unknown/bt470m), 1920x1080 [SAR 1:1 DAR 16:9], 17339 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
        creation_time : 2015-06-09 01:10:21
        Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, 2 channels, s16, 1536 kb/s (default)
        creation_time : 2015-06-09 01:10:21
        Filtering a movie 
        It is possible to split a movie into frames, process each individual frame in an image analysis program, and then re-assemble it into a movie. But this gets tedious after the first few hundred thousand frames.

        Brightening, changing the gamma, inverting, and many other functions are available in ffmpeg through the filter option. They can be very simple:
        Filtering uses the -vf option followed by a series of commands. 

        To resize a movie to 320 x 240 pixels: 
        ffmpeg -i input.avi -vf scale=320:240 output.avi 

        To invert the colors in a movie: 
        ffmpeg -i output2.avi -vf lutrgb="r=negval:g=negval:b=negval" output3.avi 

        To increase brightness by a factor of four: 
        ffmpeg -i output2.avi -vf lutyuv=y=val*4 output3.avi 

        To increase red by a factor of two: 
        ffmpeg -i output2.avi -vf lutrgb=r=val*2 output3.avi 

        To increase gamma by factor of 5: 
        ffmpeg -i output2.avi -vf 'lutyuv=y=gammaval(0.2)' output3.avi 
        The quotes are needed to prevent the shell from messing with the command. 

        To rotate a movie by 45 degrees: 
        ffmpeg -i output2.avi -vf rotate=45 output3.avi 

        The sharpen, blur, or sharpen a movie: 
        ffmpeg -i output2.avi -vf unsharp output3.avi 
        ffmpeg -i output2.avi -vf unsharp=7:7:-2:7:7:-2 output3.avi 
        ffmpeg -i output2.avi -vf unsharp=5:5:1.5:5:5:0.0 output3.avi 

        The defaults for unsharp are 5:5:1.0:5:5:0.0.
        1st = kernel of luma filter x size (odd 3 to 63)
        2nd = kernel of luma filter y size (odd 3 to 63)
        3rd = amount of luma filtering (-1.5 to 1.5 but can be any number); negative=blur, positive=sharpen
        4th = kernel of chroma filter x size (odd 3 to 63)
        5th = kernel of chroma filter y size (odd 3 to 63)
        6th = amount of chroma filtering (-1.5 to 1.5 but can be any number); negative=blur, positive=sharpen

        To draw a box or grid on the movie: 
        ffmpeg -i output2.avi -vf drawbox=x=10:y=20:w=200:h=60:color=red@0.5 output3.avi 

        ffmpeg -i output2.avi -vf drawgrid=width=100:height=100:thickness=2:color=red@0.5 output3.avi 

        More complex filters 
        Filters can also be very complex. Many seemingly simple operations require splitting the processing stream. This example crops and flips half of the image. This information is from the man page (man ffmpeg-filters).

        The input is split into two streams. One stream goes through the crop filter and the vflip filter, and is then merged back with the other stream by overlaying it on top. The start and end of each path require labels enclosed in square brackets. All these commands go on a single line, not broken up as shown here.

        ffmpeg -i inputmovie -vf "split [main][tmp]; [tmp] crop=iw:ih/2:0:0, vflip [flip]; [main][flip] overlay=0:H/2" outputmovie 

        Here are some examples of filtering. The first one uses the YUV look-up table filter to multiply the luminance by a factor of 5, which can be useful for making extremely dark images brighter. There are also commands for changing the gamma and contrast.

        ffmpeg -i DSC_6881.MOV -vf "split [main][tmp]; [tmp] lutyuv="y=val*5" [tmp2]; [main][tmp2] overlay" output.avi

        This example raises the gamma. In ffmpeg, a value less than 1.0 makes dark areas lighter and a value above 1.0 makes them darker, which is the opposite of what you'd expect: 
        ffmpeg -i DSC_6881.MOV -vf "split [main][tmp]; [tmp] lutyuv=y=gammaval(0.6) [tmp2]; [main][tmp2] overlay" output.avi

        The RGB look-up table filter is similar, and allows you to do stuff to the red, green, and blue channels separately. In this case we invert them to make a negative image.

        ffmpeg -i DSC_6887.MOV -vf "split [main][tmp]; [tmp] lutrgb="r=negval:g=negval:b=negval" [tmp2]; [main][tmp2] overlay" output.avi

        This example denoises an AVI file. This helps reduce those rectangular compression artifacts. 
        ffmpeg -i output2.avi -vf "split [main][tmp]; [tmp] dctdnoiz=4.5 [tmp2]; [main][tmp2] overlay" output3.avi

        There are numerous other options, such as deshake, delogo, drawtext, fade, lens correction, rotate, subtitles, and fft filter. Some I could get to work and some, like drawtext, I couldn't, and some take a very long time to run.

        Combining filters 
        You can put many filters together in the same command. The following rules apply:

        If the filter takes more than one parameter, separate parameters by colons. Ex: unsharp=7:7:-2:7:7:-2
        To put two or more filters together, separate them by commas. But watch out: spaces are not allowed. If you use spaces, the whole thing has to be inside quotes. 

        ffmpeg -i -vf scale=480:270, lutyuv=y=val*4, lutyuv=y=gammaval'(2.0)' output2.avi 

        ffmpeg -i -vf "scale=480:270, lutyuv=y=val*4, lutyuv=y=gammaval(2.0)" output2.avi 

        ffmpeg -i -vf scale=480:270,lutyuv=y=val*4,lutyuv=y=gammaval'(2.0)' output2.avi
        If a filter contains '(', ')', ';' or some other command that's used by the shell, you have to enclose it in single or double quotes.
        If you use the wrong syntax, it will print an error message. Pay no attention to what it says-it is often wrong.