#!/bin/sh
##
## SCRIPT: 00_ffmpeg_mp4_CROP.sh
##
## PURPOSE: Crop an area out of a '.mp4' movie file --- based on a user-specified
##          width, height, and upper-left corner of the area.
##
##          Example crop parms:
##                  out_w:out_h:x:y
##          where
##
##          - out_w is the width of the output rectangle
##          - out_h is the height of the output rectangle
##          - x and y specify the top left corner of the output rectangle
##
## METHOD OF USE: 
##   1) Put this script in the directory of '.mp4' movie files
##      that you want to crop.
##   2) Edit this script to set the input & output filenames and crop parms.
##   3) Run the script in a terminal window positioned at the directory
##      that holds this script and the movie files.
##
## REFERENCE:
## https://video.stackexchange.com/questions/4563/how-can-i-crop-a-video-with-ffmpeg
## 
## Examples:
##
## 1)
## To crop a 80×60 section, starting from position (200, 100):
## 
##   ffmpeg -i in.mp4 -filter:v "crop=80:60:200:100" -c:a copy out.mp4
##
## The audio is stream copied in this example, so re-encoding is avoided.
##
## 2)
## To crop 20 pixels from the top, and 20 from the bottom:
##
##   ffmpeg -i in.mp4 -filter:v "crop=in_w:in_h-40" -c:a copy out.mp4
##
## The filter will automatically center the crop if x and y are omitted
## such as in this example.
##
## NOTE: You can refer to the input image size with in_w and in_h
## as shown in this example. 
##
## 3)
## You can preview a crop with ffplay:
##
##   ffplay -i input -vf "crop=in_w:in_h-40"
##
## This way you can experiment and adjust your cropping without
## the need to encode, view, repeat.
##
## -vf is short for -filter:v
##
## Script started: 2021jul10
##

ffmpeg \
   -i input_40sec_640x360_h264-aac.mp4 \
   -filter:v \
   "crop=in_w:in_h-60" \
   -c:a copy \
   output_40sec_640x300_h264-aac.mp4
   
#  00_temp_crop.mp4   
 
# totem 00_temp.mp4
# ffplay 00_temp.mp4

exit