#!/bin/sh
##
## SCRIPT NAME: ffmpeg_webcamAndAudio_MovieCapture.sh
##
##+#######
## PURPOSE:
##  This script runs the 'ffmpeg' command after being provided with
##  about 14 'ffmpeg' parameters passed to this script.
##
##  This shell script is meant to be issued from the Tk GUI 'wrapper'
##  script --- 'webcamAndAudio_MovieCapture_ffmpeg_FrontEnd.tk'.
##  That Tk script is to get parameters for the 'ffmpeg' command ---
##  for the purpose of recording the webcam and audio from a computer
##  into a movie file.
##
##  The 'ffmpeg' parameters are passed into this script via *positional*
##  parameters in the order indicated below.
##
##  Having the 'ffmpeg' call in a shell script instead of embedded in the
##  Tk script facilitates testing and debugging. For example, this
##  script can be tested independently of the Tk script. ('ffmpeg'
##  is very sensitive to the order of the input parameters, as well
##  as sensitive to the container-video-audio formats selected ---
##  as evidenced by the many appeals for help on internet forums.)
##
##+######
## INPUTS:
##
## Here are example default parameters for 'ffmpeg' from the Tk script,
## preceded by the variable names used in the Tk script:
##
##    Var01:  VIDEOsize "800x600"
##    Var02:  VIDEOsource "/dev/video0"
##    Var03:  VIDEOformat "video4linux2"
##    Var04:  VIDEOrate "25"
##    Var05:  VIDEOcodec "libx264"
##    Var06:  VIDEOotherParms "-vpre /usr/share/ffmpeg/libx264-lossless_ultrafast.ffpreset"
##    Var07:  AUDIOformat "alsa"
##    Var08:  AUDIOinterface "pulse"
##    Var09:  AUDIOchannels "1"
##    Var10:  AUDIOcodec "pcm_s16le"
##    Var11:  AUDIOotherParms "-ar 22050 -ab 96k"
##    Var12:  Nthreads "1"
##    Var13:  CONTAINERformat "matroska"
##    Var14:  ENTRYfilename "$outDIR/$env(USER)_webcam_capture_movie.mkv"
##
## In this script, we will put those parameters in shell script variables
## using the same variable names as above --- except that we will
## use 'OUTfile' instead of 'ENTRYfilename' and 'CONTAINfmt' instead of
## 'CONTAINERformat'.
##
##+#########################################################################
## REFERENCE: http://ubuntuforums.org/archive/index.php/t-1392026.html
##            "HOWTO: Proper Screencasting on Linux" (as seen in 2011)
##
## "...we capture audio from pulse (pulseaudio sound server) and encode it
## to *'lossless'* raw PCM with 2 audio channels (stereo). Then, we grab a
## video stream from x11 at a frame rate of 30 and a size of 1024×768
## from the display :0.0 and encode it to *'lossless'* h264 using libx264.
## ... The resulting streams will be muxed in a Matroska container (.mkv)."
##+#########################################################################
## MAINTENANCE HISTORY:
## Started by: Blaise Montandon 2014jun02 Started based on the shell script
##                                  'ffmpeg_monitorAndAudio_MovieCapture.sh'.
## Updated by: Blaise Montandon 2014
##+#########################################################################

## FOR TESTING: (to show statements as they execute)
#    set -x

VIDEOsize="$1" 
VIDEOsource="$2"
VIDEOformat="$3"
VIDEOrate="$4"
VIDEOcodec="$5"
VIDEOotherParms="$6"
AUDIOformat="$7"
AUDIOinterface="$8"
AUDIOchannels="$9"
AUDIOcodec="$10"
AUDIOotherParms="$11"
Nthreads="$12"
CONTAINfmt="$13"
OUTfile="$14"

## FOR TESTING of this script without the Tk wrapper:
## (For stand-alone testing, change 'if test 1 = 0' to 'if test 1 = 1'.)

if test 1 = 0
then

   VIDEOsize="800x600"
   # VIDEOsize="1024x768"

   # VIDEOsource="/dev/video1"
   VIDEOsource="/dev/video0"

   VIDEOformat="video4linux2"
   # VIDEOformat="video4linux"

   VIDEOrate="25"
   # VIDEOrate="30"

   VIDEOcodec="libx264"
   # VIDEOcodec="mpeg4"
   # VIDEOcodec="mpeg2video"
   # VIDEOcodec="mpeg1video"
   # VIDEOcodec="flv"
   # VIDEOcodec="libvpx"
   # VIDEOcodec="xvid"

   VIDEOotherParms="-vpre /usr/share/ffmpeg/libx264-lossless_ultrafast.ffpreset"
   # VIDEOotherParms=""

   AUDIOformat="alsa"
   # AUDIOformat="oss"

   AUDIOinterface="pulse"
   # AUDIOinterface="hw:2,0"
   # AUDIOinterface="/dev/dsp"

   AUDIOchannels="1"
   # AUDIOchannels="2"

   AUDIOcodec="pcm_s16le"
   # AUDIOcodec="libmp3lame"
   # AUDIOcodec="libfaac"
   # AUDIOcodec "vorbis"

   AUDIOotherParms="-ar 22050 -ab 96k"
   # AUDIOotherParms="-ar 44100 -ab 128k"

   Nthreads="1"
   # Nthreads="2"
   # Nthreads="0"  ## auto-detect, max CPUs (not advisable?)

   CONTAINfmt="matroska"
   # CONTAINfmt="mpeg4"
   # CONTAINfmt="mpeg"
   # CONTAINfmt="flv"
   # CONTAINfmt="avi"
   # CONTAINfmt="webm"

   OUTfile="/tmp/${USER}_webcam_capture_movie.mkv"

fi

## FOR TESTING:
#   echo "OUTfile: $OUTfile"


## Simply exit if there is no output filename passed to this script.

if test "$OUTfile" = ""
then
   exit
fi


##+##########################################################
## Prepare to use the filename to hold the movie.
## Make sure we start with a new (empty) output file.
##+##########################################################

rm -f "$OUTfile"


##+#######################################################
## Call on the 'ffmpeg' command, which puts the movie
## in file "$OUTfile".
##
## We run ffmpeg in an 'xterm' so that we can see its messages
## and the user can stop the recording by opening the xterm
## window and typing 'q' in the window.
##
## We could move the 'xterm' call into the calling Tk script.
##
## We do not use '&' to run this process in the background,
## but the Tk script that calls this script issues the call
## as a background process, rather than foreground.
##+###############################################################
## If you have another webcam applicaton running, such as 'Cheese',
## you may get the following error:
## [video4linux2 @ 0x892f700]Cannot find a proper format.
## It apparently 'ties up' the specified device --- in this case,
## /dev/video0.
##################################################################
## If you specify the wrong input device, you may get the following
## error:
## [video4linux2 @ 0x9fd4700]Cannot open video device /dev/video1 :
## No such file or directory
## /dev/video1: I/O error occurred
##################################################################

## FOR TESTING: (to show statements as they execute)
#   set -x

xterm -bg black -fg white -hold -geometry 90x48+100+100 -e ffmpeg \
   -f $VIDEOformat -r $VIDEOrate -s $VIDEOsize -i $VIDEOsource \
   -f $AUDIOformat -ac $AUDIOchannels -i $AUDIOinterface \
   -vcodec $VIDEOcodec $VIDEOotherParms \
   -acodec $AUDIOcodec $AUDIOotherParms \
   -threads $Nthreads "$OUTfile"

## The following order of parameters (all video, then all audio) gave 
## the puzzling error message:  Unknown decoder 'libx264'
##
## (Puzzling because I knew that the 'libx264' coder was available,
##  because another order of the parameters in a different script worked.
##  This is proof that 'ffmpeg' can give VERY MISLEADING error messages.)
##
##   ffmpeg -f $VIDEOformat -r $VIDEOrate -s $VIDEOsize \
##   -i $VIDEOsource -vcodec $VIDEOcodec $VIDEOotherParms \
##   -f $AUDIOformat -i $AUDIOinterface -ac $AUDIOchannels -acodec $AUDIOcodec \
##   -threads $Nthreads "$OUTfile"
##
## It appears that 'ffmpeg' parameters should be grouped such that
## ALL the 'input' parameters (video AND audio) are to be specified BEFORE
## the 'output' (in particular, codec) parameters.