MythTV transcoding user job

For some reason I was having trouble with existing online MythTV transcoding jobs. Specifically this and MythBrake were nice but after many attempts I couldn't get HandbrakeCLI to output a decent quality video and opted to write my own using ffmpeg.

Please be aware this script will automatically cut out commercials even if mythcommflag is inaccurate.

To get started copy the script into a file on your mythbackend box. In the example below it is called transcode.sh. Then `chmod +x` and review the contents of the `./transcode.sh -h` help command like so:

[richie@localhost mythtv]$ chmod +x transcode.sh
[richie@localhost mythtv]$ ./transcode.sh -h
Transcodes a video to .mkv auto cutting commercials.
User job example: /home/richie/mythtv/transcode.sh -c %CHANID% -s %STARTTIMEUTC%

-v         show version
-h         show usage
-l         limit CPU usage
-s [arg]   starttime from mythtv. In user job %STARTTIMEUTC%
-c [arg]   chanid from mythtv. In user job %CHANID%
-u [arg]   MySql username
-p [arg]   MySql password
-o [arg]   output Directory
-t [arg]   temp Directory
-r [arg]   ffmpeg crf. See: https://trac.ffmpeg.org/wiki/Encode/H.264
-z [arg]   ffmpeg preset. See: https://trac.ffmpeg.org/wiki/Encode/H.264

Here is the script:

#!/bin/bash
# ------------------------------------------------------------------                                                      
# [Author] Richard Kanavati                                                                                               
#          A simple MythTV script to transcode video to mkv                                                               
# ------------------------------------------------------------------                                                      

# ---------User Variable Defaults-----------------------------------                                                      
# For simplicity in configuring a MythTV user job, default command                                                        
# line parameters can be specified here.                                                                                  
# These will be overridden if you supply command line parameters.                                                          
db_user="mythtv"
db_password="mythtv"
output_dir="~/"
temp_dir="/tmp"
mythtranscode_options="--mpeg2 --honorcutlist"
ffmpeg_crf=23
ffmpeg_preset="slow"
limit_cpu=1
# ------------------------------------------------------------------                                                      

set -e
trap 'exit_handler' EXIT

exit_handler()
{
    if [ -e "$temp_transcoding_file" ]; then
        rm "$temp_transcoding_file"
    fi

    if [ -e "$temp_transcoding_file.map" ]; then
        rm "$temp_transcoding_file.map"
    fi
}

display_usage() {
    local directory="$(cd "$(dirname "${0}")"; echo $(pwd))"
    local file="${directory}/$(basename "${0}")"

    echo "Transcodes a video to .mkv auto cutting commercials."
    echo "User job example: $file -c %CHANID% -s %STARTTIMEUTC%"
    echo ""
    echo "-v         show version"
    echo "-h         show usage"
    echo "-l         limit CPU usage"
    echo "-s [arg]   starttime from mythtv. In user job %STARTTIMEUTC%"
    echo "-c [arg]   chanid from mythtv. In user job %CHANID%"
    echo "-u [arg]   MySql username"
    echo "-p [arg]   MySql password"
    echo "-o [arg]   output Directory"
    echo "-t [arg]   temp Directory"
    echo "-r [arg]   ffmpeg crf. See: https://trac.ffmpeg.org/wiki/Encode/H.264"
    echo "-z [arg]   ffmpeg preset. See: https://trac.ffmpeg.org/wiki/Encode/H.264"
}

if [ $# == 0 ] ; then
    display_usage
fi

while getopts ":s:c:u:p:o:t:r:z:vhl" optname
  do
    case "$optname" in
     v)
        echo "Version $VERSION"
        exit 0;;
      c)
        chanid=${OPTARG};;
      s)
        starttime=${OPTARG};;    
      l)
        limit_cpu=1;;
      m)
        db_user=${OPTARG};;
      p)
        db_password=${OPTARG};;
      o)
        output_dir=${OPTARG};;
      t)
        temp_dir=${OPTARG};;
      r)
        ffmpeg_crf=${OPTARG};;
      z)
        ffmpeg_preset=${OPTARG};;
      h)
        display_usage;
        exit 0;;
    esac
  done

if [ -z "$chanid" ] || [ -z "$starttime" ]; then
  echo
  echo "Must supply -c and -s parameters!";
  echo
  display_usage
  exit 1
fi

if [ "$limit_cpu" -eq 1 ]; then
    renice 19 $$
    ionice -c 3 -p $$
fi

sql="                                                                                                                     
SELECT                                                                                                                    
    s.dirname as storagegroup,                                                                                            
    r.basename,                                                                                                           
    r.commflagged,                                                                                                        
    CONCAT(r.title,' ', CASE                                                                                              
                         WHEN r.season > 0                                                                                
                         THEN concat('s', lpad(r.season,2,0), 'e', lpad(r.episode,2,0), ' ')                              
                         ELSE ''                                                                                          
                        END, r.subtitle) AS title                                                                         
FROM                                                                                                                      
    recorded r                                                                                                            
    JOIN storagegroup s                                                                                                   
       ON s.groupname = r.storagegroup                                                                                    
WHERE                                                                                                                     
   r.chanid = '$chanid'                                                                                                   
   and r.starttime='$starttime'                                                                                           
LIMIT 1;                                                                                                                  
"

query_results=$(mysql -u"$db_user" -p"$db_password" -Dmythconverg -NBse  "$sql")
if [ ! "$query_results" ]; then
    echo "Could not locate video in the mythtv database."
    exit 1
fi

storage_group=$(echo "$query_results"|cut -f1)
if [ ! "$storage_group" ]; then
    echo "Could not locate storage group in the mythtv database."
    exit 1
fi

basename=$(echo "$query_results"|cut -f2)
commflagged=$(echo "$query_results"|cut -f3)
title=$(echo "$query_results"|cut -f4|sed 's/ *$//'|sed "s/[:?]/ /g"|sed "s/[.]//g")
if [ ! "$title" ]; then
    title="unknown_title_${starttime}"
fi

transcoding_file="$storage_group$basename"
temp_transcoding_file="$temp_dir/${chanid}_$starttime.mpg"
output_file="$output_dir/$title.mkv"
if [ -e "$output_file" ]; then
   output_file="$output_dir/${title}_$starttime.mkv"
fi

if [ $commflagged -eq 0 ]; then
    /usr/bin/mythcommflag --chanid "$chanid" --starttime "$starttime"
fi

/usr/bin/mythutil --chanid "$chanid" --starttime "$starttime" --gencutlist
/usr/bin/mythtranscode --chanid "$chanid" --starttime "$starttime" --allkeys --buildindex --mpeg2 --showprogress
/usr/bin/mythtranscode --chanid "$chanid" --starttime "$starttime" $mythtranscode_options -o "$temp_transcoding_file"
/usr/bin/mythcommflag --file "$temp_transcoding_file" --rebuild
/usr/bin/ffmpeg -i "$temp_transcoding_file" -c:v libx264 -preset "$ffmpeg_preset" -crf "$ffmpeg_crf" -c:a copy "$output_file"