Example Script using mythtranscode in fifodir mode

The script pipes the output of mythtranscode into ffmpeg, using libx264 to compress the video. The intended use is to set it up as a myth user job.

#!/usr/bin/ruby -w

require 'time'
require 'fileutils'
require 'tmpdir'

$stdout.reopen("/var/log/mythtv/mythar#{Time.now.strftime '%F-%T'}.log", "w")
$stderr.reopen($stdout)

def usage
    print <<-END
Usage: #{$0} --chanid <channel id> --starttime <start time> --title <title> [--subtitle <sub title>] --outdir <directory> [options]
       #{$0} --chanid <channel id> --starttime <start time> -outfile <path> [options]

       --chanid <channel id>                   The channel id for the recording. REQUIRED.
       --starttime <start time>                The start time for the recording. REQUIRED.
       --title <title>                         The title of the recording.
       --subtitle <subtitle>                   The subtitle of the recording.
       --outdir <path>                         The path of the directory for the output file. If one of
                                               --title --subtitle and --outdir are specified, then both --title and --outdir must
                                               be, and an output file will be chosen on their basis, avoiding
                                               conflict with existing files.
       --outfile <path>                        The exact path of the output file. ALTERNATIVE to
                                               --title --subtitle and --outdir.
       --vsize <width>x<height>                Scale video to specified resolution (the aspect ratio will
                                               be maintained using non-square pixels). If not specified,
                                               the source resolution will be maintained.
       --interlaced                            Assume the source is interlaced and maintain the interlace,
                                               provided --vsize not specified. If --vsize is specified then
                                               recode at double the frame rate.
       --passthrough                           Pass through the audio unaltered if possible.
       --quality <quality>                     Quality for compression (default 20.0)
    END
end

# Read arguments
chanid      = nil
starttime   = nil
title       = nil
subtitle    = nil
outdir      = nil
outfile     = nil
vsize       = nil
interlaced  = false
passthrough = false
quality     = '20.0'

processOption = Proc.new do |args|
    raise "Misspecified option: #{args.join(', ')}" unless args.length == 2
    option = args[0].sub(/^--/, '')
    val = args[1]
    eval("#{option} = val")
end

processFlag = Proc.new do |args|
    raise "Misspecified option: #{args.join(', ')}" unless args.length == 1
    option = args[0].sub(/^--/, '')
    eval("#{option} = true")
end

handler = {'--chanid'      => processOption,
           '--starttime'   => processOption,
           '--title'       => processOption,
           '--subtitle'    => processOption,
           '--outdir'      => processOption,
           '--outfile'     => processOption,
           '--vsize'       => processOption,
           '--interlaced'  => processFlag,
           '--passthrough' => processFlag,
           '--quality'     => processOption}


ARGV.slice_before{|arg| arg =~ /^--/}.each do |par|
    raise "Unrecognised option: #{par.join(', ')}" unless handler.has_key? par[0]
    handler[par[0]].call(par)
end


if chanid.nil? || starttime.nil?
    raise '--chanid and --starttime required'
end

if outfile.nil? && outdir.nil?
    raise 'Use either --outfile, or both --title --outdir, optionally with --subtitle'
end

if outfile && (title || subtitle || outdir)
    raise 'Use either --outfile, or both --title --outdir, optionally with --subtitle'
end

if (title || outdir || subtitle) && ! (title && outdir)
    raise 'Both --title and --outdir required for this mode of oparation'
end

mythPassthrough = passthrough ? '--passthrough' : ''

#Detect source formats
info=`mythtranscode -v general --chanid #{chanid} --starttime #{starttime} --fifoinfo #{mythPassthrough}`

svWidth  = nil
svHeight = nil
svAspect = nil
svRate   = nil
saFmt    = nil
saChans  = nil
saRate   = nil

info.each_line do |line|
    case line.chomp
    when / FifoVideoWidth (.*)$/       then svWidth  = $1
    when / FifoVideoHeight (.*)$/      then svHeight = $1
    when / FifoVideoAspectRatio (.*)$/ then svAspect = $1
    when / FifoVideoFrameRate (.*)$/   then svRate   = $1
    when / FifoAudioFormat (.*)$/      then saFmt    = $1
    when / FifoAudioChannels (.*)$/    then saChans  = $1
    when / FifoAudioHz (.*)$/          then saRate   = $1
    when / FifoAudioSampleRate (.*)$/  then saRate   = $1
    end
end

if !svWidth || !svHeight || !svAspect || !svRate || !saFmt || !saChans || !saRate
    print info
    raise 'Failed to derive fifo formats'
end

svSize="#{svWidth}x#{svHeight}"
svAspect = '16:9' if svAspect == '1.77778'
svAspect = '4:3'  if svAspect == '1.33333'
	


saFmt = 'latm' if saFmt == 'acc_latm'


if saFmt == 'latm'
    ext  = '.mkv'
    fFmt = 'matroska'
else
    ext  = '.mp4'
    fFmt = 'mp4'
end

# If --outfile not specified, use --outdir --title and --subtitle
if !outfile
    obName = File.join(outdir, title)
    obName += " - #{subtitle}" if (subtitle && subtitle.length > 0)

    (0..Float::INFINITY).each do |i|
        outfile = obName + (i == 0 ? "" : "(#{i})") + ext
        break if !File.exist? outfile
    end
end

# Can do pass through only with formats that ffmpeg will take as input
passthrough = false unless %w{ac3 dts mp3 latm}.include? saFmt

# Tell ffmpeg what audio to expect and what to do with it
if passthrough
    mythPassthrough = '--passthrough'
    audInDesc       = "-f #{saFmt}"
    audCodec        = 'copy'
else
    mythPassthrough = ''
    audInDesc       = "-f s16le -ac 2 -ar #{saRate}"
    audCodec        = 'ac3 -ab 160k'
end


filters = []
vFilter = nil
vRate   = nil
vFlags  = nil

filters.push("crop=#{svWidth}:1080:0:0") if svHeight == '1088'

if interlaced
    if vsize
        # If scaling interlaced video, we must deinterlace first
        filters.push('yadif=3')
        vRate   = "-r #{2 * svRate.to_i}"
    else
        # Otherwise maintain the interlace
        vFlags  = '-flags +ilme+ildct'
    end
end

if vsize
    filters.push("scale=#{vsize.sub('x', ':')}")
end

vFilter = '-vf ' + filters.join(',') if filters.length > 0

# Create fifo dir
fifoDir = Dir.mktmpdir('mythar')
fifoAudio = File.join(fifoDir, 'audout')
fifoVideo = File.join(fifoDir, 'vidout')

transcodeCmd = "/usr/bin/mythtranscode --chanid #{chanid} --starttime #{starttime} --honorcutlist #{mythPassthrough} --fifodir #{fifoDir} --cleancut"
ffmpegCmd = "/usr/bin/ffmpeg #{audInDesc} -i #{fifoAudio} -f rawvideo -top 1 -pix_fmt yuv420p -s #{svSize} -r #{svRate} -i #{fifoVideo} -threads 2 #{vFilter} -vcodec libx264 -preset medium -profile high #{vFlags} -crf #{quality} #{vRate} -aspect #{svAspect} -acodec #{audCodec} -ar #{saRate} -f #{fFmt} \"#{outfile}\""

puts transcodeCmd
puts
puts ffmpegCmd
puts

pid = 0
begin
    pid = Process.spawn(transcodeCmd)
    while !File.exist?(fifoAudio) || !File.exist?(fifoVideo)
        raise 'Transcode died before creating pipes' unless Process.wait(pid, Process::WNOHANG).nil?
        sleep(1)
    end
    system(ffmpegCmd)
ensure
    if pid != 0
        Process.kill('KILL', pid)
        Process.wait(pid)
    end
    FileUtils.rm_rf fifoDir
end