transcode-h264-v3.py

#!/usr/bin/env python3
# -*- coding: UTF-8 -*-

# 2015 Michael Stucky
#
# This script is based on Raymond Wagner's transcode wrapper stub.
# Designed to be a USERJOB of the form </path to script/transcode-h264.py %JOBID%>
#
# Modifications - Drew 7/5/2015
#
# - chanid/starttime arguments needed a couple fixes to get it working
# - added ability to cut out commercials before transcode via generate_commcutlist=True
# - added ability to implement a compression ratio
#         the compression ratio estimates the input streams encoding bitrate (all streams as a one bitrate)
#         then computes an output bitrate as a factor of this bitrate, i.e., if compressionRatio=0.75
#         then the output video will be encoded at 75% of the input video bitrate. Usually one sets
#         compressionRatio < 1, resulting in a smaller output file.
#         Note the estimated bitrate is derived from the video duration
#         and file size hence it will over estimate the true video bitrate as it does not account for the
#         encapsulation overhead of the input encoding scheme nor the bitrate of any included audio streams.
#         To enable, set estimateBitrate = True and set compressionRatio to your desired value (I use 0.7). 
# - added ability to change h264 encoding preset and constant rate factor (crf) settings for HD video
# - added loads of debug statements, I've kept them in to facilitate hacking -- sorry to the purists in advance
# - added status output from ffmpeg to the myth backend giving % complete, ETA and fps encode statistics.
# - added "smart" commercial detection - if needed it is run and on completion cancels any other mythcommflag jobs 
#         for the transcoded recording
# Modifications - Drew 1/25/2016
# - added fix for the markup data which is inaccurate, especially when commercials are removed
#
from MythTV import Job, Recorded, System, MythDB, findfile, MythError, MythLog, datetime

from optparse import OptionParser
from glob import glob
from shutil import copyfile
import sys
import os
import errno
import threading, time
from datetime import timedelta
from dateutil.parser import parse
import re, tempfile
import queue # thread-safe
########## IMPORTANT #####################
#
# YOU WILL NEED TO EDIT THE SETTINGS BELOW
#
########## IMPORTANT #####################

transcoder = '/usr/bin/ffmpeg'

# flush_commskip
#       True => (Default) the script will delete all commercial skip indices from the old file 
#      False => the transcode will leave the commercial skip indices from the old file "as is" 
flush_commskip = True

# require_commflagged
#       True => the script will ensure mythcommflag has run on the file before encoding it
#      False => (Default) the transcode will process the video file "as is" 
require_commflagged = False

# generate_commcutlist 
#       True => (Default) flagged commercials are removed from the output video file
#      False => flagged commercials are NOT removed from the output video file
generate_commcutlist = True

# estimateBitrate 
#       True => (Default) the bitrate of the input file is estimated via size & duration
#               ** Required True for "compressionRatio" option to work.
#      False => The bitrate of the input file is unknown 
estimateBitrate = True

# compressionRatio
#      0.0 - 1.0 => Set the approximate bitrate of the output relative to the 
#                   detected bitrate of the input.
#                   One can think of this as the target compression rate, i.e., the 
#                   compressionRatio = (output filesize)/(input filesize)
#                   h264 video quality is approximately equal to mpeg2 video quality
#                   at a compression ratio of 0.65-0.75
#                   * Note: When enabled, this value will determine the approximate 
#                     relative size of the output file and input file
#                   (output filesize) = compressionRatio * (input filesize)
compressionRatio = 0.65

# enforce a max (do not exceed) bitrate for encoded HD video
# to disable set hd_max_bitrate=0
hdvideo_max_bitrate = 5500  # 0 = disable or (kBits_per_sec,kbps)
hdvideo_min_bitrate = 0     # 0 = disable or (kBits_per_sec,kbps)

# number of seconds of video that can be held in playing device video buffers (typically 2-5 secs)
NUM_SECS_VIDEO_BUF=3        # secs
device_bufsize = NUM_SECS_VIDEO_BUF*hdvideo_max_bitrate # (kBits_per_sec,kbps)

# enforce a target bitrate for the encoder to achieve approximately 
#hdvideo_tgt_bitrate = 5000   # 0 = disable or (kBits_per_sec,kbps)
hdvideo_tgt_bitrate = 0   # 0 = disable or (kBits_per_sec,kbps)

# build_seektable
#       True => Rebuild myth seek table.
#               It allows accurate ffwd,rew / seeking on the transcoded output video
#      False => (Default) Do not rebuild the myth seek table. Not working for mythtv on h264 content.
build_seektable = False

# Making this true enables a bunch of debug information to be printed as the script runs.
debug = False

# TODO - override buffer size (kB), only use when necessary for a specific target device
# bufsize_override=0       # 0 = disable or (kBits_per_sec,kbps)
# h264 encode preset
# ultrafast,superfast, veryfast, faster, fast, medium, slow, slower, veryslow
preset_HD = 'fast'
preset_nonHD = 'slow'

# h264 encode constant rate factor (used for non-HD) valid/sane values 18-28
# lower values -> higher quality, larger output files,
# higher values -> lower quality, smaller output files
crf = '21'

# if HD, copy input audio streams to the output audio streams
abitrate_param_HD='-c:a copy'

# if non-HD, encode audio to AAC with libfdk_aac at a bitrate of 128kbps
abitrate_param_nonHD = '-c:a libfdk_aac -b:a 128k'

# to convert non-HD audio to AAC using ffmpeg's aac encoder
#abitrate_param_nonHD='-strict -2'

# TODO use -crf 20 -maxrate 400k -bufsize 1835k
# effectively "target" crf 20, but if the output exceeds 400kb/s, it will degrade to something more than crf 20
# TODO detect and preserve ac3 5.1 streams typically found in HD content
# TODO detect and preserve audio streams by language 
# TODO detect and preserve subtitle streams by language 
# TODO is mp4 or mkv better for subtitle support in playback
#   subtitle codecs for MKV containers: copy, ass, srt, ssa
#   subtitle codecs for MP4 containers: copy, mov_text

# Languages for audio stream and subtitle selection
# eng - English
# fre - French
# ger - German
# ita - Italian
# spa - Spanish
language = 'eng'

# interval between reads from the ffmpeg status file 
# also defines the interval when waiting for a mythcommflag job to finish 
POLL_INTERVAL=10 # secs
# mythtv automatically launched user jobs with nice level of 17 
# this will add to that level (only positive values allowed unless run as root)
# e.g., NICELEVEL=1 will run with a nice level of 18. The max nicelevel is 19.
#NICELEVEL=5
NICELEVEL=0

class CleanExit:
  pass

def runjob(jobid=None, chanid=None, starttime=None, tzoffset=None):
    global estimateBitrate
    db = MythDB()

    if jobid:
        job = Job(jobid, db=db)
        chanid = job.chanid
        utcstarttime = job.starttime
    else:
        job=None;
        #utcstarttime = datetime.strptime(starttime, "%Y%m%d%H%M%S%z")
        utcstarttime = parse(starttime)
        utcstarttime = utcstarttime + timedelta(hours=tzoffset)

    if debug:
        print('chanid "%s"' % chanid)
        print('utcstarttime "%s"' % utcstarttime)

    rec = Recorded((chanid, utcstarttime), db=db);
    utcstarttime = rec.starttime;
    starttime_datetime = utcstarttime
   
    # reformat 'starttime' for use with mythtranscode/ffmpeg/mythcommflag
    starttime = str(utcstarttime.utcisoformat().replace(':', '').replace(' ', '').replace('T', '').replace('-', ''))
    if debug:
        print('mythtv format starttime "%s"' % starttime)
    input_filesize = rec.filesize
    
    if rec.commflagged:
        if debug:
            print('Recording has been scanned to detect commerical breaks.')
        waititer=1
        keepWaiting = True
        while keepWaiting == True:
            keepWaiting=False;
            for index,jobitem in reversed(list(enumerate(db.searchJobs(chanid=chanid, starttime=starttime_datetime)))):
                if jobitem.type == jobitem.COMMFLAG:  # Commercial flagging job
                    if debug:
                        print('Commercial flagging job detected with status %s' % jobitem.status)
                    if jobitem.status == jobitem.RUNNING: # status = RUNNING?
                        job.update({'status':job.PAUSED, 
                                    'comment':'Waited %d secs for the commercial flagging job' % (waititer*POLL_INTERVAL) \
                                     + ' currently running on this recording to complete.'})
                        if debug:
                            print('Waited %d secs for the commercial flagging job' % (waititer*POLL_INTERVAL) \
                                  + ' currently running on this recording to complete.')
                        time.sleep(POLL_INTERVAL);
                        keepWaiting=True
                        waititer = waititer + 1
                        break
    else:
        if debug:
            print('Recording has not been scanned to detect/remove commercial breaks.')
        if require_commflagged:
            if jobid:
                job.update({'status':job.RUNNING, 'comment':'Required commercial flagging for this file is not found.'
                            + 'Flagging commercials and cancelling any queued commercial flagging.'})
            # cancel any queued job to flag commercials for this recording and run commercial flagging in this script
            for index,jobitem in reversed(list(enumerate(db.searchJobs(chanid=chanid,starttime=starttime_datetime)))):
                if debug:
                    if index==0:
                        print(list(jobitem.keys()))
                    print(index,jobitem.id,jobitem.chanid)

                if jobitem.type == jobitem.COMMFLAG:  # Commercial flagging job
                    if jobitem.status == jobitem.RUNNING: # status = RUNNING?
                        jobitem.cmds = jobitem.STOP # stop command from the frontend to stop the commercial flagging job
                    #jobitem.setStatus(jobitem.CANCELLED)
                    #jobitem.setComment('Cancelled: Transcode command ran commercial flagging for this recording.')
                    jobitem.update({'status':jobitem.CANCELLED, 
                                    'comment':'A user transcode job ran commercial flagging for'
                                    + ' this recording and cancelled this job.'})
            if debug:
                print('Flagging Commercials...')
            # Call "mythcommflag --chanid $CHANID --starttime $STARTTIME"
            task = System(path='mythcommflag', db=db)
            try:
                output = task('--chanid "%s"' % chanid,
                              '--starttime "%s"' % starttime,
                              '2> /dev/null')
            except MythError as e:
                # it seems mythcommflag always exits with an decoding error "eno: Unknown error 541478725 (541478725)"
                pass
                #print 'Command failed with output:\n%s' % e.stderr
                #if jobid:
                #    job.update({'status':304, 'comment':'Flagging commercials failed'})
                #sys.exit(e.retcode)


    sg = findfile(rec.basename, rec.storagegroup, db=db)
    if sg is None:
        print('Local access to recording not found.')
        sys.exit(1)

    infile = os.path.join(sg.dirname, rec.basename)
    tmpfile = '%s.tmp' % infile.rsplit('.',1)[0]
 #   tmpfile = infile
    outfile = '%s.mp4' % infile.rsplit('.',1)[0]
    if debug:
        print('tmpfile "%s"' % tmpfile)


    clipped_bytes=0;
    # If selected, create a cutlist to remove commercials via mythtranscode by running:
    # mythutil --gencutlist --chanid $CHANID --starttime $STARTTIME
    if generate_commcutlist:
        if jobid:
            job.update({'status':job.RUNNING, 'comment':'Generating Cutlist for commercial removal'})
        task = System(path='mythutil', db=db)
        try:
            output = task('--gencutlist',
                          '--chanid "%s"' % chanid,
                          '--starttime "%s"' % starttime)
#                          '--loglevel debug',
#                          '2> /dev/null')
        except MythError as e:
            print('Command "mythutil --gencutlist" failed with output:\n%s' % e.stderr)
            if jobid:
                job.update({'status':job.ERRORED, 'comment':'Generation of commercial Cutlist failed'})
            sys.exit(e.retcode)

    # Lossless transcode to strip cutlist
    if generate_commcutlist or rec.cutlist==1:
        if jobid:
            job.update({'status':job.RUNNING, 'comment':'Removing Cutlist'})
        task = System(path='mythtranscode', db=db)
        try:
            output = task('--chanid "%s"' % chanid,
                          '--starttime "%s"' % starttime,
                          '--mpeg2',
                          '--honorcutlist',
                          '-o "%s"' % tmpfile,
                          '1>&2')
#                          '2> /dev/null')
            clipped_filesize = os.path.getsize(tmpfile)
            clipped_bytes = input_filesize - clipped_filesize
            clipped_compress_pct = float(clipped_bytes)/input_filesize 
            rec.commflagged = 0
        except MythError as e:
            print('Command "mythtranscode --honorcutlist" failed with output:\n%s' % e.stderr)
            if jobid:
                job.update({'status':job.ERRORED, 'comment':'Removing Cutlist failed. Copying file instead.'})
#            sys.exit(e.retcode)
            copyfile('%s' % infile, '%s' % tmpfile)
            clipped_filesize = input_filesize
            clipped_bytes = 0
            clipped_compress_pct = 0
            pass
    else:
        if jobid:
            job.update({'status':job.RUNNING, 'comment':'Creating temporary file for transcoding.'})
        copyfile('%s' % infile, '%s' % tmpfile)
        clipped_filesize = input_filesize
        clipped_bytes = 0
        clipped_compress_pct = 0

    duration_secs = 0
    # Estimate bitrate, and detect duration and number of frames
    if estimateBitrate:
        if jobid:
            job.update({'status':job.RUNNING, 'comment':'Estimating bitrate; detecting frames per second, and resolution.'})

        duration_secs, e = get_duration(db, rec, transcoder, tmpfile);
        if duration_secs>0:
            bitrate = int(clipped_filesize*8/(1024*duration_secs))
        else:
            print('Estimate bitrate failed falling back to constant rate factor encoding.\n')
            estimateBitrate = False
            duration_secs = 0
        print(e.stderr.decode('utf-8'))
        # get framerate of mpeg2 video stream and detect if stream is HD
        r = re.compile('mpeg2video (.*?) fps,')
        m = r.search(e.stderr.decode('utf-8'))
        strval = m.group(1)
        if debug:
            print(strval)
        isHD = False
        if "1920x1080" in strval or "1280x720" in strval or "2560x1440" in strval:
            if debug:
                print('Stream is HD')
            isHD = True
        else:
            if debug:
                print('Stream is not HD')
        framerate = float(m.group(1).split(' ')[-1])
        if debug:
            print('Framerate %s' % framerate)

    # Setup transcode video bitrate and quality parameters
    # if estimateBitrate is true and the input content is HD:
    #     encode 'medium' preset and vbitrate = inputfile_bitrate*compressionRatio
    # else:
    #     encode at user default preset and constant rate factor ('slow' and 20) 
    preset = preset_nonHD
    if estimateBitrate:
        if isHD:
            h264_bitrate = int(bitrate*compressionRatio)
            # HD coding with specified target bitrate (CRB encoding)
            if hdvideo_tgt_bitrate > 0 and h264_bitrate > hdvideo_tgt_bitrate:
                h264_bitrate = hdvideo_tgt_bitrate;
                vbitrate_param = '-b:v %dk' % h264_bitrate
            else:   # HD coding with disabled or acceptable target bitrate (CRF encoding)
                vbitrate_param = '-crf:v %s' % crf
            preset = preset_HD
        else: # non-HD encoding (CRF encoding)
            vbitrate_param = '-crf:v %s' % crf            
    else:
        vbitrate_param = '-crf:v %s' % crf
    if hdvideo_min_bitrate > 0:
        vbitrate_param = vbitrate_param + ' -minrate %sk' % hdvideo_min_bitrate
    if hdvideo_max_bitrate > 0:
        vbitrate_param = vbitrate_param + ' -maxrate %sk' % hdvideo_max_bitrate
    if hdvideo_max_bitrate > 0 or hdvideo_min_bitrate > 0:
        vbitrate_param = vbitrate_param + ' -bufsize %sk' % device_bufsize

    if debug:
        print('Video bitrate parameter "%s"' % vbitrate_param)
        print('Video h264 preset parameter "%s"' % preset)

    # Setup transcode audio bitrate and quality parameters
    # Right now, the setup is as follows:
    # if input is HD: 
    #    copy audio streams to output, i.e., input=output audio
    # else:
    #    output is libfdk_aac encoded at 128kbps 
    if isHD:
        abitrate_param = abitrate_param_HD  # preserve 5.1 audio
    else:
        abitrate_param = abitrate_param_nonHD
    if debug:
        print('Audio bitrate parameter "%s"' % abitrate_param)

    # Transcode to mp4
#    if jobid:
#        job.update({'status':4, 'comment':'Transcoding to mp4'})

    # ffmpeg output is redirected to the temporary file tmpstatusfile and
    # a second thread continuously reads this file while
    # the transcode is in-process. see while loop below for the monitoring thread
    tf = tempfile.NamedTemporaryFile()
    tmpstatusfile = tf.name
#    tmpstatusfile = '/tmp/ffmpeg-transcode.txt'
    if debug:
        print('Using temporary file "%s" for ffmpeg status updates.' % tmpstatusfile)
    res = []
    # create a thread to perform the encode
    ipq = queue.Queue()
    t = threading.Thread(target=wrapper, args=(encode, 
                        (jobid, db, job, ipq, preset, vbitrate_param, abitrate_param,
                         tmpfile, outfile, tmpstatusfile,), res))
    t.start()
    # wait for ffmpeg to open the file and emit its initialization information 
    # before we start the monitoring process
    time.sleep(1) 
    # open the temporary file having the ffmeg output text and process it to generate status updates
    hangiter=0;
    with open(tmpstatusfile) as f:
        # read all the opening ffmpeg status/analysis lines
        lines = f.readlines()
        # set initial progress to -1
        prev_progress=-1
        framenum=0
        fps=1.0
        while t.is_alive():
            # read all output since last readline() call
            lines = f.readlines()
            if len(lines) > 0:
                # every ffmpeg output status line ends with a carriage return '\r'
                # split the last read line at these locations
                lines=lines[-1].split('\r')
#                if debug:
#                    print lines;
                hangiter=0
                if len(lines) > 1 and lines[-2].startswith('frame'):
                    # since typical reads will have the last line ending with \r the last status
                    # message is at index=[-2] start processing this line
                    # replace multiple spaces with one space
                    lines[-2] = re.sub(' +',' ',lines[-2])
                    # remove any spaces after equals signs
                    lines[-2] = re.sub('= +','=',lines[-2])
                    # split the fields at the spaces the first two fields for typical
                    # status lines will be framenum=XXXX and fps=YYYY parse the values
                    values = lines[-2].split(' ')
                    if len(values) > 1:
                        if debug:
                            print('values %s' % values)
                        prev_framenum = framenum
                        prev_fps = fps
                        try:
                            # framenum = current frame number being encoded
                            framenum = int(values[0].split('=')[1])
                            # fps = frames per second for the encoder
                            fps = float(values[1].split('=')[1])
                        except ValueError as e:
                            print('ffmpeg status parse exception: "%s"' % e)
                            framenum = prev_framenum
                            fps = prev_fps
                            pass
                    # progress = 0-100 represent percent complete for the transcode
                    progress = int((100*framenum)/(duration_secs*framerate))
                    # eta_secs = estimated number of seconds until transcoding is complete
                    eta_secs = int((float(duration_secs*framerate)-framenum)/fps)
                    # pct_realtime = how many real seconds it takes to encode 1 second of video
                    pct_realtime = float(fps/framerate) 
                    if debug:
                        print('framenum = %d fps = %.2f' % (framenum, fps))                
                    if progress != prev_progress:
                        if debug:
                            print('Progress %d%% encoding %.1f frames per second ETA %d mins' \
                                  % ( progress, fps, float(eta_secs)/60))
                        if jobid:
                            progress_str = 'Transcoding to mp4 %d%% complete ETA %d mins fps=%.1f.' \
                                  % ( progress, float(eta_secs)/60, fps)
                            job.update({'status':job.RUNNING, 'comment': progress_str})
                        prev_progress = progress
                elif len(lines) > 1:
                    if debug:
                        print('Read pathological output %s' % lines[-2])
            else:
                if debug:
                    print('Read no lines of ffmpeg output for %s secs. Possible hang?' % (POLL_INTERVAL*hangiter))
                hangiter = hangiter + 1
                if jobid:
                    progress_str = 'Read no lines of ffmpeg output for %s secs. Possible hang?' % (POLL_INTERVAL*hangiter)
                    job.update({'status':job.RUNNING, 'comment': progress_str})
            time.sleep(POLL_INTERVAL)
        if debug:
            print('res = "%s"' % res)

    t.join(1)
    try:
        if ipq.get_nowait() == CleanExit:
            sys.exit()
    except queue.Empty:
        pass

    if flush_commskip:
        task = System(path='mythutil')
        task.command('--chanid %s' % chanid,
                     '--starttime %s' % starttime,
                     '--clearcutlist',
                     '2> /dev/null')
        task = System(path='mythutil')
        task.command('--chanid %s' % chanid,
                     '--starttime %s' % starttime,
                     '--clearskiplist',
                     '2> /dev/null')

    if flush_commskip:
        for index,mark in reversed(list(enumerate(rec.markup))):
            if mark.type in (rec.markup.MARK_COMM_START, rec.markup.MARK_COMM_END):
                del rec.markup[index]
        rec.bookmark = 0
        rec.cutlist = 0
        rec.markup.commit()

#    tf.close();
#    os.remove(tmpstatusfile);
    rec.basename = os.path.basename(outfile)
    rec.filesize = os.path.getsize(outfile)
#    rec.commflagged = 0
    rec.transcoded = 1
    rec.seek.clean()
    rec.update()

    os.remove(infile)
    # Cleanup the old *.png files
    for filename in glob('%s*.png' % infile):
        os.remove(filename)
    os.remove(tmpfile)
    try:
        os.remove('%s.map' % tmpfile)
    except OSError:
        pass

    output_filesize = rec.filesize
    if duration_secs > 0:
        output_bitrate = int(output_filesize*8/(1024*duration_secs)) # kbps
    actual_compression_ratio = 1 - float(output_filesize)/clipped_filesize
    compressed_pct = 1 - float(output_filesize)/input_filesize

    if build_seektable:
        if jobid:
            job.update({'status':job.RUNNING, 'comment':'Rebuilding seektable'})
        task = System(path='mythcommflag')
        task.command('--chanid %s' % chanid,
                     '--starttime %s' % starttime,
                     '--rebuild',
                     '2> /dev/null')

    # fix during in the recorded markup table this will be off if commercials are removed
    duration_msecs, e = get_duration(db, rec, transcoder, outfile)
    duration_msecs = 1000*duration_msecs
    for index,mark in reversed(list(enumerate(rec.markup))):
        # find the duration markup entry and correct any error in the video duration that might be there
        if mark.type == 33:
            if debug:
                print('Markup Duration in milliseconds "%s"' % mark.data)
            error = mark.data - duration_msecs
            if error != 0:
                if debug:
                    print('Markup Duration error is "%s"msecs' % error)
                mark.data = duration_msecs
                #rec.bookmark = 0
                #rec.cutlist = 0
                rec.markup.commit()

    if jobid:
        if output_bitrate:
            job.update({'status':job.FINISHED, 'comment':'Transcode Completed @ %dkbps, compressed file by %d%% (clipped %d%%, transcoder compressed %d%%)' % (output_bitrate,int(compressed_pct*100),int(clipped_compress_pct*100),int(actual_compression_ratio*100))})
        else:
            job.update({'status':job.FINISHED, 'comment':'Transcode Completed'})

def get_duration(db=None, rec=None, transcoder='/usr/bin/ffmpeg', filename=None):
    task = System(path=transcoder, db=db)
    if filename is None:
        return -1
    try:
        output = task('-i "%s"' % filename, '1>&2')
    except MythError as e:
        err = e
        pass

    r = re.compile('Duration: (.*?), start')
    m = r.search(err.stderr.decode('utf-8'))
    if m:
        duration = m.group(1).split(':')
        duration_secs = float((int(duration[0])*60+int(duration[1]))*60+float(duration[2]))
        duration_msecs = int(1000*duration_secs)
        if debug:
            print('Duration %s' % m.group(1))
            print('Duration %s' % duration)
            print('Duration in seconds "%s"' % duration_secs)
            print('Duration in milliseconds "%s"' % duration_msecs)
        return duration_secs, err
    return -1, err

def encode(jobid=None, db=None, job=None, 
           procqueue=None, preset='slow', 
           vbitrate_param='-crf:v 18',
           abitrate_param='-c:a libfdk_aac -b:a 128k',
           tmpfile=None, outfile=None, statusfile=None):
#    task = System(path=transcoder, db=db)
    task = System(path='nice', db=db)
    try:
        output = task(
                      '-n %s' % NICELEVEL,
                      '%s' % transcoder,
                      '-i "%s"' % tmpfile,
                      # parameter to overwrite output file if present without prompt
                      '-y',
                      # parameter de-interlacing filter
                      '-filter:v yadif=0:-1:1',
                      # parameter to allow streaming content
                      '-movflags faststart',
                      # parameter needed when hdhomerun prime mpeg2 files sometime repeat timestamps
                      '-vsync passthrough',
                      # h264 video codec
                      '-c:v libx264',
                      # presets for h264 encode that effect encode speed/output filesize
                      '-preset:v %s' % preset,
                      # ##########  IMPORTANT  ############
                      # ffmpeg versions after 08-18-2015 include a change to force explicit IDR frames, 
                      # setting this flag helps/corrects myth seektable indexing h264-encoded files
                      # uncomment the  line below if you have a recent version of ffmpeg that supports this option
#                      '-forced-idr 1',
                      # parameters to determine video encode target bitrate
                      vbitrate_param,
                      # parameters to determine audio encode target bitrate
                      abitrate_param,
                      # parameter to encode all input audio streams into the output
#                      '-map 0:a',
                      # parameters to set the first output audio stream 
                      # to be an audio stream having the specified language (default=eng -> English)
#                      '-metadata:s:a:0',
#                      'language=%s' % language,
                      # parameter to copy input subtitle streams into the output
                      '-c:s copy',
#                     '-c:s mov_text',
                      # parameters to set the first output subtitle stream 
                      # to be an english subtitle stream
#                      '-metadata:s:s:0',
#                      'language=%s' % language,
                      # we can control the number of encode threads (disabled)
                      '-threads 4',
                      # output file parameter
                      '"%s"' % outfile,
                      # redirection of output to temporaryfile
                      '> %s 2>&1 < /dev/null' % statusfile)
    except MythError as e:
        print('Command failed with output:\n%s' % e.stderr)
        if jobid:
            job.update({'status':job.ERRORED, 'comment':'Transcoding to mp4 failed'})
        procqueue.put(CleanExit)
        os.remove(tmpfile)
        try:
            os.remove('%s.map' % tmpfile)
        except OSError:
            pass
        sys.exit(e.retcode)

def wrapper(func, args, res):
    res.append(func(*args))

def main():
    parser = OptionParser(usage="usage: %prog [options] [jobid]")

    parser.add_option('--chanid', action='store', type='int', dest='chanid',
            help='Use chanid with both starttime and tzoffset for manual operation')
    parser.add_option('--starttime', action='store', type='string', dest='starttime',
            help='Use starttime with both chanid and tzoffset for manual operation')
    parser.add_option('--tzoffset', action='store', type='int', dest='tzoffset',
            help='Use tzoffset with both chanid and starttime for manual operation')
    parser.add_option('-v', '--verbose', action='store', type='string', dest='verbose',
            help='Verbosity level')

    opts, args = parser.parse_args()

    if opts.verbose:
        if opts.verbose == 'help':
            print(MythLog.helptext)
            sys.exit(0)
        MythLog._setlevel(opts.verbose)

    if len(args) == 1:
        runjob(jobid=args[0])
    elif opts.chanid and opts.starttime and opts.tzoffset is not None:
        runjob(chanid=opts.chanid, starttime=opts.starttime, tzoffset=opts.tzoffset)
    else:
        print('Script must be provided jobid, or chanid, starttime and timezone offset.')
        sys.exit(1)

if __name__ == '__main__':
    debug = True
#    sys.stdout = open('/home/mythtv/logfile','a')
#    print('Starting ', str(sys.argv))
    main()