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Mythtranscode is the internal process used by the front end to transcode MythTV recordings. For lossless transcodes, calling the program through the command line has been known to work sometimes when the normal method fails.


Misc. Options:
--chanid                    Specify chanid of recording to operate on.
-i OR --infile              Input video for transcoding.
-o OR --outfile             Optional output file for transcoding.
-O OR --override-setting    Override a single setting defined by a key=value
--override-settings-file    Define a file of key=value pairs to be loaded for
                            setting overrides.
--queue                     Add a new transcoding job of the specified recording
                            and profile to the jobqueue. Accepts an optional
                            string to define the hostname.
-b OR --buildindex          Build new keyframe index.
-h OR --help OR --usage     Display this help printout, or give detailed
                            information of selected option.
--version                   Display version information.
--starttime                 Specify start time of recording to operate on.
--video                     Specifies video is not a recording.

Encoding Options:
--allkeys OR -k             Specifies the outputfile should be entirely
--audiotrack                Select specific audio track.
--avf                       Generate libavformat output file.
  --audiobitrate              Output Audio Bitrate (Kbits)
  --bitrate                   Output Video Bitrate (Kbits)
  --height                    Output Video Height
  --width                     Output Video Width
--hls                       Generate HTTP Live Stream output.
  --audiobitrate              Output Audio Bitrate (Kbits)
  --bitrate                   Output Video Bitrate (Kbits)
  --height                    Output Video Height
  --hlsstreamid               Stream ID to process
  --maxsegments               Max HTTP Live Stream segments
  --noaudioonly               Disable Audio-Only HLS Stream
  --width                     Output Video Width
-m OR --mpeg2               Specifies that a lossless transcode should be used.
-e OR --ostream             Output stream type: dvd, ts
--passthrough               Pass through raw, unprocessed audio.
-p OR --profile             Transcoding profile.
-ro OR --recorderOptions    Comma separated list of recordingprofile overrides.

Frame Server Options:
--cleancut                  Improve quality of cutting by performing it
                            partially by dropping data. Works only in fifodir
-f OR --fifodir             Directory in which to write fifos to.
--fifoinfo                  Run in fifodir mode, but stop after displaying the
                            fifo data format.
--fifosync                  Enforce fifo sync.

Logging Options:
--enable-dblog              Enable logging to database.
--loglevel                  Set the logging level.  All log messages at lower
                            levels will be discarded.
                            In descending order: emerg, alert, crit, err,
                            warning, notice, info, debug
                            defaults to info
--logpath                   Writes logging messages to a file in the directory
                            logpath with filenames in the format:
                            This is typically used in combination with --daemon,
                            and if used in combination with --pidfile, this can
                            be used with log rotators, using the HUP call to
                            inform MythTV to reload the file
--nologserver               Disable all logging but console.
-q OR --quiet               Don't log to the console (-q).  Don't log anywhere
                            (-q -q)
--showprogress              Display status info in stdout
--syslog                    Set the syslog logging facility.
                            Set to "none" to disable, defaults to none.
-v OR --verbose             Specify log filtering. Use '-v help' for level info.

Cutlist Options:
--inversecut                Inverses the cutlist, leaving only the marked off
--honorcutlist              Specifies whether to use the cutlist. (Takes an
                            optional cutlist as argument when used with -i)

Choosing a Recording

Two methods are available to choose which recording to work on. The first is to specify the channelid and start time,

--chanid 1067 --starttime 20080109223000

The other method is to specify the file,

--infile /MythTV/tv/1856_20060425200000.mpg

Important.png Note: Specifying the filepath only works if the recording's filename is formatted the default way.

When using the --infile option, mythtranscode will use the filename to lookup the recordings in the recorded table and find the corresponding chanid and start-time. Non-default filenames, such as those renamed with, prevent mythtranscode from doing so (and it complains of this), but it still proceeds with the transcode anyway, confusing the user. The resulting mythtranscode run is useless because the utility doesn't know what seektable to update with the data it found by scanning through the recording. The only way around this and have the transcoding succeed is:

  1. First rename the recording back to the default format, or
  2. Instead of using the more-convenient --infile, manually specify the data mythtranscode needs with -c and -s.

--honorcutlist Limitation

--honorcutlist only seems to work (0.19-fixes [9938]) with the "-c -s" switch combo, NOT with a specified input (-i) file, even if that file is in the mythconverg database.

Using the --buildindex Option

The --buildindex option can be used for rebuilding/repairing the seektable.

Using the --mpeg2 Option for (Virtually) Lossless MPEG2 Transcode

New in 0.19 is a virtually lossless MPEG2 transcode. What this does is let you select cut points and mythtranscode will only re-encode the frames that need to be, copying the rest directly from the stream. If you are using this to cut commercials and you cut at the black frames of a fade to black (or white of a fade to white), what you get is basically a perfect stream copy of the video with no loss to the frames that matter.

This also has some side benefits,

  • Converts the mpeg2 from a TS stream to a PS stream, possibly saving up to 20% of the file size!
  • Fixes Audio/Video sync issues in a similar fashion to ProjectX.

Using the --fifodir path Option

The --fifodir option causes mythtranscode to perform only the decoding part of transcoding, sending the raw video and raw audio to two pipes. No alteration is made to the original file. The path passed to the --fifodir option is assumed to refer to a directory. The two pipes will be created in that directory, with names audout and vidout. The intended use is for the raw data output to the pipes to be recompressed by an external program such as ffmpeg (that is how Nuvexport works). If -v general is also specified then the format of the data that will be output to the pipes is displayed. For example

2011-07-09 09:02:46.493 FifoVideoWidth 720
2011-07-09 09:02:46.493 FifoVideoHeight 576
2011-07-09 09:02:46.493 FifoVideoAspectRatio 1.77778
2011-07-09 09:02:46.493 FifoVideoFrameRate 25
2011-07-09 09:02:46.493 FifoAudioFormat raw
2011-07-09 09:02:46.493 FifoAudioChannels 2
2011-07-09 09:02:46.493 FifoAudioHz 48000

To display the format information without actually performing the transcoding, --fifoinfo can be specified, in place of --fifodir path. An example script shows mythtranscode driving ffmpeg with libx264. The script handles progressive and interlaced recordings, either maintaining resolution or downscaling.


Remove commercials from an MPEG2 recording

First, edit the recording. Then:

mythtranscode --chanid 1017 --starttime 2006-12-16-20-00-00 --mpeg2 --honorcutlist

This will drop the cut version beside the original, but with an added .tmp extension. I'm not exactly sure what it does to the database. It seems to keep the cutpoints and points at the old .mpg file, but shortens how long it thinks the movie is to the size of the .tmp file. Alternatively, you can add the -o option. This is useful for exporting to a different directory. For example

mythtranscode -c 1003 -s 20090907113000 -m -l -o /myth/video/myvid.mpg

Note that -c is --channel, -s is --starttime, -m is --mpeg2 and -l is --honorcutlist


Every once in a while, something will happen and transcoding will not be able to complete. When this happens, the Job Queue will indicate the failure by turning the job title red in color. It will also say "Job: Transcode Status: Errored", and will follow with the line "Transcode failed with status: ###"

When this happens, you can often find information in the backend logs.. otherwise you can check this list to see if your error status matches any that others have encountered:

Code Name Possible Causes References
139 SIG_SEGV System generated, segfault. Please submit a ticket with the backtrace from your core dump.
227 TRANSCODE_BUGGY_EXIT_DEADLOCK "Deadlock detected. One buffer is full when the other is empty!"
Cut list contains a cut zone with a beginning but no ending (often at the very end of the recording) none
235 TRANSCODE_EXIT_STOPPED Transcode was stopped manually by the jobqueue.
236 TRANSCODE_EXIT_ERROR_CUTLIST_UPDATE Transcode failed to clear cutlist.
237 TRANSCODE_EXIT_REMOTE_FILE File is on a remote filesystem. mythtranscode does not yet handle these files. Check if the Job runs on a slave backend. none
238 TRANSCODE_EXIT_NO_RECORDING_DATA Jobqueue entry, or matching recording, could not be found.
247 TRANSCODE_EXIT_UNKNOWN_ERROR See log files for more information. [1] [2]
250 TRANSCODE_EXIT_DB_ERROR Database could not be accessed.
252 TRANSCODE_EXIT_INVALID_CMDLINE Invalid command line. The transcoder is being called directly, improperly.
254 TRANSCODE_EXIT_NO_MYTHCONTEXT No MythContext. Could not initialize properly.
255 UNRECOVERABLE ERROR Could be you didn't setup profiles in mythbackend. Try checking mythtranscode.log

Fixing "Deadlock detected. One buffer is full when the other is empty!"

If your transcode fails because this error, you can remux the video and try again. Mythtv's keyframe index will be wrong for the remuxed file, so you must also regenerate the index. And then it's sensible to reposition your cut points incase they are off. So the procedure is

  • Determine the file for the recording in question
  • Remux the file:
 ffmpeg -i <filename> -acodec copy -vcodec copy <tmpfilename>
 rm <filename>
 mv <tmpfilename> <filename>
  • Regenerate the keyframe index:
 mythtranscode --mpeg2 --buildindex --allkeys --showprogress --infile <filename>
  • Reposition the cut points
  • Try trancoding again

If this does not fix the problem then you can try using Mythcutprojectx to perform the cutting.