Mythtranscode is the internal process used by the front end to transcode MythTV recordings.
Usage: mythtranscode <--chanid <channelid>> <--starttime <starttime>> <--profile <profile>> [options] --mpeg2 or -m: Perform MPEG2 to MPEG2 transcode. --chanid or -c: Takes a channel id. REQUIRED --starttime or -s: Takes a starttime for the recording. REQUIRED --infile or -i: Input file (Alternative to -c and -s) --outfile or -o: Output file --profile or -p: Takes a profile number or 'autodetect' recording profile. REQUIRED --honorcutlist or -l: Specifies whether to use the cutlist. --allkeys or -k: Specifies that the output file should be made entirely of keyframes. --fifodir or -f: Directory to write fifos to If --fifodir is specified, 'audout' and 'vidout' will be created in the specified directory --fifosync : Enforce fifo sync --buildindex or -b: Build a new keyframe index (use only if audio and video fifos are read independantly) --showprogress : Display status info to the stdout --verbose level or -v: Use '-v help' for level info --help or -h: Prints this help statement.
Choosing a Recording
Two methods are available to choose which recording to work on. The first is to specify the channelid and start time,
-c 1067 -s 20060424183000
Note the start time format is in YYYYMMDDHHMMSS.
The other method is to specify the file,
(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.