Repairing Damaged Recordings

From Nearline Storage
Jump to navigation Jump to search

I used this workflow to repair a damaged recording of Fleetwood Mac on Soundstage that I captured off of Palladia.
Also worked with Sunrise Earth files:

  • Convert the damaged MPG to an MKV with ffmpeg:
 ffmpeg -i "/mythdata/recordings/1209_20101122140000.mpg" -filter:v yadif -aspect 16:9 -vf crop=1920:1080:0:0 -s 1920x1080 -b 4M -vcodec libx264 -vpre hq -g 15 -threads 8 -acodec copy -async 1 -f matroska /tmp/fleetwork.mkv
  • "-g 15" means "set a keyframe every 15 frames." The "hq" preset sets "-g 250" and that's a problem because mkvmerge will only split on keyframes and 8 seconds between keyframes is too long to do decent editing. The one-half second intervals that "-g 15" gives works better. Using "-g 1" to make every frame a key frame didn't work, it resulted in a nasty shimmer in the video.
  • Both "-g 15" and "-threads 8" must come after "-vpre hq" because the preset sets those options and will override anything set on the command line before the "-vpre" option.
  • Figure out the timecodes for the edits using mplayer's -edlout option, fine-tuning the edits through trial and error using mplayer and a test edl file
 mplayer -edlout edl.list tmp/fleetwork.mkv
mplayer keys:
o : toggle OSD (turn on timecode display)
i : mark start or end of edit block in edl.list
<- and -> : backward and forward 10 seconds
up and down : backward and forward 1 minute
pgup and pgdown : backward and forward 10 minutes
To test playback with the edl.list, first edit the file and change the blocks so that they will be played rather than skipped. Then test with:
 mplayer -edl edl.list tmp/fleetwork.mkv
  • Convert the edl timecodes, which are in seconds, to hh:mm:ss.nnnnnnnn format for mkvmerge.
  • Split the big file up into little ones using mkmerge:
 mkvmerge --split timecodes:00:00:12.212,00:19:26.197998,00:21:56,00:39:07.077881,00:40:07,00:53:11.1,00:54:11,01:11:21,01:12:23,01:27:37.0625,01:28:36.5,01:41:12.1,01:43:12,02:00:14 -o fm.mkv fleetwood.mkv 
  • Merge the parts that I want to keep back into a single MKV file with mkvmerge:
 mkvmerge -o fm.edited.mkv --append-mode track fm-002.mkv +fm-004.mkv +fm-006.mkv +fm-008.mkv +fm-010.mkv +fm-012.mkv +fm-014.mkv

2010-12-22, using stock Fedora 13 packages mythtv v23, ffmpeg and mkvtoolnix