[mythtv-users] Recovering from transcode/bad seektable

Ross Boylan rossboylan at stanfordalumni.org
Sat Sep 26 21:04:22 UTC 2020

Thanks for your very concrete suggestions.  Unfortunately, I still can't
view the video.
Some details below, and a question: should I regenerate the seek table in

On Sat, Sep 26, 2020 at 12:52 PM Peter Bennett <pb.mythtv at gmail.com> wrote:

> On 9/26/20 3:33 PM, Ross Boylan wrote:
> I had a US OTA TV recording that was working fine.  Somehow a transcode
> was triggered, the seek table became corrupt and now it's not watchable.  I
> have repaired the seek table in the database (MariaDB) and regenerated the
> seek table for the recording.  But it still isn't usable, and my effort to
> convert it back failed.
> Any suggestions?

> My recommendation would be:
> 1. Clear the seektable for the recording -
> mythutil --clearseektable --chanid "$chanid" --starttime "$starttime"

> 2. repair the recording file with
> mkvmerge -o outputfile.mkv originalfile.ts
$ mkvmerge -o ${VID}.mkv $VID
mkvmerge v35.0.0 ('All The Love In The World') 64-bit
'/srv/media10/media10-barley/22002_20200215205800.ts': Using the
demultiplexer for the format 'MPEG-1/2 video elementary stream'.
'/srv/media10/media10-barley/22002_20200215205800.ts' track 0: Using the
output module for the format 'MPEG-1/2 video'.
The file '/srv/media10/media10-barley/22002_20200215205800.ts.mkv' has been
opened for writing.
Warning: Found at least one B frame without second reference in a non
closed GOP.
Progress: 100%
The cue entries (the index) are being written...
Multiplexing took 37 seconds.

But mkv does not report an audio track on the original.  I don't know if
that's normal for nuv;
it's not what I see for the original streams:

mythtv at barley:~$ mkvmerge -i $VID
File '/srv/media10/media10-barley/22002_20200215205800.ts': container:
MPEG-1/2 video elementary stream
Track ID 0: video (MPEG-1/2)
mythtv at barley:~$ mkvmerge -i
File '/srv/media10/media10-barley/22002_20200923192800.ts': container: MPEG
transport stream
Track ID 0: video (MPEG-1/2)
Track ID 1: audio (AC-3)

3. replace the file with the repaired file
> cp outputfile.mkv originalfile.ts
> (keep a copy of the original file in case this makes things worse)
> If it still will not play, try playing the file with vlc. The recording
> itself may be corrupt.
Done.  myth says "video decode error".  Should myth 30 understand the

vlc can open it, and even shows the correct recording length.
But there is neither sound nor video when it  plays.  I verified that I can
view non-mangled, non-nuv
recordings in vlc.

Should I rebuild the seek table for the recording before trying in myth?


P.S. The message that the recording was 7 hours long based on the bitrate
suggests the audio
bitrate was originally much higher, and has been erroneously labelled with
the wrong bitrate.
So if played at "normal" speed to the low bitrate, that will be like
playing the original really slowly.
Which is what I heard, apart from the static.
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