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recording to mkv generates partly corrupt files

Added by J. Z. almost 9 years ago

Hi,

about a month ago I upgraded my debian video server.
This included an upgrade to tvheadend 4.1-1362 as it comes with debian jessie. Before I used for quite some time tvheadend 3.9 I believe.

Unfortunately the recordings with the upgraded server generate somehow strange mkv files (I'm recording to mkv).

Usually I cut recordings with avidemux.
Sometimes -- with recordings from the upgraded tvheadend -- avidemux fails to cut the mkv recordings correctly.

Meanwhile I found, that that the follwing command somehow "sanitizes" the recorded files such that they can be processed w/o any trouble with avidemux.

ffmpeg -i recorded-from-tvheadend.mkv -c copy -map 0 processed-by-ffmpeg.mkv

If I take mediainfo to compare the both files (recorded-from-tvheadend.mkv with processed-by-ffmpeg.mkv), it turns out, that the delay between audio and video tracks in the both files is different -- everything else seems to be basically the same.

The strange thing about this is, that this behaviour wasn't there before I upgraded my system.
Unfortunately I don't know if the problem is really related to tvheadend, because I updgraded also the rest of the system, e.g. kernel, etc.

Any ideas about what could be the problem?


Replies (3)

RE: recording to mkv generates partly corrupt files - Added by Mark Clarkstone almost 9 years ago

You don't mention what card you're using..

RE: recording to mkv generates partly corrupt files - Added by J. Z. almost 9 years ago

I've two DVB-S2 cards:

a twin tuner TBS 6981
and a single tuner TeVii S464

I operate these cards since quite a while successfully (more than two years I guess).

My problem appears with recordings from both cards.

It appears also with both the proprietary driver for TBS 6981 and with the driver which is included in the linux kernel since kernel 4.2.

RE: recording to mkv generates partly corrupt files - Added by Martin Walter almost 9 years ago

Very interesting, because I have experienced similar problems. Like you I have not been able to use avidemux (or anything else actually) to cut out commercials of some recordings. I will report of an actual example which I have just (re-)tested after reading this thread:

(1) When I watch the original recording with VLC (incl. pre- and postpadding) everything plays fine. Video and audio are in sync.
(2) When I cut out the commercials with avidemux at the I-frame positions (copying audio and video into a mkv again) the video starts without sound. Audio only kicks in after 32 seconds. When audio eventually kicks in the VLC time suddenly jumps to 1:02. Video and audio are in sync then though
(3) I was hopeful your ffmpeg trick would fix the problem, but unfortunately didn't.

Mediainfo output of the original recording attached. Please let me know if you should need any additional information.

EDIT: I'm recording from a Digibit SAT>IP Server, FWIW.

Mediainfo.txt (4.14 KB) Mediainfo.txt
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