Erroneous file duration in mkv

[Travillion]

Hello,

I recorded an OTA broadcast off PBS using my HDHomeRun tuner and Plex. Usually this goes without a hitch, but in this case the 30-min episode lists (in ffmpeg -i, VLC player, Plex, etc.) its duration as 13:28:20.xxx. The file plays fine in VLC for its actual 30-min duration and then just ends. [More precise: I did not watch the full file, I just skipped through it in 10-s increments to the end, so seek seems to work fine.] I'm not savvy enough with header/metadata info and encoding procedures to understand why the duration field got wonky. Is there an easy way in ffmpeg or mkvtoolnix to update this field to the correct number?

[netmask56]

Post a MediaInfo report of the file - sometimes simply remuxing in MKVToolnix will fix a few problems.

[Travillion]

I will post a MediaInfo log when I get back to my main computer. However, I can answer that remuxing doesn't fix it. My first effort to fix the problem was to trim the file to 29.30--mkvmerge, no transcoding--and the file duration remained wonky.

[netmask56]

What format does the original broadcast record ie TS or MP4 etc.... If it is TS then you could run the file through TSDoctor to cleanup any transmission errors, time code etc...

[sneaker]

I will post a MediaInfo log when I get back to my main computer. However, I can answer that remuxing doesn't fix it. My first effort to fix the problem was to trim the file to 29.30--mkvmerge, no transcoding--and the file duration remained wonky.

Mkvmerge will only trim to the next video keyframe. If there is no additional keyframe at or after 00h:29m:30s then trimming will not work. Try a bit earlier, e.g. 00h:29m:25s.

[Travillion]

Attached is the MediaInfo log.

As you can see, duration is listed as 13hrs20mins, when in fact the recording is only approx. 30mins. This is confirmed by playing the file, as well as looking at the audio durations (29:58).

I don't think keyframes are the issue here when I trimmed the video. I haven't analyzed to see exactly where the keyframes are, but my understanding is that broadcoasts have frequent keyframes so that if there is a transmission error the stream is recoverable within a few seconds, or so you can seamlessly change channels, etc. I trimmed this video almost 30 seconds before the end to be safe--even by blu ray standards that would be a long stretch without a keyframe.

The original broadcast was MPEG codec in the TS container, remuxed into mkv container. I have never used TSDoctor but can give that a try. I hoped there would be a simple duration parameter I could just modify, or something like that.