From Greg Frost on 03/27/2005:
http://mysettopbox.tv/phpBB2/viewtopic.php?t=3959


From ax763@yahoo on 08/26/2003:
http://www.gossamer-threads.com/lists/m ... ing;#34932


Hello,

I have been having a problem with KnoppMyth R5A26, running on a Dell Dimension 4300, 1.7 GHz, 768 MB RAM, 10+120+160GB HD, WinTV-GO bt878 PCI card.

80% of the time things work great. I have a variety of shows or movies recorded from television, then I watch them later. But 20% of recordings have "mixed up" beginning or ending times. The file-size of the .nuv file indicates that the entire show (e.g. 2-hours) was recorded (e.g. 2 GB) but when I go to "Watch Recordings" and play the file, only a fraction (e.g. 45 minutes) is available for playback. Is this a common issue?

On Gossamer-threads, there was one message suggesting it was related to going into "Watch Recordings" screen in MythWeb while Recording is occuring. They surmised it was due to the preview screen.

I don't use MythWeb. I did confirm that if I go to the Watch Recording or Upcoming Recordings screen on the mythfrontend while a CommFlag or Transcoding job is occurring, then I will "corrupt" the show that is being processed at that moment. For example, if I go to Information Center-System Status-Job Queue, and I see that "The Simpsons" is 66% transcoded, then when I go to watch that episode later, it thinks that the show is only 20 minutes long and will play only 20 out of 30 minutes. Even though the file-size is the same as other 30-minute shows!

Sometimes the error affects the beginning time, for example it will begin playback 13 minutes into the show, and will not let me rewind further than that. But if I monkey around with it, sometimes I can get it back to 0:00. But then if I skip ahead 30-seconds, it will pop ahead to the 13:00 minute mark.

This is very frustrating, and I do not know how to begin to troubleshoot this. I thought it was a database issue, but it didn't seem to have any problems in the MySQL database (according to http://mysettopbox.tv/phpBB2/viewtopic.php?t=1043), although I am new at this. Also, I did disable preview videos, but that didn't fix it either.

I included the above posts as the only things I could find that seemed to relate to this issue. Does anyone have any guidance for me?

Thanks very much!

Have you got auto commerical skip enabled? I'm not talking about marking I'm talking about automatically taking those marks as gospel. If you watch one of the problem recordings and then go into the edit menu (M then Enter) what do you see?

Yes I do have auto-commercial skip enabled. However, disabling it doesn't solve the problem. After all, when the commercials are flagged, the total time length of the recording is not shortened, right? In other words, even if 1/3 of the 60 minute program is flagged as commercials, it is still indicated as a 60 minute program, not 40 minute program, which is the problem that I am having. (Again, I just want to reiterate that the file-size of the .NUV file seems to be the whole show, but the OSD playback only allows a fraction of it available).

if I go into the Edit menu, I see a blank blue bar on the bottom. No commercial markings are indicated. However, if I press "z" then instead of getting the commercial flags as expected, the mythfrontend quits out instantaneously. This only occurs on the "problem" recordings. The other 80% all work fine.

Also, I came across this in the MythTV HOWTO:
http://www.mythtv.org/docs/mythtv-HOWTO-22.html


When I ran mythcommflag --rebuild, it processed 3-4 files (there are about 100 or so available). Those 3-4 files were in fact some of the "problem" files, but not all of them. But this did not fix the issue anyways.

After this, I googled the term "seek table mythtv" and I found some things that sound related, but unfortunately I don't understand what the seek table is.

Also, I'm still trying to figure whether this is mythcommflag related, or mythtranscode related.

I would try turning off auto comercial skip just to make sure it's not the problem, (maybe you've got a bad mark that is causing it to skip the final section) but I'm afraid you got worse issues.

I have seen this with a few damaged or corrupted recordings in the past. They either won't play all the way through or cause editing to barf. The fact that these are transcoded recordings makes this seem even a bit more likely (more places for things to go wrong). Sadly the only solution I've found is to delete the recordings and allow them to rerecord later. The 20% rate is the worrisome part since I've seen maybe a half dozen cases like this in nearly two years.

BTW - love the handle, are your a "Futurama" fan?

Futurama is definitely one of the record-on-any-channel-at-any-time shows on the schedule!

Turning off auto-skip did not help. Trying to repair databases did not help. MythCommFlag --rebuild did not help.

So this is what I did, please tell me if my basis of understanding is correct:

By Default I was recording in RTJPEG (big file sizes, minimal CPU required) and then transcoding to MPEG-4 immediately afterwards (small file sizes, some?/lots? CPU required). So instead, I turned off the auto-transcode, changed the Default record profile to MPEG-4 directly instead of RTJPEG. This way I get small file sizes directly, and avoid the transcoding process, which as you mentioned was an additional place for the recordings to become corrupted.

However, recording in MPEG-4 means I cannot "multitask" as fluidly on the 1.7GHz computer with bt878 WinTV-GO card (recording and watching at same time). I guess this was the tradeoff.

I think that the RT in RTJPEG stands for Real Time - meaning it's a fast enough encoder to keep up with realtime. If your CPU is fast enough to encode directly to MPEG-4 that avoids one level of generational loss and makes it that much more likely that the marks are all in the right place. If it means that you can't watch live TV while doing it, that kind of sucks. There's a reason that the PVR hardware encoders are so popular after all...