[mythtv-users] 0.27.1 stores wrong length in SD mpeg2 recordings

Hika van den Hoven hikavdh at gmail.com
Sat Jun 21 01:17:58 UTC 2014


Hoi Hika,

Saturday, June 21, 2014, 2:55:33 AM, you wrote:

> Hoi Jean-Yves,

> Saturday, June 21, 2014, 2:34:10 AM, you wrote:

>> On 21 June 2014 09:41, Hika van den Hoven <hikavdh at gmail.com> wrote:
>>> Hoi Discussion,
>>>
>>> About a month ago a moved from 0.26 to 0.27 and then 0.27.1.
>>> Since then I have a problem with my recordings. I only record SD with
>>> a PVR350 and a PVR500, so hardware mpeg2 recorders.
>>> Here some statistics from first 0.26
>>> recorded from till shown length on playback
>>>      18:35-20:20   1:44:59
>>>      20:05-21:50   1:44:57
>>>      18:35-20:20   1:44:59
>>> and recent recordings
>>>      19:00-20:45   1:31:32
>>>      18:00-18:31   0:27:07
>>>       9:04-10:15   1:04:03
>>> As you see the shown length is 10 to 13% to short and also has nothing
>>> to do with the show length, which often is about that much shorter,
>>> but not for the fifth recording. (30 min)

>> in 0.26, the length reported was of the recording time, regardless of
>> what was stored.
>> In 0.27, it's actual time of what was recorded.

>> when recording, the backend count the number of frames written to disk
>> and that information is written in the database along the position in
>> bytes for that frame.

>>> I first noticed it because if I jumped back a little (I have left set
>>> to jump back 10s and right to forward 1 min) I jumped forward one to
>>> several minutes. Depending on how far I was in the recording and the
>>> time since the last jump. If the recording comes at the end of the
>>> shown length it plays on till the real end.

>> when you skip forward or backward, it knows you where you're up to
>> frame count wise, query the database for the position in bytes between
>> here+skip_value and go there.

>> While I'm getting to is that there are many thing that could cause
>> what you're seeing, and not necessarily a myth one. the first one is
>> that the PVR-500 may not produce the right amount of frames, leading
>> to an incorrect calculation size, and lead to inaccurate skips

>> have you changed/upgraded anything other than myth when upgraded from
>> 0.26 to 0.27?
>> drivers for the pvr350/500?
>> _______________________________________________

> I upgraded the whole machine, so a fresh install including a newer
> kernel 3.12.13. But as far as I know the ivtv kernel drivers haven't
> been altered for some time. As far as I can remember the old one ran
> with 3.10.7 or 3.10 17.


> Tot mails,
>   Hika                            mailto:hikavdh at gmail.com

If I try to play the first 0.27 recording outside myth Totem also
shows to short a length, but every time different. It also has problem
playing. Gnome mplayer shows it correct and has no problem.
If I look at the properties (in gnome2) it says: the correct length,
Demuxer: mpegps, Videocodec: ffmpeg2, videobitspeed 5859 kb/s, video
framespeed 25 fps.
And at a second tab: mpeg2 video, bitspeed 1563 kbps, imagespeed N/A

Also when I transcode one of the files with ffmpeg it always complains
about the first frame mot being a keyframe and in maybe 10 to 20% of
the files it reports some damaged frames (audio/video sync or no
audio)


Tot mails,
  Hika                            mailto:hikavdh at gmail.com

"Zonder hoop kun je niet leven
Zonder leven is er geen hoop
Het eeuwige dilemma
Zeker als je hoop moet vernietigen om te kunnen overleven!"

De lerende Mens



More information about the mythtv-users mailing list