[mythtv-users] Mytharchive errors

[Rod Smith]

On Monday 08 December 2008 11:20:16 am Harry Devine wrote:
> >
> >> Also, I did see the following error in my
> >> mytharchive log, and I wonder if this would go away once the transcoding
> >> problem is straightened out:
> >>
> >> WARNING: frames rates do not match
> >> The frame rate for ntsc should be 29.97 but the stream info file report
> >> a fps of
> >>  59.9401
...
> I tried using your script and it complained about not knowing what
> mencoder or midentify was.  I tried "apt-get install mencoder
> midentify", but it has no idea what midentify is.

midentify is a simple script that calls mencoder with various parameters. Here 
it is:

--------- begin midentify ---------

#!/bin/sh
#
# This is a wrapper around the -identify functionality.
# It is supposed to escape the output properly, so it can be easily
# used in shellscripts by 'eval'ing the output of this script.
#
# Written by Tobias Diedrich <ranma+mplayer at tdiedrich.de>
# Licensed under GNU GPL.

if [ -z "$1" ]; then
        echo "Usage: midentify <file> [<file> ...]"
        exit 1
fi

mplayer -vo null -ao null -frames 0 -identify "$@" 2>/dev/null |
        sed -ne '/^ID_/ {
                          s/[]()|&;<>'"'"'\\!$" []/\\&/g;p
                         }'

--------- end midentify ---------

It seems to be included with some versions of Linux but not with others.

> My recording isn't an HD recording either.

For whatever reason, the tools you're using seem to think that the video has a 
59.9401 fps frame rate. AFAIK, you're only likely to get something like that 
in progressive HD broadcasts, not in standard NTSC broadcasts. OTOH, there 
may be progressive SD broadcasts, too, but I've not encountered such things 
myself.

> If I understand you right, and mytharchive does 
> its own transcoding, then the recording that I have should be OK as it
> stands, however, I still get that error about the frame rates being
> off.  So I'm still confused about that error and the process that
> mytharchive uses to put the recording to a DVD.

The frame rate message you recorded is a *warning*, not an *error*. The two 
are very different. A warning tells you about something that might be a 
problem, but it's not something that'll stop the processing in its tracks. An 
error is more serious, and will terminate the processing.

Although it's true that you're having problems, there's little reason to think 
that the frame rate is the cause of your problems. It could be, but if I had 
to place a bet, I'd say that the frame rate is not the root of your problem. 
In my experience, MythArchive (and/or ffmpeg, upon which it relies) does a 
poor job at transcoding recordings into MPEG-2 form. My own experience is 
filled with audio/video sync problems, transcodes that crash, transcodes that 
loop forever and fill the disk with cryptic log file messages, etc. That's 
why I developed my own manual transcode script that uses mencoder; I find 
it's much more reliable than MythArchive's own method. (That said, my own 
script doesn't always work. In particular, it occasionally produces a file 
that later steps can't process fully, resulting in truncated recordings on 
the DVD.)

As to what happens when you make a DVD with MythArchive, the steps are these, 
in summary and omitting various details:

1) If necessary or if you've told it to do so, MythArchive calls ffmpeg to
   transcode the recording (in MPEG-2, MPEG-4, RTjpeg, or some other format)
   into a DVD-compliant MPEG-2 form. This seems to be the step that's failing
   for you.

2) The MPEG-2 file is demuxed into separate audio and video streams.

3) The DVD menus are created.

4) The menus and recordings are recombined into new files and stored in the
   format appropriate for a DVD.

5) The DVD files are combined into an ISO image file.

6) If you requested it, the ISO image file is burned to DVD.

-- 
Rod Smith