[mythtv-users] Transcoding for best audio

[Brenden Conte]

Thanks Michael!  This is a great script, I will give it a try with the
modifications needed to pick the "best", and let you know how it goes.

-B


On Mon, Jul 15, 2013 at 3:06 PM, Michael Stucky <mike at stucky.us> wrote:

> On Sun, Jul 7, 2013 at 7:06 PM, Michael Stucky <mike at stucky.us> wrote:
>
>> On Sun, Jul 7, 2013 at 6:00 PM, John Pilkington <J.Pilk at tesco.net> wrote:
>>
>>> On 07/07/13 21:26, Michael Stucky wrote:
>>>
>>>> On Sat, Jul 6, 2013 at 2:52 AM, Brenden Conte <brenden at thecontes.info
>>>> <mailto:brenden at thecontes.info**>> wrote:
>>>>
>>>>     Thank you everyone for your feedback; it has been quite useful!
>>>>
>>>
>>> <snip>
>>
>>> I used to use the mencoder-based script that I posted earlier as a
>>> preprocessor to get rid of the problematical extra streams that probably
>>> still come and go in DVB-T recordings.  I used mythtranscode --mpeg2
>>> --honorcutlist on the output, usually without problems, with MythArchive
>>>  with no cutlists and no transcoding then usually able to create a
>>> full-sized 4.3 GiB DVD image in less than 30 min.  Each stage of the
>>> process could be checked, but inexplicable failures still happened.
>>>
>>> For several years now I've been using ProjectX within scripts to do the
>>> job instead; currently mythDVBcut.  It's a hands-on process, but I can't
>>> really see it being anything else. Failures are rare, and rarer than
>>> before.  There are still niggly inconveniences, but the biggest worry is
>>> that changes introduced into master, or the underlying tools, will bring
>>> new problems when a new version of  -fixes makes its appearance. :-)
>>>
>>> John
>>>
>>> Thank you John for sharing your work and your advice for us all to
>> benefit from!
>>
>> Mike
>>
>
> This weekend I discovered an incredibly simple method for removing
> unwanted audio streams from mpeg2 recordings using Mythffmpeg. The result
> remains in an mpegts container, which means it is seekable and editable
> like any other recording. The surprising thing is that the recording can
> now be lossless transcoded by MythTV 0.26!!
>
> I have written a script (OK, full disclosure, this is mostly John's code
> tweaked to work as a MythTV USERJOB) that takes the first video stream and
> the first audio stream and copies them to a new file that replaces the
> original recording. I have this configured to auto-execute for every
> scheduled recording (it has been successfully working since Saturday
> evening). After this JOB runs I can go in and create my cut-list as I
> always have done in the past and schedule the "Transcode" job (this is the
> part that has never worked for me in MythTV 0.26). Now I have recording
>  (MythTV still see it as a normal recording, i.e. seekable and editable)
> with no unwanted content (ads etc.) and only the video and audio streams
> that I do want and it plays on all of my media players (Mythfronted, VLC,
> SageTV, etc.)!!
>
> Brenden, if you are still following this thread... You can setup this
> script (included below) as follows, give it a description like
>
> Remove Extra Audio Streams
>
>  and a command like
>
> /usr/local/bin/rmExtraAudioStream.sh "%FILE%"
>
> where "/usr/local/bin/rmExtraAudioStream.sh" is this script:
>
> #!/bin/bash -e
>
> # Script that works as a MythTV USERJOB to remove unwanted audio tracks
> from
> # recordings. Create a USERJOB of the form:
> # /<path to script>/rmExtraAudioStream.sh "%FILE%"
> # Where "rmExtraAudioStream.sh" is the name of this script
>
> # Change the following to your MythTV recordings directory
> RECDIR=/var/lib/mythtv/recordings
>
> if [ "$1" = "-h" ] || [ "$1" = "--help" ] ; then
> echo "Usage: "$0" <recording>"
> echo "<recording> is an mpeg2 file recorded by MythTV with a valid DB
> entry."
> echo "e.g. 1234_20100405123400.mpg in the defined RECDIR"
> echo "The output file replaces the input file which is renamed to
> <recording>.old"
> exit 0
> fi
>
> # exit if .old file exists
>
> if  [ -f ${RECDIR}/"$1".old ] ; then
>     echo " ${RECDIR}/"$1".old exists: giving up." ; exit 1
> fi
>
> cd $RECDIR
> if  [ ! -f "$1" ] ; then
>     echo " "$1" not found.  Giving up"
>     cd ~
>     exit 1
> fi
>
> # Is it an mpeg-2 recording?
>
>  mythffmpeg -i "$1" 2>&1 | grep -B 2 -A 4 "mpeg2video (Main)" | tee
> "temp$$.txt"
>
> mpeg=$(grep -c "mpeg2video (Main)" temp$$.txt)
> echo "mpeg2video (Main) stream count:  $mpeg"
> if [ $mpeg != 1 ] ; then
>   echo "Not mpeg2video (Main), or no or multiple video streams"
>    cd ~
>   exit 1
> fi
>
> #################################
> # This code was taken from John Pilkington's mythDVBcut script and
> # will need to be edited if you require something other than the first
> # video stream and the first audio stream.
> #################################
> #
> ##    Examples
> ##    Stream #0.0[0xe0]: Video: mpeg2video, yuv420p, 720x576 [PAR 64:45
> DAR 16:9], 15000 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
> ##    Stream #0.1[0xc0](deu): Audio: mp2, 48000 Hz, 2 channels, s16, 256
> kb/s
> #
> #   # Thanks to Christopher Meredith for the basic parsing magic here.
>
> VSN=`grep "mpeg2video (Main)"  temp$$.txt | head -n1 | cut -f 1,1 -d'[' |
> sed 's+.*\#++g'`
>
> # It has to be tweaked for multiple audio streams.  This (with head -n1 )
> # selects the first listed by ffmpeg.
> # You may alternatively wish to select for language, format, etc.
> # May be channel, programme, user dependent.
> ASN=`grep Audio  temp$$.txt | head -n1 | cut -f 1,1 -d'[' | sed
> 's+.*\#++g'`
>
> #####################################
>
> # Now do the actual processing
>
> mv  "$1" "$1".old
>
> # use Mythffmpeg to copy the streams.
> ionice -c3 mythffmpeg -i "$1".old -map "$VSN" -map "$ASN" -vcodec copy
> -acodec copy -f mpegts "$1"
>
> # rebuild seek table and update filesize
> ionice -c3 mythcommflag -q --rebuild --file "$1" --logpath /var/log/mythtv
>
> rm -f temp$$.txt
>
> cd ~
>
> exit 0
>
>
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