Jim Rush wrote:
> At best, I get 10% of the audio (little spurts of audio).
>
> I've figured out how the basics of converting video with ffmpeg using
> the command line:
> ffmpeg -i gs.avi -vcodec mpeg2video -acodec ac3 gs4.mpg
> I've tried mp2 and mp3 as the audio codec, but those don't seem to
> generate any audio.
Sadly, transcoding is a matter of trial-and-error with hundreds of
variables. I've been slowly toying at transcoding some shows I recorded
back in September and have only been partially successful (a few
episodes successfully converted). The big problem I'm having now is that
Mythtranscode is crashing my server (hard crash of the entire system).
But I'm also seeing some audio problems. I have a few recordings where
the audio works for the first 10 seconds or so and then drops out for
the rest of the show. I think these are ones I recorded with the RTJpeg
software codec. I later switched to the MPEG4 software codec, which I
think converts better. In my case, the audio problems aren't just when
playing back on the MVP. I also observe them in mplayer. So clearly a
conversion problem.
Your command above suggests you are using AC3 encoded audio, and that's
known to be problematic with mvpmc. MP3 audio should work, you just need
to hit upon the right parameters.
> 1. Is there a reference clip out there that I can use to insure that all
> of my problems are purely conversion issues ?
It's highly likely that your problems are conversion related. The vast
majority of the content I play though the MVP is recorded with PVR cards
directly in MPEG2 format and it plays back fine. This goes to show that
the number one way to simplify the process of using mvpmc for MythTV
playback is to select the right video capture hardware.
We should be able to make a clip available for testing. Anyone have a
suggestion as to where to upload it? We have somewhat limited storage
space on the wiki.
> 2. What are the best ffmpeg settings (or recommend another tool) for mvp
> playback ?
As noted above, I've had limited success using this script:
--------------------------------------------------------------------------------
#!/bin/sh
# To run as a user job in MythTV:
# transcode_mpeg2 %STARTTIME% %CHANID% %DIR%/%FILE%
START=$1
CHAN=$2
FILE=$3
LOG=/var/log/mythtv/transcode.log
FIFO=/tmp/fifodir_$$
mkdir -p $FIFO
(
echo $0 START `date "+%Y-%m-%d %T"`
echo $0 $*
/usr/bin/nice -n19 /usr/bin/mythtranscode -p autodetect --honorcutlist \
-c $CHAN -s $START \
-f $FIFO 2>&1 &
sleep 10
/usr/bin/nice -n19 /usr/bin/mencoder \
-aspect 1.33333333333333 -noskip \
-idx ${FIFO}/vidout \
-audiofile ${FIFO}/audout \
-demuxer 20 -audio-demuxer 20 -rawaudio rate=32000:channels=2 -demuxer
26 \
-rawvideo w=352:h=240:fps=30000/1001 \
-of mpeg -mpegopts format=dvd \
-ovc lavc -lavcopts
vcodec=mpeg2video:acodec=mp3:abitrate=128:keyint=18:vrc_buf_size=1835:vrc_maxrate=5500:vbitrate=2750
\
-vf scale=352:240 -ofps 30000:1001 \
-oac mp3lame -lameopts vbr=3:br=128 \
-o ${FILE}.mpeg2 2>&1 \
&& mv -i $FILE ${FILE}.bak \
&& mv -i ${FILE}.mpeg2 $FILE
/usr/bin/nice -n19 /usr/bin/mythcommflag --rebuild \
-c $CHAN -s $START
echo $0 END
echo
) >> $LOG
--------------------------------------------------------------------------------
This is a far simplified implementation of the conversion technique used
my nuvexport. It uses mythtranscode to decode the video recorded by
MythTV to a raw format and written to a FIFO buffer. This insures that
the script can handle anything that MythTV can produce (in theory).
The raw video is then read by mencoder, transcoded, and then
mythcommflag is ran to rebuild the seek table.
This isn't a good general solution, as my mencoder command has a bunch
of hard coded parameters for the particular video I was trying to
convert. See Roger Heflin's posting back on 09 Nov 2007 for a more
general script, though it relies purely on mencoder, which can't
directly handle the MythTV RTJpeg codec.
> 3. General question-Do people like using the MVP as a MythTV frontend ?
Yes. Though the only thing I can compare it to is using Mythfrontend on
a desktop. As I've mentioned in other postings, I think mvpmc does a
good job as a standard definition front-end, and I find that it has a
better UI for the basic day-to-day operations.
-Tom
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