[mythtv-users] Audio out of sync in Mytharchive generated DVD

[Chris Weiland]

On 4/9/07, Rod Smith <mythtv at rodsbooks.com> wrote:
>
> On Monday 09 April 2007 17:38, Chris Weiland wrote:
> > I'm trying to archive a few of my recordings to DVD using Mytharchive,
> > which worked beautifully, except that the audio was out of sync by about
> > 3-5 seconds.
>
> This is a serious problem with every tool I've tried to make DVDs,
> although
> it's worse with some tools and source files than with others. That said, a
> 3-5 second sync problem is pretty awful. The usual pattern for me is that
> the
> audio sync starts out OK but slowly drifts over the course of the
> recording.
>
> In any event, I've had better luck using mencoder to create MPEG-2 files
> from
> MPEG-4 and non-Myth sources than using MythArchive's tools (namely
> ffmpeg). I
> still use MythArchive to create the DVD, but not to transcode into MPEG-2
> format. Here's the command I use:
>
> mencoder -vf kerndeint,softskip,scale=720:480,harddup -ofps 30000/1001
> -aspect
> ${aspect} -ovc lavc -lavcopts
> vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9600:vbitrate=${vbitrate}:keyint=18:turbo:trell:dc=10:autoaspect=1
> -oac
> lavc -lavcopts acodec=ac3:abitrate=192 -of mpeg -o ${dest} ${src}
>
> Note that's one big long line; it'll be split across multiple lines by the
> e-mail transfer. Replace ${aspect} by the source's aspect ratio (1.3333 or
> 1.7777), ${vbitrate} by your desired bitrate (such as 4771000 to fit two
> hours on a 4GB DVD), ${dest} by the destination filename, and ${src} by
> the
> source filename. Of course, I've got this in a script, myself. I'm not yet
> 100% satisfied with my parameters; I'm still fiddling with them, but it's
> a
> slow process. It's also possible to add a crop option to crop the
> letterboxing off of letterboxed NTSC source material.
>
> Once I've transcoded a recording, I use MythArchive with the "always
> transcode" option DISABLED and the "don't re-encode" quality setting; the
> whole point of using mencoder is to bypass the buggy ffmpeg step.
>
> Nine times out of ten, the DVDs I get from this process have better audio
> sync
> than they do if I'd used MythArchive with its ffmpeg transcoding. I also
> get
> better deinterlacing (due to the kerndeint option) -- MythArchive/ffmpeg
> tends to produce hideous interlacing artifacts. I still have occasional
> problems with this approach, but they're less common and usually less
> severe
> than what MythArchive/ffmpeg produces.
>
> All of this applies to material that wasn't originally in MPEG-2 form or
> that
> needs processing to reduce its size or otherwise modify it. As I've got
> two
> tuners with hardware MPEG-2 encoders, when I know I'll be making a DVD
> from
> material obtained from them, I prefer to set the recording bitrate
> appropriately and then use MythArchive with the "always transcode" option
> disabled and the quality set to "don't re-encode". When I do this, though,
> I'm sure to set the recording resolution to a DVD-compatible one
> (typically
> 720x480).
>
> > The wiki
> > article also suggests setting "Always use Transcode", which was on in
> both
> > tries.
>
> I disagree that this is a good idea, at least in my experience. Maybe it
> helps
> with source files recorded with certain hardware and/or software, but not
> with the files I've used.
>
> FWIW, I've run across a few instances where my MPEG-2 hardware encoder
> produces audio that's about 100-200ms out of sync when played by MythTV,
> but
> when transcoded with mencoder and a DVD created, the audio sync is much
> better. Thus, I try not to judge the audio sync until I've got a DVD image
> on
> disk (see below).
>
> > Other than that, I don't really know what to make of it.  I don't really
> > want to mess around with it until I know what to do because each try
> takes
> > about 2 hours to burn, plus the disk.
>
> Try "burning" to an .iso image rather than directly to disc. You can then
> move
> the .iso file to your Myth Video directory to test it. If it's good, you
> can
> then burn that image to disc:
>
> growisofs -dvd-compat -Z /dev/dvd=mythburn.iso
>
> Replace mythburn.iso with the source filename, if you change it or need to
> refer to it by its complete pathname. If you were to do this blindly, it
> wouldn't take much longer than telling MythArchive to burn the disc
> directly.
> If you find a problem, though, it'll be quicker and easier to correct when
> you do it this way, and you won't waste a disc in the process.
>
> As an alternative to all of this, you could try creating a MythTV native
> backup rather than a conventional DVD. This will be quicker and will
> preserve
> the files in their original form, so if audio sync is correct when you
> play
> the recording normally, it should be OK in the DVD you burn, too. The
> trouble
> is that the DVD won't be playable on a standard DVD player; you'll need a
> computer capable of playing the files that MythTV records. (It doesn't
> necessarily have to be a MythTV system itself, though.)
>
> --
> Rod Smith
> http://www.rodsbooks.com
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>

Whoa, thanks for the detailed replay.  I'll have to give this a shot.
However, it would be nice to be able to do this from my remote control - i.e.
through mythtv's menus.
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