[mythtv-users] Re: DVD recording sync issues with PVR 350

Michael T. Dean mtdean at thirdcontact.com
Fri Jun 3 19:01:23 UTC 2005

John Goerzen wrote:

>On Fri, May 06, 2005 at 02:02:37AM -0700, John Kondis wrote:
>>out ProjectX has a CLI (command line interface).  It's
>>a little tricky to figure out, but this now works
>>great for me:
>>java -jar <compiled_projectX_file> -c
>><projectX_ini_file> -n <output_stream_basename> -o
>><dir_to_put_streams> <input_nuv_file>
>Where did you find the docs on the CLI?
Run Project X from a shell (even just starting the GUI) and look at the 
output.  The first 30 lines or so give you the command line usage.

>I am trying to find a way to squeeze down a 5.5MB PVR-350 recording so
>it fits on a single DVD.
Wow.  I've been fitting 5 hours of TV (with commercials cut) on a single 
DVD--with as much as 10MB to spare--I couldn't have set my recording 
parameters better if I had tried.

>Originally, I used replex to demux it, then ran tcrequant on the result.
>It made it smaller, but I had serious sync issues.
Yep.  Happens on all the recordings I've seen from the local cable 
company--up to 5 seconds off at the end of a 1 hour recording.  Some 
(fortunate) people only see it with recordings off a VCR.  My DISH 
network recordings only have about 1/30th second offset after an hour, 
so using replex "averages" it out to unnoticeable offset.

>I thought I might use ProjectX to demux it, then rnu tcrequant on that,
>then use mplex on it.  Tried that, but the generated DVD wouldn't play.
>Something is weird.
Since there are many steps in making a DVD, it's possible that one of 
the other steps in the process is failing.  Each step has dependencies 
on previous steps, so when you change the process, it's likely to break 
until you find out how to adapt the steps following the new step in the 
process...  In other words, without seeing the whole process--step by 
step and command by command (and explicit version numbers of each 
command)--there are way to many variables to guess what's causing the 

However, if you get the process working, I highly recommend you watch 
the DVD recording before deleting the original--especially if the 
original is valuable content.  I've noticed that although Project X will 
generally improve the sync on PVR-x50 recordings, you will get pops and 
cracks where it skips audio and in some portions of the video, the sync 
will be offset.  For example, in a 1-hour recording that showed a sync 
difference of 5sec at the end without Project X, after processing with 
Project X, sync was basically correct at the beginning, the middle, and 
the end; but when I watched the video, I noticed some areas (2 or 3 
times in the recording) where sync was off (just barely enough to 
notice--maybe 1/10sec) for up to 5 or 10 seconds.

Oh, and don't even think about processing a recording whose sync is 
fairly close--I did (just in case) and it made the sync worse than the 
original (added noticeable offsets 2 or 3 times as described above).  
So, for my DISH recordings, I "fix" the sync using replex to average it 
out.  For cable recordings, I use Project X--but only because I haven't 
found a better tool.

>Do you know if there is a command-line option to ProjectX that will
>cause it to re-encode video at a bitrate of my choosing?
Everything I've seen about Project X says it does demux well, but 
everything else (including re-encoding) not so well--i.e. Project X only 
fixes A/V sync when you demux; it won't fix sync if you re-encode.  I'd 
work on figuring which part of the process is failing.



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