[mythtv] Re:Transcoding pvr-250 files

Vinton Coffman vintonc at redzone.com
Sat Aug 30 13:48:41 EDT 2003

So I updated  mythtv CVS (Aug 30 @ 1:00 a.m. EDT) with the -C option to 
overwrite the changes I had made and pick up the commits Isaac had 
made.  Here's the latest results.

None of the settings have changed for capture or transcoding (see my 
first post for the exact settings).
I edited the cutlist (some channels seem to lend themselves to 
automatic commercial detection better than others).  It was Boston 
Public (1 hour show).

The good:  The audio seems to match the original.  The changes I tried 
earlier seemed to cause the audio pitch to be lower.  The commercials 
have be cut out.  The video seems really good too.  None of the odd lip 
movements described above.

The odd:  The transcoded file isn't significantly different in size.  
Saving only 14.35 MB after cut out all of the commercials!  The files 
were captured at 4/8 Mbps bitrate/peak bitrate 720 x 480 and transcoded 
to 4 Mbps mpeg-4 (see first post for all settings) at 640 x 480.  
Shouldn't it save 25% - 30% by removing 15 - 20 minutes of a 60 minute 

for the 1 hour show.
# ls -la |grep '20030829210000_20030829220000'
-rw-r--r--    1 mythtv   mythtv   2094915330 Aug 30 11:45 
-rw-r--r--    1 mythtv   mythtv   2109267904 Aug 29 22:00 
-rw-rw-r--    1 mythtv   mythtv      32495 Aug 30 01:31 

similar results for 30 minute show.  More precise timing.
Original length 29:56
edited length 21:33 (timed while watching original w/cutlist)
displayed total elapse time 10:44
ls -la |grep '1024_20030829220000_20030829223000'
-rw-r--r--    1 mythtv   mythtv   980055361 Aug 30 12:13 
-rw-r--r--    1 mythtv   mythtv   1052573632 Aug 29 22:30 
-rw-rw-r--    1 mythtv   mythtv      33286 Aug 30 01:31 

The same:  Elapse time still not right.  Skipping forward one 30 second 
increment yields about a 62-63 second skip real time but is indicated 
as a 30 increment in the timer.  I would expect this since the total 
elapse time is 23:02 instead of ~47:00.

Let me know if you need more info or want something tested.

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