[mythtv-commits] Ticket #4240: Recording length has doubled

[MythTV]

#4240: Recording length has doubled
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 Reporter:  tahoward at nc.rr.com  |        Owner:  janne   
     Type:  defect              |       Status:  assigned
 Priority:  blocker             |    Milestone:  0.21    
Component:  mythtv              |      Version:  head    
 Severity:  high                |   Resolution:          
  Mlocked:  0                   |  
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Comment(by bjm):

 When I first noticed this, I saw that the file sizes varied dramatically.
 This made me wonder if the quality min and max where misbehaving. However,
 after several tests I found that cutting the bitrate in half resulted in a
 file size that I would expect for the full bitrate although it might not
 be exactly 2 to 1.

 The reason the sizes varied is that with a bitrate twice the configured
 rate, "clean" signals with low motion would max out and fill the full
 bitrate.

 So, my default profile is 528x480 scaled bitrate of 2700.

 (2700 * 528 / 640) * 1024 / 8 bits = 285056bytes/sec.

 Times 1800sec should be 513100800/half-hour

 Times 3600sec should be 1026201600/hr

 The sizes of some recent 30 minute recordings are 1033069233, 1029005950
 and 1007334788.

 This suggests that it may be a simple error where something is multiplied
 or divided by 2 somewhere.

 This can be seen when recording MPEG4 with a bttv card but is probably
 easier to test by transcoding a test file to MPEG4.

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Ticket URL: <http://svn.mythtv.org/trac/ticket/4240#comment:9>
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