[mythtv-users] MythTv 0.23 recording resolution and playback issues

Raymond Wagner raymond at wagnerrp.com
Wed May 19 14:22:54 UTC 2010

On 5/19/2010 08:18, Ebsen, Mike P. wrote:
> The 10.04 release seems to always record at 1920x1080 resolution 
> independent of the broadcaster's source format.  Old TV shows, like 
> Hogan's Heros, that are still being broadcasted at a very grainy 
> 548x480 are small fields of video information with large black unused 
> bands on top, bottom, left and right edges of the 1920x1080 *.mpg 
> recorded file.

Your 2250 is a digital tuner.  The recordings it makes are /exactly/ 
what is being broadcast.  MythTV is not altering the stream in any 
manner.  If you plug in a QAM-capable TV, you will see the exact same thing.

> Another detriment of the 10.04 resolution issue is recorded file 
> sizes.  Recording the same program on the 9.10 and 10.04 with the same 
> quality setting (Normal) results in drastically different file sizes.  
> The older 9.10 release could record an old TV show at a data rate of 
> 780 MByte/half hour.  The latest 10.04 release records the same show 
> at a rate of 3.3 GByte/half hour (and a whole bunch of dark pixels 
> surrounding the relatively small image in the middle).

The quality settings on a digital tuner do absolutely nothing.  MythTV 
will store the stream exactly as it is received, and will do no 
additional processing.

>   I thought one of the attributes of the latest 10.04 release was the 
> newest H.264 codecs that were both faster and more efficient at video 
> compression.  My observations don't align with these assumptions.

MythTV does not use H.264 for video compression.  It can only use MJPEG 
and ASP, and then only for analog framegrabbers.  The claim was that a 
sync of the internal ffmpeg library prior to the release of 0.23 brought 
a better optimized H.264 video decompressor, that is roughly 15% faster 
than before.  This is irrelevant because everything you ever record off 
that 2250 will be MPEG2.

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