[mythtv-users] How to transcode to SD within mythtv - system too slow to play HD

[Zig]

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On 12/10/2013 7:42 PM, A. F. Cano wrote:
> On Mon, Dec 09, 2013 at 04:40:29PM +0000, John Pilkington wrote:
>> ...
>> First; why are you recording HD?  Is that the only version that is
>> available to you?
> As other people in another part of this thread have pointed out, that
> is the only choice I have.  I use an antenna and the material comes
> in HD.
>
>> Second; it looks as if your transcode isn't working.  Here in the UK
> Interestingly, when I tried to transcode manually with the command you
> gave below, mythffmpeg was not installed.  I installed it via aptitude.
> We'll see if this has any effect next time I record a show.
>
>> a good-quality SD recording stripped to just the video and one audio
>> channel comes at around 1.4 GB per hour; I can usually get 3
>> one-hour shows onto a DVD, with no re-encoding.
> It looks like the default parameters cause extreme lossy compression.
>  From 5.2G to 254M just by specifying 960 x 512 (1/2 the height and 1/2
> the width).  Obviously this is not the optimal setup.  I can watch other
> videos full screen (with mplayer) and they look much better even though
> they are of lower resolution.  I'll have to try with the -b:v and -b:a
> parameters.
>
> 254M Dec 10 17:45 2131_20131127030000.mpg
> 5.2G Nov 26 23:00 2131_20131127030000HD.mpg
>
>> I have done conversion from HD to SD like this:
>>
>> mythffmpeg -threads 2 -v verbose -i infile.mpg -target pal-dvd -b:v
>> 6000k -s 720x576 -acodec mp2 -b:a 256k -ac 2 -aspect 16:9
>> outfile.mpg
> This is what I tried:
>
> mythffmpeg -threads auto -v verbose -i 2131_20131127030000HD.mpg -s
> 960x512 -acodec mp2 -ac 2 -aspect 16:9 2131_20131127030000.mpg
>
> Also ran mythcommflag manually, but it finished quickly with an
> error.  It might be because the file was quite corrupted because
> of reception problems.  When I tried to watch it within myth, it
> gave a long list of errors and exited back to the "watch recordings"
> window, which incidentally still says that it's 1080i, so something
> didn't get updated properly.
>
>> and on my 2006-vintage laptop throughput is around 30 fps.  Input
>> filesize (all streams) around 3 GB per hour, output filesize around
>> 2 GB per hour.
> The above transcode took about 2:45 for the 1 hour show.
>
>> Obviously this may need modifying for location, and maybe omit
>> --threads or set it to 1, but it should give you a start if no-one
>> comes up with a Myth-based solution.  Rename the input file to
>> xxxHD.mpg, use xxx.mpg as output and when done use mythcommflag
>> --rebuild --file xxx.mpg to fix the database.
> Thanks a bunch.  At least now I can watch the highly pixelated shows
> with mplayer and the slow cpu can keep up.
>
> One other question.  I deleted a test recording from within myth.  It
> says that deleting the show from the list does not remove the file.
> Is there a way to manually remove recordings completely? the mpg file,
> the data that gets stored in the database, etc...  I'm aware that there
> is some expiration time, but since the disk is not full, myth is
> apparently not removing shows.
>
> Thanks.
>
> Augustine
>
>
That message about the deletion just "deleting the listing and not 
removing the file" sounds like you deleted from the "Previous 
Recordings" screen and not the "watch recordings" screen.  Deleting from 
the "watch recordings" screen will delete the actual file.

Deleting from the "Previous Recordings" screen just deletes the entry in 
the "previous recordings" data base so that MythTV will no longer think 
that that show was ever previously recorded.  So if Myth is asked to 
record that show again it will think that it was never previously 
recorded and will thus record it again.  Hence the message about just 
"removing the entry and not the actual file".
Ziggy
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