[mythtv-users] Transcoding issues. SD is fine, HD fails

[Neil Salstrom]

On Fri, Apr 16, 2010 at 1:58 AM, belcampo <belcampo at zonnet.nl> wrote:
> Neil Salstrom wrote:
>>
>> On Thu, Apr 15, 2010 at 12:46 PM, belcampo <belcampo at zonnet.nl> wrote:
>>
>>> Yes I prefer an original one
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>>
>> Ok, here is the original and transcoded.  Again, HDHomerun (ATSC) and
>> 720p (720_60)
>>
>> http://www.mediafire.com/?dwwd1yhyzdf
>> http://www.mediafire.com/?dnowzrnkmuk
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>
> I'm using an 'old' ffmpeg version, because current are more or less broken.
>
> Using FFmpeg version SVN-r17923 with parameters:
> ffmpeg -y -i 1021_20100415191100.mpg -acodec libfaac -ab 128k -ar 48000 -ac
> 6 -vcodec libx264 -threads 0 -b 2672k -deinterlace -flags +loop -coder 1
> -refs 2 -deblockalpha 0 -deblockbeta 0  -partitions
> +parti4x4+partp8x8+parti8x8+partb8x8 -me_method umh -subq 4 -me_range 16
>  -flags2 +dct8x8+mixed_refs -cmp +chroma -bf 0 -b_strategy 1 -g 250
> -keyint_min 25 -sc_threshold 40 -maxrate 3500k -qmin 22 -qmax 26 -croptop 10
> -cropbottom 6 -cropleft 144 -cropright 144 -aspect 992:704 -f mpegts
> 1021_20100415191100.ts
>
> and remuxing that with tsMuxerGUI, because also this ancient version can't
> write compliant MPEG-TS streams.
>
> Alternatively you can use -f matroska, you'll save one step.
> BTW. -f mp4 produces sync problems at least with this version of ffmpeg.
>
> You can get the crop-parameters with:
> mplayer 1021_20100415191100.mpg -vf cropdetect
>
> I get
> filesize 28852548 compared to 57585490 of the nuv-file, which is 50% better.
>
> Leaving out the 'crops'
>
> I get 30041272 which is 48% better, and encodes 9-10% slower.
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Thanks, I'll give this a try but I'm still wondering why Mythtv does
this in the first place and what can be done to prevent it.