[mythtv-users] mp4 videos smearing at high than 3x FF

Michael T. Dean mtdean at thirdcontact.com
Mon Oct 15 23:17:54 UTC 2012


On 10/15/2012 04:32 PM, Michael T. Dean wrote:
> On 09/12/2012 03:33 AM, Ian Evans wrote:
>> On Sun, Sep 2, 2012 at 11:51 PM, Ian Evans wrote:
>>> On Sun, Sep 2, 2012 at 4:58 AM, Ian Evans wrote:
>>>> I transcode a few SD shows to mp4 using a handbrake user job in .25.
>>>>
>>>> In the last few days I've noticed that if I fast forward at more than
>>>> 3x, the video starts to "smear". Crystal clear at 3x.
>>> Just a follow-up I played one of the files in VLC at is max of 4x and
>>> it was clear. In Myth at 5x, the frames clump together like a smudged
>>> oil painting.
>>>
>>> Again, this only happens with mp4 files. I can play an untranscoded
>>> mpg file at 100x+.
>>>
>> Wow, this problem is just driving me a little nuts. Has anyone here
>> seen anything like it? Here's the handbrakecli command used to
>> transcode the recordings:
>>
>> /usr/bin/HandBrakeCLI -i $MYTHDIR/$MPGFILE -o $newname -e x264 -q 20.0
>> -l 480 -a 1,2,3,4 -E faac -B 160 -R Auto -f mp4 --detelecine --decomb
>> -m -x b-adapt=2:rc-lookahead=50
>>
>> Any idea what could cause Mythtv to act like this on these files?
>
> IIRC, we play back at up to 3x by decoding faster, and above 3x, we 
> just skip around in the video, so it sounds like your key frames are 
> too far apart, so you're getting smearing when we skip.

Or, perhaps you've disabled the Deblocking filter:

Deblocking filter
When unchecked the deblocking loopfilter will be disabled
Disabling will significantly reduce the load on the CPU when watching HD 
H.264 but may significantly reduce video quality.

or just encoded with other-than-ideal options (though I know nothing 
about which encoding options are appropriate--I feel transcoding for any 
purpose other than making video work on a limited device, like a cell 
phone or similar that can only play a few types of video, is a waste)...

Mike


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