[MEncoder-users] Happy with encoding results but wish better understanding

[Grozdan]

On Wed, Apr 21, 2010 at 2:49 PM, Sue Morton <zytb8phzgv at snkmail.com> wrote:
>
> Hello RC,
>
>> vhq is mbd=1, so a conflict with mbd=2 in there.
>>
>> You would get the most help from adding "trell".  You might be able
>> to squeeze some more quality out of it using vlelim=-4:vcelim=7,
>> and perhaps nr=.
>>
>> I would think you'd be happy with yadif=0 and drop mcdeint,framestep=2,
>> but if performance is no issue, no reason not to keep it.
>>
>> Additionally, you'll get a big quality improvement/size reduction if you
>> crop the black borders and noise around the edges, but then it will
>> display at least a bit differently on your player, so be a bit careful.
>> If you go that way, make sure you use final dimentions that are
>> multiples of 16 for progressive, and 32 for the height when the video
>> will be interlaced.
>
> Thank you for the feedback, very much appreciated!  I will look into your
> suggestions, in detail, as soon as I have time (probably not until the
> weekend).
>
> I do already have 'trell' specified, it's right after the mbd=2 parameter --
> so I've got your suggestion in place already :-)
>
> What does 'trell' do vs. leaving it out, such that it 'helps'?  And what is
> the 'help' it gives (less motion artifacts in video, helps sync video with
> audio, etc.)?  I've done a lot of reading, and I'll go back to read the man
> pages again, but I'm not really understanding what these parameters 'do' --
> a pretty learning curve is still ahead of me I think :-)

trell is short for Trellis Quantization which helps both increase
quality and save bits
http://en.wikipedia.org/wiki/Trellis_quantization

Also, you may want to use cmp=3 and subcmp=3 which will select a
different and better (SATD Hadamard) transform comparison function for
full and subpixels, further increasing quality.
http://en.wikipedia.org/wiki/SATD

>
> I'll post back when I've had a chance to look into your suggestions.  In the
> meantime, if you (or anyone) could explain a bit what any of these
> parameters are supposed to do, it would be of help to me.
>
> Thank you again.
>
> Sue
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