[MPlayer-DOCS] Interested in contributing case studies

[Mark Pilgrim]

On 10/20/06, Jeff Clagg <snacky at ikaruga.co.uk> wrote:
> Seems to me like gpac's MP4Box is more widely used.

I've used that, and it works just as well.  Is there any reason to
prefer one over the other?

> Call me pedantic, but your statement here is not literally true. You
> CAN use b_pyramid and weight_b, but they will have no effect when
> bframes is 0 or 1. Which, I think, is what you should say instead.

OK, you're pedantic.  And I've fixed it.

> You can use i8x8 (indeed most will since it's default), but it has no
> effect without 8x8dct.

Noted and fixed.

> > +  <emphasis role="bold">Mixed reference frames</emphasis>: in
> > +  <application>QuickTime</application> 7, each whole macroblock must use the
> > +  same reference, so you must specify
> > +  <option>-x264encopts nomixed_refs</option>.
> > ...
> > +  must specify <option>-x264encopts nobime</option>.
>
> Um, extraordinary claims require extraordinary proof. Please prove that
> this is actually true before including it in the guide.

Thank you for calling me on this.  Further testing confirms that
neither statement is true, and I have removed them from the latest
draft.

However, the b-frames and 8x8dct claims *are* correct.  Test cases:

http://diveintomark.org/tmp/bframes1.mp4
http://diveintomark.org/tmp/bframes2.mp4

http://diveintomark.org/tmp/no8x8dct.mp4
http://diveintomark.org/tmp/8x8dct.mp4

> I really have no idea what you are talking about here - first we have a
> bunch of x264 treatment, then you jump into autoaspect, which is not an
> x264 option.
>
> Also, are you saying Quicktime 7 doesn't support SAR/DAR?

Sorry, that is what I was talking about.  And no, QuickTime 7 does not
support a display AR different from the sample AR.  It just assumes
they're the same and plays the video stretched or squooshed.

I'll rephrase the paragraph to make this more clear.

> 1. What's the point in telling the user to specify a bunch of options
> (no8x8dct, nomixed_refs, nobime,..) that are DEFAULT anyway? IMO this
> just confuses people about what the defaults are, and what you do/don't
> have to specify. Also, bframes=1 should be recommended but it is not
> actually required for quicktime compatibility since bframes=0 (default)
> would also work.
>
> 2. Why don't you just use turbo=n on the first pass?
>
> > +  If you have a multi-processor machine, you can add
> > +  <option>threads=2</option> to the end of <option>-x264encopts</option>.
>
> More pedantry: anyone CAN add threads=2. Only some people will want to.
> (those with 2+ cpus, who compiled with pthreads support, and who care
> a lot about the speed gain,...)

Points taken and incorporated.  New draft coming soon, after I put the
kids to bed.

-- 
Cheers,
-Mark