[MEncoder-users] How does one interlace progressive content?

[Reimar Döffinger]

Hello,
On Wed, Aug 15, 2007 at 12:38:59PM +0200, Pierre Catello wrote:
> 2007/8/14, Reimar Döffinger <Reimar.Doeffinger at stud.uni-karlsruhe.de>:
> > What means "encoded as 576 interlaced"? They could have simply used the
> > interlaced motion estimation and interlaced dct, that works perfectly
> > fine for progressive data, it just wastes lots of bits. That kind of
> 
> Of course encoding as interlaced means processing the source as separated
> fields and hence using interlaced-aware dct etc.
> You're playing on words... If "encoded as interlaced" is not clear, then
> lavc ilme, idct options are not clear, xvid interlaced encoding is not
> clear, x264 interlaced encoding is not clear etc.

No, I am not only playing with words, the original poster asked about
how to "make it interlaced", and I really don't think he meant what ilme
and ildct. Those do not make anything interlaced, they just use an
encoding method optimized for interlaced material. If you don't care
about bitrate/quality, you can use them for progressive material or you
can leave them out for interlaced material.
That is not even considering things like pullup that some people do and
some don't consider as interlacing.

> thing can happen easily if you have the usual person without a clue
> > using an encoder that is crap (and looking at some of my DVDs, there are
> > a lot of both in that field - but with most using dual layer DVDs
> > that's not really much of a problem).
> 
> You're wrong. Interlaced encoding can arise from other reasons, and with
> people who do have clues about video processing.
> But, you, do you have any clues about industrial processes (in particular
> DVD production), or broadcast processes. Do you really think that someone is
> "manually encoding" each content that you find on a DVD or a DVB stream ??
> You of course know that in many cases hardware encoder are used, or single
> pass real time encoder in the case of DVB, without information about the
> incoming or source stream.

DVB is something completely different, it can actually have realtime
constraints, though honestly if it was really wanted you could probably
change the process to use two-pass encoded stuff for at least 50 % of
content.
And in either case, there is no need for manual encoding, it only has to
be known if the source is progressive or interlaced - especially for
DVDs the effort of that compared to the effort the sometimes put into
menus etc. should be quite small (excluding DVDs where interlaced and
progressive is mixed in one title, which I haven't had so far).
But of course I do know about "industrial processes", but even if the
decisions made make perfect economic sense and the results are far in
the "good enough" range (not always the case either), that alone doesn't
make it not crap (from a technical standpoint) - especially using
hardware encoders for DVDs is not really such a great idea at least
nowadays.
Btw. there is one reason why wasting bits on DVDs actually _does_
matter - the reason is that your data rate is limited to 1x DVD speed,
which can end up hurting video quality especially with lots of
high-quality audio streams.

Greetings,
Reimar Döffinger