[MEncoder-users] Re: Tutorial?

[Gennady Ovcharov]

Ilya Zakharevich wrote:

>[A complimentary Cc of this posting was NOT [per weedlist] sent to
>Niki Kovacs 
><mencoder-users at mplayerhq.hu>], who wrote in article <4517FD76.3070505 at kikinovak.net>:
>  
>
>>My question may seem somewhat heretic, but I insist there is no troll 
>>intended. It is straightforward: is there any *comprehensive* tutorial 
>>about converting a DVD to DivX with MEncoder? Sort of a receipt that 
>>just works? I feel like someone who's been asking for a cooking receipt 
>>and having various pointers for courses about alimentary biochemistry as 
>>answers.
>>    
>>
>
>  [I must start with expressing my deepest gratitude to creator of this
>   wonderful piece of software.  However, I cannot negate that the OP
>   is fully justified in his doubts that that Mencoder needs a lot of
>   improvement to be as useful as the effort that went into its
>   creation deserves.]
>
>What the answers you got boil down is, IMO, just "mencoder is not
>designed for being easily useful".  Well, why not turn the discussion
>around and try to find regions where mencoder may be improved?
>
>(Keep in mind that my experience with mencoder is very short: one
>"kinda completed" DVD rip to XVID.  So the problems I see are very
>focussed on what I actually used.)
>
>Let me start with major problems with documentation:
>
>  0) It is unreadable; but this is not easy to fix, so let's delay this ;-)
>
>  1) xvidencopts (do not know whether discussing them belongs here, or
>     better be delegated to something XVID specific)
>
>     1a) 2pass processing: absolutely nothing is said about WHICH
>	 options are ignored with pass=1, and which with pass=1:turbo;
>	 thus one does not know which one could be changed between
>	 pass1 and pass2;
>
>     1b) bitrate: it is not clear whether it sets VIDEO BITRATE and
>	 VIDEO SIZE, or overall bitrate and overall size;
>
>     1c) interlacing option: I found no clue what should be the
>	 relationship of this to, e.g., -vf pullback;
>
>  2) What mencode is outputing on TTY is not documented.
>
>     2a) E.g., I see something like:
>
>Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough
>VDec: vo config request - 720 x 480 (preferred colorspace: Mpeg PES)
>Could not find matching colorspace - retrying with -vf scale...
>Opening video filter: [scale]
>The selected video_out device is incompatible with this codec.
>Try adding the scale filter, e.g. -vf spp,scale instead of -vf spp.
>VDecoder init failed :(
>
>	 How should I know whether it is an error, or just a normal
>	 process of enumeration of possible input options?  Especially
>	 confusing if I HAVE -vf scale specified...
>
>     2b) E.g., I see something like:
>
>Pos:3299.0s  79104f (692%)  7.33fps Trem:-153min 218mb  A-V:0.003 [3684:159]
>Pos:3299.1s  79105f (692%)  7.33fps Trem:-153min 218mb  A-V:0.003 [3684:159]
>Pos:3299.1s  79106f (-692%)  7.33fps Trem:   0min   0mb  A-V:0.005 [3684:159]
>Pos:3299.2s  79107f (-692%)  7.33fps Trem:   0min   0mb  A-V:0.006 [3684:159]
>Pos:3299.2s  79108f (-692%)  7.33fps Trem:   0min   0mb  A-V:0.009 [3684:159]
>
>         Nothing is documented.  OK, I can guess what the 1st, 2nd and
>         4th fields mean.  I can kinda guess the semantic of A-V
>         (although the details of what is done to establish
>         video-audio sync are not discussed anywhere).  But what is
>         that 692%?  And Trem?  And 218mb? And [3684:159]?
>
>  
>
[3684:159]
3684 - current video bitrate
159 - current audio bitrate

>	 OK, looking at how 692 goes to -692, I can guess that it is
>	 some bug related to too short a datatype used; but otherwise,
>	 I have no clue...
>
>  3) I got an AVI file which plays in Mplayer, but DivX will play it
>     only up to 1h25m out of 1h52m (total size about 1.3GiB).  There
>     are some vague hints scattered in documentation at shortcomings
>     of AVI format, and that sometimes only Mplayer will be able to
>     read the bastardized AVI file.  Do I get any feedback on this
>     from mencoder?
>
>  4) I must join the OP that there is no discussion of overall
>     architecture of the process of Video Conversion.  This is just
>     guesswork on my part:
>
>	A) Fundamental differences between supported video formats are:
>
>	   frame rate, CFR vs VFR, frame size, constant frame size vs
>	   variable frame size, interlacing, methods if inclusing of
>	   autogenerated frames, methods of creation of black border,
>	   CBR vs VBR (what else)?
>
>        B) When doing conversion, user should decide on the following
>	   types of handling these differences: list???
>
>	C1) The following differences can be transparently handled by
>	    Mencoder: list???
>
>	C2) Mencoder can apply some heuristics to handle the following
>	    differences: list???  To do this, you need to specify
>	    following options???
>
>	C3) The following differences can be reported by Mencoder: list???
>
>	C4) The following differences detected by Mencoder can be
>	    handled by the following types of options: list???
>
>	C5) Currently, the following differences cannot be detected,
>	    and need a visual inspection: list???  When vgrepping,
>	    look at the following features: list???  If you detect X,
>	    specify following options to handle it: list???  Also see
>	    documentation of the following options: list???
>
>     Since without understanding the general architecture, the
>     scrupulous discussion of separate options is not very fruitful, I
>     think this area deserves to be addressed in the docs.
>
>Thanks,
>Ilya
>
>_______________________________________________
>MEncoder-users mailing list
>MEncoder-users at mplayerhq.hu
>http://lists.mplayerhq.hu/mailman/listinfo/mencoder-users
>
>  
>