From: Zach Bartels <no@...>
Date: 2010-02-15T05:55:07+09:00
Subject: Theory behind proof of concept for  automatic IVTC decimation

Hi again,

This relates to my video editing project.   Now that I have a list of
patterns I can (for sake of ease) hard code into my program I have
been googling about  file operations.   But I have not been able to
find an answer to my question..

This post originally started as a question on file operations, but
seems to have evolved into an outline for  my proof of concept program
and what I'd like it to do / how it should work..

Again not asking anyone to code the whole thing for me..  But  for
questions mentioned in the post,  or where it seems I don't understand
how something works,   pointing me in the right direction with links
to  tutorials and such,  or  general advice on better ways to do
something,  or if you are inclined to give practical examples on how
to achieve my goals,  it would be greatly appreciated.


I am interested in how you would do several different things,  such
as:

Start reading a file at a specific line,  that is not guaranteed to be
the same line every time..   I.e  while the  [MATCHES]  section in  a
Yatta Project file might start on  line 300 in one case,   in another
where the user has done different tasks (more, or less)  there may be
more or less information stored,  and the [MATCHES] section might not
be on line 300  every single time..

[MATCHES] is the header that proceeds  the list of matches for the
frames Yatta is working on.   So  I assume  I need to  search the file
and stop at the first occurance of  [MATCHES].

Then start reading line by line, one at a time.    Each frame is
listed on one line, with one character for the pattern..  So  a
parttern of  CCCNN would be presented as 5 lines in the text file like
so:

C
C
C
N
N

I am supposing I should iterate through each line,  and  store the
results in an array?   I think this is best,  because  array indices
also start with 0,  just like video frame counts.    Frame 0  would
amount to  Array[0].   Easy  to keep track of..      If I understand
things right, I don't need to worry about getting the frame count
beforehand and  creating a  pre-defined  matrix  with  "X number of
spots" to fill..  I can just expand the array on the fly and the
appropriate index number will be given?

(Array.push?)


So the question is,  how do I open the yatta project file (just a text
file AFAIK)   then search until [MATCH]  is found -  then start
counting on the actual  line the pattern  data was started on?   There
are no blank lines between [MATCH]  and the first frame.   However
after the last frame in the video  there IS a white space,   and then
the next section header [POSTPROCESS]  occurs.

So I guess I would want it to iterate through all  lines  AFTER the
line  [MATCHES]  is found on,  and then stop  iterating and pushing
data into the array  at the first  blank line it  comes across  (which
is after the last frame in the video).

An abbreviated structure of the section would look like this

[MATCHES]
c
c
c
n
n
c
c
c
n
n
		<--  note the white space / blank line
[POSTPROCESS]


The hope is I end up with an array,  containing the following (using
the above section example):

MyArray  [c, c, c, n, n, c, c, c, n, n]   which in order of index
would be...   0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10   -  and would exactly
match the frame count  numerations..  MyArray[0]  ==  Frame 0 of my
video file..      Sound correct so far?

Meanwhile..  storing the patterns to match against..   Maybe I am
overcomplicating it,  but I thought about making  object instances
(Pattern 1, Pattern 2, etc)  that were arrays themselves  and then
using a loop to  find the pattern the section matches..

Of course how would you tell Ruby to compare only  5 individual chunks
of the array (0-4, 5-9, 10-14, etc) incrementing by 5 each time so it
doesn't lose its place,  backtrack, etc and counts up properly?    I
know how to make an  iteration loop to loop through all possible
patterns until a match is found -  but not how to specify  sections of
an array,  much less  doing so in a manner that I don't mess up and
compared 0-4,  and then 1-5,  or  skip/miss  things in other ways.

Would it be simpler to simply  read in the patterns  5 lines at a
time,  keeping each 5 line "chunk" of data  inside  an array as
mentioned before,  but  using the object method to reference it,  and
store  all objects generated inside a master  array ?

Like:

MasterList:  an array holding a list of all items generated from
reading the file.

Section1:  a 5 frame pattern from the file comprised of  frames 0 - 4
Section2: same as above  but  frames 5 - 10 
ad nauseum

I suspect I would use object references  throughout  as well,  and not
necesarrily  rely on  array indices, to keep things simple  since by
breaking it up into multiple arrays you could lose track of the real
frame numbers..


Well I'm having too many ideas now..  So I should probably cut this
short.  Sorry to be so long winded,  but hopefully  everyone gets an
idea of what I am aiming to do..    More than anything  I just need an
answer on   the  file manipulation problems,   once I can get the data
into memory, the rest should be pretty simple for me to  play around
with and find the best method to use.

-Zach