Re: Theory behind proof of concept for automatic IVTC decimation

On Sunday 14 February 2010 02:55:07 pm Zach Bartels wrote:

> 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..

In other words, you want to start reading once you get to [MATCHES].

> [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].

Yes.

There shouldn't be anything hard about this. Read each line of the file until 
you find one that matches [MATCHES]. You might look at the each_line method.

> 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?

Probably. It depend very much what you want to do with them.

> 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?)

Yes.

> 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 let me guess -- each header line will be [SOMETHING], right?

So you could just do this:

open 'filename' do |file|
  lines = file.each_line
  line = lines.next.chomp
  until line == '[MATCH]'
    line = lines.next.chomp
  end
  # Now you're at the MATCH line.
  array = []
  until line =~ /^\s*$/
    line = lines.next.chomp
    array.push line
  end
end

I'm sorry, it was way easier to just do that than to try to explain how to do 
it.

> 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..

I have no idea why you would want to do that. But at least get the above 
working before you overcomplicate it.

What I would do is use a regex to look for anything that looks like [FOO], and 
store their contents (as arrays) in a hash. Then you would be able to pull out 
the MATCHES section by doing some_hash['MATCHES'].

Even better -- this file looks suspiciously like an INI file. If it is, find a 
gem to do it for you.

> 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?

Now you've lost me. What's special about 5?

> 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.

Look at Array#splice. Better yet, go to ruby-doc.org and read up on the Array 
documentation.

> 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

Or you could stick them in a giant array and do something like each_slice -- 
that one is in the Enumerable module, which is included in Array.

> 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..

Erm... do you need the real frame numbers? That's easy enough to add. 
Something like, say you have a variable called 'array' that's a raw list of 
frames, and you want a list of 5-element frames which each contain the frame 
number... Try this:

array = array.each_with_index.each_slice(5).to_a