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• Started Programming Young

  6 septembre 2011, par Multimedia Mike — Programming

  I have some of the strangest memories of my struggles to jump into computer programming.

  Back To BASIC
  I remember doing some Logo programming on Apple II computers at school in 5th grade (1987 timeframe). But that was mostly driving turtle graphics. Then I remember doing some TRS-80 BASIC in 7th grade, circa 1989. Emboldened by what very little I had learned in perhaps the week or 2 we took in a science class to do this, I tried a little GW-BASIC on my family’s “IBM-PC compatible” computer (they were still called that back then). I still remember what my first program consisted of. Even back then I was interested in manipulating graphics and color on a computer screen. Thus :

  10 color 1
  20 print "This is color 1"
  30 color 2
  40 print "This is color 2"
  ...
  

  And so on through 15 colors. Hey, it did the job– it demonstrated the 15 different colors you could set in text mode.

  What’s FOR For ?
  That 7th grade computer unit in science class wasn’t very thick on computer science details. I recall working with a lab partner to transcribe code listings into a computer (and also saving my work to a storage cassette). We also developed form processing programs that would print instructions to input text followed by an “INPUT I$” statement to obtain the user’s output.

  I remember there was some situation where we needed a brief delay between input and printing. The teacher told us to use a construct of the form :

  10 FOR I = 1 TO 20000
  20 NEXT I
  

  We had to calibrate the number based on our empirical assessment of how long it lasted but I recall that the number couldn’t be much higher than about 32000, for reasons that would become clearer much later.

  Imagine my confusion when I would read and try to comprehend BASIC program code I would find in magazines. I would of course see that FOR..NEXT construct all over the place but obviously not in the context of introducing deliberate execution delays. Indeed, my understanding of one of the fundamental building blocks of computer programming — iteration — was completely skewed because of this early lesson.

  Refactoring
  Somewhere along the line, I figured out that the FOR..NEXT could be used to do the same thing a bunch of times, possibly with different values. A few years after I had written that color program, I found it again and realized that I could write it as :

  10 for I = 1 to 15
  20 color I
  30 print I
  40 next I
  

  It still took me a few more years to sort out the meaning of WHILE..WEND, though.

• ftp: enhanced status code handling

  29 mai 2013, par Lukasz Marek

  ftp: enhanced status code handling
  Reimplementation of ftp_status function.
  
  New version requires explicit list of expected codes.
  
  It flush data connection input before sending a command
  
  and blocks until expected result appears.
  

  • [DH] libavformat/ftp.c

• ffmpeg output seeking not accurate even after -i [closed]

  3 septembre 2023, par hl037_

  In the documentation of ffmpeg, it is stated that if -ss is passed after -i, then it is frame accurate (Other questions are for -ss before -i).

  


  Here is my command :

  


  ffmpeg -i vid.mkv -ss 53 -codec copy test.mkv -y 


  


  However, it is still not accurate, and seems to jump to the nearest keyframe. Am i missing something ?

  


  Note : the problem only occurs when the video steam is copied. If reencoded or discarded, it works as expected

  


  Note2 (As I am doing other tries) : There are also strange things with audio :

  


  ffmpeg -i vid.mkv -ss 53 -codec copy test1.mkv -y 
ffmpeg -i vid.mkv -ss 54 -codec copy test2.mkv -y 
ffmpeg -i test1.mkv -vn -c:a copy test1a.mkv -y
ffmpeg -i test2.mkv -vn -c:a copy test2a.mkv -y


  


  

  • test1.mkv is reported to be the right lenght, but the first frame correspond to the frame at 0:50 in original (end is good)

  


  • test2.mkv is reported to be the right lenght, but the first frame correspond to the frame at 0:55 in original (end is good)

  


  • test1a.mkv is the expected audio (starts at 0:53 of the original)

  


  • test2a.mkv is the expected audio (starts at 0:54 of the original)