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• avformat/http: support relative url redirection

  4 juillet 2013, par Zhang Rui

  avformat/http: support relative url redirection
  see also http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-17#section-9.5
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavformat/http.c

• Programming Language Levels

  20 mai 2011, par Multimedia Mike — Programming

  I’ve been doing this programming thing for some 20 years now. Things sure do change. One change I ponder from time to time is the matter of programming language levels. Allow me to explain.

  The 1990s
  When I first took computer classes in the early 1990s, my texts would classify computer languages into 3 categories, or levels. The lower the level, the closer to the hardware ; the higher the level, the more abstract (and presumably, easier to use). I recall that the levels went something like this :

  • High level : Pascal, BASIC, Logo, Fortran
  • Medium level : C, Forth
  • Low level : Assembly language

  Keep in mind that these were the same texts which took the time to explain the history of computers from mainframes -> minicomputers -> a relatively recent phenomenon called microcomputers or "PCs".

  Somewhere in the mid-late 1990s, when I was at university, I was introduced to a new tier :

  • Very high level : Perl, shell scripting

  I think there was some debate among my peers about whether C++ and Java were properly classified as high or very high level. The distinction between high and very high, in my observation, seemed to be that very high level languages had more complex data structures (at the very least, a hash / dictionary / associative array / key-value map) built into the language, as well as implicit memory management.

  Modern Day
  These days, the old hierarchy is apparently forgotten (much like minicomputers). I observe that there is generally a much simpler 2-tier classification :

  • Low level : C, assembly language
  • High level : absolutely every other programming language in wide use today

  I find myself wondering where C++ and Objective-C fit in this classification scheme. Then I remember that it doesn’t matter and this is all academic.

  Relevancy
  I think about this because I have pretty much stuck to low-level programming all of my life, mostly due to my interest in game and multimedia-type programming. But the trends in computing have favored many higher level languages and programming paradigms. I woke up one day and realized that the kind of work I often do — lower level stuff — is not very common.

  I’m not here to argue that low or high level is superior. You know I’m all about using the appropriate tool for the job. But I sometimes find myself caught between worlds, having the defend and explain one to the other.

  • On one hand, it’s not unusual for the multitudes of programmers working at the high level to gasp and wonder why I or anyone else would ever use C or assembly language for anything when there are so many beautiful high level languages. I patiently explain that those languages have to be written in some other language (at first) and that they need to run on some operating system and that most assuredly won’t be written in a high level language. For further reading, I refer them to Joel Spolsky’s great essay called Back to Basics which describes why it can be useful to know at least a little bit about how the computer does what it does at the lowest levels.
  • On the other hand, believe it or not, I sometimes have to defend the merits of high level languages to my low level brethren. I’ll often hear variations of, "Any program can be written in C. Using a high level language to achieve the same will create a slow and bloated solution." I try to explain that the trade-off in time to complete the programming task weighed against the often-negligible performance hit of what is often an I/O-bound operation in the first place makes it worthwhile to use the high level language for a wide variety of tasks.

    Or I just ignore them. That’s actually the best strategy.

• FFMPEG 2 Videos transcoded and side by side in 1 frame ?

  3 mars 2016, par dcoffey3296

  I have 2 videos : HEADSHOT.MOV and SCREEN.MOV. They are both large files and I am looking to both shrink (size, bitrate, etc) and place these two side by side in the same, very wide, video frame. The end result would be that when you play the output_video.mp4, you would have a very wide frame with both videos in sync and playing at the same rate.

  Here is the syntatically incorrect version of what I am trying to do :

  ffmpeg -i HEADSHOT.MOV -t 00:02:00 -acodec libfaac -ab 64k -vcodec libx264 -r 30 -pass 1 -s 374x210 -vf "movie=SCREEN.MOV [small]; [in][small] -an -r 30 -pass 1 -s 374x210 overlay=10:10 -t 00:02:00 [out]" -threads 0 output_movie.mp4

  In the above example, I also tried to set a test movie duration for 2 minutes which raises another question, What is the best way to handle 2 movies of varying length (if they are close) ?

  The resources I have found helpful so far are :

  Multiple video sources combined into one and

  http://ffmpeg.org/ffmpeg.html#overlay-1

  Any help/advice is greatly appreciated. I am having trouble with the FFMPEG syntax ! Thank you !