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• 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.

• Arguments set but not used in GPAC

  30 avril 2022, par M faiz zeeshann

  I am trying to do the tiling of a 360-degree video with the following command.

  


  MP4Box -dash 1000 test.mp4 :"desc_as="

  


  it creates an MPD file but without tiles and gives the following errors.

  


  Arg segdur set but not used,
Arg mpeg set but not used,
Arg dash set but not used,
Arg srd set but not used,
Arg 2014 set but not used,

  


• rtmp module stream do not , how to solve that ?

  24 avril 2019, par Duxo

  I have some problem with configuring nginx+rtk-©module.
  I need to stream a video from IP camera to web-site. I use MPEG-DASH.My server configuration is lower. Files .m4a, .m4v are creating and I also have stream.mpd file. But in browser it doen’t work, inifinity loading. some logs from dash.js
  

  Time: 0
  
  dash.all.js:2:10794
  
  Array(6) [ {…}, {…}, {…}, {…}, {…}, {…} ]
  
  dash.all.js:2:10818
  
  Index for time 0 is -1
  
  dash.all.js:3:8722
  
  Checking for stream end...
  
  dash.all.js:3:8722
  
  Live never ends! (TODO)
  
  dash.all.js:3:8722
  
  Stream finished? false
  
  dash.all.js:3:8722
  
  Got a request.
  
  dash.all.js:3:8722
  
  null
  
  dash.all.js:3:8722
  
  BufferController video setState to:READY
  
  dash.all.js:3:8722
  
  Working time is video time: 0
  
  dash.all.js:3:8722
  
  BufferController.validate() video | state: READY
  
  dash.all.js:3:8722
  
  video Playback rate: 0
  
  dash.all.js:3:8722
  
  video Working time: 0
  
  dash.all.js:3:8722
  
  video Video time: 0
  
  dash.all.js:3:8722
  
  Current video buffer length: 0
  
  dash.all.js:3:8722
  
  BufferController video setState to:VALIDATING
  
  dash.all.js:3:8722
  
  ABR enabled? (true)
  
  dash.all.js:3:8722
  
  Check ABR rules.
  
  dash.all.js:3:8722
  
  Checking download ratio rule...
  
  dash.all.js:3:8722
  
  Total time: 0.009s
  
  dash.all.js:3:8722
  
  Download time: 0.009s
  
  dash.all.js:3:8722
  
  The ratios are NaN, bailing.
  
  dash.all.js:3:8722
  
  Checking insufficient buffer rule...
  
  dash.all.js:3:8722
  
  Not enough information for rule.
  
  dash.all.js:3:8722
  
  Array [ {…}, {…} ]
  
  dash.all.js:3:8722
  
  New quality of 0
  
  dash.all.js:3:8722
  
  video Playback quality: 0
  
  dash.all.js:3:8722
  
  Populate video buffers.
  
  dash.all.js:3:8722
  
  Quality didn't change.
  
  dash.all.js:3:8722
  
  Loading the video fragment for time: 0
  
  dash.all.js:3:8722
  
  Getting the request for time: 0
  
  dash.all.js:3:8722
  
  Got segments.
  
  dash.all.js:3:8722
  
  Array(6) [ {…}, {…}, {…}, {…}, {…}, {…} ]
  
  dash.all.js:3:8722
  
  Got a list of segments, so dig deeper.
  
  dash.all.js:3:8722
  
  Couldn't figure out a time!
  
  dash.all.js:2:10751
  
  Time: 0
  
  dash.all.js:2:10794
  
  Array(6) [ {…}, {…}, {…}, {…}, {…}, {…} ]
  
  dash.all.js:2:10818
  
  Index for time 0 is -1
  
  dash.all.js:3:8722
  
  Checking for stream end...
  
  dash.all.js:3:8722
  
  Live never ends! (TODO)
  
  dash.all.js:3:8722
  
  Stream finished? false
  
  dash.all.js:3:8722
  
  Got a request.
  
  dash.all.js:3:8722
  
  null
  
  dash.all.js:3:8722
  
  BufferController video setState to:READY
  
  dash.all.js:3:8722
  
  Working time is video time: 0
  
  dash.all.js:3:8722
  
  BufferController.validate() video | state: READY
  
  dash.all.js:3:8722
  
  video Playback rate: 0
  
  dash.all.js:3:8722
  
  video Working time: 0
  
  dash.all.js:3:8722
  
  video Video time: 0
  
  dash.all.js:3:8722
  
  Current video buffer length: 0
  
  dash.all.js:3:8722
  
  BufferController video setState to:VALIDATING
  
  dash.all.js:3:8722
  
  ABR enabled? (true)
  
  dash.all.js:3:8722
  
  Check ABR rules.
  
  dash.all.js:3:8722
  
  Checking download ratio rule...
  
  dash.all.js:3:8722
  
  Total time: 0.009s
  
  dash.all.js:3:8722
  
  Download time: 0.009s
  
  dash.all.js:3:8722
  
  The ratios are NaN, bailing.

  user some_user;
  
  worker_processes  1;
  
  
  
  events {
  
      worker_connections  1024;
  
  }
  
  
  
  rtmp {
  
      live on;
  
      dash on;
  
      server {
  
          listen 1935;
  
          application cams {
  
          dash_path /cams;
  
      }
  
          exec_static ffmpeg -i
  
   rtsp://admin:admin@192.168.0.51/1/Streaming/Channels/1/ -c:v libx264 -q:v 31 -an -profile:v baseline -ar 44100
  
   -f flv rtmp://0.0.0.0/cams/stream;
  
  
  
      }
  
  }
  
  
  
  http {
  
      include       mime.types;
  
      default_type  application/octet-stream;
  
  
  
      sendfile        on;
  
  
  
      #keepalive_timeout  0;
  
      keepalive_timeout  65;
  
  
  
  
  
      server {
  
          listen       80;
  
          server_name  localhost;
  
  
  
          location / {
  
              root /;
  
          }
  
  
  
          error_page   500 502 503 504  /50x.html;
  
          location = /50x.html {
  
              root   html;
  
          }
  
  
  
  }

  Can someone explain me why stream is not working and how to issue that ?thanks