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• Writing Live-Multimedia-Application using OpenGL & Co. saving output to disc [closed]

  21 janvier 2013, par user1997286

  I want to write an application that does the following thing :

  • Getting Commands via ArtNET (DMX over Ethernet, a Control Protocol) for each object (called Layer)
  • each Layer could be one of the following : Live Camera Stream, Movie, Image
  • each layer could be translated, rotated or stretched
  • on each layer I can set filters (Like a Kaleidoscope Effect, Blur, Color Correction, etc.)
  • the rsulting video-stream is in the 3d-space
  • I want to display each part of the image on one Projector (in total up to 3 ones) using a TripleHead2GO (3 Projectors display a different region of my DVI-Output). Each Projecector-Image should have own Soft-Edge and Keystone parameters.
  • the resulting image will also be shown on a Preview-Screen with some Information overlay.

  I think all that should be possible with opengl and openal (for the movie audio)

  I think I'll use C++, OpenGL for Graphics, OpenAL for Audio, if needed ffmpeg for Video conversion, Ubuntu/Debian as OS.

  The software is used to do Multimedia-Shows on Concerts including Cameras & Co.

  All that should happen Live (On a FullHD output), Having i7 3770, GLX 670 and 16GB of Ram for at least 8 Layers. (4 Live-Images at once + Some Overlays like the Actors Name and some Logos)

  But now comes the question.

  Is it also Posible to do the following with that setting :

  • Writing the output Image with all the 3d translations to a Movie File (To Master a DVD later) with Audio
  • Mixing Audio from different Inputs & Files (Ambience Mics, Signal from the Sound Mixer, Playbacks from my own application) to more than one Mix (eg. one Mix for the Recording, one Mix for Live)
  • Stream that Output Complete or in Parts (e.g. the left Part of the Image) over the Network (For example, Projector 1 is near the Server, so I connect it using DVI, Projector 2+3 is connected to a Computer that receives the streams for that two projectors (with soft edge on each stream) and Screen 4 is outside the Concert Hall and shows the complete Live-Stream.
  • What GUI-Framework should I use for that ?
  • is it perhaps event performant enough to use Java for that ?
  • is it posible to use that mechanism for just rendering (eg. I have stored the cut points on Disc and saved every single camera stream to change some errors later or cut out some parts)

• Can FFMPEG be used to change the transparency of a single PNG ?

  19 juillet 2020, par Chameleon

  I know that FFMPEG can manipulate transparency using fade in/fade out over a series of frames. I just haven't found a way to generate a png with a specified transparency setting.

  


  I am in the process of creating a lot (20 in first set) of procedurally-generated videos. Each video requires several starts and stops, where with each stop, a png overlay describing what is seen will be displayed for several (actual number TBD, and may vary) frames. I'd like each overlay to fade in over x frames, display for y frames at full opacity and then fade out over y frames. The documentation on FFMPEG really sucks at explaining fade effects, and no one I've found showing usage actually explains what all of the parameters do.

  


  The original sources for the videos are CGI png frames with a transparent background. I will be making the descriptive overlays with transparent backgrounds (same resolution as the CGI frames) - I'm really hoping to not have to manually save each overlay (8 overlays per video at a minimum) with 4 to 6 (or more) transparency settings - The company is being real indecisive as to the length of the fade in/out or the "hang time" of the descriptive overlays.

  


  I have already created a Python script that uses FFMPEG to place overlays on specific frames, then uses FFMPEG to stitch all frames into a single video, adds a background to the video and then places the company's watermark on the video. It already manages the key frames and what images should be overlaid (and for how many frames). It is working well, but the company doesn't like the lack of fade. I already have the framework in place to manage the fade in/out duration (I'm just missing the answer to this question). I created the script because I have no doubt that I'll have to generate the final output on the first couple of videos a number of times to appease the stakeholders.

  


  I'm really hoping to find a fairly easy way to hand FFMPEG a png with a transparent background and have FFMPEG hand me a copy of the image whose non-transparent part is now "x percent" transparent (or "y percent" opaque). I know from failed attempts that FFMPEG doesn't choke trying to make a region more than 100% transparent.

  


  It's a real pain to get approval to install new software on the workstation, so I'm not actually interested in any suggestion that doesn't use FFMPEG or a pretty vanilla Python installation. - It's not that the other software might not be useful, it just means that if other software is needed, I'll have to manually create the frames.

  


• Anomalie #4543 : Accessibilité des chargements ajax (live regions)

  4 septembre 2020, par RastaPopoulos ♥

  Moi j’ai pas participé à ces ajouts hein mais j’essaye de comprendre.

  On est d’accord que aria-live=polite, ça fait que lorsque l’utilisateur ne fait rien d’important (le polite), alors ça va relire le morceau qui a été "actualisé en live", s’il a changé ? c’est bien ça ?

  Ce que je dis c’est que 99% des utilisations de l’ajax de SPIP, concernent effectivement un cas où l’utilisateurice a cliqué volontairement et s’attend donc à ce que ça lui lise ce qui vient de changer (et c’est bien le bloc parent entier que SPIP recharge, quel est le problème ?).

  Si sur le site de cette région, ya pas mal d’ajax qui se recharge "tout seul" sans interaction, possible oui ça va pas du tout, mais ce n’est vraiment pas le plus courant dans l’utilisation classique de SPIP, et il me semblait que vu la proportion, c’était plutôt bien si par défaut ça relisait le bloc rechargé (volontairement par un clic, dans l’immense majorité des cas).

  Mais du coup on parle que théoriquement, et sûrement que je pige pas du tout oui… il faudrait plutôt parler sur des cas concrets (genre tel bloc ajax de telle page avec une pagination qu’on clique volontairement et qui recharge alors telle portion de la page).

  En tout cas cette utilisation (majoritaire encore une fois) semblait correspondre à la doc de base (sur MozDev par ex) :

  Normalement, seul aria-live="polite" est utilisé. Toute zone recevant une mise à jour qu’il est important de faire suivre à l’utilisateur, mais pas au point de le déranger dans sa navigation, devrait recevoir cet attribut. Le lecteur d’écran lira les changements dès que l’utilisateur sera inoccupé.

  Si ça reste par défaut, peut-être qu’il faudrait un critère pour ne pas générer ces attributs quand on sait qu’il va s’agir d’un bloc ajax rechargé automatiquement, non volontairement ?