Recherche avancée

Sur d’autres sites (2377)

• Fade out in ffmpeg when creating a video from a still image is wonky ?

  13 juin 2017, par Matt W

  I’m creating a video that :

  • uses a still image as a source
  • has a text overlay
  • fades in and out
  • has a silent stereo audio track.

  So far, I have this, and it (almost) works correctly :

  ffmpeg -f lavfi -i "aevalsrc=0|0" -loop 1 -i turtle-2.jpg  -c:v libx264 -t 5 -r 30 -s 1920x1080 -aspect 16:9 -pix_fmt yuv420p -filter:v drawtext="fontsize=130:fontfile=comic.ttf:text='hello world':x=(w-text_w)*.25:y=(h-text_h)*.75",fade=in:0:60,fade=out:90:60 -acodec aac turtle11.mp4

  The only problem is that the fade out doesn’t seem to be going to black, even tho this is a 150 frame video and I believe I am following the ffmpeg documentation correctly.

  The resulting video is here :

  http://video.blivenyc.com/vid-from-image/turtle11.mp4

  Any thoughts ?

• Bypass Nvidia's 2 Stream Encode Limit On Windows

  28 novembre 2018, par Nimble

  I’m trying to encode 3 video streams simultaneously in FFmpeg but due to Nvidia’s 2 stream encode limit on GTX / RTX GPUs I have to encode one of the streams with my CPU. This forces me to output multiple files as opposed to one properly mapped file containing all audio and video streams which has many drawbacks involving synchronization and ease of use.

  Before actually considering investing $1000+ in a comparable Quadro GPU, which has no encode stream limits, I thought I’d search around to see if anyone has bypassed said limit. Eventually I came across this GitHub repository :
  https://github.com/keylase/nvidia-patch

  It seems to actually work... but it’s Linux only. Much of my hardware is incompatible with Linux so migration just isn’t an option for me. Not being smart enough to learn from this method and apply it to a Windows environment I kept looking and came across this repository :
  https://github.com/Matviy/nvidia-NVENC-multi-session-patch

  It would seem this is a method to bypass the limit on Windows but the instructions are way over my head. I’ve asked a few of my buddies who are experienced in coding but each one only seems to understand each method to a point and can’t really help.

  Was hoping someone could give some insight on the subject, possibly offering a solution, or confirming that the instructions are simply too vague.

• Web-based video editor

  10 octobre 2014, par Danny

  We have a web-based editor currently that allows users to build animated web apps. The apps are made up of shapes, text, images, and videos. Except for videos, all other elements can also be animated around the screen. The result of building a animated app is basically a big blob of JSON.

  The playback code for the web app is web-based as well. It takes the JSON blob and constructs the HTML, which ends up playing back in some sort of browser environment. The problem is that most of the time this playback occurs on lower-end hardware like televisions and set-top boxes.

  These performance issues go away if there is some way to be able to convert a digital sign to video. Then the STB/smart TV simply plays a video, which is much more performant than playing back animations in a web view.

  Given a blob of JSON describing each layer and how to draw each type of object, its animation points, etc, how could I somehow take that and convert it to video on the server ?

  My first attempt at this was using PhantomJS to load the playback page in a headless browser, take a series of screenshots, and then use ffmpeg to merge those screenshots into a video. That worked great so long as there is no video. But it does not work with video since there is no HTML5 video tag support in PhantomJS, and even if there was, I would lose any audio.

  The other way I was thinking of doing it would be to again load the playback page in PhantomJS, but turn off the video layers and leave them transparent, then take screenshots as a series of PNGs with transparency. I would then combine these with the video layers.

  None of this feels very elegant though. I know there are web-based video editors out there that basically do what I’m trying to accomplish, so how do they do it ?