Recherche avancée

Sur d’autres sites (6156)

• On WebP and Academic Exercises

  2 octobre 2010, par Multimedia Mike — General

  Yesterday, Google released a new still image format called WebP. To those skilled in the art, this new format will be recognizable as a single VP8 golden frame with a 20-byte header slapped on the front (and maybe a little metadata thrown in for good measure). We have a MultimediaWiki page and a sample ready to go.

  Further, I submitted a patch to ffmpeg-devel for FFmpeg’s img2 handling system to decode these files. FFmpeg should support processing these files soon… if anyone cares. This leads into…

  The Point, or Lack Thereof
  Since yesterday’s release, I have read a whirlwind of commentary about this format, much of it critical and of the “what’s the point ?” variety. For my part, I can respect academic exercises, a.k.a., just trying random stuff to see if you can make it work. That’s pretty much this blog’s entire raison d’être. But WebP transcends mere academic exercise ; Google seems to be trying to push it as a new web standard. I don’t see how the format can go anywhere based on criticisms raised elsewhere — e.g., see Dark Shikari’s thoughtful write-up — which basically boil down to WebP not solving any real problems, technical, legal, or otherwise.

  How did WebP come to be ? I strongly suspect some engineers noticed that JPEG is roughly the same as an MPEG-1 intraframe, so why not create a new still frame format based on VP8 intraframes ? Again, I can respect that thinking– I have pondered how a still image format would perform if based on VP3/Theora or Sorenson Video 1.

  Technically
  Google claims a significant size savings for WebP vs. standard JPEG. Assuming that’s true (and there will be no shortage of blog posts to the contrary), it will still be some time before WebP support will find its way into the majority of the web browser population.

  But this got me thinking about possible interim solutions. A website could store images compressed in both formats if it so chose. Then it could serve up a WebM image if the browser could support it, as indicated by the ‘Accept’ header in the HTTP request. It seems that a website might have to reference a generic image name such as <img src="some-picture.image"> ; the web server would have to recognize the .image extension and map it to either a .jpg or a .webp image depending on what the browser claims it is capable of displaying.

  Leftovers
  I appreciate that Dark Shikari has once again stuck his neck out and made a valiant — though often futile — effort to educate the internet’s masses. I long ago resigned myself to the fact that many people aren’t going to understand many of the most basic issues surrounding multimedia technology (i.e., moving pictures synchronized with audio). But apparently, this extends to still image formats as well. It was simultaneously humorous and disheartening to see commenters who don’t even understand the application of, e.g., PNG vs. JPEG : Ahem, “We already have a great replacement for jpg : .PNG”. Coupled with the typical accusations of MPEG tribalism, I remain impressed D. Shikari finds the will to bother.

  Still, I appreciate that the discussion has introduced me to some new image formats of which I was previously unaware, such as PGF and JPEG XR.

• Python get Audio/Video frames separately from video file

  3 juillet 2016, par AlvaroAV

  What i’m trying to do :

  Hi !

  I’m trying to store the Video and Audio information from a video file. I would like to store video frames and audio frames separately in different variables.

  My intention is to manage video/files and do some actions with the audio and video frame list, but to do what I’m plannign to do I need to store this audio/video frames separately. I’ve read a lot of questions in StackOverflow about python and audio/video managing.

  Most people recommend to use OpenCV or ffmpeg to manage videos. I saw some scripts using these libraries to get video(only video) frames, but none of them are getting audio, most of them are just getting video frames and save them as RGB images. I also check some scripts where people get audio frames from a mp3 file, but I’m not sure if you can do that in a video file

  Most important thing to me is to know the best way to manage video and audio separately. I’m not looking for people to do my code, just asking to point me in a good direction.

  One of the things I’m trying to do is to send this information via socket, but as I said I need the audio and video frames to be in separated variables (yes, i’m wondering about an stream app, but that’s not the only thing I’m trying to do)

  I know I should give more information, and maybe show some code, but I don’t have any concret code I tried some things, but I’ve never been capable to separate audio and video. I know that each format has his own encryption, and at the end I decided to use "mp4" as video format but I don’t know neither if this is the best format for what I’m trying to do.

  Resume :

  Is openCV the best way to manage video and audio separately ?

  Wich is the easiest way to separate video and audio frames ? Is it possible ?

  Wich is the best documentation I should read to learn about video/audio management ?

  I would like to do the things with my own code, and use in the less way possible openCV or other libraries.

  My "basic" idea is to get a "list" of audio and video frames, and then I would like to do some operations, but right now I can’t find the best way for me to manage a vide using python. I even wonder if could be possible to manage a video as raw data

  I need to know wich is the best library to manage videos using python, for me the best library, will be the one that allows me to manage the videos more "freely"

  I’ve already checked :

  I’ve read too many questions on this theme, the most recent are :

  How to extract audio from video file

  Split audio video separately from given video using MLT

  Embed audio video in python gui

• Dreamcast Development Desktop

  28 mars 2011, par Multimedia Mike — Sega Dreamcast

  Some people are curious about what kind of equipment is required to program a Sega Dreamcast. This is my setup :

  
  
  

  It’s a bit overcomplicated. The only piece in that picture which doesn’t play a role in the Dreamcast development process is the scanner. The Eee PC does the heavy lifting of development (i.e., text editing and cross compilation) and uploads to the Dreamcast via a special serial cable. Those are the most essential parts and are really the only pieces necessary for a lot of algorithmic stuff (things that can be validated via a serial console). But then I have to go up a level where I output video. That’s where things get messy.

  
  
  

  The Mac Mini and giant monitor really just act as a glorified TV in this case. Ideally, it will be more than that. The DC outputs audio and video via composite cables to a Canopus DV capture bridge. That’s connected via FireWire to the external hard drive underneath the Mac Mini, which is connected to the Mac. Adobe Premiere Pro handles the DV capture / display.

  One day I hope to have something worthwhile to capture.