Recherche avancée

Sur d’autres sites (4014)

• Meaning of "ffprobe -v trace demo.mp4" output

  17 mai 2019, par bluesky

  The ’mdat box’ of Mp4 file may at the last of file. I want to know the position of ’mdat’ box using ’ffmpeg’ or ’ffprobe’.

  Mp4 consists of ’ftyp’, ’moov’ and ’mdat’ BOX. each BOX consists of "BoxHeader" and "BoxData". "BoxHeader" consists of "BoxSize(4Byte)", "BoxType(4Byte)", "BoxLargesize(8Byte, only have when box size exceeding the range of 4Byte expression, then the value of BoxSize is 1)".

  In program, you could first read 8 Byte and know the size of ’ftyp box’, then seek the size and read 8 Byte to know if the next box is ’moov box’. If not ’moov’, it shoud be ’mdat box’, then seek cross ’mdat box’ to find ’mdat box’...

  But I want to use ’ffprobe’ to find the position of ’moov’. I use ’ffprobe -v trace demo.mp4’, and output is like below

  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fc8fd000e00] Format mov,mp4,m4a,3gp,3g2,mj2 probed with size=2048 and score=100
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fc8fd000e00] type:'ftyp' parent:'root' sz: 28 8 41044500
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fc8fd000e00] ISO: File Type Major Brand: mp42
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fc8fd000e00] type:'moov' parent:'root' sz: 17943 36 41044500
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fc8fd000e00] type:'mvhd' parent:'moov' sz: 108 8 17935

  I want to know the meaning of type:'ftyp' parent:'root' sz: 28 8 41044500 :
  type:'ftyp' parent:'root'is easy to know, sz: 28 8 41044500 is really make me confused, I guess 28 is size of ftyp box,but the meaning of 8 41044500 is what ?

  Could you explain the meaning of sz: 28 8 41044500, and where could find the doc ?

• Use FFMPEG to put images separately inside a "box" and keeping their original positions of the X and Y boundaries and maybe modify their offsets

  14 septembre 2020, par karl-police

  I have a collection of images, for this example, I created 3 images that have different sizes, but the image itsself is the same, except it is moved more down or left or right.

  


  1 : 2 : 3 :

  


  These are the images. The total sizes of all images together is 35x39, so that means that they need to go inside an 35x39 image so it can later be used to craft them into a GIF as example. Since "crop" does not really work as it crops it smaller and can't make them bigger and I can't imagine it being the best solution for that anyway, perhaps.

  


  So this is the invisible 35x39 sized box.

  


  image :

  


  So what I'm trying to do is to figure out how I can put each of these images separately in the 35x39 sized box, but maintaining the original X position or the Y position or both, from the boundaries of the images. I'm trying to figure out how I can do this for other transparent images for similar things, mostly used to craft animations. Here into a GIF out of image collections, but the images need to be fixed first.

  


  I tried to look in the FFMPEG documentation, but there's many many filters and etc. that I had a few issues finding the right thing. I'm also not sure if it is also then possible to change the offset of the X and Y, because I think if there's something to make it keep the original position of X and Y, then I also think that there's probably something to change the offset of it aswell.

  


   

  


  End result of the images could basically be :

  


  1 : 2 : 3 :

  


  This end result example of the images, basically have their X aligned on the top and Y aligned on the left. I'm not sure if you can call it "original X position", because if I compare it to Photoshop's special paste and keep at original position, it puts the first image a bit more down as example, for some reason. So I just moved the X all the way to the top and the Y all the way to the left.

  


• Is there any memory problem that "Too many active WebGL contents." keeps coming out in my web console

  18 novembre 2022, par jerry

  

  


  Now I'm using RTSP stream with jsmpeg, ffmpeg, node-rtsp-stream in React.js

  


  I set multiple streaming in react component about 1 to maximum 25

  


  and when I change route to many , It apeard my console

  


  I'm a little afraid of if it caused by memory leak problem

  


  I cannot figure out it is okay or critical problem

  


  Could you tell me how to solve this problem or is it fine

  


  &#xA;// out of component&#xA;const streams: Streams = {};&#xA;&#xA;...&#xA;&#xA;  const { preset } = props;&#xA;&#xA;  const elementsRef = useRef<any>(new Array(preset?.partition).fill(0).map((v) => createRef()));&#xA;&#xA;&#xA;  // Mount&#xA;  useEffect(() => {&#xA;    const { JSMpeg } = window;&#xA;&#xA;    const sortedStream = _.sortBy(preset?.stream, ["position"]);&#xA;    console.log(sortedStream);&#xA;&#xA;&#xA;    sortedStream.forEach((v, i: number) => {&#xA;&#xA;      const player = new JSMpeg.Player(v.camera_monitoring.ws, {&#xA;        canvas: elementsRef?.current[v.position]?.current, // Canvas should be a canvas DOM element&#xA;      });&#xA;      console.dir(elementsRef?.current[v.position]?.current);&#xA;&#xA;      streams[v.id] = player;&#xA;    });&#xA;  }, []);&#xA;&#xA;  // UnMount&#xA;  useEffect(() => {&#xA;    return () => {&#xA;      Object.keys(streams).forEach((v) => {&#xA;        console.log("unmount key:", v);&#xA;        if (streams[v] !== null) {&#xA;          streams[v].destroy();&#xA;          streams[v] = null;&#xA;        }&#xA;      });&#xA;    };&#xA;  }, []);&#xA;&#xA;&#xA;&#xA;... &#xA;</any>

  


  https://github.com/phoboslab/jsmpeg

  


  above library `jsmpeg.min.js` is set by global ( in public directory and set in my html )

  


  actually my code are so many antipattern in contrast react style, To make an excuse, It is my limits of one's ability