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• Parsing NAL units using FFMPEG

  6 novembre 2013, par 2ndlife

  I am new to MPEG-4 and taking baby steps to learn it. I am using FFMPEG as reference.

  1. I understand that all mpeg-4 are encoded into NAL units and wrt to FFMPEG av_read_frame() function returns one NAL unit, Am I right ? Is frame a NAL unit ? (though it can be a combination of multiple NALs)

  2. I also saw that h264_parser.c implements a function called h264_parse which is calling parse_nal_units() inside, If i need to get NAL units how can I use this parse_nal_units from my main function ?

  3. What is av_parse_Parse2() function do ? does it return decoded NAL units ?

  4. OR FFMPEG has -vbsf h264_mp4toannexb switch to dump raw NAL units, Can somebody help me understand how I can use the same from my main function ?

  Please help me out here...
   ash5

• How to resolve the issue of FFmpeg.wasm not working about SharedArrayBuffer error properly when using Nginx as a server and use Vite no error ?

  18 décembre 2023, par bully

  I am using FFmpeg.wasm for some frontend transcoding work. I know that due to certain browser policies, I need to configure some response headers in the Vite server options :
 server: { headers: { 'Cross-Origin-Opener-Policy': 'same-origin', 'Cross-Origin-Embedder-Policy': 'require-corp' } },

  


  This works fine and doesn't throw the SharedArrayBuffer error.

  


  Then, I ran yarn run build to generate the dist directory and copied it to my Nginx proxy server. I also configured similar response headers in Nginx as follows :

  


    server {
    listen 80;
    server_name ...My IP;
    add_header 'Cross-Origin-Embedder-Policy' 'require-corp';
    add_header 'Cross-Origin-Opener-Policy' 'same-origin';
    add_header 'Cross-Origin-Resource-Policy' "cross-origin";
    add_header 'Access-Control-Allow-Origin' '*';
  
    location / {
        add_header 'Cross-Origin-Embedder-Policy' 'require-corp';
        add_header 'Cross-Origin-Opener-Policy' 'same-origin';
    }

    root /www/audioserver/dist;
    ...
    }


  


  However, it doesn't work in this setup. I have been trying for a while but haven't been able to solve it.

  


  Here is my code for loading ffmpeg.wasm. It works fine in the development environment. The blob is the cached file of the wasm saved in IndexedDB :

  


  `const blob = await getWasmCoreWasm();
await this.ffmpegInstance.load({
    coreURL: await toBlobURL(`${baseURL}/ffmpeg-core.js`, 'text/javascript'),
    wasmURL: await toBlobURL(URL.createObjectURL(blob), 'application/wasm'),
    workerURL: await toBlobURL(`${baseURL}/ffmpeg-core.worker.js`, 'text/javascript'),
});
`


  


  I have tried checking the response headers of the links, updating Nginx, and even modifying the version of FFmpeg. They all seem to be fine, but I don't know how to resolve this issue. I would really appreciate it if someone could help me out. Thank you very much !

  


• "No Java virtual machine has been registered" error when using "mediacodec"

  12 septembre 2018, par Mohammed_BEY

  I successfully cross-compiled FFmpeg with "mediacodec" (developed in Java) library for aarch64 ARM architecture under Android OS.
  When I try to run FFmpeg on Android without "mediacodec", it works just fine.
  However, when I run it with "mediacodec" option I got an error :
  "No Java virtual machine has been registered"
  Here is the command line I used :
  ./ffmpeg -vcodec hevc_mediacodec -i jellyfish-20-mbps-hd-hevc.mkv -f null out.null

  1) is is the problem of JRE ?
  2) if so, could someone guide me to enable JRE on Android, or cross-compile it ?

  Actually, I tried many times to cross-compile "openjdk" for aarch64 but none works.