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• How to use ffmpeg in JavaScript to decode H.264 frames into RGB frames

  17 juin 2020, par noel

  I'm trying to compile ffmpeg into javascript so that I can decode H.264 video streams using node. The streams are H.264 frames packed into RTP NALUs so any solution has to be able to accept H.264 frames rather than a whole file name. These frames can't be in a container like MP4 or AVI because then the demuxer needs to needs the timestamp of every frame before demuxing can occur, but I'm dealing with a real time stream, no containers.

  



  Streaming H.264 over RTP

  



  Below is the basic code I'm using to listen on a udp socket. Inside the 'message' callback the data packet is an RTP datagram. The data portion of the data gram is an H.264 frame (P-frames and I-frames).

  



  var PORT = 33333;
var HOST = '127.0.0.1';

var dgram = require('dgram');
var server = dgram.createSocket('udp4');

server.on('listening', function () {
    var address = server.address();
    console.log('UDP Server listening on ' + address.address + ":" + address.port);
});

server.on('message', function (message, remote) {
    console.log(remote.address + ':' + remote.port +' - ' + message);
    frame = parse_rtp(message);

    rgb_frame = some_library.decode_h264(frame); // This is what I need.

});

server.bind(PORT, HOST);  


  



  I found the Broadway.js library, but I couldn't get it working and it doesn't handle P-frames which I need. I also found ffmpeg.js, but could get that to work and it needs a whole file not a stream. Likewise, fluent-ffmpeg doesn't appear to support file streams ; all of the examples show a filename being passed to the constructor. So I decided to write my own API.

  



  My current solution attempt

  



  I have been able to compile ffmpeg into one big js file, but I can't use it like that. I want to write an API around ffmpeg and then expose those functions to JS. So it seems to me like I need to do the following :

  



  

  1. Compile ffmpeg components (avcodec, avutil, etc.) into llvm bitcode.

  


  2. Write a C wrapper that exposes the decoding functionality and uses EMSCRIPTEN_KEEPALIVE.

  


  3. Use emcc to compile the wrapper and link it to the bitcode created in step 1.

  


  



  I found WASM+ffmpeg, but it's in Chinese and some of the steps aren't clear. In particular there is this step :

  



  emcc web.c process.c ../lib/libavformat.bc ../lib/libavcodec.bc ../lib/libswscale.bc ../lib/libswresample.bc ../lib/libavutil.bc \


  



   :( Where I think I'm stuck

  



  I don't understand how all the ffmpeg components get compiled into separate *.bc files. I followed the emmake commands in that article and I end up with one big .bc file.

  



  2 questions

  



  1. Does anyone know the steps to compile ffmpeg using emscripten so that I can expose some API to javascript ?
  
 2. Is there a better way (with decent documentation/examples) to decode h264 video streams using node ?

  


• Anomalie #2707 : page=spip_pass : opération rejetée si l’auteur n’a pas de mot de passe en base

  15 mai 2012, par kent1 -

  Je confirme et me dit aussi que c’est assez chiant... J’ai pas envie de créer des users non plus en choisissant un pass leur disant qu’ils peuvent le modifier etc etc... Qui plus est en général dans ces cas là, on les envoie par email... pb de sécu et toutiquanti... Peut être intéressant de (...)

• avcodec/mips/h264qpel_mmi.c : Version 2 of the optimizations for loongson mmi

  25 mai 2016, par ZhouXiaoyong

  avcodec/mips/h264qpel_mmi.c : Version 2 of the optimizations for loongson mmi
  1. no longer use the register names directly and optimized code format
  
  2. to be compatible with O32, specify type of address variable with mips_reg and handle the address variable with PTR_ operator
  
  3. use uld and mtc1 to workaround cpu 3A2000 gslwlc1 bug (gslwlc1 instruction extension bug in O32 ABI)
  
  4. h264qpel use hepldsp optimizations
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/mips/h264qpel_mmi.c