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• avcodec/mips/h264dsp_mmi : Version 2 of the optimizations for loongson mmi

  13 mai 2016, par ZhouXiaoyong

  avcodec/mips/h264dsp_mmi : 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. optimize some unaligned loads and stores
  
  4. use uld and mtc1 to workaround cpu 3A2000 gslwlc1 bug (gslwlc1 instruction extension bug in O32 ABI)
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/mips/h264dsp_mmi.c

• 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 ?

  


• 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