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• FFmpeg inaccurate outputs [closed]

  27 juillet 2012, par user1557780

  Possible Duplicate :
  ffmpeg : videos before and after conversion aren't the same length

  Recently, I've been trying to use FFmpeg for an application which requires a VERY accurate manipulation when it comes to the time parameter (milliseconds resolution). Unfortunately, I was surprised to find out that FFmpeg's manipulation functionalities return some inaccurate results.

  Here is the output of 'ffmpeg' :

  ffmpeg version 0.11.1 Copyright (c) 2000-2012 the FFmpeg developers
  
    built on Jul 25 2012 19:55:05 with gcc 4.2.1 (Apple Inc. build 5664)
  
    configuration: --enable-gpl --enable-shared --enable-pthreads --enable-libx264 --enable-libmp3lame
  
    libavutil      51. 54.100 / 51. 54.100
  
    libavcodec     54. 23.100 / 54. 23.100
  
    libavformat    54.  6.100 / 54.  6.100
  
    libavdevice    54.  0.100 / 54.  0.100
  
    libavfilter     2. 77.100 /  2. 77.100
  
    libswscale      2.  1.100 /  2.  1.100
  
    libswresample   0. 15.100 /  0. 15.100
  
    libpostproc    52.  0.100 / 52.  0.100

  Now, let's assume I want to rip the audio track of 'foo.mov'. Here is the relevant output of 'ffmpeg -i foo.mov' :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'foo.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 0
  
      compatible_brands: qt  
  
      creation_time   : 2012-07-24 23:16:08
  
    Duration: 00:00:40.38, start: 0.000000, bitrate: 805 kb/s
  
      Stream #0:0(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p, 480x360, 733 kb/s, 24.46 fps, 29.97 tbr, 600 tbn, 1200 tbc
  
      Metadata:
  
        rotate          : 90
  
        creation_time   : 2012-07-24 23:16:08
  
        handler_name    : Core Media Data Handler
  
      Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, mono, s16, 63 kb/s
  
      Metadata:
  
        creation_time   : 2012-07-24 23:16:08
  
        handler_name    : Core Media Data Handler

  As you probably noticed, the video file duration is 00:00:40.38. Using the following command, I ripped it's audio track :

  'ffmpeg -i foo.mov foo.wav'

  Output :

  Output #0, wav, to 'foo.wav':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 0
  
      compatible_brands: qt  
  
      creation_time   : 2012-07-24 23:16:08
  
      encoder         : Lavf54.6.100
  
      Stream #0:0(und): Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono, s16, 705 kb/s
  
      Metadata:
  
        creation_time   : 2012-07-24 23:16:08
  
        handler_name    : Core Media Data Handler
  
  Stream mapping:
  
    Stream #0:1 -> #0:0 (aac -> pcm_s16le)
  
  Press [q] to stop, [?] for help
  
  size=3482kB time=00:00:40.42 bitrate= 705.6kbits/s    
  
  video:0kB audio:3482kB global headers:0kB muxing overhead 0.001290%

  As you can see, the output file is longer than the file in the input.

  Another example is audio (and video) file trimming :
  Let's assume I would like to use ffmpeg for audio file trimming. I used the next command :

  'ffmpeg -t 00:00:10.000 -i foo.wav trimmed_foo.wav -ss 00:00:25.000'

  Output :

  [wav @ 0x10180e800] max_analyze_duration 5000000 reached at 5015510
  
  Guessed Channel Layout for  Input Stream #0.0 : mono
  
  Input #0, wav, from 'foo.wav':
  
    Duration: 00:00:40.42, bitrate: 705 kb/s
  
      Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono, s16, 705 kb/s
  
  Output #0, wav, to 'trimmed_foo.wav':
  
    Metadata:
  
      encoder         : Lavf54.6.100
  
      Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono, s16, 705 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (pcm_s16le -> pcm_s16le)
  
      Press [q] to stop, [?] for help
  
  size=864kB time=00:00:10.03 bitrate= 705.6kbits/s    
  
  video:0kB audio:864kB global headers:0kB muxing overhead 0.005199%

  Again, the output file is 30 milliseconds longer than I expected.

  I tried, for a long time, to research the issue without any success. When I use audacity for the same functionality, it does it very accurately !

  Does anyone have any idea how to solve this problem ?

• libavfi/dnn : add LibTorch as one of DNN backend

  15 mars 2024, par Wenbin Chen

  libavfi/dnn : add LibTorch as one of DNN backend
  PyTorch is an open source machine learning framework that accelerates
  
  the path from research prototyping to production deployment. Official
  
  website : https://pytorch.org/. We call the C++ library of PyTorch as
  
  LibTorch, the same below.
  To build FFmpeg with LibTorch, please take following steps as
  
  reference :
  
  1. download LibTorch C++ library in
  
   https://pytorch.org/get-started/locally/,
  
  please select C++/Java for language, and other options as your need.
  
  Please download cxx11 ABI version :
  
   (libtorch-cxx11-abi-shared-with-deps-*.zip).
  
  2. unzip the file to your own dir, with command
  
  unzip libtorch-shared-with-deps-latest.zip -d your_dir
  
  3. export libtorch_root/libtorch/include and
  
  libtorch_root/libtorch/include/torch/csrc/api/include to $PATH
  
  export libtorch_root/libtorch/lib/ to $LD_LIBRARY_PATH
  
  4. config FFmpeg with ../configure —enable-libtorch \
  
   —extra-cflag=-I/libtorch_root/libtorch/include \
  
   —extra-cflag=-I/libtorch_root/libtorch/include/torch/csrc/api/include \
  
   —extra-ldflags=-L/libtorch_root/libtorch/lib/
  
  5. make
  To run FFmpeg DNN inference with LibTorch backend :
  
  ./ffmpeg -i input.jpg -vf \
  
  dnn_processing=dnn_backend=torch:model=LibTorch_model.pt -y output.jpg
  The LibTorch_model.pt can be generated by Python with torch.jit.script()
  
  api. https://pytorch.org/tutorials/advanced/cpp_export.html. This is
  
  pytorch official guide about how to convert and load torchscript model.
  
  Please note, torch.jit.trace() is not recommanded, since it does
  
  not support ambiguous input size.
  Signed-off-by : Ting Fu <ting.fu@intel.com>
  
  Signed-off-by : Wenbin Chen <wenbin.chen@intel.com>
  
  Reviewed-by : Guo Yejun <yejun.guo@intel.com>
  

  • [DH] configure
  • [DH] libavfilter/dnn/Makefile
  • [DH] libavfilter/dnn/dnn_backend_torch.cpp
  • [DH] libavfilter/dnn/dnn_interface.c
  • [DH] libavfilter/dnn_filter_common.c
  • [DH] libavfilter/dnn_interface.h
  • [DH] libavfilter/vf_dnn_processing.c

• Splitting more then once with a HTML5 video splitter

  12 mai 2017, par Fearhunter

  I am doing a research for split video’s in four files for example. I was looking at this repository on github.

  https://github.com/vdaubry/html5-video-splitter

  It’s a very nice repo how to split a video. My question is : how can I split more files then only one cut ? When I split for the second time it will overwrite the previous one. Here is the open source code of the splitting :

  var childProcess = require("child_process");
  
  childProcess.spawn = require('cross-spawn');
  
  
  
  var http = require('http');
  
  var path = require("path"); 
  
  var fs = require("fs"); 
  
  var exec = require('child_process').exec;
  
  
  
  http.createServer(function (req, res) {
  
    if (req.method === 'OPTIONS') {
  
        console.log('!OPTIONS');
  
        var headers = {};
  
        headers["Access-Control-Allow-Origin"] = "*";
  
        headers["Access-Control-Allow-Methods"] = "POST, GET, PUT, DELETE, OPTIONS";
  
        headers["Access-Control-Allow-Credentials"] = false;
  
        headers["Access-Control-Max-Age"] = '86400';
  
        headers["Access-Control-Allow-Headers"] = "X-reqed-With, X-HTTP-Method-Override, Content-Type, Accept";
  
        res.writeHead(200, headers);
  
        res.end();
  
    } 
  
    else if (req.method == 'POST') {
  
      var body = '';
  
      req.on('data', function (data) {
  
          body += data;
  
      });
  
      req.on('end', function () {
  
          var data = JSON.parse(body);
  
          var localPath = __dirname;
  
          var inputFilePath = localPath+"/videos/"+data.inputFilePath;
  
          var outputFilePath = localPath+"/videos/output-"+data.inputFilePath
  
          var start = data.begin;
  
          var end = data.end;
  
  
  
          var command = "ffmpeg -y -ss "+start+" -t "+(end-start)+" -i "+inputFilePath+" -vcodec copy -acodec copy "+outputFilePath;
  
          exec(command, function(error, stdout, stderr) {
  
            var msg = ""
  
            if(error) {
  
              console.log(error);
  
              msg = error.toString();
  
              res.writeHead(500, {'Content-Type': 'text/plain'});
  
            }
  
            else {
  
              console.log(stdout);
  
              res.writeHead(200, {'Content-Type': 'text/plain'});
  
            }
  
            res.end(msg);
  
          });
  
      });
  
    }
  
    else if (req.method == 'GET') {
  
      var filename = "index.html";
  
      if(req.url != "/") {
  
        filename = req.url
  
      }
  
  
  
      var ext = path.extname(filename);
  
      var localPath = __dirname;
  
      var validExtensions = {
  
        ".html" : "text/html",      
  
        ".js": "application/javascript", 
  
        ".css": "text/css",
  
        ".txt": "text/plain",
  
        ".jpg": "image/jpeg",
  
        ".gif": "image/gif",
  
        ".png": "image/png",
  
        ".ico": "image/x-icon"
  
      };
  
      var mimeType = validExtensions[ext];
  
  
  
      if (mimeType) {
  
        localPath += "/interface/"+filename;
  
        fs.exists(localPath, function(exists) {
  
          if(exists) {
  
            console.log("Serving file: " + localPath);
  
            getFile(localPath, res, mimeType);
  
          } else {
  
            console.log("File not found: " + localPath);
  
            res.writeHead(404);
  
            res.end();
  
          }
  
        });
  
  
  
      } else {
  
        console.log("Invalid file extension detected: " + ext)
  
      }
  
    }
  
  }).listen(1337, '127.0.0.1');
  
  console.log('Server running at http://127.0.0.1:1337/');
  
  
  
  function getFile(localPath, res, mimeType) {
  
    fs.readFile(localPath, function(err, contents) {
  
      if(!err) {
  
        res.setHeader("Content-Length", contents.length);
  
        res.setHeader("Content-Type", mimeType);
  
        res.statusCode = 200;
  
        res.end(contents);
  
      } else {
  
        res.writeHead(500);
  
        res.end();
  
      }
  
    });
  
  }

  I have installed FFMPEG also to do this.

  Kind regards