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• How to extract Images from MP4 video on upload - FFMPEG

  11 février 2015, par michael hanon

  I am putting together a training site for my company and we need to extract an image from each mp4 video we upload. I have searched lots and decided to try FFMPEG.

  Here is what I have so far. I’m not getting errors, but no image in the specified folder.

  Any help would be appreciated.

             string inputfile = Server.MapPath("/Report/TrainingLibrary/Material/Videos/RMSIMAILSignature.mp4");
           //string withouttext;
           string thumbpath;
           string thumbname;
           string thumbargs;
           //string thumbre;
          thumbpath = AppDomain.CurrentDomain.BaseDirectory + "Reports\\ TrainingLibrary\\Material\\Videos\\";
           thumbname = thumbpath + "Image" + "%d" + ".jpg";
           thumbargs = "-i " + inputfile + " -vframes 1 -ss 00:00:07 -s 150x150 " + thumbname;
           Process thumbproc = new Process();
           thumbproc = new Process();
           thumbproc.StartInfo.FileName = "C:\\FFMPEG\\Bin\\ffmpeg.exe";
           thumbproc.StartInfo.Arguments = thumbargs;
           thumbproc.StartInfo.UseShellExecute = false;
           thumbproc.StartInfo.CreateNoWindow = false;
           thumbproc.StartInfo.RedirectStandardOutput = false;
           try
           {
               thumbproc.Start();
           }
           catch (Exception ex)
           {
               Response.Write(ex.Message);
           }
           thumbproc.WaitForExit();
           thumbproc.Close();

• Non-Monotonous DTS error in current ffmpeg builds causing frame drops, but not on ffmpeg 1.2

  11 avril 2021, par pentinex

  I'm sorry to ask about such a frequently mentioned subject, but I looked through so many threads and I could never figure out what exactly is wrong, so I'm at the end of my wits. Basically, I want to concat a bunch of .ts files using ffmpeg. I use this command line :

  


  ffmpeg -allowed_extensions ALL -fflags +igndts -i chunklist.m3u8 -c copy "output.mkv"

  


  The .m3u8 file contains all the .ts parts. When I do this and it throws Non-Monotonous DTS errors, the result ends up having dropped frames where the DTS errors occur. I have tried multiple approaches :

  


  

  1. As you see above, I added "-fflags +igndts" at one point, though it doesn't help.

  


  2. I experimented with "-fflags +genpts" just out of desperation. Predictably, this made it worse.

  


  3. I tried muxing video and audio separately, to no avail.

  


  


  But weirdly enough, there is one "solution" : when I use ffmpeg 1.2, the resulting video plays smoothly. It doesn't come without issues. The resulting video always reports a frame rate of half of what it should be (14.98 when it should be 29.97). But it plays just like it should. Ideally though, I wouldn't want to use such an old version of ffmpeg, since I'm sure there are things in the background that may go wrong and I'm not even noticing those, so I'd hope I could get these kinds of results on current builds of ffmpeg.

  


  Does anybody have an idea ? I'm kind of losing my mind with this one.

  


• Why does hard-coding subtitles into MKV cause resulting video length to be wildly incorrect ?

  21 mai 2018, par BudJB

  I am trying to encode an existing MKV with a video, audio, and several subtitle streams, such that video encodes with H264, audio encodes with AAC, and the second subtitle track is hard-coded into the video stream. I am using the myffmpeg GUI frontend, but can view and modify the ffmpeg command before it’s run.

  Every time that I run the encode, the MKV reports that the duration is 1195 hours and change, where it’s supposed to be around 2 hours, plus some change. If I encode without the hard-coded subtitles, things turn out alright.

  Here’s the command that’s run, with the latest ffmpeg :

  ffmpeg.exe -probesize 50M -analyzeduration 100M -i "D:\Video\in.mkv" -c:a aac -ac 6 -strict -2 -async 1 -c:v libx264 -crf 20 -r 24000/1001 -s 1920x1080 -aspect 16:9 -pix_fmt yuv420p -preset fast -partitions default  -b-pyramid 1 -weightb 1 -8x8dct 1 -fast-pskip 0 -direct-pred 1 -coder ac -trellis 1 -me_method hex -subq 6 -me_range 16 -bf 3 -b_strategy 1 -refs 3 -flags +loop -sws_flags fast_bilinear -sc_threshold 40 -keyint_min 24 -g 48 -qmin 3 -qmax 51 -qdiff 4 -filter_complex "[0:v][0:s:2]overlay[out]" -map [out]  -map 0:a:0 -sn -y "D:\Video\out.mkv"

  I’ve tried a couple other MKV’s with the same results. Anyone else run into this or know what’s going on ?