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• How to convert a Stream on the fly with FFMpegCore ?

  18 octobre 2023, par Adrian

  For a school project, I need to stream videos that I get from torrents while they are downloading on the server.
When the video is a .mp4 file, there's no problem, but I must also be able to stream .mkv files, and for that I need to convert them into .mp4 before sending them to the client, and I can't find a way to convert my Stream that I get from MonoTorrents with FFMpegCore into a Stream that I can send to my client.

  


  Here is the code I wrote to simply download and stream my torrent :

  


  var cEngine = new ClientEngine();

var manager = await cEngine.AddStreamingAsync(GenerateMagnet(torrent), ) ?? throw new Exception("An error occurred while creating the torrent manager");

await manager.StartAsync();
await manager.WaitForMetadataAsync();

var videoFile = manager.Files.OrderByDescending(f => f.Length).FirstOrDefault();
if (videoFile == null)
    return Results.NotFound();

var stream = await manager.StreamProvider!.CreateStreamAsync(videoFile, true);
return Results.File(stream, contentType: "video/mp4", fileDownloadName: manager.Name, enableRangeProcessing: true);


  


  I saw that the most common way to convert videos is by using ffmpeg. .NET has a package called FFMpefCore that is a wrapper for ffmpeg.

  


  To my previous code, I would add right before the return :

  


  if (!videoFile.Path.EndsWith(".mp4"))
{
    var outputStream = new MemoryStream();
    FFMpegArguments
        .FromPipeInput(new StreamPipeSource(stream), options =>
        {
            options.ForceFormat("mp4");
        })
        .OutputToPipe(new StreamPipeSink(outputStream))
        .ProcessAsynchronously();
    return Results.File(outputStream, contentType: "video/mp4", fileDownloadName: manager.Name, enableRangeProcessing: true);
}


  


  I unfortunately can't get a "live" Stream to send to my client.

  


• Find video resolution and video duration of remote mediafile

  22 février 2012, par osgx

  I want to write an program which can find some metainformation of mediafile. I'm interested in popular video formats, such as avi, mkv, mp4, mov (may be other popular too). I want basically to get :

  • Video size (720, 1080, 360 etc)
  • Total runtime of video (may be not very exact)
  • Number of audio streams
  • Name of video codec
  • Name of audio codec

  There is already the mediainfo, but in my program I want to get information about remote file, which may be accessed via ftp, http, samba ; or even torrent (there are some torrent solutions, which allows to read not-yet downloaded file).

  MediaInfo library have no support of samba (smb ://) and mkv format (for runtime).

  Also, I want to know, how much data should be downloaded to get this information. I want not to download full videofile because I have no enough disk space.

  Is this information in the first 1 or 10 or 100 KiloBytes of the file ? Is it at predictable offset if I know the container name and total file size ?

  PS : Platform is Linux, Language is C/C++

• stream_decoder : fix memory leak after seek table read error

  14 juillet 2016, par Max Kellermann

  stream_decoder : fix memory leak after seek table read error
  When read_metadata_seektable_() fails, the has_seek_table flag is
  
  never set to true, and thus free() is never called.
  Example valgrind output :
   11,185,464 bytes in 1 blocks are definitely lost in loss record 62 of 62
  
      at 0x4C2BC0F : malloc (vg_replace_malloc.c:299)
  
      by 0x4C2DE6F : realloc (vg_replace_malloc.c:785)
  
      by 0x40A7880 : safe_realloc_ (alloc.h:159)
  
      by 0x40A7911 : safe_realloc_mul_2op_ (alloc.h:205)
  
      by 0x40AB6B5 : read_metadata_seektable_ (stream_decoder.c:1654)
  
      by 0x40AAB2D : read_metadata_ (stream_decoder.c:1422)
  
      by 0x40A9C79 : FLAC__stream_decoder_process_until_end_of_metadata (stream_decoder.c:1055)
  It is easy to craft a FLAC file which leaks megabytes of memory on
  
  every attempt to open the file.
  This patch fixes the problem by removing checks which are unnecessary
  
  (and harmful).  Checking the has_seek_table flag is not enough, as
  
  described above.  The NULL check is not harmful, but is not helpful
  
  either, because free(NULL) is documented to be legal.
  After running this code block, we’re in a well-known safe state, no
  
  matter how inconsistent pointer and flag may have been before, for
  
  whatever reasons.
  Signed-off-by : Erik de Castro Lopo <erikd@mega-nerd.com>
  

  • [DH] src/libFLAC/stream_decoder.c