Recherche avancée

Sur d’autres sites (12779)

• cbs_mpeg2 : Improve checks for invalid values

  22 mai 2019, par Andreas Rheinhardt

  cbs_mpeg2 : Improve checks for invalid values
  MPEG-2 contains several elements that mustn't be zero according to the
  
  specifications : horizontal/vertical_size_value, aspect_ratio_information,
  
  frame_rate_code, the quantiser matrices, the colour_description
  
  elements, picture_coding_type, the f_code[r][s] values and
  
  quantiser_scale_code. It is now checked that the invalid values don't
  
  occur.
  The colour_description elements are treated specially in this regard :
  
  Given that there are files in the wild which use illegal values for the
  
  colour_description elements (some of them created by mpeg2_metadata),
  
  they will be corrected to the value meaning "unknown" (namely 2) during
  
  reading. This has been done in such a way that trace_headers will
  
  nevertheless report the original value, together with a message about
  
  the fixup.
  Furthermore, the trace_headers output of user_data has been beautified.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/cbs_mpeg2.c
  • [DH] libavcodec/cbs_mpeg2_syntax_template.c

• How to convert from .h264 to .ts using FFmpeg wrapper for C#/.NET ?

  9 décembre 2020, par juan_marti

  Context

  


  I'm using FFMpegCore in my .NET Core API project that receives a .h264 file (sent in a binary format that is received and converted into a byte array) to be converted to a .ts.

  


  I want to convert a .h264 stream into a .ts output stream using FFmpeg.

  


  Current Approach

  


  (...)

byte[] body;
using ( var ms = new MemoryStream() )
{
    await request.Body.CopyToAsync( ms ); // read sent .h264 data
    body = ms.ToArray();
}

var outputStream = new MemoryStream();

// FFMpegCore
await FFMpegArguments
                .FromPipeInput( new StreamPipeSource( new MemoryStream( body ) ) )
                .OutputToPipe( new StreamPipeSink( outputStream ), options => options
                .ForceFormat( VideoType.MpegTs ) )
                .ProcessAsynchronously();

// view converted ts file
await File.WriteAllBytesAsync( "output.ts", outputStream.ToArray() );

(...)


  


  Problem

  


  I'm not getting a working .ts file. What I'm a doing wrong ? Could you please give some hint or help me with this ? Even if you have other FFmpeg wrappers that you consider more suitable for this problem.

  


  Notes :

  


  

  • I don't have the physical location of the files since this will receive the content of the files over HTTP. So, I will only have the byte array meaning that I need to use the input stream to convert to another format.

  


  • FFmpeg command used to test the conversion from .h264 to .ts (using files) : ffmpeg -i file.h264 -an -vcodec copy -f mpegts output.ts

  


  


• find the timestamp of a sound sample of an mp3 with linux or python

  23 juin 2020, par cardamom

  I am slowly working on a project which where it would be very useful if the computer could find where in an mp3 file a certain sample occurs. I would restrict this problem to meaning a fairly exact snippet of the audio, not just for example the chorus in a song on a different recording by the same band where it would become more some kind of machine learning problem. Am thinking if it has no noise added and comes from the same file, it should somehow be possible to locate the time at which it occurs without machine learning, just like grep can find the lines in a textfile where a word occurs.

  


  In case you don't have an mp3 lying around, can set up the problem with some music available on the net which is in the public domain, so nobody complains :

  


  curl https://web.archive.org/web/20041019004300/http://www.navyband.navy.mil/anthems/ANTHEMS/United%20Kingdom.mp3 --output godsavethequeen.mp3


  


  It's a minute long :

  


  exiftool godsavethequeen.mp3 | grep Duration
Duration                        : 0:01:03 (approx)


  


  Now cut out a bit between 30 and 33 seconds (the bit which goes la la la la..) :

  


  ffmpeg -ss 30 -to 33 -i godsavethequeen.mp3 gstq_sample.mp3


  


  both files in the folder :

  


  $ ls -la
-rw-r--r-- 1 cardamom cardamom   48736 Jun 23 00:08 gstq_sample.mp3
-rw-r--r-- 1 cardamom cardamom 1007055 Jun 22 23:57 godsavethequeen.mp3


  


  This is what am after :

  


  $ findsoundsample gstq_sample.mp3 godsavethequeen.mp3
start 30 end 33


  


  Am happy if it is a bash script or a python solution, even using some kind of python library. Sometimes if you use the wrong tool, the solution might work but look horrible, so whichever tool is more suitable. This is a one minute mp3, have not thought yet about performance just about getting it done at all, but would like some scalability, eg find ten seconds somewhere in half an hour.