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• Can you write a video file with out of order (input) frames ?

  14 juin 2024, par Blindy

  I know video files can (and do) contain frames that are encoded out of order, which is why dts and pts exist, but can you send your frames in an arbitrary order, with their correct pts, and expect the video file to play ?

  


  Specifically I'm wondering about concatenating video files, can I decode both inputs in parallel and send the frames with the correct merged pts as they get decoded ? And if so, what would the playback performance implications be ?

  


• Invalid data found when processing input on ffmpeg m4s to mp4 transfer

  1er mars 2020, par keith scott

  The result of the power shell window

  I saw a post on here about converting m4s to mp4 and I have followed the steps of concatenating all the files into another m4s file that I called all.m4s and when I use the command ffmpeg -i allm4s.m4s -c copy video.mp4. I made the combined m4s file by coding an exe to add all the m4s files that have the word video in them to the m4s file. Here is the source code written in c# if you compile the code then that is the code I have used to make the m4s

  using System;
  
  using System.Collections.Generic;
  
  using System.Linq;
  
  using System.Text;
  
  using System.Threading.Tasks;
  
  using System.IO;
  
  
  
  namespace files
  
  {
  
      class Program
  
      {
  
          static void Main(string[] args)
  
          {
  
              string dir = Directory.GetCurrentDirectory();
  
              string[] info = Directory.GetFiles(dir);
  
              Console.WriteLine(dir + "\\allm4s.m4s");
  
              Console.ReadKey();
  
              foreach (string name in info)
  
              {
  
                  if (Path.GetFileName(name).Contains(".m4s") && Path.GetFileName(name).Contains("video"))
  
                  {
  
                      using (Stream srcStream = File.OpenRead(name))
  
                      {
  
                          using (Stream destStream = File.OpenWrite(dir+"\\allm4s.m4s"))
  
                          {
  
                              srcStream.CopyTo(destStream);
  
                              Console.WriteLine(destStream+name);
  
                          }
  
                      }
  
                  }
  
              }
  
              Console.ReadKey();
  
          }
  
      }
  
  }

  I think if there is to be an issue it is to do with this allm4s.m4s file as the file size is about 1.5mb even though each segment m4s is about 750kb each and there are quite a lot.If anyone has a way of adding concatenating lots of files together through a program/application that would be useful.

• lavu/pixdesc : handle xv30be in av_[read|write]_image_line

  4 décembre 2022, par Philip Langdale

  lavu/pixdesc : handle xv30be in av_read_image_line
  xv30be is an obnoxious format that I shouldn't have included in the
  
  first place. xv30 packs 3 10bit channels into 32bits and while our
  
  byte-oriented logic can handle Little Endian correctly, it cannot
  
  handle Big Endian. To avoid that, I marked xv30be as a bitstream
  
  format, but while that didn't produce FATE errors, it turns out that
  
  the existing read/write code silently produces incorrect results, which
  
  can be revealed via ubsan.
  In all likelyhood, the correct fix here is to remove the format. As
  
  this format is only used by Intel vaapi, it's only going to show up
  
  in LE form, so we could just drop the BE version. But I don't want to
  
  deal with creating a hole in the pixfmt list and all the weirdness that
  
  comes from that. Instead, I decided to write the correct read/write
  
  code for it.
  And that code isn't too bad, as long as it's specialised for this
  
  format, as the channels are all bit-aligned inside a 32bit word.
  

  • [DH] libavutil/pixdesc.c