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• Turn image sequence into video with transparency

  29 janvier 2014, par Cody Hatch

  I've got what seems like it should be a really simple problem, but it's proving much harder than I expected. Here's the issue :

  I've got a fairly large image sequence consisting of numbered frames (output from Maya, for what its worth). The images are currently in Targa (.tga) format, but I could convert them to PNGs or other arbitrary format if that matters. The important thing is, they've got an alpha channel.

  What I want to do is programatically turn them into a video clip. The format doesn't really matter, but it needs to be lossless and have an alpha channel. Uncompressed video in a Quicktime container would probably be ideal.

  My initial thought was ffmpeg, but after wasting most of a day on it it seems it's got no support at all for alpha channels. Either I'm missing something, or the underlying libavcodec just doesn't do it.

  So, what's the right way here ? A command line tool like ffmpeg would be nice, but any solution that runs on Windows and could be called from a script would be fine.

  Note : Having an alpha chanel in your video isn't actually all that uncommon, and it's really useful if you want to composite it on top of another video clip or a still image. As far as I know uncompressed video, the Quicktime Animation codec, and the Sorenson Video 3 codec all support tranparency, and I've heard H.264 does as well. All we're really talking about is 32-bit color depth, and that's pretty widely supported ; both Quicktime .mov files and Windowss .avi files can handle it, and probably a lot more too.

  Quicktime Pro is more than happy to turn an image sequence into a 32-bit .mov file. Hit export, change color depth to "Millions of Colors+", select the Animation codec, crank the quality up to 100, and there you are - losslessly compressed video, with an alpha chanel, and it'll play back almost anywhere since the codec has been part of Quicktime since version 1.0. The problem is, Quicktime Pro doesn't have any sort of command-line interface (at least on Windows). ffmpeg supports encoding using the Quicktime Animation codec (which it calls qtrle), but it only supports a bit-depth of 24 bits.

  The issue isn't finding a video format that supports an alpha channel. Quicktime Animation would be ideal, but even uncompressed video should work. The problem is finding a tool that supports it.

• Qt6.4.1 QProcess cannot call external program FFmpeg [closed]

  21 décembre 2022, par Xingchen

  Based on the official Qt example, slightly modified to call the external ffmpeg.exe for transcoding operations

  


  QProcess *p = new QProcess(this);
QString program = "C:\\Users\\kyrio\\Documents\\Qt_Project\\build-test-Desktop_Qt_6_4_1_MinGW_64_bit-Debug\\debug";
QStringList arguments;
arguments << "ffmpeg" << "-i" << "C:\\Users\\kyrio\\Videos\\222.mp4" << "C:\\Users\\kyrio\\Videos\\223.mov";
p->start(program, arguments);


  


  Run no results, try a variety of writing methods also no results, get the output is empty, and no FFmpeg-related processes under the task manager
  
Try to call cmd, task manager can see the sub-processes under the new cmd.exe
  
command is fine, can be called in the terminal, but need to add ./or.
  
can be successfully run in the terminal

  


  Try prefixing arguments with.\or.\or./, still no response
  
Tried to get the exact path to the ffmpeg.exe file in the program string, still no response
  
I want to be able to successfully call ffmpeg.exe to achieve the video transcoding needs

  


  I have made the "program" exact to ffmpeg.exe and this is still unresponsive.No process, no errorString output.The output of exitCode is also absent.

  


  QString program = "C:\\Users\\kyrio\\Documents\\Qt_Project\\build-test-Desktop_Qt_6_4_1_MinGW_64_bit-Debug\\debug\\ffmpeg.exe";


  


  Running results

  


  I tried to start cmd and connected the errorOccurred signal, but there is no output, it is worth noting that the process cmd appears in the task manager
  
no output
task manager

  


• avfilter/vf_deshake : replace qsort with AV_QSORT

  31 octobre 2015, par Ganesh Ajjanagadde

  avfilter/vf_deshake : replace qsort with AV_QSORT
  qsort is called indirectly in filter_frame, suggesting its performance
  
  criticality. AV_QSORT is substantially faster due to the inlining of the
  
  comparison callback. Thus, the increase in performance should be worth
  
  the increase in binary size.
  This optimization is just a low hanging fruit. The trac ticket 1430 is
  
  a request for an improved deshake filter.
  Sample benchmark (x86-64, Haswell, GNU/Linux) :
  
  File : original from https://trac.ffmpeg.org/ticket/1430
  
  command : ffmpeg -stream_loop 8 -i file.webm -vf deshake=rx=64:ry=64 -f null -
  Timer truncated at 1024 runs.
  
  new :
  
  28260 decicycles in qsort,       1 runs,      0 skips
  
  35570 decicycles in qsort,       2 runs,      0 skips
  
  39010 decicycles in qsort,       4 runs,      0 skips
  
  46897 decicycles in qsort,       8 runs,      0 skips
  
  40442 decicycles in qsort,      16 runs,      0 skips
  
  41611 decicycles in qsort,      32 runs,      0 skips
  
  40345 decicycles in qsort,      64 runs,      0 skips
  
  38967 decicycles in qsort,     128 runs,      0 skips
  
  38647 decicycles in qsort,     256 runs,      0 skips
  
  40238 decicycles in qsort,     512 runs,      0 skips
  
  39676 decicycles in qsort,    1024 runs,      0 skips
  old :
  
  1740280 decicycles in qsort,       1 runs,      0 skips
  
   923560 decicycles in qsort,       2 runs,      0 skips
  
   511330 decicycles in qsort,       4 runs,      0 skips
  
   309720 decicycles in qsort,       8 runs,      0 skips
  
   194900 decicycles in qsort,      16 runs,      0 skips
  
   142686 decicycles in qsort,      32 runs,      0 skips
  
   112516 decicycles in qsort,      64 runs,      0 skips
  
    98166 decicycles in qsort,     128 runs,      0 skips
  
    88147 decicycles in qsort,     256 runs,      0 skips
  
    88706 decicycles in qsort,     512 runs,      0 skips
  
    86783 decicycles in qsort,    1024 runs,      0 skips
  Reviewed-by : Nicolas George <george@nsup.org>
  
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  

  • [DH] libavfilter/vf_deshake.c