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• ffmpeg convert one png to DNxHD

  15 mars 2019, par bcvery1

  I’m trying to create a DNxHD file from one PNG file. The output should be "24000/1001" fps, 1920x1080, using the dnxhd codec. Every frame should be the same. The outputted stream must be 20 seconds in length.

  I have a solution which uses filter_complex to loop the PNG for each frame, however this results in extremely large files. Given that I will be combining possibly multiple hundred DNxHD files into one AAF file, the output file size is too large.

  Is there any improvement I can make on the command below which would achieve this file size reduction ?

  ffmpeg -i INFILE.png -y -nostdin -an -vcodec dnxhd -pix_fmt yuv422p -vb 36M  -framerate 24000/1001 -filter_complex loop=479:1:0 OUFILE.dnxhd

  I do not know ffmpeg all that well, this command has been constructed by copying parts of commands I have found online.

• C - FFmpeg streaming from a C program ?

  16 août 2017, par golmschenk

  I’m looking to replicate an FFmpeg command-line command in my C code. Specifically I would like to be able to run :

  ffmpeg -re -i video.mp4 -f mpegts udp://localhost:7777

  One thing I’ve noticed when looking at people’s code who have used the libraries of FFmpeg in their own code is that they often have a few hundred lines of code for a single command similar to an FFmpeg command-line command. I’m guessing this is just because they are doing something very specific, because if I can run that short command on my command line and get what I want it should probably only take about ten lines of code to do the same thing in my C code. This should only take about that much work right ? Why would it take much more ?

  I’m having a bit of difficulty finding explanations on how to use the streaming capabilities of the FFmpeg libraries that aren’t overly complex because they’re for a very specific purpose. Can anyone explain how I might go about writing the code for the above command ? Or at the very least point me to some documentation explaining how to write such a script/program ? Thank you much !

  EDIT : I do hope to run this from an iPhone app eventually so I won’t just be able to straight up call FFmpeg from my program. I’ll need to use the libraries used by FFmpeg.

• C - FFmpeg streaming from a C program ?

  8 août 2016, par golmschenk

  I’m looking to replicate an FFmpeg command-line command in my C code. Specifically I would like to be able to run :

  ffmpeg -re -i video.mp4 -f mpegts udp://localhost:7777

  One thing I’ve noticed when looking at people’s code who have used the libraries of FFmpeg in their own code is that they often have a few hundred lines of code for a single command similar to an FFmpeg command-line command. I’m guessing this is just because they are doing something very specific, because if I can run that short command on my command line and get what I want it should probably only take about ten lines of code to do the same thing in my C code. This should only take about that much work right ? Why would it take much more ?

  I’m having a bit of difficulty finding explanations on how to use the streaming capabilities of the FFmpeg libraries that aren’t overly complex because they’re for a very specific purpose. Can anyone explain how I might go about writing the code for the above command ? Or at the very least point me to some documentation explaining how to write such a script/program ? Thank you much !

  EDIT : I do hope to run this from an iPhone app eventually so I won’t just be able to straight up call FFmpeg from my program. I’ll need to use the libraries used by FFmpeg.