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• How to create videos with small file size but large resolution ?

  13 février 2017, par Gregory Magarshak

  Is there a programmatic way to create videos that capture, essentially, a powerpoint presentation, that would be not much larger than the audio + screenshots of the powerpoint itself ?

  I want to make software that produces videos with the full resolution of a powerpoint on a large screen, and with a person speaking over it and wvwn doodling. Kind of like "bcontext" software. And then I want to export videos for youtube and other places to be hosted. But I want them to be SMALL. So they can be downloaded by people with slow connections eg in India.

  What factors can affect video size and how can i take advantage of the relative "stillness" of most pixels at most times to make the compression preserve the full sharpness and yet take advantage of the lack of visual changes ? What software do you recommend ?

• ffmpeg : "Error setting profile" ; how to keep original resolution odf odd sized videos ; getting Quicktime compatible output ; fixing pixel format

  26 février 2017, par P. Reid

  I’ve been having trouble using ffmpeg to compress videos to something readable by quicktime. My goal in the end is to have a simple command that I can use to compress high bitrate videos (ie screencaptures) to something more reasonable to be able to share them with people.

  I want to use a command I found here as a starting point :

  ffmpeg -i input-file.avi -codec:v libx264 -profile: high -preset slow -b:v 500k -maxrate 500k -bufsize 1000k -vf scale=-1:480 -threads 0 -codec:a libfdk_aac -b:a 128k output_file.mp4

  Unfortunately I get this error :

  [libx264 @ 0x7f92ab81c200] Error setting profile high.
  
  [libx264 @ 0x7f92ab81c200] Possible profiles: baseline main high high10 high422 high444
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  
  Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  If I take out the -profile: high the command functions but the output still doesn’t open in quicktime (it does in VLC). I can’t find the keyword -profile on the ffmpeg man page : https://ffmpeg.org/ffmpeg.html so I don’t know if this is important or what to do about it.

  Does anyone know what might be causing my problem ? What should I do to try and debug this problem ? I would describe myself as inexperienced so sorry if I’m missing something obvious.

  Thanks in advance for your help,
  Peter

  This is my ffmpeg version :

  ffmpeg version 3.2.4 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with Apple LLVM version 7.0.2 (clang-700.1.81)

• avcodec/vp56 : Clear dimensions in case of failure in the middle of a resolution change

  1er mars 2017, par Michael Niedermayer

  avcodec/vp56 : Clear dimensions in case of failure in the middle of a resolution change
  Similar code is used elsewhere in vp56 to force a more complete reinit in the future.
  
  Fixes null pointer dereference
  
  Fixes : 707/clusterfuzz-testcase-4717453097566208
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/vp56.c