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• Suggestion query : Someone should add 'percent-complete' to ffmpeg's status line

  19 février 2018, par Dave

  I use the PC-platform’s ffmpeg (on Windows and Linux). I’ve always
  wondered why, down on that bottom dynamic status line, it does NOT
  show a ’percent-complete’ value.

  e.g. There’s already a line showing what time-line value is being worked
  on, so I’d expect it would be straight-forward to grab total duration, compute percent-complete, and show it, right after the running time value. Or,
  if based on frames, then show it in parentheses after the frame value.

  The reason I think it would be straight-forward is because I see it
  discussed in detail, for ffmpeg on Android, here :
  How to add progress bar to FFMPEG android
  and it talks about time-values and frame-count based calculations.

  Any volunteers to tackle this ? ^ ;)

• FFMPEG lossless simple & efficient format

  30 octobre 2016, par Adminy

  I took a sample video and ran this code for each image format like this :

  ffmpeg -i test.mkv png/%d.png
  
  ffmpeg -i test.mkv bmp/%d.bmp

  What I noted is that BMP at 1080P has a fixed size of 5.97 MB (6,266,934 bytes)

                                                             !6,220,800

  Then I did some maths :

  1 byte = 2^8 == 256 possible combinations
  
  r + g + b form a color (0-255,0-255,0-255)
  
  bmp = 3 * 1920 * 1080 = 6,220,800 bytes

  So extra is just the file headers ?! (46134 bytes for just headers ?)

  Next thing I noted that PNG size is dynamic and when the image has a lot of repetition is somewhere 2.5mb. Usually its between 10mb and 12mb.

  Also decoding BMP seemed a lot quicker compared to PNG. So there is no point in even looking at PNG. I would like to know why is it so huge over BMP if it has (zlib) compression factor.

  What is the best format to export to in terms of speed and size, preferred if its as simple as reading the file of color bytes ?

• How to change encoding bitrate adaptively to bandwidth during live rtmp publish using ffmpeg ?

  9 mars 2019, par Jaehong Kim

  I am currently using ffmpeg to read the recorded video by native frame rate and publish the stream to nginx rtmp server.

  The command looks something like this

  ffmpeg -re -i [video file] \
  
  -vcodec libx264 -r 60 -g 120 -keyint_min 120 -vb [bitrate]\
  
  -f flv -y rtmp://[server url];

  I want to change the encoding bitrate of the software encoder manually,
  according to the bandwidth fluctuation. For example,

  If 2kbps< estimated_bandwidth <4kbps,  
  
       change ffmpeg bitrate to 3kbps, 1280x720 size 

  However, I couldn’t find any framework or codec that supports dynamic bitrate change during encoding.

  Is there a way that I could achieve this ?
  Last thing that I want to do is to implement the codec myself because I have no background.