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• Transcode from a live m3u8 using -ss

  20 août 2015, par pgm

  I’m trying to create a VOD hls clip from a live hls stream on adobe media server using ffmpeg and nodejs.

  An example of the command I’m using looks like this :

  ffmpeg -report -analyzeduration 999999999 -probesize 999999999 -ss 50 -i http://live.m3u8 -y -r 29.97 -threads 0 -hls_list_size 0 -c:v copy -a:v copy streamoutput.m3u8

  The problem is the -ss param (start time) is calculating the start time from the live point on the stream, rather than from the first ’ts’ fragment. I’d like to be able to encode inside of a "DVR window," meaning seeking from the beginning of the stream, not from the live point of the stream.

  Example : I use the param -ss 50 and it won’t encode for 50 seconds until the live stream catches up, outputting this in the ffmpeg log :

  [h264 @ 0000000002beae00] non-existing PPS 0 referenced
  
  [h264 @ 0000000002beae00] non-existing PPS 0 referenced
  
  [h264 @ 0000000002beae00] decode_slice_header error

  Once the live stream catches up to the 50 second delay it begins encoding. It works this way when I use -ss as either an input parameter or output parameter.

  Is there a way to accomplish this ? I’ve noticed that if I leave -ss completely out of the command, it will start at the beginning of the stream, but as soon as it’s there, even as a 0, it will start at the "live point."

  Any help is much appreciated !

• avcodec/qtrleenc : Fix negative linesizes, don't use NULL + offset

  26 mars 2021, par Andreas Rheinhardt

  avcodec/qtrleenc : Fix negative linesizes, don't use NULL + offset
  Before commit f1e17eb446577180ee9976730aacb46563766518, the qtrle
  
  encoder had undefined pointer arithmetic : Outside of a loop, two
  
  pointers were set to point to the ith element (with index i-1) of
  
  a line of a frame. At the end of each loop iteration, these pointers
  
  were decremented, so that they pointed to the -1th element of the line
  
  after the loop. Furthermore, one of these pointers can be NULL (in which
  
  case all pointer arithmetic is automatically undefined behaviour).
  Commit f1e17eb44 added a check in order to ensure that the elements
  
  never point to the -1th element of the array : The pointers are only
  
  decremented if they are bigger than the frame's base pointer
  
  (i.e. AVFrame.data[0]). Yet this check does not work at all in case of
  
  negative linesizes ; furthermore in case the pointer that can be NULL is
  
  NULL initializing it still involves undefined pointer arithmetic.
  This commit fixes both of these issues : First, non-NULL pointers are
  
  initialized to point to the element after the ith element and
  
  decrementing is moved to the beginning of the loop. Second, if a pointer
  
  is NULL, it is just made to point to the other pointer, as this allows
  
  to avoid checks before decrementing it.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/qtrleenc.c

• How do I use the CLI interface of FFMpeg from a static build ?

  13 décembre 2019, par deek0146

  I have added this (https://github.com/kewlbear/FFmpeg-iOS-build-script) version of ffmpeg to my project. I can’t see the entry point to the library in the headers included.

  How do I get access to the same text command based system that the stand alone application has, or an equivalent ?

  I would also be happy if someone could point me towards documentation that allows you to use FFmpeg without the command line interface.

  This is what I am trying to execute (I have it working on windows and android using the CLI version of ffmpeg)

  ffmpeg -framerate 30 -i snap%03d.jpg -itsoffset 00:00:03.23333 -itsoffset 00:00:05 -i soundEffect.WAV -c:v libx264 -vf fps=30 -pix_fmt yuv420p result.mp4