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• avformat/matroskadec : Improve handling of circular SeekHeads

  30 avril 2020, par Andreas Rheinhardt

  avformat/matroskadec : Improve handling of circular SeekHeads
  There can be more than one SeekHead in a Matroska file, but most of the
  
  other level 1 elements can only occur once.* Therefore the Matroska
  
  demuxer only allows one entry per ID in its internal list of level 1
  
  elements known to it ; the only exception to this are SeekHeads.
  The only exception to this are SeekHeads : When one is encountered
  
  (either directly or in the list of entries read from SeekHeads),
  
  a new entry in the list of known level-1 elements is always added,
  
  even when this entry is actually already known.
  This leads to lots of seeks in case of circular SeekHeads : Each time a
  
  SeekHead is parsed, a new entry for a SeekHead will be added to the list
  
  of entries read from SeekHeads. The exception for SeekHeads mentioned
  
  above now implies that this SeekHead will always appear new and unparsed
  
  and parsing will be attempted. This continued until the list of known
  
  level-1 elements is full.
  Fixing this is pretty simple : Don't add a new entry for a SeekHead if
  
  its position matches the position of an already known SeekHead.
  * : Actually, there can be multiple Tags and several other level 1
  
  elements are "identically recurring" which means they may be resent
  
  multiple times, but each instance must be absolutely identical to the
  
  previous.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskadec.c

• lavc/flacdsp : do not assume maximum R-V VL

  24 mai 2024, par Rémi Denis-Courmont

  lavc/flacdsp : do not assume maximum R-V VL
  This loop correctly assumes that VLMAX=16 (4x128-bit vectors
  
  with 32-bit elements) and 32 >= pred_order > 16. We need to alternate
  
  between VL=16 and VL=t2=pred_order-16 elements to add up to pred_order.
  The current code requests AVL=a2=pred_order elements. In QEMU and on
  
  thte K230 hardware, this sets VL=16 as we need. But the specification
  
  merely guarantees that we get : ceil(AVL / 2) <= VL <= VLMAX. For
  
  instance, if pred_order equals 27, we could end up with VL=14 or VL=15
  
  instead of VL=16. So instead, request literally VLMAX=16.
  

  • [DH] libavcodec/riscv/flacdsp_rvv.S

• how to implement siti filter using ffmpeg

  18 septembre 2023, par hse

  I've asked this before, but I've tried and failed to implement siti filter with opencv, so I wanted to try implementing it with ffmpeg.

  


  Here's the reference : https://ffmpeg.org/ffmpeg-filters.html#Examples-122

  


  I followed that link and made sure the calculateSITI function was working.

  


  export async function calculateSITI(filePath) {
  const filterGraph = `siti=print_summary=1`;

  const args = [filePath, "-v", filterGraph, "-f", "null", "- "];
  const t = await runFfmpeg(args);
  console.log(t);
}


  


  filePath : C :\xxxx\xxx\xxxx\ffmpeg-6.0-essentials_build\ffmpeg-6.0-essentials_build\bin

  


  -v siti=level=1 -f null -
Invalidoglevel "siti=level=1". Possible levels are numbers or :
"quiet"
"panic"
"fatal"
"error"
"warning"
"info"
"verbose"
"debug"
"trace"

  


  error, and I've been trying to troubleshoot it, but there seems to be very little documentation out there.
Anyone familiar with ffmpeg ?