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• Trouble with frame accuracy applying subcaps using .ass files to 23.976fps video [closed]

  25 août 2023, par WhatsYourFunction

  Currently testing .ass subcaps in a VFX workflow.
The goal is to drop specfic text over specific shots and the in/out points have to be frame accurate
We're working in a 23.976 project.

  


  Currently having no trouble using FFmpeg to generate frame-accurate subclips of individual shots from a full-show export by converting hh:mm:ss:ff to seconds and then handling the 24 to 23.976 offset, using the following alorithm :

  


  InPoint_Seconds = ConvertToSeconds(InPoint_Hmsf_FullShow) - ConvertToSeconds(Start_Hmsf_FullShow) // Convert from SMTPE Time Code to seconds.
InPoint_Seconds = InPoint_Seconds * (1001 / 1000) //Handle 24 to 23.976 offset
OutPoint_Seconds = [Same idea as above]
Duration_Seconds = Output_Seconds - InPoint_Seconds

> ffmpeg -ss InPoint_Seconds -t Duration_Seconds -i SourcePath -c copy DestPath


  


  So generating frame-accurate copies of portions of a larger file works with perfect accuracy

  


  BUT when applying the same logic to subcaps using .ass files, sometimes they land with frame accuracy, and sometimes they don't (They'll be 1 frame late at most, and it does not increase over the span of the source clip).

  


  Curious if anyone has any ideas.

  


• How would I create a radially offset mosaic of rtsp streams that transitions to a logo

  18 juillet 2018, par Jack

  I’m new to stack overflow, but I’ve been researching how to do this for a couple weeks to no avail. I’m hoping perhaps one of you has some knowledge I haven’t seen online yet.

  Here is a crude illustration of what I hope to accomplish. I have a video wall of eight monitors - four each of two different sizes. The way it’s set up now, all eight monitors are treated together as one big monitor displaying an oddly shaped cutout of a desktop.

  Eventually I need each individual monitor to display a separate RTSP stream for about thirty seconds, then have the entire display - all eight monitors in conjunction - to fade out into a large logo.

  My problem right now is that I don’t know of a way to mask an rtsp stream so it looks like this rather than this, let alone how to arrange them into a weirdly spaced, oddly angled, multiple aspect-ratio mosaic like in the original illustration.

  Thank you all for your time. I’m just an intern here without insane technical knowhow, but I’ll try to clarify as much as I can.

  -J

• Revision af660715c0 : Make coefficient skip condition an explicit RD choice. This commit replaces zru

  28 juin 2013, par Ronald S. Bultje

  Changed Paths :
   Modify /vp9/common/vp9_rtcd_defs.sh

  
   Modify /vp9/encoder/vp9_block.h

  
   Modify /vp9/encoder/vp9_onyx_int.h

  
   Modify /vp9/encoder/vp9_quantize.c

  
   Modify /vp9/encoder/vp9_rdopt.c

  
   Modify /vp9/encoder/x86/vp9_error_sse2.asm

  
  
  Make coefficient skip condition an explicit RD choice.

  This commit replaces zrun_zbin_boost, a method of biasing non-zero
  coefficients following runs of zero-coefficients to be rounded towards
  zero, with an explicit skip-block choice in the RD loop.

  The logic is basically that if individual coefficients should be rounded
  towards zero (from a RD point of view), the trellis/optimize loop should
  take care of it. If whole blocks should be zero (from a RD point of
  view), a single RD check is much more efficient than a complete
  serialization of the quantization loop.

  Quality change : derf +0.5% psnr, +1.6% ssim ; yt +0.6% psnr, +1.1% ssim.
  SIMD for quantize will follow in a separate patch. Results for other
  test sets pending.

  Change-Id : Ife5fa641163ac5150ac428011e87188f1937c1f4