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• FFMPEG delaying the start of video when using between

  11 décembre 2019, par Michael Joseph Aubry

  ffmpeg -i "in.mp4" -i "./watermark.png" -f lavfi -i color=c=white:s=1080x1920 -filter_complex " [0:v]scale=2560:1440[ovr1], [1:v]scale=458:58[ovr2], [2:v][ovr1]overlay=-740:240:enable='between(t,2,7)'[int1], [int1][ovr2]overlay=W-500:H-100:enable='between(t,0,15)' [main] " -map "[main]" -ac 2 -vcodec libx264 -preset veryfast -crf 27 -vb 20M -t 00:00:15 out.mp4

  This command takes my second input (watermark) it overlays it on my first input (video). It also scales both of them accordingly. It also sets the times to appear and disappear throughout the video.

  The problem is [2:v][ovr1]overlay=-740:240:enable='between(t,2,7)'[int1] when I set my video input to appear between 2 seconds and 7 seconds. The result is as such, however, when it appears at the 2-second mark, the video is also starting at the 2-second mark when the video should start at its own 0-second mark within the new video.

  How can I adjust the ffmpeg command above to start the video input at 2 seconds within the video but have it start at the input video’s 0-second mark ?

• Revision 8d7f53f04c : Account for rate error in GF group Q calculation. When GF group adaptive maxQ i

  20 février 2015, par paulwilkins

  Changed Paths :
   Modify /vp9/encoder/vp9_firstpass.c

  
   Modify /vp9/vp9_cx_iface.c

  
  
  Account for rate error in GF group Q calculation.

  When GF group adaptive maxQ is enabled this patch accounts
  somewhat for accumulated error in the rate control.

  This improves accuracy quite a bit on many clips especially
  when there is overshoot.

  Examples when the overshoot and undershoot command line
  parameters are set to 100 :

  Hall @ 1200 overshoot is reduced from 67-24%.
  Akiyo @ 400 undershoot is reduced from 28%-15%.

  Setting a lower value for undershoot or overshoot still
  reduces the error further.

  Impact on metrics is mixed with some gains in average psnr
  but generally a little lower (e.g. 0.5%) on overall and ssim.

  The GF group adaptation is still off by default in this patch.
  Compared to with the head, enabling this mode now gives
  big average psnr gains on the YT sets (e.g. YT_HD >11.2%),
  a drop in overall PSNR (YT-HD 3.9%) and a smaller drop or
  neutral for SSIM.

  Change-Id : If4b32cd0740d3fb941317b374f9c2951954eee90

• lavc/aacpsdsp : precompute constant factors

  20 septembre 2022, par Rémi Denis-Courmont

  lavc/aacpsdsp : precompute constant factors
  The input complex factors are constant for each iterations. This
  
  substitudes 4 loads, 2 additions and 2 subtractions per iteration of
  
  the inner-loop with another 4 loads. Thus effectively 4 arithmetic
  
  operations per iteration of the inner loop are avoided, i.e. 24
  
  operations per iteration of the outer loop, or 24 * (n - 1) operations
  
  in total.
  If the inner loop is not unrolled by the compiler, this also might
  
  also save some pointer arithmetic as most instruction sets do not
  
  have addressing modes with negated register offsets (12 - j). Unless
  
  the compiler is optimising for code size, this is unlikely though.
  

  • [DH] libavcodec/aacpsdsp_template.c