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• ffmpeg masks more than one overlay, how can I mask only one ?

  6 juin 2020, par Jonathan Winger-Lang

  I am trying to use an alpha mask to mask the corners of a video, it works. But then I try to add another image on top of them and it is also masked.

  



  How can I mask only the one video, not subsequent layers ?

  



  

  



  Here you can see that the phone frame is also masked, since it does not goo beyond the (x-axis) edges of the phone.

  



  My script :

  



  ffmpeg -i input.mp4 \
   -loop 1 -i mask.png \
   -i background.png \
   -loop 1 -i frame2.png \
-filter_complex \
   "[0][1]             alphamerge                                         [masked_video];    \
    [masked_video][3]  overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2  [phone];           \
    [phone]            scale=(iw*0.5):(ih*0.5)                            [scaled_phone];    \
    [2][scaled_phone]  overlay=100:100" \
-shortest out.mp4


  



  Thank you

  


• ffmpeg combine a video and the srt with multiple lines ?

  9 avril 2022, par Sunshine

  I know how to combine a video 1.mp4 and a srt 1.srt document by ffmpeg,
ffmpeg -i 1.mp4 -i 1.srt -map 0 -map 1 -c copy -crf 23 video-with-subtitles.mkv
but here I want to add the subtitles on the right hand side of my screen with multi-line on the RHS scrolling up as the time goes. Is there some command in ffmpeg to do it ?
Allow the video picture and the subtitle coincide here.
I need to find one parameter to control the position of the subtitles and
also one parameter to control the number of multi-lines.

  


• armv6 : Accelerate ff_imdct_half for general case (mdct_bits != 6)

  11 juillet 2014, par Ben Avison

  armv6 : Accelerate ff_imdct_half for general case (mdct_bits != 6)
  The previous implementation targeted DTS Coherent Acoustics, which only
  
  requires mdct_bits == 6. This relatively small size lent itself to
  
  unrolling the loops a small number of times, and encoding offsets
  
  calculated at assembly time within the load/store instructions of each
  
  iteration.
  In the more general case (codecs such as AAC and AC3) much larger arrays
  
  are used - mdct_bits == [8, 9, 11]. The old method does not scale for
  
  these cases, so more integer registers are used with non-unrolled versions
  
  of the loops (and with some stack spillage). The postrotation filter loop
  
  is still unrolled by a factor of 2 to permit the double-buffering of some
  
  VFP registers to facilitate overlap of neighbouring iterations.
  I benchmarked the result by measuring the number of gperftools samples
  
  that hit anywhere in the AAC decoder (starting from aac_decode_frame())
  
  or specifically in ff_imdct_half_c / ff_imdct_half_vfp, for the same
  
  example AAC stream :
                    Before          After
  
                    Mean   StdDev   Mean   StdDev  Confidence  Change
  
  aac_decode_frame  2368.1 35.8     2117.2 35.3    100.0%      +11.8%
  
  ff_imdct_half_*   457.5  22.4     251.2  16.2    100.0%      +82.1%
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/arm/mdct_vfp.S