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• lavc/opusdsp : simplify R-V V postfilter

  16 décembre 2023, par Rémi Denis-Courmont

  lavc/opusdsp : simplify R-V V postfilter
  This skips the round-trip to scalar register for the sliding 'x'
  
  coefficients, improving performance by about 5%. The trick here is that
  
  the vector slide-up instruction preserves elements in destination vector
  
  until the slide offset.
  The switch from vfslide1up.vf to vslideup.vi also allows the elimination
  
  of data dependencies on consecutive slides. Since the specifications
  
  recommend sticking to power of two offsets, we could slide as follows :
          vslideup.vi v8, v0, 2
  
          vslideup.vi v4, v0, 1
  
          vslideup.vi v12, v8, 1
  
          vslideup.vi v16, v8, 2
  However in the device under test, this seems to make performance slightly
  
  worse, so this is left for (in)validation with future better hardware.
  

  • [DH] libavcodec/riscv/opusdsp_rvv.S

• Expand (extend) a video to an specific duration

  8 février 2013, par BorrajaX

  Do VLC or FFmpeg (or AVconv) have any feature to force the duration of a video to a certain number of seconds ?

  Let's say I have a... 5 minutes .mp4 video (without audio). Is there a way to have any of the aforementioned tools "expanding" the video to a longer duration ? The video comes from a Power Point slideshow, but it's too short (running too fast, to say so). The idea would be automatically inserting frames so it reaches an specified duration. It looks like something pretty doable (erm... for a total newbie in video encoding/transcoding as I am) : A 5 minutes video, at 30fps means I have 9000 frames... To make it be 10 times longer, get the first "real" frame, copy it ten times, then get the second "real" frame, copy it ten times... and so on.

  I'm using Ubuntu 12.04, but I can install/compile any required software, if needed. So far, I have VLC, AVConv and FFmpeg (FFmpeg in an specific folder, so it won't conflict with AVConv)

  Thank you in advance.

• Expand (extend) a video to an specific duration [closed]

  1er octobre 2020, par BorrajaX

  Do VLC or FFmpeg (or AVconv) have any feature to force the duration of a video to a certain number of seconds ?

  



  Let's say I have a... 5 minutes .mp4 video (without audio). Is there a way to have any of the aforementioned tools "expanding" the video to a longer duration ? The video comes from a Power Point slideshow, but it's too short (running too fast, to say so). The idea would be automatically inserting frames so it reaches an specified duration. It looks like something pretty doable (erm... for a total newbie in video encoding/transcoding as I am) : A 5 minutes video, at 30fps means I have 9000 frames... To make it be 10 times longer, get the first "real" frame, copy it ten times, then get the second "real" frame, copy it ten times... and so on.

  



  I'm using Ubuntu 12.04, but I can install/compile any required software, if needed. So far, I have VLC, AVConv and FFmpeg (FFmpeg in an specific folder, so it won't conflict with AVConv)

  



  Thank you in advance.