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• lavc/vc1dsp : fix R-V V avg_mspel_pixels

  1er juin 2024, par Rémi Denis-Courmont

  lavc/vc1dsp : fix R-V V avg_mspel_pixels
  The 8x8 pixel arrays are not necessarily aligned to 64 bits, so the
  
  current code leads to Bus error on real hardware. This reproducible
  
  with FATE's vc1_ilaced_twomv test case.
  The new "pessimist" code can trivially be shared for 16x16 pixel
  
  arrays so we also do that. FWIW, this also nominally reduces the
  
  hardware requirement from Zve64x to Zve32x.
  T-Head C908 :
  
  vc1dsp.avg_vc1_mspel_pixels_tab[0][0]_c :      14.7
  
  vc1dsp.avg_vc1_mspel_pixels_tab[0][0]_rvv_i32 : 3.5
  
  vc1dsp.avg_vc1_mspel_pixels_tab[1][0]_c :       3.7
  
  vc1dsp.avg_vc1_mspel_pixels_tab[1][0]_rvv_i32 : 1.5
  SpacemiT X60 :
  
  vc1dsp.avg_vc1_mspel_pixels_tab[0][0]_c :      13.0
  
  vc1dsp.avg_vc1_mspel_pixels_tab[0][0]_rvv_i32 : 3.0
  
  vc1dsp.avg_vc1_mspel_pixels_tab[1][0]_c :       3.2
  
  vc1dsp.avg_vc1_mspel_pixels_tab[1][0]_rvv_i32 : 1.2
  

  • [DH] libavcodec/riscv/vc1dsp_init.c
  • [DH] libavcodec/riscv/vc1dsp_rvv.S

• lavc/h264dsp : R-V V 8-bit h264_weight_pixels

  4 juillet 2024, par Rémi Denis-Courmont

  lavc/h264dsp : R-V V 8-bit h264_weight_pixels
  There are two implementations here :
  
   a generic scalable one processing two columns at a time,
  
   a specialised processing one (fixed-size) row at a time.
  Unsurprisingly, the generic one works out better with smaller widths.
  
  With larger widths, the gains from filling vectors are outweighed by
  
  the extra cost of strided loads and stores. In other words, memory
  
  accesses become the bottleneck.
  T-Head C908 :
  
  h264_weight2_8_c :        54.5
  
  h264_weight2_8_rvv_i32 :  13.7
  
  h264_weight4_8_c :       101.7
  
  h264_weight4_8_rvv_i32 :  27.5
  
  h264_weight8_8_c :       197.0
  
  h264_weight8_8_rvv_i32 :  75.5
  
  h264_weight16_8_c :      385.0
  
  h264_weight16_8_rvv_i32 : 74.2
  SpacemiT X60 :
  
  h264_weight2_8_c :        48.5
  
  h264_weight2_8_rvv_i32 :   8.2
  
  h264_weight4_8_c :        90.7
  
  h264_weight4_8_rvv_i32 :  16.5
  
  h264_weight8_8_c :       175.0
  
  h264_weight8_8_rvv_i32 :  37.7
  
  h264_weight16_8_c :      342.2
  
  h264_weight16_8_rvv_i32 : 66.0
  

  • [DH] libavcodec/riscv/h264dsp_init.c
  • [DH] libavcodec/riscv/h264dsp_rvv.S

• Is there a simple way to create 8 or 16 bit grayscale videos using matplotlib ?

  19 avril 2022, par user18544920

  I have been reading for 3 days however still can't quite wrap my head around how to do the following. We have been asked to produce a simulation video from matplotlib to evaluate a programme that only accepts u8 or u16 grayscale videos. I have managed to produce the required animated scatterplot using the following code, however only know how to convert to grayscale using the second chunk of code in CV2 that results in a lot of compression.

  


  I would get marked down for both the heavy compression and not doing it within the animation code, however I don't know of a way to do it during the animation code.

  


  Animation code

  


  pixelx = 250  # length of x for resulting movie in pixels
pixely = 250  # length of y for resulting movie in pixels
fig2d = plt.figure(figsize=(pixelx/72, pixely/72), dpi=72)
ax2d = fig2d.add_axes([0,0,1,1])
ax2d.set_axis_off()
scatter2d = ax2d.scatter([], [], s=(pixelx*particle.rad/Env.X)**2, marker='o', edgecolors='none', c='#000000', cmap='gray')
ax2d.set_aspect('auto')
ani2d = FuncAnimation(fig2d, update2d, frames=(duration * fps), init_func=initial2d, blit=False, interval=1000/fps,
                      repeat=True)
ani2d.save('x.avi', writer='ffmpeg', fps=fps, dpi=72)


  


  RGB to grayscale code

  


  import cv2
source = cv2.VideoCapture('x.avi')
frame_width = int(source.get(3))
frame_height = int(source.get(4))
size = (frame_width, frame_height)
result = cv2.VideoWriter('xG.avi',
                         cv2.VideoWriter_fourcc(*'MJPG'), 200, size, 0)
while True:

    ret, img = source.read()

    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

    result.write(gray)

    cv2.imshow("frame", gray)

    key = cv2.waitKey(1)
    if key == ord("q"):
        break

cv2.destroyAllWindows()
source.release()


  


  Any help would be greatly apprciated