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• ffmpeg - Text fontcolor is changed (faded) because of alpha(I think). Is there any possibility to avoid this behavior ?

  13 mai 2019, par Bedrule Paul

  I am using following command

      ffmpeg -i ~/Desktop/input.mp4 -filter_complex  "color=black:100x100[c];\
  
  [c][0]scale2ref[ct][mv]; \
  
  [ct]setsar=1,split=1[t1]; \
  
  [t1]drawtext=text='Test Text 1':fontsize=36:fontcolor=#13348b\
  
  ,split[text1][alpha1]; \
  
  [text1][alpha1]alphamerge,rotate=30:ow=rotw(30)\
  
  :oh=roth(30):c=black@0[txta1]; \
  
  [mv][txta1]overlay=x='min(0,-H*sin(30))+500':\
  
  y='min(0,W*sin(30))+350':shortest=1" \
  
  ~/Desktop/result.mp4 -y

  I think alpha is the problem, but I don’t know how to avoid it.

• Enhance text image in x264 encoding

  24 août 2016, par useprxf

  I’m making use of x264 for remote desktop streaming. The goal is to achieve both low bitrate and high video quality within the computation budget. The current parameter set I used almost achieve this goal, but it fails in handling images with many texts (e.g. browsing websites scene). The text in image is blurred and affects the user experience.

  I think it’s the quantization in x264 that causes this. The quantization after DCT transform will eliminate high frequency sinals which mainly correspond to texts in image.

  So, my question is how to improve the text quality in x264 encoding ?

  My idea : when the bitrate stays at a low level for a period of time,

  1. set crf to be 0 (lossless) ;
  2. encode current frame as an IDR frame and then send it ;
  3. recover the crf.

  Also, a flag should be used to prevent resending when bitrate keeps low for a long time. I haven’t try this method since I don’t know how to mark a frame as an IDR frame manully and then encode it.

• avcodec/mips : [loongson] refine process of setting block as 0 in h264dsp_mmi.

  28 juillet 2019, par Shiyou Yin

  avcodec/mips : [loongson] refine process of setting block as 0 in h264dsp_mmi.
  In function ff_h264_add_pixels4_8_mmi, there is no need to reset '%[ftmp0]'
  
  to 0, because it's value has never changed since the start of the asm block.
  
  This patch remove the redundant 'xor' and set src to zero once it was loaded.
  In function ff_h264_idct_add_8_mmi, 'block' is seted to zero twice.
  
  This patch removed the first setting zero operation and move the second one
  
  after the load operation of block.
  In function ff_h264_idct8_add_8_mmi, 'block' is seted to zero twice too.
  
  This patch just removed the second setting zero operation.
  This patch mainly simplifies the implementation of functions above,
  
  the effect on the performance of whole h264 decoding process is not obvious.
  
  According to the perf data, proportion of ff_h264_idct_add_8_mmi decreased from
  
  0.29% to 0.26% and ff_h264_idct8_add_8_mmi decreased from 0.62% to 0.59% when decoding
  
  H264 format on loongson 3A3000(For reference only , not very stable.).
  Reviewed-by : Reimar Döffinger <Reimar.Doeffinger@gmx.de>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/mips/h264dsp_mmi.c