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• Encode uncompressed avi from webcam

  17 août 2013, par shaun

  I have to record videos for a project I'm doing. Two of these are USB cameras and another is a n IP overhead camera.All three are connected to a laptop computer. After recording the videos I need to be able to open them in an editor (not for editing particularly but for modeling stuff in them for which I need a timeline). I have chosen Sony Vegas Pro for my editor. I have been able to record the uncompressed avi using gstreamer with this command :

  gst-launch v4l2src device=/dev/video0 ! 'video/x-rawyuv,width=640,height=480,framerate=10/1' ! mux. avimux name=mux ! filesink location=temp.avi

  I had to set the framerate to 10 because I was using two USB cameras and a framerate of 30 on both could not be accomodated in the bandwidth of the USB controller. I do not care about audio in my file so I don't grab audio. Similary, while encoding I wouldn't care about audio as well. This is raw uncompressed avi. I was not able to open this in Sony Vegas Pro. I believe I need to encode this uncompressed avi using a codec that will be opened by Sony Vegas Pro (I don't know which codecs Sony likes, so I'll probably try different ones until one of them opens).

  For encoding this video, I have several options : mencoder, ffmpeg, gstreamer. But I am not able to figure out how to use these tools to get what I want. Ideally, I would like just to sort of "insert" a codec with other settings remaining the same. I don't really care about the how much space the resulting video takes since the length of the videos are not going to be more than 3 minutes and I have space available, so lossless codecs also work. I believe Sony reads mpeg avi's so if I can get that, it'll be great.

  Thanks for reading and I appreciate all the help.

• FFMPEG - Palettegen for animations is not working

  18 juillet 2018, par deanhodges

  I have a script taken from the correct answer at https://superuser.com/questions/1002562/convert-multiple-images-to-a-gif-with-cross-dissolve, but I am getting no results.

  Even copying the code word for word does not work for me.

  However, if I run $ffmpeg = shell_exec("ffmpeg -i images/image001.jpg -vf palettegen palette_test.png"); on a single image, it works fine. But because I need it for an animation, I need to create a pallete for all images.

  Unless of course, on each image in the GIF sequence I can load a new palette ?

  $q = "ffmpeg -f image2 -framerate 0.5 -i ../view/client/files/".$dir."/%*.jpg -i palettePro.png -lavfi paletteuse -y .." . $save_path . '/' . $filename . " -report";

• how the packuswb instruction works ? (in low level bit operation)

  17 avril 2019, par MaikonNascimento

  Studying ffmpeg convertion from yuv to rgb , I came across the equation being implemented in assembly, yuv2rgb_template.c located in ffmpeg/libswscale/x86.

  I want to know how the instruction packuswb works ? Google says it :

  Converts 4 signed word integers from mm and 4 signed word integers from mm/m64 into 8 unsigned byte integers in mm using unsigned saturation.

      DEST[7:0] ← SaturateSignedWordToUnsignedByte DEST[15:0];
  
      DEST[15:8] ← SaturateSignedWordToUnsignedByte DEST[31:16];
  
      DEST[23:16] ← SaturateSignedWordToUnsignedByte DEST[47:32];
  
      DEST[31:24] ← SaturateSignedWordToUnsignedByte DEST[63:48];
  
      DEST[39:32] ← SaturateSignedWordToUnsignedByte SRC[15:0];
  
      DEST[47:40] ← SaturateSignedWordToUnsignedByte SRC[31:16];
  
      DEST[55:48] ← SaturateSignedWordToUnsignedByte SRC[47:32];
  
      DEST[63:56] ← SaturateSignedWordToUnsignedByte SRC[63:48];

  Since I dont know Assembly x86, it is even hard to simulate it or debug the current code.

  I want to know how they fit 16 bits in 8 bits ?