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• What to do when opening a video and decodec AVFrame.pkt_dts doesn't start at the beggining

  6 mai 2020, par Milo

  I have a few video files (.mpg) that are cut from a larger video file and are probably encoded incorrectly. So when decoded, the received AVFrame.pkt_dts is set around half a second into the file.

  



  And since I'm calculating the current frame based on pkt_dts my current frame starts from 13. 
I can detect this and calculate the frame offset with

  



  frame_offset = (pFrame->pkt_dts/pFrame->pkt_duration)


  



  This however isn't much of an issue, but when implementing seeking with

  



  // seek to frame 500 and seek back to first key frame
seekTarget = 500;  
av_seek_frame(videoState_->ptrFormatCtx_, -1, seekTarget, AVSEEK_FLAG_FRAME  | AVSEEK_FLAG_BACKWARD);


  



  I usually get a first key frame and then just decode next frame until my specified frame. But with these files, av_seek_frame() will always put me exactly on the frame I seek but it's missing data because parent I frame is not decoded.
I'm guessing this happens because of incorrect pkt_dts from the start.

  



  I can kind of fix this by using the frame_offset again but is that really a correct approach to this issue ? It seems a little hacky.

  


• Vertically stack two images, draw a box on the bottom image then write multiline text in that box

  31 août 2020, par Sarmad S.

  I am trying to make a video from two images, where the two images should be vertically stacked. This is easy and can be done with the vstack command. I also managed to write text on the bottom image with the drawtext command. However I want to draw a blue box that covers half of the bottom image (the bottom part of the image) and write the text in that blue box.

  


  How do I go about doing so ?

  


  My code so far :

  


  ffmpeg -loop 1 -i image1 -i image2 -c:v libx264 -t 3 -pix_fmt yuv420p -filter_complex "[1]drawtext=my-font.otf: text='some multiline text': fontcolor=white: fontsize=50: x=(w-text_w)/2: y=(h-text_h)/2[v1], drawbox; [0][v1]vstack" -s 1080:1920 output.mp4"


  


  I also want to zoom slowly in the images (not the box or the text). Anyone can help me connect things ?

  


  I am able to zoom, drawbox, write text etc, but not able to combine them together.

  


• FFmpeg transcode GIF into Mp4 and Mp4 to AVI using GPU

  9 octobre 2023, par Cristian

  I'm trying to convert GIF animated to mp4 and mp4 to AVI with FFmpeg.

  


  I started to use just the CPU, but I have to process millions of GIFs/mp4 content pieces. So, I started to have a lot of errors processing them, and it ended as a bottleneck. Therefore, I'm trying to use GPU to process the videos.

  


  Converting GIF to mp4 with CPU, I run the following command :

  


  ffmpeg -i animated.gif -movflags faststart -pix_fmt yuv420p -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" video.mp4


  


  Using the GPU I'm trying the following :

  


  ffmpeg
  -y
  -hwaccel nvdec
  -hwaccel_output_format cuda
  -i gifInputPath
  -threads 1
  -filter_threads 1
  -c:v h264_nvenc
  -vf hwupload_cuda,scale_cuda=-2:320:240:format=yuv420p
  -gpu 0
   mp4VideoPath


  


  The above command generates an exit status 1.

  


  The following is the dmesg command log

  


  Converting mp4 videos to AVI videos I'm running the following command

  


  ffmpeg
-i videoInputPath
-vcodec rawvideo
-pix_fmt yuv420p
-acodec pcm_s16le
-ar 44100
-ac 2
-s 320x240
-r 4
-f avi
aviOutputVideoPath


  


  For GPU I tried :

  


  ffmpeg
 -y
 -hwaccel cuda
 -hwaccel_output_format cuda
 -i videoInputPath
 -threads 1
 -filter_threads 1
 -c:a pcm_s16le
 -ac 2
 -ar 44100
 -c:v h264_nvenc
 -vf hwupload_cudascale_cuda=-2:320:240:format=yuv420p
 -r 4
 -f avi
 -gpu 0
 aviOutputVideoPath


  


  The following is the dmseg output is log

  


  


  1. What should be the best command for converting the GIF into Mp4 and Mp4 into AVI based on CPU configuration using the GPU(Amazon Nvidia t4) for best performance, low CPU, and moderated GPU consumption ?

     


  


  2. What are the best suggestions to Process these content pieces concurrently using GPU ?

     


  


  


  Note : I'm using Golang to execute the FFmpeg commands.