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• Copy PTS from original video stream to processed video stream using ffmpeg and opencv

  25 janvier 2019, par Krishna Prasad Yellapragada

  I have two video files in webm format. First is the original video, captured using Chrome’s MediaRecorder API. The second is a processed video generated by processing each frame of the original video using OpenCV. How do I override the PTS of frames in processed video with PTS from original video. The number of frames between the two is same.

  The processed video is generated from a sequence of images using ffmpeg.

  ffmpeg -i frames/frame_%d.png -pix_fmt yuv420p ffmpeg-cfr.mp4

  This results in a CFR of 25fps. I have tried using the steps from the link, Can I create a VFR video from timestamped images ?. This only works on mp4 videos, and not on webm. The process of encoding to MP4 and converting back to webm results in very bad video quality and takes 3x time for each video.

  Along with the sequence of images, I am also writing the PTS of the original video for each frame in a timecodes.txt file. Are there any options in ffmpeg similar to mp4fpsmod (https://github.com/nu774/mp4fpsmod) ?
  I expect that when I dump block-wise timestamps in webm for original video and processed video, the PTS for each block match between the two.

• FFMPEG drops supposedly corrupt frames from original video while transcoding using h264 encoder

  19 février 2019, par t6nand

  I am using h264 for optimising MP4 for web. I have a video which has some supposedly corrupt frame(s) within it’s initial 1-2 seconds. (Frame provided below)

  On transcoding using :

  ffmpeg -i orig.mp4 -c:v libx264 -crf 25 -vf scale="-2:min(ih\,720)" -b:v 600K -g 90 -c:a libfdk_aac output.mp4

  The output MP4 has these frames dropped out and I have my output with it’s start about 1 to 2 seconds delayed from original video, thus resulting in overall less time duration in output video.

  Moreover, most media players also skip these frames in playback (like quicktime player, etc). But VLC media player was able to play this video without skipping these frames.

  Is there a way to not drop frames using ffmpeg ? And if possible is it possible to identify and fix these frames in a video ?

  Note : I tried encoding same video using AWS Elastic transcoder which actually fixed these frames (Frame provided below) :
  

  Note : Original video can be found here -
  https://drive.google.com/file/d/0B9VkhR9Zu60ybXFDeno3RGpQTUE/view?usp=sharing
  Video transcoded by AWS Elsatic transcoder can be found here -
  https://drive.google.com/file/d/0B9VkhR9Zu60yWUVHQk5MTk05QVk/view?usp=sharing

  EDIT1 : As suggested by @Mulvya in comments, TS-transcoded video can be found here - (https://drive.google.com/file/d/0B9VkhR9Zu60yU0t6T0dMME9ZMmc/view?usp=sharing)

• Revision 0bba4042c2 : Merge "Skip fetching original frame pointers for UV in background check"

  18 avril 2014, par Jingning Han

  Merge "Skip fetching original frame pointers for UV in background check"