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• Android - merge videos taken with front and back cameras

  3 mai 2023, par Raz Leshem

  I am having an orientation problem when merging videos taken with front and back cameras in portrait, recorded using Android CameraX.

  


  This issue is explained here, but I am yet to find a working solution. I have tried multiple solutions, such as using mp4parser as suggested in the issue explanation, but the result is a that every alternate camera video is upside down.
I also tried using FFmpeg for android - mobile-ffmpeg.
Using ffmpeg Concat demuxer resulted in the same result as mp4parser did.

  


  Concat demuxer command I used : ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4

  


  I also tried changing the rotation metadata of the videos to match before concatenating, similar to how it's done here, but that did not seem to have any effect on the end result.

  


  Lastly, I used ffmpeg Concat filter. That solution took longer obviously because of the re-encoding of the video but it did fix the problem of the orientation of the videos, but the output video quality was poor.

  


  Concat filter command :

  


  ffmpeg -i front1.mp4 -i rear1.mp4 -i front2.mp4 \
-filter_complex "[0:v] [0:a] [1:v] [1:a] [2:v] [2:a] \
concat=n=3:v=1:a=1 [v] [a]" \
-map "[v]" -map "[a]" output.mp4


  


  Has anyone found a solution on how to fix the orientation problem in android ? or maybe how can I keep the videos quality as much as possible when using the FFmpeg Concat filter to merge the videos ?

  


• FFMPEG Conact Demuxer Re-Encoding When Trying to Merge MP4s

  6 avril 2022, par Kyle Sinko

  I am trying to merge MP4 recordings straight out of OBS together into one MP4. From what I understand, I am using the concat demuxer to achieve this as it merges the files "extremely quickly" without re-encoding.

  


  I am using the command

  


  ffmpeg.exe -f concat -safe 0 -i "mylist.txt" -c copy video.mp4


  


  as explained in this post

  


  


  

  2. concat demuxer Use this method when you want to avoid a re-encode and your format does not support file-level concatenation (most files
used by general users do not support file-level concatenation).

  


  


  


  The command runs successfully, but the process takes a very long time. I assume the videos are being re-encoded as this is what shows :

  


  


  Output #0, mp4, to 'video.mp4' : Metadata :
encoder : Lavf58.51.100
Stream #0:0(und) : Video : h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x2160 [SAR 1:1 DAR 8:9], q=2-31, 1

  


  


  I'm unsure as to why the process is taking so long and want to know how I can merge the MP4 files into a single MP4 output file almost instantly.

  


• How to add a watermark to the saved video with CameraX api in saving time

  14 novembre 2022, par Nino Sand

  I am using the CameraX api approach to record the videos and saving them as explained in the documents : https://developer.android.com/training/camerax/video-capture
  
I tried with ffmpeg-android-java but clearly it needs to process the saved video not adding to the saved frames in real time.
  
  
Now, I want to add a watermark to all saved videos in easy and not costly way and without the need to reprocess the video ?
  
Also, if there is no way, what the best and fastest approach to process the video to only add a watermark ?