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• How to set frame offset for source and reference video for calculating using FFMpeg commandline ?

  1er septembre 2018, par Souvik Das

  I have a scenario where I am streaming a reference video on a server machine and receiving it at a client machine with exact same codec, using FFMpeg via UDP/RTP.

  So, I have a reference.avi file and a recording.ts file with me. Now, due to a network side issue and FFMpeg discarding old frames, often the recording.ts lacks exactly 12 FRAMES from the beginning. Sometimes, it may lack more frames in-between but that’d due to general network traffic and packet loss reason and I don’t plan to account for that. Anyways, due to those 12 frames, when I calculate the PSNR, it drops down to 13, even though remaining frames may/may not be affected.

  So, my aim is to discard first 12 frames from reference.ts and then compare. For that, I would also need to adjust the frames from recording.ts.

  Consider the following scenario :

  reference.ts has 1500 frames. So naturally I am going to cut-short it 1488. Then we have the following cases :

  1. recording.ts has 1500 frames. This is not affected. Still I will remove 12 frames to match the count. So frame 1 would then represent frame 13.
  2. recording.ts has 1496 frames. This is not affected. Still I will remove 12 frames even though it’d get to 1484 count assuming that frame 1 would then represent frame 13.
  3. recording.ts has 1488 frames. This is affected. No need to remove frames.
  4. recording.ts has 1480 frames. This is affected. No need to remove frames.

  Once that is done, then I will calcualte the PSNR. So, my FFMpeg should be able to do all this, hopefully in a single command on bash.

  A better alternative would be for FFMpeg to find the where the 13th frame is in recording.ts and then cut-short from the beginning. That’d be more preferred and even more if there is no cut-shorting required, i.e. if offset could be set in-line to command and no additional video output is generated for use in PSNR comparison.

  Current I am using the following command to calculate the PSNR.

  ffmpeg -i 'recording.ts' -vf "movie='reference.avi', psnr=stats_file='psnr.txt'" -f rawvideo -y /dev/null

  It’d be great if somebody could help me in this regard. Thanks.

• How can I change slice_type which is show in Elecard stream analyzer using ffmpeg ?

  10 octobre 2018, par Tooraj Jam

  I’m not ffmpeg and encodding expert and am trying to encode a MP4 file to MPEG-4 h264 .ts file.

  When Elecard stream analyzer is analyzing my result .ts file, it shows slice_type = 7 for all of i-frames as you can see in the attached screenshot.

  How can I change all these to slice_type = 2 ?

  My ffmpeg command :

  -i Source.mp4 \
  
  -filter:v 'setpts=0+PTQ-STARTPTS' -metadata:s:v:0 start_time=0 \
  
  -f adts -c:a libfdk_aac  -profile:a aac_he  -strict -2 -ar 48000 -b:a 48k \
  
  -f mpegts -c:v libx264  -vbsf h264_mp4toannexb -strict experimental -    profile:v main -level:v 3.0 -preset:v slow -movflags faststart -pat_period 100 \
  
  -x264opts nal-hrd=cbr:force-cfr=1 -crf 25 -vf scale=w=640:h=360 -aspect 16:9 \
  
  -bf 1  -sc_threshold 0 -keyint_min 2*25 -g 2*25 \
  
  -force_key_frames "expr:gte(t,n_forced*50)" -max_muxing_queue_size 1500k \
  
  -coder 1  -refs 2 \
  
  -b:v 750k -minrate 750k -maxrate 750k -bufsize 1500k \
  
  -vsync 1 -framerate 25000/1001 \
  
  -x264opts "bitrate=750:vbv-maxrate=750:vbv-bufsize=1500"\
  
  -pix_fmt yuv420p  -r 25 -x264opts force-cfr \
  
  -mbs_per_slice 1 -y dest.ts

  

• Get duration from multiple video files ?

  22 mai 2022, par Soyal7

  I want to extract video duration metadata from every video file in a specified directory and then view the total duration.

  



  I need to extract the data from as much as thousands of videos overall. In Windows I can view the total duration for many files manually when selecting them in the explorer and going into details. For 1500 mp4 files it takes about 20 seconds to make the calculations and view the total time. It's relatively much faster then what I'm currently getting when iterating with FFprobe.

  



  How fast I am currently getting the result with FFprobe.

  



  for filename in dirFiles:
   print(subprocess.check_output(['ffprobe', '-i', filename, '-show_entries','format=duration', '-sexagesimal' ,'-v', 'quiet', '-of', 'csv=%s' % ("p=0")]))


  



  What is the faster way to do this ?