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• Why does the PyAV-encoded video have a different total time in seconds than the original file

  13 octobre 2023, par Diego Medeiros

  I'm taking a mp4 file, decoding it frame by frame and reencoding it. I'm using PyAV and the reencoding is running on h265.
When the code is running, it seems that all frames are passed from the decoder to the encoder, but at the end I have a file with 3 seconds less. For longer videos I'll have bigger differences.

  


  I have already checked the fps, it comes out with a very small variation, even if I use the Fraction type to avoid decimal differences.

  


  I'd like to know if it's some parametrization error, or if this is something to do with the encoder itself like keyframes and all those sort of things. Is there a way to fix it ?

  


  import av


container = av.open('input.mp4')

# create an output container to receive the transcoded video packets
output_container = av.open('output.mp4', 'w', format='mp4')
# add a stream to output container with same fps as input and h265 codec
output_stream = output_container.add_stream(
    'libx265', rate=container.streams.video[0].average_rate)
# set the output stream size
output_stream.width = 640
output_stream.height = 480

print('Starting transcoding...')

actual_frame = 0
container_total_frames = container.streams.video[0].frames

# start decoding packets and reading frames from the container
try:
    for packet_input in container.demux():
        if packet_input.dts is None:
            break
        for frame in packet_input.decode():

            try:
                actual_frame += 1
                # convert the frame to a numpy array
                img = frame.to_ndarray(format='bgr24')

                # prepare the ndarray frame and encode it
                frame_nd = av.VideoFrame.from_ndarray(img, format='bgr24')
                packet_output = output_stream.encode(frame_nd)
                output_container.mux(packet_output)
                print('Frame: {}/{}'.format(actual_frame, container_total_frames))
            except Exception as e:
                print("Error writing frame: ", e)
                break
except Exception as e:
    print('Finished transcoding')

output_container.close()

print('Finished transcoding')



  


• Batch encode then compare file size vs original and delete larger

  6 novembre 2019, par PolarBear

  Currently running a batch script to mass convert media clips to save some storage space. I’d like to also add automation to the script that after the conversion will delete which ever ends up being the larger file. Not entirely sure how to best set that up at the end of each conversion.

  pushd "%2"
  
  
  
  ::Default variables
  
  SET paths=paths.txt
  
  ::paths lets you put a bunch of folder paths in a text file and run this across those, instead of individually. I use this to run overnight on a LOT of footage folders at once. Thanks to Aayla for a lot of these upgrades
  
  ::Fun tip - select your folders (15 max at a time) and shift+rig-!click and click "copy as paths"
  
  SET /A ffmpeg_qv=24
  
  ::change CQP value here so you only have to type it once. 22 is lossless for HEVC.
  
  
  
  ::for /R %%A in (*.mp4, *.avi, *.mov, *.wmv, *.ts, *.m2ts, *.mkv, *.mts) do (
  
  ::    echo Processing %%A
  
  ::    ffmpeg -hwaccel auto -i "%%A" -pix_fmt p010le -map 0:v -map 0:a -c:v hevc_nvenc -rc constqp -qp 21 -b:v 0K -c:a libfdk_aac -vbr 5 -movflags +faststart "%%A~dnpA_CRF%ffmpeg_qv%_HEVC.mp4"
  
  ::    echo Processed %%A
  
  ::)
  
  ::pause
  
  ::Test if the paths file exists and iterate through it
  
  if EXIST %paths% (
  
      for /f "tokens=*" %%a in (%paths%) do (
  
          echo Changing to directory %%a
  
          pushd "%%a"
  
          CALL :ffmpeg
  
      )
  
  ) else (
  
      ::It doesn't exist
  
      CALL :ffmpeg
  
  )
  
  pause
  
  EXIT /B %ERRORLEVEL%
  
  ::Don't run the function when they're first defined because that's a thing Batch does for some reason???
  
  :ffmpeg
  
      for /R %%A in (*.mp4, *.avi, *.mov, *.wmv, *.ts, *.m2ts, *.mkv, *.mts) do (
  
          echo Processing "%%A"
  
          ffmpeg -hwaccel auto -i "%%A" -pix_fmt yuv420p -map 0:v -map 0:a -map_metadata 0 -c:v hevc_nvenc -rc constqp -qp %ffmpeg_qv% -b:v 0K -c:a aac -b:a 128k -movflags +faststart -movflags use_metadata_tags "%%A~dnpA_CRF%ffmpeg_qv%_HEVC.mp4"
  
          :: "-map_metadata 0" copies all metadata from source file
  
          :: "-movflags +faststart" helps with audio streaming
  
          echo Processed %%A
  
          :: echo inFile %%A outFile %%A~dnpA_CRF%ffmpeg_qv%_HEVC.mp4
  
          :: code here to check if A>B or B<a then="then" delete="delete" the="the" larger="larger" of="of" two="two" goto="goto"></a>code>

• Black screen when recording specific screen / window using ffmpeg [closed]

  16 mai, par Mark Brin

  Issue :
I'm trying to capture the specific window using ffmpeg & i've tried these below command for that :

  


  ffmpeg -f gdigrab -framerate 30 -i title="Window Title" -b:v 3M -pix_fmt yuv420p output_FILENAME.webm


  


  And also try changing output format to .mp4

  


  ffmpeg -f gdigrab -framerate 30 -i title="Window Title" -b:v 3M -pix_fmt yuv420p output_FILENAME.mp4


  


  but the output video just shows the black screen with cursor.

  


  What i've tried :

  


  


  • Tried online solutions like Recording Screen with FFmpeg, How to record a specific window using ffmpeg ?, Record specific window using ffmpeg, but none of them worked.

    


  


  • even tried some of the tweaks like removing flags like -pix_fmt yuv420p also tried -f d3d11grab but didn't work.

    


  


  • When i try desktop capture it works completely fine.

    


  


  • I'm using this command to confirm that i'm using correct window title

    


  


  


  Get-Process |
  Where-Object { $_.MainWindowTitle -ne "" } |
  Select-Object -Unique MainWindowTitle


  


  System I'm using :

  


  Windows 11