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• How to extract frame types along with motion vectors using extract_mvs.c from ffmpeg

  26 février 2018, par helmo

  I have been researching ways to get frame types (I, P, B) along with the motion vector data returned from extract_mvs.c in the examples folder in ffmpeg.

  The extract_mvs.c file after it is compiled, returns information like this :

  framenum,source,blockw,blockh,srcx,srcy,dstx,dsty,flags
  
  2,-1,16,16,   8,   8,   8,   8,0x0
  
  2, 1,16,16,   8,   8,   8,   8,0x0
  
  2, 1,16,16,  24,   8,  24,   8,0x0
  
  2, 1,16,16,  40,   8,  40,   8,0x0
  
  2, 1,16,16,  56,   8,  56,   8,0x0
  
  2, 1,16,16,  72,   8,  72,   8,0x0
  
  2, 1,16,16,  88,   8,  88,   8,0x0
  
  ...
  
  297, 1,16,16, 248, 280, 248, 280,0x0
  
  297, 1,16,16, 264, 280, 264, 280,0x0
  
  297,-1,16,16, 278, 279, 280, 280,0x0
  
  297, 1,16,16, 280, 280, 280, 280,0x0
  
  297, 1,16,16, 296, 280, 296, 280,0x0
  
  297, 1,16,16, 312, 280, 312, 280,0x0
  
  297, 1,16,16, 328, 280, 328, 280,0x0
  
  297, 1,16,16, 344, 280, 344, 280,0x0

  Along with this information, I would like to output frame type so that I know framenum = 2 is, for example, a ’B’ frame.

  I tried different things, one of which was using a separate command :

  ffprobe input.mp4 -show_frames | grep -E 'pict_type|coded_picture_number'

  But the problem with this command is that it returns data like :

  pict_type=I
  
  coded_picture_number=0
  
  pict_type=B
  
  coded_picture_number=2
  
  pict_type=P
  
  coded_picture_number=1
  
  pict_type=B
  
  coded_picture_number=4
  
  pict_type=P
  
  coded_picture_number=3
  
  ....
  
  pict_type=P
  
  coded_picture_number=293
  
  pict_type=B
  
  coded_picture_number=297
  
  pict_type=B
  
  coded_picture_number=296

  And there is no much I can relate here between coded_picture_number and framenum. The former starts counting from 0 and the later from 2. I assume framenum starting from 2, means the count from this variable is actually from 1, and it ignored 1 in the extraction process as it is maybe an I frame thus no motion vectors.

  So, how can we use only extract_mvs.c to get not only that information it provides but also the frame types in the returned table. Any hints either syntax/command-wise or in editing the c file would be appreciated. Thanks in advance.

• subprocess.call can't find file/shutil.which failed in pycharm

  4 décembre 2022, par Percy Yang

  I am trying to transform a mp3 to a wav file in pycharm using subprocess

  


  import subprocess
subprocess.call(['ffmpeg', '-i','test.mp3','test.wav'])


  


  It returns error of not finding file, so I change the 'ffmpeg' to its path on my pc and it work.

  


  The problem is that I am making an app and others might install ffpmeg on other's location (since it is download with zip and can be unzip at any place), but I don't know how to get its full path.

  


  I tried using os module

  


  import os
print(os.path('ffmpeg.exe'))


  


  but it seems like it is not able to get the path of exe

  


  Traceback (most recent call last):&#xA;  File "C:\Users\Percy\PycharmProjects\APP\test3.py", line 8, in <module>&#xA;    print(os.path(&#x27;ffmpeg.exe&#x27;))&#xA;TypeError: &#x27;module&#x27; object is not callable&#xA;</module>

  


  I also tried shutil module

  


  import shutil
print(shutil.which('ffmpeg'))
print(shutil.which('ffmpeg.exe'))


  


  but it returns 2 None (prob wrong cause I am 100% sure I have installed ffmpeg)

  


  None
None


  


  I want to ask if there is any way to get the full path of ffmpeg in pycharm or any method that I can make ffmpeg install in designated path with the app when it is downloaded by users

  


• FFMPEG : invalid data found when processing input, but same input works in FFPLAY

  20 janvier 2023, par SoerenS

  I have a TCP stream with raw 8-bit image data (1280x720) that I receive and display with FFPLAY without problems, but it´s not possible to process the same input with FFMPEG.

  


  This works :

  


  ffplay -i tcp://127.0.0.1:8485\?listen -f rawvideo -pixel_format gray -video_size 1280x720

  


  But when I try to process the same stream with FFMPEG, it always immediatly returns after the first frame with :

  


  tcp://127.0.0.1:8485\?listen: Invalid data found when processing input

  


  I tried the following commands :

  


  ffmpeg -i tcp://127.0.0.1:8485\?listen -f rawvideo -pixel_format gray -video_size 1280x720
ffmpeg -i tcp://127.0.0.1:8485\?listen -f rawvideo -pixel_format gray -video_size 1280x720 -c:v mjpeg -f mjpeg -qscale 6 test.avi

  


  Same behavior under Windows and Ubuntu. FFMPEG and FFPLAY are from the same set of prebuilt binaries. Version command returns N-107067-g5d5a014199-20220609. Unfortunately I have no access to the code of the stream origin. Any idea about a potential root-cause and what I could try ?