Help Needed With Python ffprobe Script

[chris319]

The following code runs OK from a Windows command prompt:

ffprobe -select_streams v -i output.mpg -show_entries "frame=pkt_pts_time,pkt_duration_time,interlaced_frame" -pretty -print_format json -of json > output.mpg.json

but I don't know Python or ffprobe well enough to get this Python script to work:

import os, sys, subprocess, shlex, re
from subprocess import call

def probe_file(filename):

    cmnd = ['ffprobe.exe','-select_streams v', '-i output.mpg',' -show_entries, "frame=pkt_pts_time','pkt_duration_time','interlaced_frame'",'-pretty',' -print_format json',-of json > output.mpg.json]

    p = subprocess.Popen(cmnd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

    out, err =  p.communicate()
#    print ("==========output==========")

#    print (out)

    if err:
        print ("========= error ========")
        print (err)

probe_file('test_pattern_709.mp4')

Any help is appreciated.

Thank you.

[Ant_G]

Its pretty long time since i use FFMPEG stuff with python so forgive me if i make some mistake
but pretty sure that cmnd var can be written directly by using single quotes to wrap the whole command

cmnd = 'ffprobe -select_streams v -i output.mpg -show_entries "frame=pkt_pts_time,pkt_duration_time,interlaced_frame" -pretty -print_format json -of json > output.mpg.json'

[chris319]

I'll give that a try, thanks.

[chris319]

I got it to run without error but I'm not seeing the output I expect. It's not printing the format like it does when run as a batch file.

#!/usr/bin/python
import os, sys, subprocess, shlex, re
from subprocess import call

cmnd = ''
err = 0

def probe_file(filename):

  cmnd = 'ffprobe -select_streams v -i output.mpg -show_entries "frame=pkt_pts_time,pkt_duration_time,interlaced_frame" -pretty -print_format json -of json > output.mpg.json'


  p = subprocess.Popen(cmnd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
  #print (filename)
  
#  out, err =  p.communicate()
  out =  p.communicate()

  print ("==========output==========")

  print (out)

if err:
        print ("========= error ========")
        print (err)

probe_file('test_pattern_709.mp4')

[_Al_]

I ried this and it worked, for windows:

import subprocess
import os

def probe_file(ffprobe, filename):
    cmnd = [ffprobe , '-i', filename, '-show_entries' ,  'frame=pkt_pts_time,pkt_duration_time,interlaced_frame']  #'-print_format',  'json',  '-of',  'json'
    basename = os.path.basename(filename)
    with open(f'{basename}.txt', 'w') as log:
        p = subprocess.Popen(cmnd, stdout=log, stderr=subprocess.PIPE) #, shell = True #to not show pop up cmd window
        print(filename)
        out, err =  p.communicate()
        if out:  #if you redirect output to text file , there is no output here, out is None
            print("==========output==========")
            print(out.decode('utf-8'))
        if err:
            print("========= error ========")
            print(err.decode('utf-8'))
        
ffprobe = r'C:\path_to_ffprobe\ffprobe.exe'  #not having ffprobe in PATH
input = r'C:\path_to_file\videofile.mp4'

probe_file(ffprobe, input)

for linux:

import subprocess
import os

def probe_file(filename):
    cmnd = ['ffprobe' ,  '-show_entries' ,  'frame=pkt_pts_time,pkt_duration_time,interlaced_frame',  filename]  #'-print_format',  'json',  '-of',  'json'
    basename = os.path.basename(filename)
    with open(f'{basename}.txt', 'w') as log:
        p = subprocess.Popen(cmnd, stdout=log, stderr=subprocess.PIPE) 
        print(filename)
        out, err =  p.communicate()
        if err:
            print("========= error ========")
            print(err.decode('utf-8'))

input = /home/path_to_file/videofile.mp4'
probe_file(input)

linux has input file at the end

you can also pass a directory for storing logs, so you can redirect it to other disk etc.

[Ant_G]

import os
import subprocess
from pathlib import Path

ffprobe = Path(r"\ffprobe.exe")


def probe_file(_file):
    print("\non progress please wait...")
    cmnd = '"{0}" -hide_banner -select_streams v -i {1} -show_entries "frame=pkt_pts_time,pkt_duration_time,interlaced_frame" -pretty -print_format json -of json'.format(ffprobe, _file)

    a = subprocess.run(cmnd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=True)
    b = a.returncode

    if b == 0:
        print("=========output=========")
        c = open(Path(r"\output.mpg.json"), "w")
        c.write(a.stdout)
    else:
        print("\n=========error!=========")
        print(a.stderr)


print("Enter your File path...")
probe_file(Path(input()))

edit: because of your question i have a good time by making this

[chris319]

Thanks, Al - it works! Except it is printing the output as one big error message so I swapped the order of "out" and "err" on line 10:

import subprocess
import os

def probe_file(ffprobe, filename):
    cmnd = [ffprobe , '-i', filename, '-show_entries' ,  'frame=pkt_pts_time,pkt_duration_time,interlaced_frame']  #'-print_format',  'json',  '-of',  'json'
    basename = os.path.basename(filename)
    with open(f'{basename}.txt', 'w') as log:
        p = subprocess.Popen(cmnd, stdout=log, stderr=subprocess.PIPE) #, shell = True #to not show pop up cmd window
        print(filename)
        err, out =  p.communicate() # <- swapped order of "out" and "err"
        if out:  #if you redirect output to text file , there is no output here, out is None
            print("==========output==========")
            print(out.decode('utf-8'))
        if err:
            print("========= error ========")
            print(err.decode('utf-8'))

ffprobe = r'ffprobe.exe'  #not having ffprobe in PATH
input = r'test_pattern_709.mp4' #C:\path_to_file\videofile.mp4'

probe_file(ffprobe, input)

[_Al_]

it is printing the output as one big error message so I swapped the order of "out" and "err" on line 10:

        err, out =  p.communicate() 
      
probe_file(ffprobe, input)

it will work but it is a booby trap sort of, if it is swapped like that, you call out as err and err as out. It is quite normal that information is in stderr, so I'd leave it as err, except change comments to info, for example:

        out, err =  p.communicate()
        if err:
            print("========= info ========")
            print(err.decode('utf-8'))

so this way it is clear that ffprobe puts info into stderr

[chris319]

That's weird, but I've changed it as you have it.

[_Al_]

not sure what you mean, in your last example you have: err, out = p.communicate(), where it might rather be: out, err= p.communicate()
from manual: communicate() returns a tuple: (stdoutdata, stderrdata)

[chris319]

Here is the complete program, per your suggestion:

import subprocess
import os

def probe_file(ffprobe, filename):
    cmnd = [ffprobe , '-i', filename, '-show_entries' ,  'frame=pkt_pts_time,pkt_duration_time,interlaced_frame']  #'-print_format',  'json',  '-of',  'json'
    basename = os.path.basename(filename)
    with open(f'{basename}.txt', 'w') as log:
        p = subprocess.Popen(cmnd, stdout=log, stderr=subprocess.PIPE) #, shell = True #to not show pop up cmd window
            #print(filename)
        out,err =  p.communicate()
        if out:  #if you redirect output to text file , there is no output here, out is None
            print("==========output==========")
            print(out.decode('utf-8'))
        if err:
            print("========= info ========")
            print(err.decode('utf-8'))

ffprobe = r'ffprobe.exe'  #not having ffprobe in PATH
input = r'test_pattern_709.mp4' #C:\path_to_file\videofile.mp4'

probe_file(ffprobe, input)

[_Al_]

oh, ok, weird in a sense that info is in stderr. It helps to think of it something like two band channel. Out and err are just labels and devoleper channels whatever into whatever channel. Thanks to that, ffprobe can do a thing you want and still prints its own log. Or you can take out those labels and just use indexing, first item in that tuple has index 0, second 1:

        p = subprocess.Popen(cmnd, stdout=log, stderr=subprocess.PIPE)
        results = p.communicate()
        if results[1]:
            print("========= info ========")
            print(results[1].decode('utf-8'))