How to pipe output from ffmpeg using python?

Question

I am trying to pipe output from FFmpeg in Python. I am reading images from a video grabber card and I am successful in reading this to an output file from the command line using dshow. I am trying to grab the images from the card to my OpenCv code to be able to further play with the data. Unfortunately, when I pipe out the images, I just get a display of the video as shown in the link:

link: s000.tinyupload.com/?file_id=15940665795196022618.

The code I used is as shown below:

import cv2
import subprocess as sp
import numpy
import sys
import os
old_stdout=sys.stdout
log_file=open("message.log","w")
sys.stdout=log_file

FFMPEG_BIN = "C:/ffmpeg/bin/ffmpeg.exe"
command = [ FFMPEG_BIN, '-y',
            '-f', 'dshow', '-rtbufsize', '100M',
            '-i', 'video=Datapath VisionAV Video 01' ,
             '-video_size', '640x480',
              '-pix_fmt', 'bgr24', '-r','25',  
          '-f', 'image2pipe', '-' ]    
pipe = sp.Popen(command, stdout = sp.PIPE, bufsize=10**8)

while True:
    # Capture frame-by-frame
    raw_image = pipe.stdout.read(640*480*3)
      # transform the byte read into a numpy array
    image =  numpy.frombuffer(raw_image, dtype='uint8')
    print(image)
    image = image.reshape((480,640,3))          
    if image is not None:
        cv2.imshow('Video', image)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
    pipe.stdout.flush()
sys.stdout=old_stdout
log_file.close()
cv2.destroyAllWindows()

Please do provide me some pointers to fix this issue. Help is greatly appreciated.

@Muhammad Furqan adding -f image2pipe in the end before '-' in the ffmpeg command does not seem to give me the video still. Do you have any other suggestions? — user10890282
– user10890282, Commented Mar 5, 2019 at 12:40
Try to modify the comand as follow [ FFMPEG_BIN, '-y', '-f', 'dshow', '-rtbufsize', '100M', '-i', 'video=Datapath VisionAV Video 01' ,'-f', 'image2pipe', '-video_size', '640x480', '-pix_fmt', 'bgr24', '-r','25', '-' ] — asendjasni
– asendjasni, Commented Mar 5, 2019 at 16:56

Garid · Accepted Answer · 2021-11-01 01:42:58Z

1

Try:

command = [ FFMPEG_BIN,
            '-rtbufsize', '100M',
            '-i', '/dev/video0' , #change to here to your camera device
            '-video_size', '640x480',
            '-pix_fmt', 'bgr24',# '-r','25',
            '-f', 'image2pipe', #'-'
            '-vcodec', 'rawvideo', '-an', '-'
            ]

I don't know how '-vcodec', 'rawvideo', '-an', '-' this helps, and without it my code doesn't work.

answered Nov 1, 2021 at 1:42

Garid

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Comments

asendjasni · Accepted Answer · 2023-09-04 07:41:51Z

1

After you call the sp.Popen you have to communicate with it.You can use the following code:

try:    
    pipe = sp.Popen(command, stdout=sp.PIPE, stderr=sp.STDOUT, universal_newlines=True)`

    ffmpeg_output, _ = pipe.communicate()

except  sp.CalledProcessError as err:
     print("FFmpeg stdout output on error:\n" + err.output)

Finally, you can print the output to make sure the above commands worked:

print(ffmpeg_output)

The above statement is going to display the output returned by the communication with the process.

edited Sep 4, 2023 at 7:41

answered Mar 5, 2019 at 13:32

asendjasni

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20 Comments

user10890282 Over a year ago

I tried this by adding these lines before the opencv read. But i get nothing printed on the command line. This program aims to get a continous stream from the video grabber card. I do not know if this is the reason if nothing seems to get printed on the command line.. Any ideas?

asendjasni Over a year ago

No, I edited my answer. I suggest you test the commands in a script apart so you make sure it's working.

user10890282 Over a year ago

this is what I got : <_io.TextIOWrapper name=3 encoding='cp1252'> @SenDjasni

asendjasni Over a year ago

My Bad, try the update, I test it on my terminal and it worked.

asendjasni Over a year ago

@user10890282 Also, put those command in a try: except: subprocess.CalledProcessError since the subprocess calls could generate exceptions.

|

Thomas Ertl · Accepted Answer · 2020-06-07 14:24:45Z

0

I struggled longer with the console application FFmpeg, and finally gave up. It's easier with this extension:

pip install ffmpeg-python

Karl Kroening has published here a very good integration of FFmpeg into Python. With these examples a solution should be possible: https://github.com/kkroening/ffmpeg-python

answered Jun 7, 2020 at 14:24

Thomas Ertl

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1 Comment

Thư Sinh Over a year ago

It does not work with multiple INPUT named pipe

HAL 9000 · Accepted Answer · 2021-10-07 22:33:07Z

0

This works for me

import subprocess as sp
import json
import os
import numpy
import PIL
from imutils.video import FPS
import cv2 


def video_frames_ffmpeg():
    width = 640
    height = 360
    iterator = 0
    cmd = ['ffmpeg', '-loglevel', 'quiet',
           '-f', 'dshow',
           '-i', 'video=HD USB Camera',
           #'-vf','scale=%d:%d,smartblur'%(width,height),
           '-preset' ,'ultrafast', '-tune', 'zerolatency',
           '-f', 'rawvideo',
           '-pix_fmt','bgr24',
           '-']
    p = sp.Popen(cmd, stdout=sp.PIPE)

    while True:
        arr = numpy.frombuffer(p.stdout.read(width*height*3), dtype=numpy.uint8)
        iterator += 1 
        if len(arr) == 0:
            p.wait()
            print("awaiting")
            #return
        if iterator >= 1000:
            break

        frame = arr.reshape((height, width,3))
        cv2.putText(frame, "frame{}".format(iterator), (75, 70),
                cv2.cv2.FONT_HERSHEY_SIMPLEX, 0.7, (255,255,255), 2)
        im = Image.fromarray(frame)
        im.save("ffmpeg_test/test%d.jpeg" % iterator)

        yield arr


from PIL import Image
from imutils.video import FPS
for i, frame in enumerate(video_frames_ffmpeg()):
    if i == 0:
        fps = FPS().start()
    else: fps.update()
fps.stop()
print("[INFO] approx. FPS: {:.2f}".format(fps.fps()))
cv2.destroyAllWindows()

edited Oct 7, 2021 at 22:33

answered Oct 7, 2021 at 12:31

HAL 9000

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2 Comments

HAL 9000 Over a year ago

while using "gray" instead of "bgr24" i get more fps

Community Over a year ago

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