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• How to create a video from svg files using a pipe with ffmpeg ?

  5 juillet 2023, par Max Chr.

  I want to create a video from svg graphic stored in a database. My procedure would be the following to archive that :

  


  

  1. connect to database

  


  2. create ffmpeg command which takes a pipe as input

  


  3. spawn the ffmpeg child process

  


  4. Wait for the output of the process.

  


  


  start another thread :
For all svg files do :

  


  

  1. download the svg from the database into a byte buffer

  


  2. write the byte buffer to stdin of the ffmpeg child process

  


  


  When running my code I encounter a problem when piping the svg files to ffmpeg.
Another possibility would be to download all the svg files to a temp directory and then using ffmpeg, but I want to avoid this.

  


  I used ffmpeg -f image2pipe -c:v svg -i - -c:v libx264 -y Downloads/out.mp4. But then ffmpeg gives me the following error :

  


  [image2pipe @ 0x562ebd74c300] Could not find codec parameters for stream 0 (Video: svg (librsvg), none): unspecified size
Consider increasing the value for the 'analyzeduration' (0) and 'probesize' (5000000) options


  


  I found out that there's a svg_pipe format in ffmpeg, so I tried that - without success, same error.

  


  Do you have any ideas how to make this work ?

  


• can't pipe in numpy arrays (images) to ffmpeg subprocess in python

  21 juin 2023, par Kevin

  I'm trying to capture webcam video stream using opencv and pipe raw frames into ffmpeg subprocess, apply 3d .cube lut, bring back those lut applied frames into opencv and display it using cv2.imshow.

  


  This is my code :

  


  import cv2
import subprocess as sp
import numpy as np

lut_cmd = [
            'ffmpeg', '-f', 'rawvideo', '-pixel_format', 'bgr24', '-s', '1280x720', '-framerate', '30', '-i', '-', '-an', '-vf',
            'lut3d=file=lut/luts/lut.cube', '-f', 'rawvideo', 'pipe:1'
        ]

lut_process = sp.Popen(lut_cmd, stdin=sp.PIPE, stdout=sp.PIPE)

width = 1280
height = 720

video_capture = cv2.VideoCapture(0)

while True:
    ret, frame = video_capture.read()

    if not ret:
        break
 
    # Write raw video frame to input stream of ffmpeg sub-process.
    lut_process.stdin.write(frame.tobytes())
    lut_process.stdin.flush()
    print("flushed")

    # Read the processed frame from the ffmpeg subprocess
    raw_frame = lut_process.stdout.read(width * height * 3)
    print("read")
    frame = np.frombuffer(raw_frame, dtype=np.uint8).reshape(height, width, 3)

    cv2.imshow('Video', frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

lut_process.terminate()
video_capture.release()

cv2.destroyAllWindows()



  


  code gets stuck at reading from ffmpeg part :
raw_frame = lut_process.stdout.read(width * height * 3)

  


  this is what i get when i run the code :

  


  flushed
Input #0, rawvideo, from 'fd:':
  Duration: N/A, start: 0.000000, bitrate: 663552 kb/s
  Stream #0:0: Video: rawvideo (BGR[24] / 0x18524742), bgr24, 1280x720, 663552 kb/s, 30 tbr, 30 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> rawvideo (native))
Output #0, rawvideo, to 'pipe:1':
  Metadata:
    encoder         : Lavf60.3.100
  Stream #0:0: Video: rawvideo (BGR[24] / 0x18524742), bgr24(progressive), 1280x720, q=2-31, 663552 kb/s, 30 fps, 30 tbn
    Metadata:
      encoder         : Lavc60.3.100 rawvideo
frame=    0 fps=0.0 q=0.0 size=       0kB time=-577014:32:22.77 bitrate=  -0.0kbits/s speed=N/A  


  


  "read" never gets printed. ffmpeg is stuck at 0fps. cv2.imshow doesn't show up.

  


  I tried changing lut_process.stdin.write(frame.tobytes()) 
to lut_process.stdin.write(frame.tostring()), but result was same.

  


  I tried adding 3 seconds pause before first write to ffmpeg begin, thinking maybe ffmpeg was not ready to process frames, but result was same.

  


  I'm sure that my webcam is working, and I know it's video stream is 1280x720 30fps.

  


  I was successful at
Displaying webcam stream just using opencv,
set FFmpeg input directly to my webcam and get output result using stdout.read, displaying it using opencv.

  


  have no idea what should I try next.

  


  I am using macOS 12.6, openCV 4.7.0, ffmpeg 6.0, python 3.10.11, and visual studio code.

  


  Any help would be greatly appreciated.

  


• can't pipe in opencv frames to ffmpeg subprocess in python

  19 juin 2023, par Kevin

  I'm trying to capture webcam video stream using opencv and pipe raw frames into ffmpeg subprocess, apply 3d .cube lut, bring back those lut applied frames into opencv and display it using cv2.imshow.

  


  This is my code :

  


  import cv2
import subprocess as sp
import numpy as np

lut_cmd = [
            'ffmpeg', '-f', 'rawvideo', '-pixel_format', 'bgr24', '-s', '1280x720', '-framerate', '30', '-i', '-', '-an', '-vf',
            'lut3d=file=lut/luts/lut.cube', '-f', 'rawvideo', 'pipe:1'
        ]

lut_process = sp.Popen(lut_cmd, stdin=sp.PIPE, stdout=sp.PIPE)

width = 1280
height = 720

video_capture = cv2.VideoCapture(0)

while True:
    ret, frame = video_capture.read()

    if not ret:
        break
 
    # Write raw video frame to input stream of ffmpeg sub-process.
    lut_process.stdin.write(frame.tobytes())
    lut_process.stdin.flush()
    print("flushed")

    # Read the processed frame from the ffmpeg subprocess
    raw_frame = lut_process.stdout.read(width * height * 3)
    print("read")
    frame = np.frombuffer(raw_frame, dtype=np.uint8).reshape(height, width, 3)

    cv2.imshow('Video', frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

lut_process.terminate()
video_capture.release()

cv2.destroyAllWindows()



  


  code gets stuck at reading from ffmpeg part :
raw_frame = lut_process.stdout.read(width * height * 3)

  


  this is what i get when i run the code :

  


  flushed
Input #0, rawvideo, from 'fd:':
  Duration: N/A, start: 0.000000, bitrate: 663552 kb/s
  Stream #0:0: Video: rawvideo (BGR[24] / 0x18524742), bgr24, 1280x720, 663552 kb/s, 30 tbr, 30 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> rawvideo (native))
Output #0, rawvideo, to 'pipe:1':
  Metadata:
    encoder         : Lavf60.3.100
  Stream #0:0: Video: rawvideo (BGR[24] / 0x18524742), bgr24(progressive), 1280x720, q=2-31, 663552 kb/s, 30 fps, 30 tbn
    Metadata:
      encoder         : Lavc60.3.100 rawvideo
frame=    0 fps=0.0 q=0.0 size=       0kB time=-577014:32:22.77 bitrate=  -0.0kbits/s speed=N/A  


  


  "read" never gets printed. ffmpeg is stuck at 0fps. cv2.imshow doesn't show up.

  


  I tried changing lut_process.stdin.write(frame.tobytes()) 
to lut_process.stdin.write(frame.tostring()), but result was same.

  


  I tried adding 3 seconds pause before first write to ffmpeg begin, thinking maybe ffmpeg was not ready to process frames, but result was same.

  


  I'm sure that my webcam is working, and I know it's video stream is 1280x720 30fps.

  


  I was successful at
Displaying webcam stream just using opencv,
set FFmpeg input directly to my webcam and get output result using stdout.read, displaying it using opencv.

  


  have no idea what should I try next.

  


  I am using macOS 12.6, openCV 4.7.0, ffmpeg 6.0, python 3.10.11, and visual studio code.

  


  Any help would be greatly appreciated.