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• How to create a named pipe in Windows ?

  10 février 2023, par Che

  Is it possible without much effort (e.g. in command line or powershell), to create a named pipe ?

  


  My goal is to write continously to that pipe from a ffmpeg-process.

  


  Without opening a Pipe at first the following command

  


  ffmpeg -i "path\to\my\File\name of my File" -f webm \\.\pipe\from_ffmpeg


  


  fails to

  


  


  "\.\pipe\from_ffmpeg : No such file or directory"

  


  


  In the big picture, I want to read a Live-Web-Video-Stream to analyze it and take live-actions based on that.
I am working with OpenCV in Java on a Windows machine. At the moment I have different ffmpeg-processes, which record different sectors (i.e. pixels (45, 45, 100, 100) and (200, 200, 100, 100) (x, y, height, width). The results are saved as jpg files in the filesystem and are then opened in a Java Process. This works, but I think I would significantly gain performance by not taking the long way over the files but to directly pipe my input into the Java-Process.

  


  I know there's an option to live-capture videostreams via open-CV but the framework does not support as many formats as ffmpeg does.

  


• How can I pipe JPEG files into FFMPEG and create an RTSP, H.264 stream ?

  25 janvier 2023, par Michael Schmidt

  I have an input RTSP stream that I would like to manipulate on a frame-by-frame basis using openCV. After these changes are applied, I'd like to create a separate RTSP stream from those frames. I'm piping the resulting JPEG images to FFMPEG via STDIN. I need the intermediate frame to be a JPEG.

  


  In other words, I must conform to this pattern :
RTSP IN -> Create JPEG as input -> manipulation, JPEG out -> RTSP

  


  The PROBLEM I'm trying to solve deals with a codec at this point. See the last few lines of FFMPEG's output error message.

  


  Here is what I have :

  


  def open_ffmpeg_stream_process():
    args = (
        "ffmpeg -re -stream_loop -1 "
        "-f jpeg_pipe "
        "-s 512x288 "
        "-i pipe:0 "
        "-c:v h264 "
        "-f rtsp "
        "rtsp://localhost:8100/out0"
    ).split()
    return subprocess.Popen(args, stdin=subprocess.PIPE)

video_source = cv2.VideoCapture('rtsp://localhost:9100/in0')

frame_cnt = 0
FRAME_SKIP = 30

ffmpeg_process = open_ffmpeg_stream_process()
while video_source.isOpened():

    frame_cnt += 1
    if frame_cnt % FRAME_SKIP:
      continue
    else:
      frame_cnt = 0

    _, frame = video_source.read()
    _, jpg = cv2.imencode('.jpg', frame)

    # Work on the JPEG occurs here, and the output will be a JPEG

    ffmpeg_process.stdin.write(jpg.astype(np.uint8).tobytes())

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

video_source.release()


  


  Here is FFMPEG's output :

  


  ffmpeg version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
  configuration: ---- noisy configuration stuff ----
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, jpeg_pipe, from 'pipe:0':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: mjpeg, rgb24(bt470bg/unknown/unknown), 512x288, 25 fps, 25 tbr, 25 tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> h264 (libx264))
[libx264 @ 0x562a1ffc5840] using SAR=1/1
[libx264 @ 0x562a1ffc5840] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x562a1ffc5840] profile High, level 3.1, 4:2:0, 8-bit
[libx264 @ 0x562a1ffc5840] 264 - core 163 r3060 5db6aa6 - H.264/MPEG-4 AVC codec - Copyleft 2003-2021 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=18 lookahead_threads=3 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
[tcp @ 0x562a20826c00] Connection to tcp://localhost:8100?timeout=0 failed: Connection refused
Could not write header for output file #0 (incorrect codec parameters ?): Connection refused
Error initializing output stream 0:0 -- 
Conversion failed!


  


  How does one create an H.264, RTSP stream from a series of JPEG frames using FFMPEG.

  


  Notes : The FFMPEG command/subproccess might need unrelated improvements, feel free to comment on my crappy code.

  


  Edit : Oof, I just found out the FFMPEG command doesn't even work stand alone.

  


• avformat/file : add fd option for pipe

  14 décembre 2022, par Zhao Zhili

  avformat/file : add fd option for pipe
  Signed-off-by : Zhao Zhili <zhilizhao@tencent.com>
  

  • [DH] doc/protocols.texi
  • [DH] libavformat/file.c
  • [DH] libavformat/version.h