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• How to read errors when compiling from source code

  28 décembre 2022, par slyfox1186

  Goal :

  


  Compile multiple libraries from source code to ultimately install a fully compiled version of FFmpeg with desirable libraries attached.

  


  Problem :

  


  During the compilation, all libraries (seemingly) are successful until liblv2 is reached.

  


  Error output via terminal :

  


  building lv2 - version 1.18.10
=======================
Downloading https://lv2plug.in/spec/lv2-1.18.10.tar.xz as lv2-1.18.10.tar.bz2
... Done
Extracted lv2-1.18.10.tar.bz2
$ python3 ./waf configure --prefix=/home/jman/tmp/ffmpeg/ffmpeg-build/workspace --lv2-user
python3: can't open file '/home/jman/tmp/ffmpeg/ffmpeg-build/packages/lv2-1.18.10/./waf': [Errno 2] No such file or directory

Failed to Execute python3 ./waf configure --prefix=/home/jman/tmp/ffmpeg/ffmpeg-build/workspace --lv2-user


  


  Where I need guidance :

  


  python3: can't open file '/home/jman/tmp/ffmpeg/ffmpeg-build/packages/lv2-1.18.10/./waf': [Errno 2] No such file or directory


  


  My question :

  


  What does this part mean ?

  


  lv2-1.18.10/./waf'

specifically the part /./


  


  My best guess so far is it :

  


  

  1. obviously is looking for a directory it can't find (perhaps because it truly doesn't exist)

  


  2. The missing 'waf' directory should be located inside either the "${PACKAGES}" or "${WORKSPACE}" directory.

  


  


  The ${PACKAGES}" path in this script should = /home/jman/tmp/ffmpeg/ffmpeg-build/packages

  


  The ${WORKSPACE}" path in this script should = /home/jman/tmp/ffmpeg/ffmpeg-build/workspace

  


  The full build script :

  


  https://github.com/slyfox1186/ffmpeg-build-script/blob/master/scripts/build-ffmpeg

  


  I tried my best to make this worth sometimes time without giving too much info... sorry if I don't meet the expectations of this forum.

  


  Am I even close ?

  


• pthread_frame : do not run hwaccel decoding asynchronously unless it’s safe

  24 novembre 2016, par Anton Khirnov

  pthread_frame : do not run hwaccel decoding asynchronously unless it’s safe
  Certain hardware decoding APIs are not guaranteed to be thread-safe, so
  
  having the user access decoded hardware surfaces while the decoder is
  
  running in another thread can cause failures (this is mainly known to
  
  happen with DXVA2).
  For such hwaccels, only allow the decoding thread to run while the user
  
  is inside a lavc decode call (avcodec_send_packet/receive_frame).
  Merges Libav commit d4a91e65.
  Signed-off-by : wm4 <nfxjfg@googlemail.com>
  
  Tested-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/avcodec.h
  • [DH] libavcodec/hwaccel.h
  • [DH] libavcodec/pthread_frame.c
  • [DH] libavcodec/vaapi_h264.c
  • [DH] libavcodec/vaapi_mpeg2.c
  • [DH] libavcodec/vaapi_mpeg4.c
  • [DH] libavcodec/vaapi_vc1.c
  • [DH] libavcodec/vdpau_h264.c
  • [DH] libavcodec/vdpau_hevc.c
  • [DH] libavcodec/vdpau_mpeg12.c
  • [DH] libavcodec/vdpau_mpeg4.c
  • [DH] libavcodec/vdpau_vc1.c

• OpenCV is able to read the stream but VLC not

  25 avril 2023, par Ahmet Çavdar

  I'm trying to stream my webcam frames to an UDP address. Here is my sender code.

  


  cmd = ['ffmpeg', '-y', '-f', 'rawvideo', '-pixel_format', 'bgr24', '-video_size', f'{width}x{height}', 
       '-i', '-', '-c:v', 'mpeg4','-preset', 'ultrafast', '-tune', 'zerolatency','-b:v', '1.5M',
       '-f', 'mpegts', f'udp://@{ip_address}:{port}']
p = subprocess.Popen(cmd, stdin=subprocess.PIPE)
camera = cv2.VideoCapture(0)
while True:
    ret, frame = camera.read()
    cv2.imshow("Sender",frame)
    if not ret:
        break
    p.stdin.write(frame.tobytes())
    p.stdin.flush()
    if cv2.waitKey(1) & 0xFF == ord('q'):
            break


  


  This Python code can make stream successfully. I can read the stream with this receiver code.

  


  q = queue.Queue()
def receive():
    cap = cv2.VideoCapture('udp://@xxx.x.xxx.xxx:5000')
    ret, frame = cap.read()
    q.put(frame)
    while ret:
        ret, frame = cap.read()
        q.put(frame)
def display():
    while True:
        if q.empty() != True:
            frame = q.get()
            cv2.imshow('Receiver', frame)
        k = cv2.waitKey(1) & 0xff
        if k == 27:  # press 'ESC' to quit
            break
tr = threading.Thread(target=receive, daemon=True)
td = threading.Thread(target=display)
tr.start()
td.start()
td.join()


  


  But I can not watch the stream from VLC. I'm going to Media->Open Network Stream->
udp ://@xxx.x.xxx.xxx:5000 to watch stream. After some seconds, the timer that located bottom left of VLC starts to increase but there are no frames in screen, just VLC icon.

  


  I checked firewall rules, opened all ports to UDP connections. I am using my IP address to send frames and watch them.
Also, I tried other video codecs like h264, hvec, mpeg4, rawvideo.
Additionally, I tried to watch stream by using Windows Media Player but it didn't work.

  


  What should I do to fix this issue ?