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• Some videos fail to chromecast with error MEDIA_UNKNOWN

  1er juin 2020, par JonasVautherin

  Using mkchromecast to cast local mp4 files, some videos work, and some don't (as in : the screen hangs on the blue chromecast logo, suggesting that the initial connection worked). I can reproduce exactly the issue described here.

  



  So I decided to go one level lower, with pychromecast, and try to see what actually happens when it hangs on the blue logo. I converted two videos to HLS format, and exposed them through an http server. The video that works with mkchromecast also works with my setup, but the one that fails, well... fails on both. With pychromecast, I don't get much more information than :

  



  


  ERROR, code 100 : MEDIA_UNKNOWN.

  


  



  From the Cast documentation, this error means :

  



  


  The media element encountered an unknown error fired from platform. The media element encountered an error that did not indicate it's one of MediaError.MEDIA_ERR_*. This should be rare.

  


  



  It is not rare for me at all, though. I thought that maybe the failing video was in an unsupported format, as described in the documentation. So I tried to compare both videos with the following command :

  



  ffprobe -v quiet -print_format json -show_streams 


  



  Video that works :

  



  {
    "streams": [
        {
            "index": 0,
            "codec_name": "h264",
            "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
            "profile": "High",
            "codec_type": "video",
            "codec_time_base": "1001/48000",
            "codec_tag_string": "avc1",
            "codec_tag": "0x31637661",
            "width": 1920,
            "height": 1080,
            "coded_width": 1920,
            "coded_height": 1088,
            "has_b_frames": 2,
            "sample_aspect_ratio": "1:1",
            "display_aspect_ratio": "16:9",
            "pix_fmt": "yuv420p",
            "level": 50,
            "chroma_location": "left",
            "refs": 1,
            "is_avc": "true",
            "nal_length_size": "4",
            "r_frame_rate": "24000/1001",
            "avg_frame_rate": "24000/1001",
            "time_base": "1/24000",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 47127080,
            "duration": "1963.628333",
            "bit_rate": "5527977",
            "bits_per_raw_sample": "8",
            "nb_frames": "47080",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            },
            "tags": {
                "language": "und",
                "handler_name": "VideoHandler"
            }
        },
        {
            "index": 1,
            "codec_name": "aac",
            "codec_long_name": "AAC (Advanced Audio Coding)",
            "profile": "LC",
            "codec_type": "audio",
            "codec_time_base": "1/48000",
            "codec_tag_string": "mp4a",
            "codec_tag": "0x6134706d",
            "sample_fmt": "fltp",
            "sample_rate": "48000",
            "channels": 2,
            "channel_layout": "stereo",
            "bits_per_sample": 0,
            "r_frame_rate": "0/0",
            "avg_frame_rate": "0/0",
            "time_base": "1/48000",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 94254528,
            "duration": "1963.636000",
            "bit_rate": "125776",
            "max_bit_rate": "125776",
            "nb_frames": "92048",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            },
            "tags": {
                "language": "und",
                "handler_name": "SoundHandler"
            }
        }
    ]
}


  



  Video that does NOT work :

  



  {                                               
    "streams": [
        {
            "index": 0,
            "codec_name": "h264",
            "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
            "profile": "High",
            "codec_type": "video",
            "codec_time_base": "125/5994",
            "codec_tag_string": "avc1",
            "codec_tag": "0x31637661",
            "width": 1920,
            "height": 1040,
            "coded_width": 1920,
            "coded_height": 1040,
            "has_b_frames": 2,
            "sample_aspect_ratio": "1:1",
            "display_aspect_ratio": "24:13",
            "pix_fmt": "yuv420p",
            "level": 41,
            "chroma_location": "left",
            "refs": 1,
            "is_avc": "true",
            "nal_length_size": "4",
            "r_frame_rate": "2997/125",
            "avg_frame_rate": "2997/125",
            "time_base": "1/11988",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 97032000,
            "duration": "8094.094094",
            "bit_rate": "2499644",
            "bits_per_raw_sample": "8",
            "nb_frames": "194064",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            },
            "tags": {
                "creation_time": "2020-03-27T09:56:39.000000Z",
                "language": "und",
                "handler_name": "L-SMASH Video Media Handler"
            }
        },
        {
            "index": 1,
            "codec_name": "aac",
            "codec_long_name": "AAC (Advanced Audio Coding)",
            "profile": "LC",
            "codec_type": "audio",
            "codec_time_base": "1/48000",
            "codec_tag_string": "mp4a",
            "codec_tag": "0x6134706d",
            "sample_fmt": "fltp",
            "sample_rate": "48000",
            "channels": 6,
            "channel_layout": "5.1",
            "bits_per_sample": 0,
            "r_frame_rate": "0/0",
            "avg_frame_rate": "0/0",
            "time_base": "1/48000",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 388516320,
            "duration": "8094.090000",
            "bit_rate": "224000",
            "max_bit_rate": "224000",
            "nb_frames": "379413",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            },
            "tags": {
                "creation_time": "2020-03-27T09:56:39.000000Z",
                "language": "eng",
                "handler_name": "SoundHandler"
            }
        }
    ]
}


  



  For what I can see, the codecs are the same, and the only difference I can make is in the aspect ratio.

  



  What could be the reason for this "MEDIA_UNKNOWN" error on the chromecast side ? Is there something more I could compare between those two videos ? Could it be that the chromecast fails because of the aspect ratio ?

  


• libavfilter/scale : Populate ow/oh when using 0 as w/h

  14 juin 2017, par Kevin Mark

  libavfilter/scale : Populate ow/oh when using 0 as w/h
  The input width and height is known at parse time so there's no
  
  reason ow/oh should not be usable when using 0 as the width or
  
  height expression.
  Previously in "scale=0:ow" ow would be set to "0" which works,
  
  conveniently, as "scale=0:0" is perfectly valid input but this breaks
  
  down when you do something like "scale=0:ow/4" which one could
  
  reasonably expect to work as well, but does not as ow is 0 not the
  
  real value.
  This change handles the 0 case for w/h immediately so the ow/oh
  
  variables work as expected. Consequently, the rest of the code does
  
  not need to handle 0 input. w/h will always be > 0 or < 0.
  The second explicit (int) cast ensures that ow/oh appear as integers
  
  as a user might expect when dealing with pixel dimensions.
  Signed-off-by : Kevin Mark <kmark937@gmail.com>
  
  Signed-off-by : Ronald S. Bultje <rsbultje@gmail.com>
  

  • [DH] libavfilter/scale.c

• Can you stream video with ffmpeg and opencv without long buffers

  13 septembre 2019, par steve

  I’m successfully getting a video stream using ffmpeg, and displaying with opencv, but the video starts and stops very often and is not as smooth as when played on a browser. Is there a way to get the video stream to be as smooth as on a browser ?

  I’ve tried playing with ffmpeg parameters as well as having multiple pipes to stitch together a single video.

  import cv2
  
  import numpy as np
  
  import subprocess as sp
  
  import time
  
  
  
  
  
  # Playlist manifest for video from Nevada DOT traffic camera
  
  VIDEO_URL = "https://wowza1.nvfast.org/bmw3/charleston_and_fremont_public.stream/playlist.m3u8"
  
  
  
  width = 360
  
  height = 240
  
  
  
  pipe = sp.Popen([ 'ffmpeg', "-i", VIDEO_URL,
  
              "-loglevel", "quiet", # no text output
  
              "-an",   # disable audio
  
              "-f", "image2pipe",
  
              "-pix_fmt", "bgr24",
  
              "-r", "15", # FPS
  
              "-hls_list_size", "3", 
  
              #"-hls_time", "8" 
  
              "-vcodec", "rawvideo", "-"],
  
              stdin = sp.PIPE, stdout = sp.PIPE)
  
  
  
  while True:
  
  
  
          # Convert bytes to image
  
          raw_image = pipe.stdout.read(width*height*3) # read 432*240*3 bytes (= 1 frame)
  
          img =  np.fromstring(raw_image, dtype='uint8').reshape((height,width,3))
  
          raw_image = np.copy(img)
  
  
  
          # Show image
  
          cv2.imshow('pipe', img)
  
          cv2.waitKey(1)
  
          time.sleep(0.05) # This is to slow down the video so it plays more naturally

  The expected output is a opencv window that displays the video just like in https://cctv.nvfast.org/

  I assume the problem lies in ffmpeg not getting the video chunks.