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• How does ffprobe determine duration ?

  10 janvier 2019, par jasongullickson

  I’m using ffprobe to analyze media files stored on a remote server. This seems to work well, but for some files the duration is missing or incorrect (usually longer than it should be). Other times it returns this information accurately, and it doesn’t seem to be related to the media type (codec, etc.).

  Here’s an example of a command that works :

  ffprobe -v quiet -print_format json -show_streams -show_format http://host.com/file.aiff

  {
  
  "streams": [
  
      {
  
          "index": 0,
  
          "codec_name": "pcm_s16be",
  
          "codec_long_name": "PCM signed 16-bit big-endian",
  
          "codec_type": "audio",
  
          "codec_time_base": "1/44100",
  
          "codec_tag_string": "[0][0][0][0]",
  
          "codec_tag": "0x0000",
  
          "sample_fmt": "s16",
  
          "sample_rate": "44100",
  
          "channels": 2,
  
          "bits_per_sample": 16,
  
          "r_frame_rate": "0/0",
  
          "avg_frame_rate": "0/0",
  
          "time_base": "1/44100",
  
          "start_pts": 0,
  
          "start_time": "0.000000",
  
          "duration_ts": 8494248,
  
          "duration": "192.613333",
  
          "bit_rate": "1411200",
  
          "nb_frames": "8494248",
  
          "disposition": {
  
              "default": 0,
  
              "dub": 0,
  
              "original": 0,
  
              "comment": 0,
  
              "lyrics": 0,
  
              "karaoke": 0,
  
              "forced": 0,
  
              "hearing_impaired": 0,
  
              "visual_impaired": 0,
  
              "clean_effects": 0,
  
              "attached_pic": 0
  
          }
  
      }
  
  ],
  
  "format": {
  
      "filename": "http://host.com/file.aiff",
  
      "nb_streams": 1,
  
      "nb_programs": 0,
  
      "format_name": "aiff",
  
      "format_long_name": "Audio IFF",
  
      "start_time": "0.000000",
  
      "duration": "192.613333",
  
      "probe_score": 100
  
  }
  
  }

  Here’s an example of one that doesn’t :

  ffprobe -v quiet -print_format json -show_streams -show_format "http://host.com/file.wav"

  Which generates this result :

  {
  
  "streams": [
  
      {
  
          "index": 0,
  
          "codec_name": "pcm_s16le",
  
          "codec_long_name": "PCM signed 16-bit little-endian",
  
          "codec_type": "audio",
  
          "codec_time_base": "1/44100",
  
          "codec_tag_string": "[1][0][0][0]",
  
          "codec_tag": "0x0001",
  
          "sample_fmt": "s16",
  
          "sample_rate": "44100",
  
          "channels": 2,
  
          "bits_per_sample": 16,
  
          "r_frame_rate": "0/0",
  
          "avg_frame_rate": "0/0",
  
          "time_base": "1/44100",
  
          "bit_rate": "1411200",
  
          "disposition": {
  
              "default": 0,
  
              "dub": 0,
  
              "original": 0,
  
              "comment": 0,
  
              "lyrics": 0,
  
              "karaoke": 0,
  
              "forced": 0,
  
              "hearing_impaired": 0,
  
              "visual_impaired": 0,
  
              "clean_effects": 0,
  
              "attached_pic": 0
  
          }
  
      }
  
  ],
  
  "format": {
  
      "filename": "http://host.com/file.wav",
  
      "nb_streams": 1,
  
      "nb_programs": 0,
  
      "format_name": "wav",
  
      "format_long_name": "WAV / WAVE (Waveform Audio)",
  
      "bit_rate": "1411200",
  
      "probe_score": 99
  
  }
  
  }

  These two examples are different formats, but I’ve seen it work and not work when the format is the same, I just don’t have an example handy.

  What I’d like to know is if there is something I can change about the parameters I’m using with ffprobe to allow the duration to be determined consistently and accurate, or any information I can find as to how ffprobe works so I figure out how I might change the input files, etc. so they work correctly.

  Alternatively, if there is a different tool that works more reliably (it would need to be an open-source Linux tool) any suggestions or recommendations are welcome.

• How to determine how much of a video stream buffer is filled ?

  17 août 2018, par jjulianf

  On my Ubuntu machine, I am encoding a video with the x265 codec using ffmpeg.
  Then I want to stream the video from a server to a client.

  Since the available bandwidth is limited in specific scenarios, I want to observe the moment when the transmission is starting to stutter.

  Therefore I want to compare the amount of data being sent at this scenario with the amount of data which is already stored in the buffer (and which was sent a few frames earlier) at the client’s side.

  Is there any way to determine how much data is stored in the buffer of the decoding client ? Maybe some ffmpeg command for it ?

  Since I am playing the stream with the VLC player at the client side, is there a vlc-CLI-command to check the buffer status ?

  It would be perfect if I could get the current fill of the buffer for every second so that I can graph it like this :

• ffmpeg - Determine what parameters

  27 juin 2018, par AdmiralJonB

  I’ve got a video file that I’m trying to determine what parameters I can use to reproduce the encoding with ffmpeg.

  Here’s the ffprobe of the particular stream in question.

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4': Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.51.107   
  
  Duration: 00:05:02.84, start: 0.000000, bitrate: 4324 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuvj420p(pc, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 4323 kb/s, 25 fps, 25 tbr, 1200k tbn, 2400k tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler

  The key part is that I’m noticing that the bitrate is quite low at 4324 kb/s, but this is actually an incredibly high quality video. To approach this sort of quality, I’ve only been able to make videos at 40000 kb/s (which is a huge increase in filesize). I also notice that it mentions yuvj420p which is an image format, but I have no idea what parameters with ffmpeg could produce that image format (if this at all would make a difference).

  Would appreciate any help I can get.

  Edit :

  Here’s the output based on the comment below :

  [STREAM]
  
  index=0
  
  codec_name=h264
  
  codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
  
  profile=Main
  
  codec_type=video
  
  codec_time_base=123187/3701760
  
  codec_tag_string=avc1
  
  codec_tag=0x31637661
  
  width=1920
  
  height=1080
  
  coded_width=1920
  
  coded_height=1080
  
  has_b_frames=0
  
  sample_aspect_ratio=1:1
  
  display_aspect_ratio=16:9
  
  pix_fmt=yuvj420p
  
  level=41
  
  color_range=pc
  
  color_space=bt709
  
  color_transfer=bt709
  
  color_primaries=bt709
  
  chroma_location=center
  
  field_order=unknown
  
  timecode=N/A
  
  refs=1
  
  is_avc=true
  
  nal_length_size=4
  
  id=N/A
  
  r_frame_rate=15/1
  
  avg_frame_rate=1850880/123187
  
  time_base=1/15360
  
  start_pts=0
  
  start_time=0.000000
  
  duration_ts=246374
  
  duration=16.039974
  
  bit_rate=13795677
  
  max_bit_rate=N/A
  
  bits_per_raw_sample=8
  
  nb_frames=241
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  DISPOSITION:default=1
  
  DISPOSITION:dub=0
  
  DISPOSITION:original=0
  
  DISPOSITION:comment=0
  
  DISPOSITION:lyrics=0
  
  DISPOSITION:karaoke=0
  
  DISPOSITION:forced=0
  
  DISPOSITION:hearing_impaired=0
  
  DISPOSITION:visual_impaired=0
  
  DISPOSITION:clean_effects=0
  
  DISPOSITION:attached_pic=0
  
  DISPOSITION:timed_thumbnails=0
  
  TAG:language=und
  
  TAG:handler_name=VideoHandler
  
  [/STREAM]

  Edit 2 :

  Here’s information from mediainfo

  Video
  
  ID                                       : 1
  
  Format                                   : AVC
  
  Format/Info                              : Advanced Video Codec
  
  Format profile                           : Main@L4.1
  
  Format settings, CABAC                   : Yes
  
  Format settings, RefFrames               : 1 frame
  
  Format settings, GOP                     : M=1, N=32
  
  Codec ID                                 : avc1
  
  Codec ID/Info                            : Advanced Video Coding
  
  Duration                                 : 5 min 2 s
  
  Bit rate                                 : 4 323 kb/s
  
  Width                                    : 1 920 pixels
  
  Height                                   : 1 080 pixels
  
  Display aspect ratio                     : 16:9
  
  Frame rate mode                          : Constant
  
  Frame rate                               : 25.000 FPS
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:0
  
  Bit depth                                : 8 bits
  
  Scan type                                : Progressive
  
  Bits/(Pixel*Frame)                       : 0.083
  
  Stream size                              : 156 MiB (100%)
  
  Color range                              : Full
  
  Color primaries                          : BT.709
  
  Transfer characteristics                 : BT.709
  
  Matrix coefficients                      : BT.709