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• Detecting video volume

  27 décembre 2016, par Johnathan Kanarek

  I’m streaming few RTMP streams through nginx and I want to check every few seconds what stream has the highest volume.
  Specifically these streams are of talking heads and I assume that usually only one of them is speaking at a time, and I’m trying to find which one.
  Since nginx can output hls (Apple http live streaming) I decided to check every few seconds the last segment of each stream using ffmpeg.
  Example :

  ffmpeg -f mp3 -i /my/path/camera67/123.ts -af "volumedetect" -f null /dev/null

  For some reason the max_volume is always zero (max_volume : 0.0 dB) and mean_volume seems meaningless regarding the volume.

  1. Do you have any idea why it’s always zero ?
  2. Is there a helpful way to understand mean_volume ?
  3. Can you think of a different tool that may give me the volume (e.g. mediainfo or ffprobe) ?

  I also tried :

  ffmpeg -f lavfi -i amovie=/my/path/camera67/123.ts,volumedetect

  This time I got :

  [mpegts @ 0x130bf40] start time for stream 1 is not set in estimate_timings_from_pts
  [mpegts @ 0x130bf40] Could not find codec parameters for stream 1 (Audio : aac ([15][0][0][0] / 0x000F), 0 channels, fltp) : unspecified sample rate
  Consider increasing the value for the ’analyzeduration’ and ’probesize’ options
  [Parsed_amovie_0 @ 0x130bcc0] No audio stream with index ’-1’ found
  [lavfi @ 0x130abc0] Error initializing filter ’amovie’ with args ’/my/path/camera67/123.ts’
  amovie=/my/path/camera67/123.ts,volumedetect : Invalid argument

  Any idea ?

  Thanks,
  T.

• How to Simply Remove Duplicate Frames from a Video using ffmpeg

  29 janvier 2017, par Skeeve

  First of all, I’d preface this by saying I’m NO EXPERT with video manipulation,
  although I’ve been fiddling with ffmpeg for years (in a fairly limited way). Hence, I’m not too flash with all the language folk often use... and how it affects what I’m trying to do in my manipulations... but I’ll have a go with this anyway...

  I’ve checked a few links here, for example :
  ffmpeg - remove sequentially duplicate frames

  ...but the content didn’t really help me.

  I have some hundreds of video clips that have been created under both Windows and Linux using both ffmpeg and other similar applications. However, they have some problems with times in the video where the display is ’motionless’.

  As an example, let’s say we have some web site that streams a live video into, say, a Flash video player/plugin in a web browser. In this case, we’re talking about a traffic camera video stream, for example.

  There’s an instance of ffmpeg running that is capturing a region of the (Windows) desktop into a video file, viz :-

  ffmpeg -hide_banner -y -f dshow ^
  
        -i video="screen-capture-recorder" ^
  
        -vf "setpts=1.00*PTS,crop=448:336:620:360" ^
  
        -an -r 25 -vcodec libx264 -crf 0 -qp 0 ^
  
        -preset ultrafast SAMPLE.flv

  Let’s say the actual ’display’ that is being captured looks like this :-

  123456789 XXXXX 1234567 XXXXXXXXXXX 123456789 XXXXXXX
  
  ^---a---^ ^-P-^ ^--b--^ ^----Q----^ ^---c---^ ^--R--^ 

  ...where each character position represents a (sequence of) frame(s). Owing to a poor internet connection, a "single frame" can be displayed for an extended period (the ’X’ characters being an (almost) exact copy of the immediately previous frame). So this means we have segments of the captured video where the image doesn’t change at all (to the naked eye, anyway).

  How can we deal with the duplicate frames ?... and how does our approach change if the ’duplicates’ are NOT the same to ffmpeg but LOOK more-or-less the same to the viewer ?

  If we simply remove the duplicate frames, the ’pacing’ of the video is lost, and what used to take, maybe, 5 seconds to display, now takes a fraction of a second, giving a very jerky, unnatural motion, although there are no duplicate images in the video. This seems to be achievable using ffmpeg with an ’mp_decimate’ option, viz :-

       ffmpeg -i SAMPLE.flv ^                      ... (i)
  
          -r 25 ^
  
          -vf mpdecimate,setpts=N/FRAME_RATE/TB DEC_SAMPLE.mp4

  That reference I quoted uses a command that shows which frames ’mp_decimate’ will remove when it considers them to be ’the same’, viz :-

       ffmpeg -i SAMPLE.flv ^                      ... (ii)
  
          -vf mpdecimate ^
  
          -loglevel debug -f null -

  ...but knowing that (complicated formatted) information, how can we re-organize the video without executing multiple runs of ffmpeg to extract ’slices’ of video for re-combining later ?

  In that case, I’m guessing we’d have to run something like :-

  • user specifies a ’threshold duration’ for the duplicates
    (maybe run for 1 sec only)
  • determine & save main video information (fps, etc - assuming
    constant frame rate)
  • map the (frame/time where duplicates start)->no. of
    frames/duration of duplicates
  • if the duration of duplicates is less than the user threshold,
    don’t consider this period as a ’series of duplicate frames’
    and move on
  • extract the ’non-duplicate’ video segments (a, b & c in the
    diagram above)
  • create ’new video’ (empty) with original video’s specs
  • for each video segment
    extract the last frame of the segment
    create a short video clip with repeated frames of the frame
    just extracted (duration = user spec. = 1 sec)
    append (current video segment+short clip) to ’new video’
    and repeat

  ...but in my case, a lot of the captured videos might be 30 minutes long and have hundreds of 10 sec long pauses, so the ’rebuilding’ of the videos will take a long time using this method.

  This is why I’m hoping there’s some "reliable" and "more intelligent" way to use
  ffmepg (with/without the ’mp_decimate’ filter) to do the ’decimate’ function in only a couple of passes or so... Maybe there’s a way that the required segments could even be specified (in a text file, for example) and as ffmpeg runs it will
  stop/restart it’s transcoding at specified times/frame numbers ?

  Short of this, is there another application (for use on Windows or Linux) that could do what I’m looking for, without having to manually set start/stop points,
  extracting/combining video segments manually...?

  I’ve been trying to do all this with ffmpeg N-79824-gcaee88d under Win7-SP1 and (a different version I don’t currently remember) under Puppy Linux Slacko 5.6.4.

  Thanks a heap for any clues.

• want to stream mobile camera using ffserver and ffmpeg

  6 janvier 2017, par Vinay Pandya

  First i will tell you my requirement than i will tell you what i have done.

  i am noob in media streaming i am learning and i am very confused about it.

  basically i want to do following thing

  1 : mobile app will stream video on server through URL (which is on my laptop)
  2 : My laptop should run ffserver/ffmpeg which store video stream which is coming from mobile app and allow other client to watch it (here i am talking about VLC as client).

  so this is my requirement.

  i ham running ffserver on my laptop

  my ff server config is like :

  HTTPPort 8090
  
  HTTPBindAddress 0.0.0.0
  
  
  
  RTSPPort 8091
  
  RTSPBindAddress 0.0.0.0
  
  
  
  
  
  MaxHTTPConnections 2000
  
  MaxClients 1000
  
  MaxBandwidth 1000
  
  CustomLog -
  
  
  
  #NoDaemon
  
  
  
  <feed>
  
      File /tmp/feed1.ffm
  
      FileMaxSize 200K
  
      ACL allow 127.0.0.1
  
  </feed>
  
  
  
  # if you want to use mpegts format instead of flv
  
  # then change "live.flv" to "live.ts"
  
  # and also change "Format flv" to "Format mpegts"
  
  <stream>
  
      Format flv
  
      Feed feed1.ffm
  
  
  
      VideoCodec libx264
  
      VideoFrameRate 30
  
      VideoBitRate 512
  
      VideoSize 320x240
  
      AVOptionVideo crf 23
  
      AVOptionVideo preset medium
  
      # for more info on crf/preset options, type: x264 --help
  
      AVOptionVideo flags +global_header
  
  
  
      AudioCodec aac
  
      Strict -2
  
      AudioBitRate 128
  
      AudioChannels 2
  
      AudioSampleRate 44100
  
      AVOptionAudio flags +global_header
  
  </stream>
  
  
  
  ##################################################################
  
  # Special streams
  
  ##################################################################
  
  <stream>
  
      Format status
  
      # Only allow local people to get the status
  
      ACL allow localhost
  
      ACL allow 192.168.0.0 192.168.255.255
  
  </stream>
  
  
  
  # Redirect index.html to the appropriate site
  
  <redirect>
  
      URL http://www.ffmpeg.org/
  
  </redirect>
  
  ##################################################################

  than i am adding following url to my mobile app to stream video.
  rtsp ://:8091/feed1.ffm
  my mobile app start streaming my mobile developer team said that.
  but i am not getting any log on ffserver, when i am stooping streaming the TEARDOWN request is comming

  [TEARDOWN] "rtsp://192.168.1.57:8091/feed1.ffm RTSP/1.0" 200 7034

  i have done this is so far, i dont know how to use ffmpeg with live streaming. please tell me some example for that.

  i am not able to watch that live stream on VLC client. also tell me what URL should i enter in VLC for streaming i have tried almost every url combination.

  and one more thing i want to do it with RTSP protocol.

  i think this info will help you to understand my requirement.