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• ffmpeg dash Segment offset

  18 mars 2019, par inkubux

  I’m trying to integrate live-transcoding like "plex" or "emby" with my application.

  I am able to serve dash content over to shaka-player or dash.js but only in ’live-mode’. But I want to enable seeking through the player.

  I looked at plex and to enable this they create their own mpd file with duration so the player will have a full seekbar.

  However when seeking the player will ask for a segment number eg : 449. I need to stop ffmpeg and restart with an offset (-ss &lt;<segment>>)</segment>, but ffmpeg will just restart a transcode session from segment 0 with an initial segment.

  What I want is to tell ffmpeg to start at a seekpoint but only output from segment number and now-on.

  When playing with hls and mpegts, I can tell ffmpeg to output at a certain segment : with the option -segment_start_number but this is not available for dash. And plex use their own transcoder based of ffmpeg with the option -skip_to_segment

  I tried to ’hack’ around by keeping a manual offset on my web-server, even if I serve the "supposed" right segment after the seek point dash.js and shaka-player can’t recover the stream.. VLC on the other habd is able to (probably more tolerent) to errors in segments.

  Is the supposed right segment after a seek in dash (contains the initial segment) or only the segment.

  Is ffmpeg able to start segmenting dash as a supposed segment (for seek and resume)

  The same technique works in hls with forced key frames and a custom m3u8 (with all the "predicted" segments) but calculating the right segment length and the right bandwidth is much harder and hackish and dash is more tolerant to variation.

  I would really like to be able to seek through my live transcoding video.

  For reference here is a custom mpd file I serve to enable "seeking" :

  <mpd xmlns="urn:mpeg:dash:schema:mpd:2011" profiles="urn:mpeg:dash:profile:isoff-live:2011" type="static" suggestedpresentationdelay="PT1S" mediapresentationduration="PT49M2.920S" maxsegmentduration="PT2S" minbuffertime="PT10S">
  
      <period start="PT0S" duration="PT49M2.920S">
  
          <adaptationset segmentalignment="true">
  
              <segmenttemplate timescale="1" duration="1" initialization="$RepresentationID$/initial.mp4" media="$RepresentationID$/$Number$.m4s" startnumber="1">
  
              </segmenttemplate>
  
              <representation mimetype="video/mp4" codecs="avc1.640029" bandwidth="3766000" width="1920" height="1080">
  
              </representation>
  
          </adaptationset>
  
          <adaptationset segmentalignment="true">
  
              <segmenttemplate timescale="1" duration="1" initialization="$RepresentationID$/initial.mp4" media="$RepresentationID$/$Number$.m4s" startnumber="1">
  
              </segmenttemplate>
  
              <representation mimetype="audio/mp4" codecs="mp4a.40.2" bandwidth="188000" audiosamplingrate="48000">
  
                  <audiochannelconfiguration schemeiduri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="6"></audiochannelconfiguration>
  
              </representation>
  
          </adaptationset>
  
      </period>
  
  </mpd>

  And here is the ffmpeg command to pull it off :

  ffmpeg -ss 0 -i movie.mkv -y -acodec aac -vcodec libx264 -f dash -min_seg_duration 1000000 -individual_header_trailer 0 -pix_fmt yuv420p -vf scale=trunc(min(max(iw\,ih*dar)\,1920)/2)*2:trunc(ow/dar/2)*2 -bsf:v h264_mp4toannexb -profile:v high -level 4.1 -map_chapters -1 -map_metadata -1 -preset veryfast -movflags frag_keyframe+empty_moov -use_template 1 -use_timeline 0 -remove_at_exit 1 -crf 23 -bufsize 7532k -maxrate 3766k -start_at_zero -threads 0 -force_key_frames expr:if(isnan(prev_forced_t),eq(t,t),gte(t,prev_forced_t+1)) -init_seg_name $RepresentationID$/0_initial.mp4 -media_seg_name $RepresentationID$/0_$Number$.m4s /transcoding_temp/Z1GVWEc/index.mpd

  The media_seg_name is where I prepend the custom seek_point let’s say I want to seek to segment 1233 the template would be :

  -media_seg_name $RepresentationID$/1233_$Number$.m4s

  and the segments would be 1233_1 1233_2 1233_* So I can serve the right segment after seek. but the player does not recover and still downloading subsequent segments. I guess since a new initial segment is generated and I somehow miss headers for continuous playback after seek but I’m probably wrong.

  Thanks for your help

• ffmpeg generate thumbnails on GPU

  22 juin 2018, par Oleksandr Kyrpa

  I try to generate thumbnails with acceleration on GPU, so compile ffmpeg 3.4.1 and run command :

  ./ffmpeg  -i ~/Videos/1080.mp4 -vf "hwupload_cuda,thumbnail_cuda=100,scale_cuda=107:60,hwdownload,format=yuv420p" -vframes 1 -y ~/Videos/thumbs/thumb%03d.jpg

  But I get wrong output picture (the color of thumbnail is green) :

  

  Correct image must be black.
  How to make first image with correct color ?

  

  log : -loglevel verbose

  ffmpeg version N-89707-g89b84cb Copyright (c) 2000-2018 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  
    configuration: --cpu=native --enable-pthreads --extra-version=hd --enable-gnutls --enable-vaapi --enable-vdpau --enable-nonfree --enable-gpl --enable-swscale --enable-libx264 --enable-version3 --enable-nvenc --enable-libnpp --enable-cuda --enable-cuvid --enable-cuda-sdk --enable-filter=scale_cuda --enable-filter=thumbnail_cuda --extra-cflags=-I/usr/local/cuda-8.0/include --extra-ldflags=-L/usr/local/cuda-8.0/lib64
  
    libavutil      56.  7.100 / 56.  7.100
  
    libavcodec     58.  9.100 / 58.  9.100
  
    libavformat    58.  3.100 / 58.  3.100
  
    libavdevice    58.  0.100 / 58.  0.100
  
    libavfilter     7. 11.100 /  7. 11.100
  
    libswscale      5.  0.101 /  5.  0.101
  
    libswresample   3.  0.101 /  3.  0.101
  
    libpostproc    55.  0.100 / 55.  0.100
  
  [h264 @ 0x392ed40] Reinit context to 1920x1088, pix_fmt: yuv420p
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/alex/Videos/1080.mp4':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: isommp42
  
      creation_time   : 2012-05-30T20:01:34.000000Z
  
    Duration: 00:01:14.21, start: 0.000000, bitrate: 5476 kb/s
  
      Stream #0:0(und): Video: h264 (High), 1 reference frame (avc1 / 0x31637661), yuv420p(left), 1920x1080 (1920x1088), 5321 kb/s, 29.97 fps, 29.97 tbr, 60k tbn, 59.94 tbc (default)
  
      Metadata:
  
        creation_time   : 1970-01-01T00:00:00.000000Z
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 152 kb/s (default)
  
      Metadata:
  
        creation_time   : 2012-05-30T20:01:34.000000Z
  
        handler_name    : IsoMedia File Produced by Google, 5-11-2011
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> mjpeg (native))
  
  Press [q] to stop, [?] for help
  
  [h264 @ 0x3a38280] Reinit context to 1920x1088, pix_fmt: yuv420p
  
  [Parsed_thumbnail_cuda_1 @ 0x4e3d8c0] batch size: 100 frames
  
  [graph 0 input from stream 0:0 @ 0x4e8b640] w:1920 h:1080 pixfmt:yuv420p tb:1/60000 fr:30000/1001 sar:0/1 sws_param:flags=2
  
  [auto_scaler_0 @ 0x4e8ca00] w:iw h:ih flags:'bicubic' interl:0
  
  [format @ 0x4e8b540] auto-inserting filter 'auto_scaler_0' between the filter 'Parsed_format_4' and the filter 'format'
  
  [Parsed_scale_cuda_2 @ 0x4e89380] w:1920 h:1080 -> w:107 h:60
  
  [swscaler @ 0x4ebf0c0] deprecated pixel format used, make sure you did set range correctly
  
  [auto_scaler_0 @ 0x4e8ca00] w:107 h:60 fmt:yuv420p sar:0/1 -> w:107 h:60 fmt:yuvj420p sar:0/1 flags:0x4
  
  Output #0, image2, to '/home/alex/Videos/thumbs/thumb%03d.jpg':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: isommp42
  
      encoder         : Lavf58.3.100
  
      Stream #0:0(und): Video: mjpeg, 1 reference frame, yuvj420p(pc, left), 107x60, q=2-31, 200 kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc (default)
  
      Metadata:
  
        creation_time   : 1970-01-01T00:00:00.000000Z
  
        handler_name    : VideoHandler
  
        encoder         : Lavc58.9.100 mjpeg
  
      Side data:
  
        cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
  
  [Parsed_thumbnail_cuda_1 @ 0x4e3d8c0] frame id #76 (pts_time=2.535867) selected from a set of 100 images
  
  No more output streams to write to, finishing.
  
  frame=    1 fps=0.9 q=3.1 Lsize=N/A time=00:00:02.56 bitrate=N/A speed=2.26x    
  
  video:2kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
  
  Input file #0 (/home/alex/Videos/1080.mp4):
  
    Input stream #0:0 (video): 115 packets read (134655 bytes); 101 frames decoded; 
  
    Input stream #0:1 (audio): 1 packets read (9 bytes); 
  
    Total: 116 packets (134664 bytes) demuxed
  
  Output file #0 (/home/alex/Videos/thumbs/thumb%03d.jpg):
  
    Output stream #0:0 (video): 1 frames encoded; 1 packets muxed (1864 bytes); 
  
    Total: 1 packets (1864 bytes) muxed

  UPDATE, working !
  Add format=nv12 before hwupload

  -vf "format=nv12,hwupload_cuda,thumbnail_cuda,scale_cuda=1280:72‌​0,hwdownload,format=‌​nv12"

• How can i make drawtext filter start the text scrolling from the center while scrolling from right to left

  16 janvier 2018, par Femzy

  Hello How can i make the text start from the center when the video play ? Currently it start from the left side and people dont see the first words before it goes. I want the text to start from either the center of the video or the right while moving from right to left. Thanks in advance for helping me...
  This is my code that currently works for the text, but it starts from the edge of the of the left while moving from right to left

  echo shell_exec('ffmpeg -loop 1 -i slide2.jpg -vf scale=-2:1080,drawtext="textfile=text.txt:expansion=normal:fontfile=FreeSerif.otf: y=h-line_h-20:x=-200*t: fontcolor=white: fontsize=50" -pix_fmt yuv420p -t '.$words_count.' -movflags +faststart textover10.mp4 -report');