Recherche avancée

Sur d’autres sites (10363)

• How to use subtitles filter to a video VFR ( variable frame rate ) video ? [migrated]

  14 février 2019, par iaaflaafc

  I have created a VFR (variable frame rate) video from a list of images by using the following ffmpeg command.

  ffmpeg -f concat -i concat.txt -vsync vfr -pix_fmt yuv420p output.mp4

  where the concat.txt is a text file which contains the list of the image locations and durations in the below format.

  file image01.png
  
  duration 3
  
  file image02.png
  
  duration 5
  
  file image02.png

  I have a subtitle file (.srt file) that I would like to add to the generated video by using the subtitles filter.

  I tried to use the subtitles filter by running the following command

  ffmpeg -i output.mp4 -codec:a copy -vf subtitles=subtitles.srt -max_muxing_queue_size 4096 outputWithSubtitles.mp4

  I find that the resultant output file does not show any subtitles.

  I find that if instead of VFR video if constant frame rate video is generated, then this issue is not observed i.e., during the generation of the first video from images if -vsync vfr option is not used, then a constant frame rate video is generated and using subtitles filter works.

  Is there a way to use the subtitles filter on a VFR video ?

• ffmpeg issues "501 Not Implemented" while recording an RTSP stream

  28 février 2019, par atsushi

  I have a 4K camera (Sony SNC-VB770) streaming RTSP.

  I’m trying to record the stream into files (each has handy length, say, 1hour)
  using a simple script to repeatedly launch ffmpeg (ver 4.1) :

  while : ; do
  
    # (set $url and $outfile, and then)
  
    ffmpeg -rtsp_transport tcp -t 3600 -y -i $url -c copy -map 0:0 -b:v 16000k $outfile
  
  done

  If I run the script on a local PC directly connected to the camera, it works (longer than a week, at least).
  However, if I do the same on a server machine located in a data center, it fails randomly with no error message.
  Sometimes it runs for a few days, sometimes it dies in one minutes.

  Typical output looks like the following :

  # devname: snc-vb770
  
  # url: rtsp://10.40.35.90/media/video1
  
  # vb: 16000k
  
  # datefmt %d%H
  
  # addtimestamp 0
  
  no timestamp
  
  ffmpeg version 4.1 Copyright (c) 2000-2018 the FFmpeg developers
  
    built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-18)
  
    configuration: --prefix=/usr/local/ffmpeg-4.1 --enable-openssl --enable-gpl --enable-version3 --enable-nonfree --enable-shared --enable-libx264 --enable-libvorbis --enable-filter=drawtext --enable-libfreetype --enable-libfribidi --enable-fontconfig
  
    libavutil      56. 22.100 / 56. 22.100
  
    libavcodec     58. 35.100 / 58. 35.100
  
    libavformat    58. 20.100 / 58. 20.100
  
    libavdevice    58.  5.100 / 58.  5.100
  
    libavfilter     7. 40.101 /  7. 40.101
  
    libswscale      5.  3.100 /  5.  3.100
  
    libswresample   3.  3.100 /  3.  3.100
  
    libpostproc    55.  3.100 / 55.  3.100
  
  Input #0, rtsp, from 'rtsp://10.40.35.90/media/video1':
  
    Metadata:
  
      title           : Sony RTSP Server
  
    Duration: N/A, start: 0.066667, bitrate: N/A
  
      Stream #0:0: Video: h264 (High), yuv420p(tv, bt709, progressive), 3840x2160 [SAR 1:1 DAR 16:9], 14.99 fps, 14.99 tbr, 90k tbn, 29.97 tbc
  
  Output #0, mp4, to './2811.mp4':
  
    Metadata:
  
      title           : Sony RTSP Server
  
      encoder         : Lavf58.20.100
  
      Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 3840x2160 [SAR 1:1 DAR 16:9], q=2-31, 16000 kb/s, 14.99 fps, 14.99 tbr, 90k tbn, 90k tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
  Press [q] to stop, [?] for help
  
  [mp4 @ 0x24e4ec0] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
  
  [mp4 @ 0x24e4ec0] pts has no value
  
  [mp4 @ 0x24e4ec0] Non-monotonous DTS in output stream 0:0; previous: 0, current: 0; changing to 1. This may result in incorrect timestamps in the output file.
  
  frame=   33 fps=0.0 q=-1.0 size=    1792kB time=00:00:02.00 bitrate=7332.9kbits/s speed=3.57x
  
  ...
  
  frame=  104 fps=8.4 q=-1.0 Lsize=    6532kB time=00:00:06.74 bitrate=7939.6kbits/s speed=0.548x
  
  video:6531kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.023506%

  I’ve looked into RTSP packet and found an "RTSP/1.0 501 Not Implemented" is sent from ffmpeg to the camera.
  After that the camera eventually sent back "RTSP/1.0 505 RTSP Version not supported" and then ffmpeg quits shortly.

  The "501" packet seems to be generated by libavformat/rtsp.c:ff_rtsp_read_reply(),
  when ffmpeg receive a malformed RTSP packet with method=(null), status_code=0.
  I don’t know why such packets arrive at random timing and who is wrong (maybe the camera, maybe any of network switches or routers in the middle of the network path from the camera to the server machine).
  But anyway, I don’t want the recording to be stopped
  due to those malformed packets.

  Is there any workaround to make ffmpeg ignore invalid RTSP packets and just continue the recording ?

  Additional information :

  • I’ve tested the recording with both ffmpeg ver4.1 and 2.8.4 and no difference observed.

  • No difference observed at lower resolution nor at lower bitrate.

  • I have 3 cameras from various manufacturers in the same network environment.
    All of the three are working without problem for more than a month.
    Only the Sony SNC-VB770 shows the strange behavior.

• How to compress gif effectively to reduce size ?

  12 avril 2021, par RSJ

  We use gifs for our blog extensively. We used to embed tenor nano gifs(90px height maintaining aspect ratio, used for GIF previews and shares on mobile) in it. Now we wanted to create our own gifs and are using the following command to convert mp4 to gif while maintaining the properties of tenor's nano gif. using ffmpeg version 4.1.4

  



  But we observed a huge difference in size between the gif we created and the one created using tenor.

  



  ffmpeg -i input.mp4 -filter_complex "[0:v]fps=10,scale=-1:90:flags=lanczos,split [a][b];[a] palettegen [p];[b][p] paletteuse" -y output.gif

  



  [Original MP4] - 845KB

  



  Tenor Nano gif - 42KB

  



  ffmpeg gif - 106KB

  



  We even tried changing dithering algorithm to further reduce size but it ended up adding noise and damaged the gif quality

  



  paletteuse=dither=bayer:bayer_scale=5:diff_mode=rectangle

  



  We tried tweaking colour quantization in gifsicle as well but it was of no use.

  



  gifsicle --resize _x90 --colors 256 --color-method diversity --dither=ordered --resize-method sample input.gif > output.gif