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• FFMPEG udp input stream and input stream play local file

  15 décembre 2017, par liewjls

  Hoping someone can guide me to the right place. I have a application is being the "middle man" receiving a video stream from a source via UDP and passing this video stream to a ffmpeg instance on a server and record a certain period of the video (without audio), on a certain occasion it will need to play the video from recorded video instead of passing the live video stream to the ffmepg instance on the server.

  /ffmpeg -an -f mpegts -i udp://@:7100/?fifo_size=2000&overrun_nonfatal=1 -analyzeduration 150 -f rawvideo -map 0:0 -vcodec rawvideo -pix_fmt bgra - -af volumedetect -vn -sn -dn -map 0:1 -f mpegts -y -flush_packets 0 udp://127.0.0.1:7208?pkt_size=1316

  I managed to record the video without audio frm Extracting the h264 part of a video file (demuxing)

  The difference is i save the recorded file as "mpegts"

  avformat_alloc_output_context2(&ofmt_ctx_a, NULL,  "mpegts", out_filename_a);

  As soon i need to play from this recorded file, i read every 1316 packets from this file and pass it to the ffmpeg via the localhost port.

  The problem is the ffmpeg seems doesn’t like my recorded file and i noticed it has error msg "DTS 18635855 < 24133055 out of order"

  How do i resolve this issue ?

  Thanks.

• lavc : Use av_gettime_relative

  6 mai 2014, par Olivier Langlois

  lavc : Use av_gettime_relative
  Whenever av_gettime() is used to measure relative period of time,
  
  av_gettime_relative() is prefered as it guarantee monotonic time
  
  on supported platforms.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/dct-test.c
  • [DBH] libavcodec/fft-test.c

• ffmpeg timestamp information using fps filter isn't aligned with ffprobe

  16 juillet 2018, par Jose.OC

  I’m using ffmpeg to extract images (thumbnails) from a video using the filter fps so that I get an image every 0.5 seconds. This is the command I use :

  ffmpeg -i video.mp4 -f image2 -filter:v fps=1/0.5 -y out_%3d.png

  I want to know the timestamp for these images and I’ve found out that ffmpeg behaves differently than ffprobe.

  First of all, I haven’t found a way to get the timestamps as metadata (log files or whatever) but I got to overlay the timestamp in the images themselves using ffmpeg :

  ffmpeg -i video.mp4 \
  
  -vf "fps=fps=1/5,drawtext=fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf: text='%{pts\:hms}': x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" \
  
  out_with_timestamp_%03d.png

  However, using ffprobe you can simulate the use of the same fps filter and ffprobe allows you to get some information from the frames. This command is supposed to simulate the ffmpeg one and provides some metadata where you can extract the timestamps from :

  fprobe -hide_banner \
  
  -i "movie=video.mp4,fps=fps=1/0.5[out0]" \
  
  -f lavfi -show_frames -show_entries frame=pkt_pts_time -of csv=p=0

  The problem is that the timestamps that ffmpeg prints into the images are different than the ones that ffprobe gives, and ffprobe ones are wrong while the ones given by ffmpeg are right.
  The timetamps given by ffmpeg are in the middle of the period of time while the ones given by ffprobe are in the very begining of the window.

  Is there any way to extract thumbnails and its timestamp from a video using ffmpeg ?

  You can find all the steps to be able to reproduce this behaviour here :
  https://www.joseoc.com/en/video/ffmpeg/extract-images-from-video/#getting-the-timestamp-for-the-images