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• ffmpeg drop frames on purpose to lower filesize

  20 octobre 2014, par max

  Our security system records and archives our IP cameras streams with ffmpeg -use_wallclock_as_timestamps 1 -i rtsp://192.168.x.x:554/mpeg4 -c copy -t 60 my_input_video.avi

  I run it with crontab every minute so it creates videos of 60 seconds ( 15Mb) for each camera every minute. When an intrusion occurs, the camera sends a picture through FTP and a script called by incrontab :

  1- forwards immediately the picture by email

  2- selects the video covering the minute the intrusion occured, compress it with h264 (to 2,6Mb) and sends it by email

  It is working really well but if a thief crosses the path of various cameras, the connection to the SMTP server is not fast enough so video emails are delayed. I’d like to compress the videos even more to avoid that. I could lower the resolution (640x480 to 320x240 for example) but sometimes 640x480 is handy to zoom on something which looks to be moving...

  So my idea is to drop frames in the video in order to lower the filesize. I don’t care if the thief is walking like a "stop motion Lego" on the video, the most important is I know there is someone so I can act.

  mediainfo my_input_video.avi says Frame rate = 600.000 fps but it is of course wrong. FPS sent by IP cameras are always false because it varies with the network quality ; this is why i use "-use_wallclock_as_timestamps 1" in my command to record the streams.

  with ffmpeg -i  my_input_video.avi -vcodec h264 -preset ultrafast -crf 28 -acodec mp3 -q:a 5 -r 8 output.avi the video is OK but filesize is higher (3Mb)

  with ffmpeg -i  my_input_video.avi -vcodec h264 -preset ultrafast -crf 28 -acodec mp3 -q:a 5 -r 2 output.avi the filesize is lower (2,2Mb) but the video doesn’t work (it is blocked at the first frame).

  Creating a mjpeg video (mjpeg = not interlaced frames) in the middle of the process (first exporting to mjpeg with less frames and then exporting to h264) creates same results.

  Do you know how I can get my thief to walk like a "stop motion Lego" to lower the filesize to a minimum ?

  Thanks for any help

• Why UA sniffing is generally bad, real-world example #1048577 : "That time a missing /s on navigator.userAgent (based on single-digit UA version assumptions) broke SM2 on iOS 8+ devices."

  1er septembre 2014, par scottschiller

  Why UA sniffing is generally bad, real-world example #1048577 : "That time a missing /s on navigator.userAgent (based on single-digit UA version assumptions) broke SM2 on iOS 8+ devices."
  The upside : The fix is adding \s to a UA regex check targeting legacy iOS devices with broken HTML5 Audio support, so that the "OS 10 " portion of the UA string does not match the pattern "OS 1 ".
  This is a pre-emptive fix for the pending iOS 8 release, which reportedly includes the string "iPhone OS 10_10 like Mac OS X". Due to SM2 checking for /os ([12|3_0|3_1])/i which had broken HTML5 Audio() support, and not considering the far future possibility of "iOS 10" being included in the userAgent string at the time, HTML5 audio is incorrectly disabled on iOS 8 beta 3 and is likely to apply to the final iOS 8 release.
  This is a good example and reminder of why UA checks are generally bad, and dangerous ; similar issues hit other libraries doing UA and plugin checks both client and server-side when IE hit 10, and Flash hit version 10, so this iOS pattern change may affect some other libraries targeting iOS as well.
  

• No such file or directory FFMpeg Error on MAC

  20 novembre 2014, par Nitesh

  I am trying to build a ffmpeg binary using the following link

  http://ffmpegmac.net/HowTo/

  I was successful in creating the binary.
  I could convert video files easily
  This is the code i run in the terminal

  ffmpeg -i Test.mp4 -b:v 64k -bufsize 64k test2.flv

  This works fine totally
  But when i run

  ./ffmpeg -re -i  test2.flv  -acodec libfaac -ar 44100 -ab 96k -c: v libx264  -level 41 -      profile baseline -bufsize 20000k -maxrate 25000k -g 250 -r 20 -s 480x270 -flags  -global_header -map 0 -f segment -segment_time 4 -segment_list test.m3u8 -segment_format mpegts stream%05d.ts 

  I get a "test2.flv : No such file or directory error" even though the test2.flv exists in the folder. Can you tell me where i might be going wrong.
  I am doing the above operation to stream the video to my iPhone over air.

  (Note- The command to build the ffmpeg binary i am using is as follows-
  ./configure —prefix=$TARGET —enable-nonfree —enable-gpl —enable-pthreads —enable-version3 —enable-libspeex —enable-libvpx —disable-decoder=libvpx —enable-libfaac —enable-libmp3lame —enable-libtheora —enable-libvorbis —enable-libx264 —enable-avfilter —enable-libopencore_amrwb —enable-libopencore_amrnb —enable-filters —arch=x86_64 —enable-runtime-cpudetect && make -j 4 && make install
  )

  Thanks in advance for your help
  Regards