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• Accurate FFmpeg capture start time

  28 juillet 2016, par Adam

  I’m using ffmpeg from the command line to capture from a webcam to a file using the following :

  ffmpeg -y -rtbufsize 702000k -f dshow -s 320x240 -r 25 -i video="<device>" -t 10 -vcodec mjpeg -q:v 2 out.mp4
  
  </device>

  There is a slight delay between executing the command and the start of the capture ( 0.5 sec).
  I’m trying to find a way to accurately determine the start time (UTC/GMT) of the capture.

  My initial thought was to use the file-creation time as this might accurately reflect when the first frame was encoded (as opposed to when the command was executed). Unfortunately the file creation time is only accurate to the second which is not precise enough (and I’m not sure this would have given an accurate result anyway).

  My next thought was to use ffmpegs timestamp option. According to the documentation (http://www.ffmpeg.org/ffmpeg.html) :

  ‘-timestamp time (output)’

  Set the recording timestamp in the container. The syntax for time is:
  
  
  
  now|([(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...])|(HHMMSS[.m...]))[Z|z])

  If the value is "now" it takes the current time. Time is local time unless ’Z’ or
  ’z’ is appended, in which case it is interpreted as UTC. If the year-month-day part
  is not specified it takes the current year-month-day.

  So I added the option :

  ffmpeg -y -rtbufsize 702000k -f dshow -s 320x240 -r 25 -i video="<device>" -t 10 -vcodec mjpeg -q:v 2 -timestamp now out.mp4
  
  </device>

  Unfortunately ffmpeg doesn’t seem to like this :

  Option timestamp (set the recording timestamp (’now’ to set the
  current time)) cannot be applied to output file out.mp4 — you are
  trying to apply an input option to an output file or vice versa. Move
  this option before the file it belongs to.

  Error parsing options for output file out.mp4.

  Error opening output files : Error number -22 occurred

  The documentation says -timestamp is an output option and it appears to be applied to the output file so I’m confused by this error.

  Can anyone suggest a way to accurately determine the capture start time ?

  Does anyone know why the -timestamp option gives an error ?

• RTSP/RTMP Video Streaming Client iOS [closed]

  28 mai 2015, par nathansizemore

  I’m in need of a open source solution/library to stream RTSP/RTMP to an iOS Application. I need to build an app that connects to a media server, and opens the provided video stream. I believe there has to be libraries out there, but I have yet to find one that is open source, compiles, actually works, and runs on iOS 5+, iPhone 4+. I do not have a preference, RTMP or RTSP will suffice. Preferably the one with the least amount of work. I have RTSP working on the Android side, but nothing for iOS yet.

  This is what I already know from research today -

  RTSP

  • Seems possible using Live555/FFMPEG
  • MooncatVenture Group - Old FFMPEG, not compatible with ARMv7s (No updates/blogs/commits in over a year)
  • DFURTSPPlayer - This is a working example.

  RTMP

  • Seems possible using Live555/FFMPEG
  • A few libraries are out there for data messaging, but that is all
  • MidnightCoders Project - Does not seem video support is build yet, as Audio is not.

  I’ve never messed with anything video related before, so encoding, frame rate, key frame, chunks, etc... is pretty foreign to me. Right now, it seems building a static binary from Live555/FFMPEG is the only solution to my problem. If so, can anyone give me a simple quickstart guide or links to a blog/example someone has out there ? I’m not looking for anything crazy, just a simple

  1. Download This - LINK
  2. Compile it like this - LINK
  3. Place it into X Folder in Xcode
  4. Create X Object
  5. Read Stream API here - LINK

  If not, anyone want to point me to a working open source library ?

  Oh yeah, this happens to be my first iPhone app and first time in Objective-C. Awesome first project, yeah ?

• doc/faq : remove "-profile option fails when encoding H.264 video with AAC audio"...

  3 janvier 2014, par Stefano Sabatini

  doc/faq : remove "-profile option fails when encoding H.264 video with AAC audio" entry
  The error was fixed in commit ce9bd303794fcc94aa232c116bece13c5994b55b
  
  more than one year ago, and does not affect all the currently supported
  
  versions.
  In particular, fix trac issue #1535.
  

  • [DH] doc/faq.texi