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• Revision eec3def7c5 : Modified no memory rate control. This 2-pass rate control setting allocates bit

  16 octobre 2013, par Paul Wilkins

  Changed Paths :
   Modify /vp9/encoder/vp9_onyx_if.c

  
   Modify /vp9/encoder/vp9_onyx_int.h

  
   Modify /vp9/encoder/vp9_ratectrl.c

  
  
  Modified no memory rate control.

  This 2-pass rate control setting allocates bits based
  on first pass stats to each kf group, gf group and individual
  frame but does not correct the bits left and allocation after
  each frame.

  In other words it recommends a bit allocation for each frame
  but does not try and correct any over or under spend on a
  frame over the remainder of the clip. This reduces the accuracy
  of rate control in terms of hitting an average bitrate but prevents
  problems that may arise because early frames either use to many
  or too few bits. This mode is currently more inclined to undershoot
  than overshoot (particularly at higher data rates).

  Also minor changes to rate of adaption when recode loop is not
  enabled.

  This mode is currently enabled by default for VBR.
  It gives the following % performance gains.

  derf +0.467, +1.072
  yt 2.962, 2.645
  stdhd 1.682, 1.595,
  yt-hd 2.3, 2.174

  Change-Id : I3c84a9bf8884e5b345698ff0e19187f792c2f3a0

• Capture user-defined segment of RTSP video using FFmpeg

  10 janvier 2019, par Tom Larcher

  I’m endeavouring to capture a segment of video from an RTSP (static not live) video stream using FFmpeg, however I’m not certain how this is achieved.

  I am presently able to cut a segment of video from a local video file using a command similar to the one below :

  ffmpeg -y -i input_video.mp4 -ss 0:04:41.215 -to 0:07:17.335 output_video.mp4

  However commands similar to the above don’t seem to be working for remote (RTSP) video files. I’ve taken a look around for ways in which this can be achieved, to no avail. I’ve come across information on capturing individual frames as well as methods of capturing RTSP video files for storage locally, but I can’t seem to connect the dots to capture only a selected portion of the RTSP video.

  Any help on this would be immensely appreciated.

• How do I bind a specific wlan interface to an ffmpeg/ffplay call without modifying the source ?

  5 mai 2017, par Falimond

  I have two wifi USB adapters connected to a Raspberry Pi running Raspbian jessie with their respective wlan0 and wlan1 interfaces set up. I can successfully use wpa_supplicant to connect to two individual, identical devices from which I can individually access a UDP video stream using ffplay. Now I need to simultaneously bring up both UDP streams. This would be easy if the access URLs were different, but they are not and I cannot change the IP addresses, requiring another solution.

  Unless I am mistaken, there is no way to specify an interface in the call to ffplay/ffmpeg. I have looked through the FFmpeg source relevant to the UDP protocol and know that I can specify an interface in the appropriate setsockopt calls in libavformat/udp.c, but modifying the source in this way is rather involved and I’d like to avoid it if possible.

  I looked into adding namespaces using ip but this doesn’t seem like it will work because I can only bind the wireless hardware device phy0, not the separate wlan interfaces associated with phy0.

  Are there alternate means of dealing with such a situation where the UDP streams’ URLs are the same or am I stuck with modifying the FFmpeg source code ?