Recherche avancée

Sur d’autres sites (5246)

• Understanding ffmpeg re parameter

  4 septembre 2024, par formatkaka

  I was reading about the -re option in ffmpeg .
What they have mentioned is

  



  


  From the docs

  
 


  -re (input)

  
 


  Read input at the native frame rate. Mainly used to simulate a grab device, or live input stream (e.g. when reading from a file). Should not be used with actual grab devices or live input streams (where it can cause packet loss). By default ffmpeg attempts to read the input(s) as fast as possible. This option will slow down the reading of the input(s) to the native frame rate of the input(s). It is useful for real-time output (e.g. live streaming).

  


  



  My doubt is basically the part of the above description that I highlighted. It is suggested to not use the option during live input streams but in the end, it is suggested to use it in real-time output.

  



  Considering a situation where both the input and output are in rtmp format, should I use it or not ?

  


• ffmpeg : avoid possible undefined behavior

  9 octobre 2015, par Ganesh Ajjanagadde

  ffmpeg : avoid possible undefined behavior
  On lines 1633,1634 FFABS(pts) is performed. However, if av_stream_get_end_pts
  
  returns AV_NOPTS_VALUE always, pts remains stuck at INT64_MIN, leading
  
  to undefined behavior on FFABS.
  One could conceive of a solution using FFNABS. However, such a solution
  
  has to deal with the implementation defined rounding of integer division
  
  with at least one negative operand in ANSI C89. C99 forces truncation to
  
  zero, but I am not sure that all of our platforms compile with full C99
  
  support, and in particular whether we can safely assume a fixed
  
  rounding behavior across all platforms.
  This solution is simple, and I doubt changing INT64_MIN to INT64_MIN + 1
  
  has any practical loss - if it is stuck at its initial value, the stream
  
  is messed up anyway.
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] ffmpeg.c

• Sending AMF Metadata Via RTMP Using FFmpeg Libraries

  20 janvier 2016, par EncodedNybble

  I’m doing some experimentation with streaming to a Wowza host via RTMP. I’m using ffmpeg libraries (libavformat, libavcodec, etc.) along with rtmpdump (for librtmp, etc.) to stream some raw H264 frames. So far everything is working well.

  I wanted to add some AMF metadata (rotation) to particular video frames of my stream but I can’t seem to find a good way of approaching it. I’m currently using AVPacket’s "side data" to specify a rotation matrix, but it seems that the "side data" isn’t being converted to metadata when I call av_write_interleaved_packet because Wowza isn’t receiving onMetaData calls and using WireShark, etc. only shows metadata being send at stream startup.

  Has anyone been able to use libavcodec etc. to send per packet AMF metadata via RTMP ?

  [EDIT] So, I’ve found that if I add a third stream (my first two being audio and video) to my output format and have the third stream be based on coded with ID of AV_CODEC_ID_TEXT (all other IDs give an invalid/not found error when using flv encoder) that I can write a single bit of text as metadata with the AVPacket. Unfortunately, this isn’t quite 100% what I’d like to do as I’d like to have more control over what is injected (currently it injects "type : Text text:your text here"). It also seems to prepend "@setDataFrame."

  I’m still at a loss to achieve the behavior that I want.