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• ffmpeg with double ethernet interfaces works wrong

  21 janvier 2019, par CharlesCui

  A server with double interfaces.

  1. One(eht0) is used for WAN which provides http/ssh services for internet users.

  2. The other(eth1) is used to receive multicast data from intranet.

  218.108.132.177 is public network gateway.

  125.210.198.1 is private network gateway.

  233.49.3.*/24 is multicast address.

  10.0.11.*/24 is the source of multicast data.

  When the route table is like below, ffmpeg can’t read the udp data from eth1, ffmpeg hung up :

  rrca@rcasnap02:~$ route
  
  Kernel IP routing table
  
  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  
  218.108.132.176 *               255.255.255.252 U     0      0        0 eth0
  
  125.210.198.0   *               255.255.255.240 U     0      0        0 eth1
  
  default         218.108.132.177 0.0.0.0         UG    100    0        0 eth0
  
  default         125.210.198.1   0.0.0.0         UG    100    0        0 eth1

  or

  rrca@rcasnap02:~$ route
  
  Kernel IP routing table
  
  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  
  218.108.132.176 *               255.255.255.252 U     0      0        0 eth0
  
  125.210.198.0   *               255.255.255.240 U     0      0        0 eth1
  
  default         218.108.132.177 0.0.0.0         UG    100    0        0 eth0
  
  10.0.11.0       125.210.198.1   0.0.0.0         UG    100    0        0 eth1

  or

  rrca@rcasnap02:~$ route
  
  Kernel IP routing table
  
  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  
  218.108.132.176 *               255.255.255.252 U     0      0        0 eth0
  
  125.210.198.0   *               255.255.255.240 U     0      0        0 eth1
  
  default         218.108.132.177 0.0.0.0         UG    100    0        0 eth0
  
  233.49.3.0      125.210.198.1   255.255.255.0   UG    100    0        0 eth1

  I want to the ffmpeg work right,but now I think the two default route in route table disturb eachother, and I take a try, when the public gateway route is deleted, or the private gateway route is at the head of public default gateway route, ffmpeg works well, I think it read multicast from eth1.But the route table is not thus, ffmpeg can’t read data from eth1, I think it read data on eth0(which is not private network interface).

  How to do ffmpeg works well with two interfaces at the same time ?

• ffmpeg to change video from 30 to 60fps to double speed without re-encoding

  29 novembre 2018, par user3144514

  First, I have looked at the older questions asking the same, but the responses do not work.
  Adding -r 30 or 60 to the input file does not impact the output, nor does setting it for the output, which remains unchanged.

  I am handling a very large number of files from 1 to 22 gigs recorded (with audio) in 30fps that need to be re-posted as 60pfs, with the corresponding speed increase.

  I toyed with ffmpeg a bit and came up with this..

  -filter_complex "[0:v]setpts=0.50*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" -vcodec:v libx264

  It works fine, but to have to wait out a complete re-encoding of the video and audio to produce the same video with the fps changed seems like an insane waste of time.

  Am I missing something simple ? Is there not a way to -c copy with a new fps playback rate on the resulting file ?
  (if it still has to recode the audio to maintain sync that’s fine, audio is quick enough it doesn’t much matter)

• ffmpeg custom buffer sink filter

  25 novembre 2018, par NadavRub

  Environment

  • Ubuntu 18.04
  • C++
  • ffmpeg 3.4 (git master)
  • ffmpeg is used as a shared lib (InProc) via the C++ API

  Use-case

  • Per this link I am trying to use the ’avfilter_graph_*’ APIs to create ffmpeg graph
  • I would like the graph output to be sent out to my custom code ( part of the hosting application )

  Considered implementations

  • [A] Implement a custom sink filter ( part of libavfilter ) to implement my custom logic
  • [B] Implement a custom sink filter to grab the output samples and send them out to my application ( something similar to DShow SampleGrabber )

  Problem at hand

  With either of the above mentioned approaches the ffmpeg code has to be modified, and this impose an overhead in supporting future ffmpeg releases

  I wonder if there is any straight forward approach for an external ( hosting ) application to grab the graph output w/ minimal copying of the payload.

  Is there any way to use a custom AVIOContext to achieve that ? can I construct a graph connected to an output AVIOContext ? can I create a custom filter implemented in a module external to libavfilter and associate it w/ the graph using ’AVFilterContext’ ?