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• checkasm : use perf API on Linux ARM*

  1er septembre 2017, par Clément Bœsch

  checkasm : use perf API on Linux ARM*
  On ARM platforms, accessing the PMU registers requires special user
  
  access permissions. Since there is no other way to get accurate timers,
  
  the current implementation of timers in FFmpeg rely on these registers.
  
  Unfortunately, enabling user access to these registers on Linux is not
  
  trivial, and generally involve compiling a random and unreliable github
  
  kernel module, or patching somehow your kernel.
  Such module is very unlikely to reach the upstream anytime soon. Quoting
  
  Robin Murphin from ARM :
  > Say you do give userspace direct access to the PMU ; now run two or more
  
  > programs at once that believe they can use the counters for their own
  
  > "minimal-overhead" profiling. Have fun interpreting those results...
  
  >
  
  > And that's not even getting into the implications of scheduling across
  
  > different CPUs, CPUidle, etc. where the PMU state is completely beyond
  
  > userspace's control. In general, the plan to provide userspace with
  
  > something which might happen to just about work in a few corner cases,
  
  > but is meaningless, misleading or downright broken in all others, is to
  
  > never do so.
  As a result, the alternative is to use the Performance Monitoring Linux
  
  API which makes use of these registers internally (assuming the PMU of
  
  your ARM board is supported in the kernel, which is definitely not a
  
  given...).
  While the Linux API is obviously cross platform, it does have a
  
  significant overhead which needs to be taken into account. As a result,
  
  that mode is only weakly enabled on ARM platforms exclusively.
  Note on the non flexibility of the implementation : the timers (native
  
  FFmpeg vs Linux API) are selected at compilation time to prevent the
  
  need of function calls, which would result in a negative impact on the
  
  cycle counters.
  

  • [DH] configure
  • [DH] tests/checkasm/checkasm.c
  • [DH] tests/checkasm/checkasm.h

• Getting troubles when I generate rtsp stream as an output with ffmpeg from static images as an input

  10 août 2013, par Ilya Yevlampiev

  I'm trying to start the rtsp stream via feeding ffmpeg with static images and feeding ffserver with ffmpeg output.

  The first problem appears from the ffserver.config :

  Port 12345
  
  RTSPPort 8544
  
  BindAddress 0.0.0.0
  
  MaxHTTPConnections 2000
  
  MaxClients 1000
  
  MaxBandwidth 1000
  
  CustomLog /var/log/ffserver-access.log
  
    <feed>
  
  File /tmp/videofeed.ffm
  
  FileMaxSize 3M
  
  #Launch ffmpeg -s 640x480 -f video4linux2 -i /dev/video0
  
  #Launch ffmpeg http://localhost:8090/videofeed.ffm
  
  Launch ffmpeg -loop 1 -f image2 -r 20 -b 9600 -i Janalif.jpg -t 30 http://127.0.0.1:8090/videofeed.ffm -report
  
  ACL allow 127.0.0.1
  
    </feed>
  
    <stream>
  
  Format rtsp
  
  #rtsp://localhost:5454/test1-rtsp.mpg
  
  Feed videofeed.ffm
  
  #webcam.ffm
  
  Format flv
  
  VideoCodec flv
  
  VideoFrameRate 30
  
  VideoBufferSize 80000
  
  VideoBitRate 200
  
  VideoQMin 1
  
  VideoQMax 5
  
  VideoSize 640x480
  
  PreRoll 1
  
  NoAudio
  
    </stream>
  
    <stream>
  
  Format status
  
    </stream>

  Please ignore codecs etc in stream part. The problem appears for RTSPPort, after starting the server nmap shows no binding to 8544, only 12345 port is used.

  8090/tcp  open  unknown
  
  12345/tcp open  netbus

  I can download mpeg stream through http from http://localhost:12345/test1-rtsp.mpg. How can I setup 8544 port working ?

  and another question is about Launch part of the stream. Am I right, that ffserver executes the content of Launch line ? If so, how can i configure ffserver to wait the stream in some particular port, but start streaming at the moment I desire ?

  P.S. The solution looks like Säkkijärven polkka, hoowever the idea behind this construct is to provide the controlled rtsp stream to emulate the camera output. In future I plan to substitute the command line for ffmpeg with some java bindings for it to produce the program-controlled images to the camera input to test the computer vision, that's why I need a way to launch ffmpeg independently on ffserver.

• Why ffmpeg can play h264 even when flag —disable-libx264 is set ? [closed]

  2 décembre 2020, par Jams

  To be complient with x264 licensing (for a commercial software I'm making) I plan to use a compiled version of ffmpeg without x264 support.
Here is the ouput of the command line ffmpeg -L :

  


  


  ffmpeg version n4.3.1-20-g8a2acdc6da Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 9.3-win32 (GCC) 20200320
configuration : —prefix=/ffbuild/prefix —pkg-config-flags=—static —pkg-config=pkg-config —cross-prefix=x86_64-w64-mingw32- —arch=x86_64 —target-os=mingw32 —enable-version3 —disable-debug —enable-shared —disable-static —disable-debug —enable-iconv —enable-zlib —enable-libxml2 —enable-libfreetype —enable-libfribidi —enable-gmp —enable-lzma —enable-fontconfig —enable-opencl —enable-libvmaf —disable-vulkan —enable-libvorbis —enable-amf —enable-libaom —disable-avisynth —enable-libdav1d —disable-libdavs2 —enable-ffnvcodec —enable-cuda-llvm —disable-libglslang —enable-libass —enable-libbluray —enable-libmp3lame —enable-libopus —enable-libtheora —enable-libvpx —enable-libwebp —enable-libmfx —enable-libopencore-amrnb —enable-libopencore-amrwb —enable-libopenjpeg —enable-librav1e —enable-schannel —enable-sdl2 —enable-libsoxr —enable-libsrt —enable-libtwolame —disable-libvidstab —disable-libx264 —disable-libx265 —disable-libxavs2 —disable-libxvid —enable-libzimg —extra-cflags=-DLIBTWOLAME_STATIC —extra-cxxflags= —extra-ldflags=-pthread —extra-libs=-lgomp
libavutil 56. 51.100 / 56. 51.100
libavcodec 58. 91.100 / 58. 91.100
libavformat 58. 45.100 / 58. 45.100
libavdevice 58. 10.100 / 58. 10.100
libavfilter 7. 85.100 / 7. 85.100
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
ffmpeg is free software ; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation ; either version 3 of the License, or
(at your option) any later version.

  


  


  But when I play a video encoded with h264 it plays perfectly.
Is expected ? How to be sure I'm not infringing the license ?

  


  Here is where I downloaded the binaries :
https://github.com/BtbN/FFmpeg-Builds/releases
  
And I picked a release with the following name : win64-gpl-shared-4.3.zip

  


  Thanks.