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• FFMPEG video audio sync

  23 février 2023, par user1774074

  There are many questions regarding audio and video sync when processing videos with FFMPEG, but I couldn't find the answer for this one :

  


  I record rtsp stream with the following command :

  


  ffmpeg -rtsp_transport udp -i rtsp://streamAddress  -vcodec copy -acodec copy  -copyts -flags +bitexact -ss 00:00:02 -y output.avi


  


  I extract the audio with the following command :

  


  ffmpeg  -y -i output.avi -vn -flags +bitexact -f wav output.wav


  


  I search for event from output.wav and generate timestamps startTime and duration

  


  I cut and transcode the original video with the following command :

  


  ffmpeg  -y -i output.avi -cpu-used 16 -r 100 -threads 15 -b:v 2400k -vcodec libvpx -s 850x480 -an -ss startTime -t duration final.webm


  


  I can see this procedure loses the sync between video and audio but I can't find the reason. in Which part of commands the sync is lost and why ?

  


  My rtsp stream specs are :

  


  Profile Name : H.264

  


  Resolution 1280x720

  


  Output Frame Rate : 100

  


  GOP : 15

  


  Stream Mode : CBR

  


  Bitrate : 5 Mbps

  


• Ffmpeg not compiling

  25 mai 2018, par Robin Betka

  I’m trying to compile ffmpeg 4.0 for Android (using Ubuntu 64 bit) but I can not get it to work.
  I was able to compile it for Linux itself fairly fast, but now struggling using the NDK. I’m unexperienced with this so I might have some major flaw somewhere. All paths and files exist. Github tutorials are extremely outdated and don’t work as well for me with different errors.

  Getting following error :

  In file included from ./libavformat/internal.h:24:0,
  
               from libavdevice/alldevices.c:23:
  
  /home/lit/Android/Sdk/ndk-bundle/toolchains/arm-linux-androideabi- 
  
  4.9/prebuilt/linux-x86_64/lib/gcc/arm-linux- 
  
  androideabi/4.9.x/include/stdint.h:9:26: fatal error: stdint.h: No such file 
  
  or directory
  
  # include_next 
  
                        ^
  
  compilation terminated.
  
  ffbuild/common.mak:60: recipe for target 'libavdevice/alldevices.o' failed
  
  make: *** [libavdevice/alldevices.o] Error 1

  My build script :

  SYSROOT=/home/lit/Android/Sdk/ndk-bundle/platforms/android-14/arch-arm/
  
  TOOLCHAIN=/home/lit/Android/Sdk/ndk-bundle/toolchains/arm-linux-androideabi- 
  
  4.9/prebuilt/linux-x86_64
  
  
  
  cd ffmpeg/ffmpeg && \
  
  PATH="$HOME/bin:$PATH" PKG_CONFIG_PATH="$HOME/ffmpeg_build/lib/pkgconfig" 
  
  ./configure \
  
  --prefix="$HOME/ffmpeg_build" \
  
  --pkg-config-flags="--static" \
  
  --extra-cflags="-O3 -Wall -pipe -ffast-math -fstrict-aliasing -Werror=strict- aliasing -Wno-psabi -Wa,--noexecstack -DANDROID -DNDEBUG-march=armv5te -mtune=arm9tdmi -msoft-float"\
  
  --extra-ldflags="-L$HOME/ffmpeg_build/lib" \
  
  --bindir="$HOME/bin" \
  
  --arch=arm \
  
  --target-os=linux \
  
  --enable-cross-compile \
  
  --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
  
  --cpu=armv5te \
  
  --sysroot=$SYSROOT \
  
  --enable-gpl \
  
  --enable-small \
  
  --enable-nonfree && \
  
  
  
  PATH="$HOME/bin:$PATH" make && \
  
  make -j2 && \
  
  make install && \
  
  hash -r

  Thank you for your help.

• How to build ffmpeg for arm ? [on hold]

  11 décembre 2014, par fatsissy

  I have an arm cross compiler on my ubuntu machine and tried to build ffmeg libraries for arm but got the following error

  cd ffmpeg-2.5
  
  ./configure --host=arm-linux-gnueabihf
  
  Unknown option "--host=arm-linux-gnueabihf"

  I did read the ./configure —help file and there is an option "—arch=ARCH" but im not sure how to set this or if its the correct option.
  thanks !