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• Re-sampling H264 video to reduce frame rate while maintaining high image quality

  31 mars 2016, par BrianTheLion

  Here’s the mplayer output for a video of interest :

  br@carina:/tmp$ mplayer foo.mov 
  
  mplayer: Symbol `ff_codec_bmp_tags' has different size in shared object, consider re-linking
  
  MPlayer 1.0rc4-4.5.2 (C) 2000-2010 MPlayer Team
  
  mplayer: could not connect to socket
  
  mplayer: No such file or directory
  
  Failed to open LIRC support. You will not be able to use your remote control.
  
  
  
  Playing foo.mov.
  
  libavformat file format detected.
  
  [lavf] stream 0: video (h264), -vid 0
  
  [lavf] stream 1: audio (aac), -aid 0, -alang eng
  
  VIDEO:  [H264]  1280x720  24bpp  59.940 fps  2494.2 kbps (304.5 kbyte/s)
  
  ==========================================================================
  
  Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
  
  Selected video codec: [ffh264] vfm: ffmpeg (FFmpeg H.264)
  
  ==========================================================================
  
  ==========================================================================
  
  Opening audio decoder: [faad] AAC (MPEG2/4 Advanced Audio Coding)
  
  AUDIO: 44100 Hz, 2 ch, s16le, 128.0 kbit/9.07% (ratio: 15999->176400)
  
  Selected audio codec: [faad] afm: faad (FAAD AAC (MPEG-2/MPEG-4 Audio))
  
  ==========================================================================
  
  AO: [pulse] 44100Hz 2ch s16le (2 bytes per sample)
  
  Starting playback...
  
  Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.
  
  VO: [vdpau] 1280x720 => 1280x720 Planar YV12

  I’d like to use ffmpeg, mencoder, or some other command-line video transcoder to re-sample this video to a lower framerate without loss of image quality. That is, each frame should remain as crisp as possible.

  Attempts

  ffmpeg -i foo.mov -r 25 -vcodec copy bar.mov

  • The target frame rate — 25fps — is achieved but individual frames are "blocky."

  mencoder -nosound -ovc copy foo.mov -ofps 25 -o bar.mov

  • Videos are effectively un-viewable.

  Help !

  This seems like a simple enough use case. I’m very surprised that obvious things are not working. Is there something wrong with my approach ?

• Revision fba3110b09 : arm : Move the definition of bilinear_taps_coeff to within the section Previousl

  21 novembre 2012, par Martin Storsjo

  Changed Paths :
   Modify /vp8/common/arm/neon/vp8_subpixelvariance16x16_neon.asm

  
  
  arm : Move the definition of bilinear_taps_coeff to within the section

  Previously, the microsoft arm assembler errored out, saying that
  bilinear_taps_coeff was an undefined symbol.

  Change-Id : Ib938f0b454c41ccbd801e70a7c9acc0fa04e3c55

• ffmpeg on iOS 5.1 Undefined Symbols Error

  25 avril 2012, par AndyDunn

  So I've spent several hours now working through the scant amount of information available online about building ffmpeg for iOS. The building process seems to work well and I end up with fat files for armv6 and armv7 which I drag over into my project.

  However, whenever I try to use the "avcodec_init()" command I get the following error :

  Undefined symbols for architecture armv7 :
  "_avcodec_init", referenced from :

   -[FirstViewController viewDidLoad] in FirstViewController.o

  ld : symbol(s) not found for architecture armv7

  clang : error : linker command failed with exit code 1 (use -v to see invocation)

  The library files are included in the 'Link Binary with Libraries' of the project settings, so they are definitely compiled into the app. I just can't for the life of me work out why I'm getting an error on this.

  I've tried several different projects, and downloaded some existing project files from the web and get the same error.

  This is the build script I used :

  export PLATFORM="iPhoneOS" export MIN_VERSION="4.0" export
  MAX_VERSION="5.1" export
  DEVROOT=/Volumes/Lion/Applications/Xcode.app/Contents/Developer/Platforms/$PLATFORM.platform/Developer
  export SDKROOT=$DEVROOT/SDKs/$PLATFORM$MAX_VERSION.sdk export
  CC=$DEVROOT/usr/bin/llvm-gcc export LD=$DEVROOT/usr/bin/ld export
  CPP=$DEVROOT/usr/bin/cpp export CXX=$DEVROOT/usr/bin/llvm-g++ export
  AR=$DEVROOT/usr/bin/ar export LIBTOOL=$DEVROOT/usr/bin/libtool export
  NM=$DEVROOT/usr/bin/nm export CXXCPP=$DEVROOT/usr/bin/cpp export
  RANLIB=$DEVROOT/usr/bin/ranlib

  COMMONFLAGS="-pipe -gdwarf-2 -no-cpp-precomp -isysroot $SDKROOT
  -marm -fPIC" export LDFLAGS="$COMMONFLAGS -fPIC" export CFLAGS="$COMMONFLAGS -fvisibility=hidden" export
  CXXFLAGS="$COMMONFLAGS -fvisibility=hidden
  -fvisibility-inlines-hidden"

  FFMPEG_LIBS="libavcodec libavdevice libavformat libavutil libswscale"

  echo "Building armv6..."

  make clean ./configure \
  —cpu=arm1176jzf-s \
  —extra-cflags='-arch armv6 -miphoneos-version-min=$MIN_VERSION -mthumb' \
  —extra-ldflags='-arch armv6 -miphoneos-version-min=$MIN_VERSION' \
  —enable-cross-compile \
  —arch=arm \
  —target-os=darwin \
  —cc=$CC \
  —sysroot=$SDKROOT \
  —prefix=installed \
  —disable-network \
  —disable-decoders \
  —disable-muxers \
  —disable-demuxers \
  —disable-devices \
  —disable-parsers \
  —disable-encoders \
  —disable-protocols \
  —disable-filters \
  —disable-bsfs \
  —enable-decoder=h264 \
  —enable-decoder=svq3 \
  —enable-gpl \
  —enable-pic \
  —disable-doc perl -pi -e 's/HAVE_INLINE_ASM 1/HAVE_INLINE_ASM 0/' config.h make -j3

  mkdir -p build.armv6 for i in $FFMPEG_LIBS ; do cp ./$i/$i.a
  ./build.armv6/ ; done

  echo "Building armv7..."

  make clean ./configure \
  —cpu=cortex-a8 \
  —extra-cflags='-arch armv7 -miphoneos-version-min=$MIN_VERSION -mthumb' \
  —extra-ldflags='-arch armv7 -miphoneos-version-min=$MIN_VERSION' \
  —enable-cross-compile \
  —arch=arm \
  —target-os=darwin \
  —cc=$CC \
  —sysroot=$SDKROOT \
  —prefix=installed \
  —disable-network \
  —disable-decoders \
  —disable-muxers \
  —disable-demuxers \
  —disable-devices \
  —disable-parsers \
  —disable-encoders \
  —disable-protocols \
  —disable-filters \
  —disable-bsfs \
  —enable-decoder=h264 \
  —enable-decoder=svq3 \
  —enable-gpl \
  —enable-pic \
  —disable-doc perl -pi -e 's/HAVE_INLINE_ASM 1/HAVE_INLINE_ASM 0/' config.h make -j3

  mkdir -p build.armv7 for i in $FFMPEG_LIBS ; do cp ./$i/$i.a
  ./build.armv7/ ; done

  mkdir -p build.universal for i in $FFMPEG_LIBS ; do lipo -create
  ./build.armv7/$i.a ./build.armv6/$i.a -output ./build.universal/$i.a ;
  done

  for i in $FFMPEG_LIBS ; do cp ./build.universal/$i.a ./$i/$i.a ; done

  make install