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• Can't compile project with ffmpeg-light

  27 octobre 2016, par wowofbob

  Compilation of any project which uses openFile function from Codec.FFmpeg.Decode fails with error :

  Couldn't match type ‘GHC.IO.Exception.IOException’ with ‘[Char]’
           arising from a functional dependency between:
             constraint ‘mtl-2.2.1:Control.Monad.Error.Class.MonadError
                           String IO’
               arising from a use of ‘openFile’
             instance ‘mtl-2.2.1:Control.Monad.Error.Class.MonadError
                         GHC.IO.Exception.IOException IO’
               at <no location="location" info="info"></no>

  As an example, compilation of this fails :

  openVideoFile :: String -> IO ()
  
  openVideoFile filePath = do
  
  
  
    initFFmpeg
  
  
  
    avFmtCtx <- openFile filePath
  
  
  
    return ()

  I guess the reason is that there is no ready instance of MonadError String IO. But, when I add a dummy instance like this :

  instance MonadError String IO where
  
    throwError _   = undefined
  
    catchError _ _ = undefined

  I’m getting another error :

  Functional dependencies conflict between instance declarations:
 instance MonadError String IO
   -- Defined at src/Video/Play/Base.hs:20:10
 instance [safe] MonadError GHC.IO.Exception.IOException IO
   -- Defined in ‘Control.Monad.Error.Class’

  I don’t know how to force compiler to use MonadError String IO instace here.

  • Should I assure GHC that my instance is better ?
  • Do I have a wrong environment setup ? I’m using ffmpeg-light clone from here and resolver lts-7.2. Host OS is Ubuntu.
  • There is commit which replaces import of Control.Monad.Error.Class by Control.Monad.Except. But, Control.Monad.Error.Class is still used in Codec.FFmpeg.Common. First time I thought it caused a problem. But it turns out that Control.Monad.Except just re-exports MonadError class from Control.Monad.Error.Class. So, it’s not a problem.

• ffmpeg cross compiles nicely for aarch64, but when linking with my project, gives Relocations in generic ELF (EM : 62)

  29 août 2019, par Lucas Zanella

  Here’s how I’m configuring ffmpeg :

          ./configure \
  
          --prefix=${BUILD_DIR}/desktop/aarch64 \
  
          --disable-doc \
  
          --enable-cross-compile \
  
          --cross-prefix=aarch64-linux-gnu-\
  
          --target-os=linux \
  
          --arch=aarch64 \
  
          --extra-cflags="-O3 -fPIC" \
  
          --enable-shared \
  
          --disable-static \
  
          --disable-debug \
  
          --disable-runtime-cpudetect \
  
          --disable-programs \
  
          --disable-muxers \
  
          --disable-encoders \
  
          --disable-decoders \
  
          ${DECODERS_TO_ENABLE} \
  
          --disable-bsfs \
  
          --disable-pthreads \
  
          --disable-avdevice \
  
          --disable-network \
  
          --disable-postproc 
  
  
  
          make clean
  
          make -j$(nproc)
  
          make install

  It compiles fine. Then, when I try to link my project with this compiled ffmpeg, it gives me

  /usr/bin/ld: ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a(allcodecs.o): Relocations in generic ELF (EM: 62)
  
  /usr/bin/ld: ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a(allcodecs.o): Relocations in generic ELF (EM: 62)
  
  /usr/bin/ld: ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a(allcodecs.o): Relocations in generic ELF (EM: 62)
  
  /usr/bin/ld: ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a(allcodecs.o): Relocations in generic ELF (EM: 62)
  
  /usr/bin/ld: ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a(allcodecs.o): Relocations in generic ELF (EM: 62)
  
  /usr/bin/ld: ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a(allcodecs.o): Relocations in generic ELF (EM: 62)
  
  /usr/bin/ld: ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a(allcodecs.o): Relocations in generic ELF (EM: 62)
  
  /usr/bin/ld: ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a(allcodecs.o): Relocations in generic ELF (EM: 62)
  
  /usr/bin/ld: ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a(allcodecs.o): Relocations in generic ELF (EM: 62)
  
  ../../../deps/ffmpeg/build/desktop/aarch64/lib/libavcodec.a: error adding symbols: File in wrong format

  In this answer : https://stackoverflow.com/a/23185739/10116440 he says that CC is missing. I’m also not using CC but shouldn’t CC be the same as --cross-prefix ?

  I also found http://lakm.us/logit/2012/11/cross-compiling-ubuntu-arm-ffmpeg/ in where he says that I should use --cross-prefix=arm-linux-gnueabi-, in my case arm should be aarch64. However, there’s no aarch64-linux-gnueabi- toolchain, only aarch64-linux-gnu-. Can it be the problem ? I think no because eabi looks like its for 32 bits, I guess

  It’s worth noticing that I’m bulding ffmpeg on a amd64 but using the static library to build my project on a aarch64.

• flv reencode to mp4 for iphone/ipod via ffmpeg and x264 (quality issue)

  3 octobre 2011, par zeroasterisk

  There are a lot of questions on this topic, and I've read most of them and most of the google search results I could come up with.

  When I use FFMPEG to convert a FLV to a iphone3 compatble MP4 file, it just doesn't preserver enough of the quality. Yes, I've worked the hell out of -sameq and -b and -bt settings, text just isn't readable.

  Next I tried to split the video out and process it directly, using these instructions :
  https://sites.google.com/site/linuxencoding/x264-encoding-guide

  The problem is myplayer (via ffmpeg) was not able to determine the duration of the FLV (even though the metadata was set).

  (I assume) Because of that unknown duration, when I create the MP4 file, the resulting x264 file plays through super-fast while the audio plays at the normal rate.

  user@server:/tmp# mplayer -nosound -benchmark -sws 9 -vf dsize=640:480:0,scale=0:0,expand=640:480 -vo yuv4mpeg:file=>(x264 --demuxer y4m --crf 0 --preset slow --threads auto --output output.264 - 2>x264.log) 'input.flv'
  
  MPlayer 1.0rc4-4.4.5 (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 input.flv.
  
  libavformat file format detected.
  
  [flv @ 0x1202460]Estimating duration from bitrate, this may be inaccurate
  
  [lavf] stream 0: video (vp6f), -vid 0
  
  [lavf] stream 1: audio (nellymoser), -aid 0
  
  VIDEO:  [VP6F]  1680x992  0bpp  1000.000 fps   33.4 kbps ( 4.1 kbyte/s)
  
  Clip info:
  
   audiocodecid: 6
  
   audiodatarate: 86
  
   audiosamplerate: 44100
  
   audiosamplesize: 16
  
   audiosize: 6097005
  
   canSeekToEnd: true
  
   datasize: 8609138
  
   duration: 567
  
   framerate: 2
  
   hasAudio: true
  
   hasCuePoints: false
  
   hasKeyframes: true
  
   hasMetadata: true
  
   hasVideo: true
  
   height: 992
  
   lasttimestamp: 567
  
   metadatacreator: flvtool++ (Facebook, Motion project, dweatherford)
  
   stereo: false
  
   totalframes: 1043
  
   videocodecid: 4
  
   videodatarate: 33
  
   videosize: 2316256
  
   width: 1680
  
  Using (default) progressive frame mode.Opening video filter: [expand w=640 h=480]
  
  Expand: 640 x 480, -1 ; -1, osd: 0, aspect: 0.000000, round: 1
  
  Opening video filter: [scale w=0 h=0]
  
  Opening video filter: [dsize=640:480:0]
  
  ==========================================================================
  
  Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
  
  Selected video codec: [ffvp6f] vfm: ffmpeg (FFmpeg VP6 Flash)
  
  ==========================================================================
  
  Audio: no sound
  
  Starting playback...
  
  Movie-Aspect is undefined - no prescaling applied.
  
  [swscaler @ 0x7f0c738b9620]Lanczos scaler, from yuv420p to yuv420p using MMX2
  
  VO: [yuv4mpeg] 640x480 => 641x480 Planar YV12

  I have also tried specifying FPS, but no change in results

  user@server:/tmp# mplayer -nosound -fps 25-benchmark -sws 9 -vf dsize=640:480:0,scale=0:0,expand=640:480 -vo yuv4mpeg:file=>(x264 --demuxer y4m --fps 25 --crf 0 --preset slow --threads auto --output output.264 - 2>x264.log) 'input.flv'

  Can someone tell me how to either :

  1. fix my split A/V processing/timing/duration issues ?
  2. improve the
     quality of the FFMPEG conversion of FLV to iphone3 compatible
     format ?