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• Creating thumbnails with FFmpeg

  3 janvier 2012, par Calin-Andrei Burloiu

  I am using FFmpeg to extract thumbnails from specific positions of video files.

  I found on the web two approaches to do this :

  1. With -ss (seek) parameter before -i (input) parameter :

     ffmpeg -y -ss $SEEK_POINT -i input.ogv -vcodec mjpeg -vframes 1 -an -s 120x90 -f rawvideo output.jpg

  2. With -ss (seek) parameter after -i (input) parameter :

     ffmpeg -y -i input.ogv -vcodec mjpeg -ss $SEEK_POINT -vframes 1 -an -s 120x90 -f rawvideo output.jpg

  The first method generates a bad thumbnail with gray spots, but works very fast. The error returned is [theora @ 0x8097240] vp3: first frame not a keyframe.

  The second method always works but show an error which cause the extraction to take a lot of time. This amount of time is not fixed and it depends on the seek point as I noticed. Sometimes it takes a few seconds and other times several minutes to extract a thumbnail. I get the error Buffering several frames is not supported. Please consume all available frames before adding a new one. in the following output :

  Input #0, ogg, from 'input.ogv':
  
    Duration: 00:21:52.76, start: 0.000000, bitrate: 844 kb/s
  
      Stream #0.0: Video: theora, yuv420p, 800x600 [PAR 4:3 DAR 16:9], 25 fps, 25 tbr, 25 tbn, 25 tbc
  
      Stream #0.1: Audio: vorbis, 44100 Hz, stereo, s16, 192 kb/s
  
      Metadata:
  
        ENCODER         : Lavf52.102.0
  
  Incompatible pixel format 'yuv420p' for codec 'mjpeg', auto-selecting format 'yuvj420p'                                                                         
  
  [buffer @ 0x9250840] w:800 h:600 pixfmt:yuv420p                                 
  
  [scale @ 0x92508a0] w:800 h:600 fmt:yuv420p -> w:120 h:90 fmt:yuvj420p flags:0x4
  
  Output #0, rawvideo, to 'output.jpg':
  
    Metadata:
  
      encoder         : Lavf53.2.0
  
      Stream #0.0: Video: mjpeg, yuvj420p, 120x90 [PAR 4:3 DAR 16:9], q=2-31, 200 kb/s, 90k tbn, 25 tbc
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
  Press ctrl-c to stop encoding
  
  [buffer @ 0x9250840] Buffering several frames is not supported. Please consume all available frames before adding a new one.                                    
  
  frame=    0 fps=  0 q=0.0 size=       0kB time=10000000000.00 bitrate=   0.0kbit
  
  Last message repeated 15448 times
  
  frame=    1 fps=  0 q=3.4 Lsize=       3kB time=0.04 bitrate= 598.8kbits/s    
  
  video:3kB audio:0kB global headers:0kB muxing overhead 0.000000%

  How can I extract thumbnails without any problems using FFmpeg from a custom position of a video regardless of the input format ?

• Undefined Reference - ffmpeg on android ndk

  28 décembre 2012, par Gabriel Simões

  I´ve spent many hours trying to figure out why I still get "undefined reference" when trying to link to ffmpeg.
  I´ve already read most if not all posts and sites about the subject, so I think I´m missing something little here and I hope you can help me.

  What I have :

  I´m using windows 7 + cygwin + crystax r4.
  I´ve compiled FFMPEG using RockPlayer's ffmpeg source plus some modifications I did (only to include / exclude demuxes, decoders, encoders, ...)
  After compiling, I get :

  • a new folder named armv5te, which includes :
  • a folder named "include" with all folders for each libs' .h
  • a folder named "lib" which includes all libs' .a
  • a shared library named libffmpeg.so (checked soname and it is libffmpeg)

  The shared library isn´t also placed on project/lib/armeabi/libffmpeg.so

  After compiling I tried to compile my project and link it. While my .cpp compiles ok, I get many undefined references.

  here is my build script :

  NDK=/cygdrive/c/Gabriel/Desenvolvimento/SDKs/Android/android-ndk-r4-crystax
  
  PLATFORM=$NDK/build/platforms/android-8/arch-arm/
  
  PREBUILT=$NDK/build/prebuilt/windows/arm-eabi-4.4.0
  
  
  
  
  
  function build_one
  
  {
  
  
  
  ./configure --target-os=linux \
  
      --prefix=$PREFIX \
  
      --enable-cross-compile \
  
      --extra-libs="-lgcc" \
  
      --arch=arm \
  
      --cc=$PREBUILT/bin/arm-eabi-gcc \
  
      --cross-prefix=$PREBUILT/bin/arm-eabi- \
  
      --nm=$PREBUILT/bin/arm-eabi-nm \
  
      --sysroot=$PLATFORM \
  
      --extra-cflags=" -O2 -fpic -DANDROID -DHAVE_SYS_UIO_H=1 -Dipv6mr_interface=ipv6mr_ifindex -fasm -Wno-psabi -fno-short-enums  -fno-strict-aliasing -finline-limit=300 $OPTIMIZE_CFLAGS " \
  
      --disable-shared \
  
      --enable-static \
  
      --extra-ldflags="-Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib  -nostdlib -lc -lm -ldl -llog" \
  
      --disable-stripping \
  
      --disable-debug \
  
      --disable-symver \
  
      --disable-ffprobe \
  
      --disable-devices \
  
      --disable-avfilter \
  
      --disable-swscale \
  
      --disable-ffplay \
  
      --disable-ffserver \
  
      --disable-network \
  
          (many more ...)
  
      --enable-asm \
  
      $ADDITIONAL_CONFIGURE_FLAG
  
  
  
  #make clean
  
  make  -j4 install
  
  
  
  $PREBUILT/bin/arm-eabi-ar d libavcodec/libavcodec.a inverse.o
  
  
  
  $PREBUILT/bin/arm-eabi-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib  -soname libffmpeg.so -shared -nostdlib  -z,noexecstack -Bsymbolic --whole-archive --no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavformat/libavformat.a libavutil/libavutil.a  -lc -lm -lz -ldl -llog  --warn-once  --dynamic-linker=/system/bin/linker $PREBUILT/lib/gcc/arm-eabi/4.4.0/libgcc.a
  
  
  
  }
  
  
  
  #arm v5
  
  CPU=armv5te
  
  OPTIMIZE_CFLAGS="-marm -march=$CPU"
  
  PREFIX=./android/$CPU 
  
  ADDITIONAL_CONFIGURE_FLAG=
  
  build_one

  Here is my android.mk :

  LOCAL_PATH := $(call my-dir)
  
  
  
  #declare the prebuilt library
  
  include $(CLEAR_VARS)
  
  LOCAL_MODULE := ffmpeg-prebuilt
  
  LOCAL_SRC_FILES := $(LOCAL_PATH)/ffmpeg/android/armv5te/libffmpeg.so
  
  LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/ffmpeg/android/armv5te/include
  
  LOCAL_PRELINK_MODULE := true 
  
  include $(PREBUILT_SHARED_LIBRARY)
  
  
  
  include $(CLEAR_VARS)
  
  LOCAL_MODULE    := audiocodec
  
  LOCAL_SRC_FILES := ffmpeg_audio.cpp
  
  LOCAL_SHARED_LIBRARY := libffmpeg
  
  LOCAL_C_INCLUDES := $(LOCAL_PATH)/ffmpeg/android/armv5te/include
  
  LOCAL_LDLIBS    := -llog -ljnigraphics -lz -lm $(LOCAL_PATH)/ffmpeg/android/armv5te/libffmpeg.so
  
  include $(BUILD_SHARED_LIBRARY)

  The result :

  Compile++ thumb: audiocodec <= /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFM
  
  PEG/jni/ffmpeg_audio.cpp
  
  SharedLibrary  : libaudiocodec.so
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/obj/local/armeabi/objs/audi
  
  ocodec/ffmpeg_audio.o: In function `Java_gabriel_audioslower_pro_ffmpegDecoder_r
  
  eadSamples':
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:172: u
  
  ndefined reference to `avcodec_decode_audio3(AVCodecContext*, short*, int*, AVPa
  
  cket*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:178: u
  
  ndefined reference to `av_read_frame(AVFormatContext*, AVPacket*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/obj/local/armeabi/objs/audi
  
  ocodec/ffmpeg_audio.o: In function `Java_gabriel_audioslower_pro_ffmpegDecoder_s
  
  eekToPosMS':
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:147: u
  
  ndefined reference to `av_rescale_q(long long, AVRational, AVRational)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:150: u
  
  ndefined reference to `av_seek_frame(AVFormatContext*, int, long long, int)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:151: u
  
  ndefined reference to `avcodec_flush_buffers(AVCodecContext*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:152: u
  
  ndefined reference to `av_read_frame(AVFormatContext*, AVPacket*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/obj/local/armeabi/objs/audi
  
  ocodec/ffmpeg_audio.o: In function `Java_gabriel_audioslower_pro_ffmpegDecoder_c
  
  loseFile':
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:82: un
  
  defined reference to `avcodec_close(AVCodecContext*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:83: un
  
  defined reference to `av_free(void*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:84: un
  
  defined reference to `av_close_input_file(AVFormatContext*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/obj/local/armeabi/objs/audi
  
  ocodec/ffmpeg_audio.o: In function `Java_gabriel_audioslower_pro_ffmpegDecoder_o
  
  penAudioFile':
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:37: un
  
  defined reference to `av_open_input_file(AVFormatContext**, char const*, AVInput
  
  Format*, int, AVFormatParameters*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:44: un
  
  defined reference to `av_find_stream_info(AVFormatContext*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:52: un
  
  defined reference to `avcodec_find_decoder(CodecID)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:60: un
  
  defined reference to `avcodec_open(AVCodecContext*, AVCodec*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:67: un
  
  defined reference to `av_malloc(unsigned int)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:70: un
  
  defined reference to `av_read_frame(AVFormatContext*, AVPacket*)'
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/obj/local/armeabi/objs/audi
  
  ocodec/ffmpeg_audio.o: In function `JNI_OnLoad':
  
  /cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/jni/ffmpeg_audio.cpp:25: un
  
  defined reference to `av_register_all()'
  
  collect2: ld returned 1 exit status
  
  make: *** [/cygdrive/c/Gabriel/Desenvolvimento/Workspace/FFMPEG/obj/local/armeab
  
  i/libaudiocodec.so] Error 1

  Something interesting is that some functions from ffmpeg, as av_register_all(), do now show up on the list of undefined references.

  Any ideas on what I can do to fix it ? I´ve spent 3 days trying to make things work ..
  Thanks !

• FFmpeg / Create video / Add caption (timestamp) of each jpg file to generate mp4

  17 août 2012, par low

  I've got some pictures, as screenshot-1.jpg, ..., screenshot-345.jpg, cycle of automatic capture from my computer (cycle of 30 seconds). I use FFmpeg to generate a video mp4 format, but, I want to add on the video the timestamp of each jpg file.

  This is my command line of FFmpeg :

  ffmpeg.exe -f image2 -r 4 -i screenshot-%0d.jpg -b 512000 -s 3840x1200 -sameq video.mp4

  In this case, I can show the date/time during de video play.

  Thanks.
  Low