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• ffmpeg link errors when building on iPhone 4.3 SDK

  12 septembre 2011, par YuzaKen

  After a rather trying few days, I finally got ffmpeg to compile under Xcode 4 with SDK 4.3. The issue no is a series (39) link errors. They fall into at least two cases : assembly language routines and static arrays defined in header files. My believe is that it is generating C method names for the assembly routines while the .c files containing the reference to the routine is generating a different method name (munging).

  Undefined symbols for architecture armv7 :

    "_ff_vector_fmul_vfp", referenced from:
  
        _ff_dsputil_init_vfp in libavcodec.a(dsputil_init_vfp.o)
  
    "_main", referenced from:
  
        start in crt1.3.1.o
  
    "_av_solve_lls", referenced from:
  
        _ff_lpc_calc_coefs in libavcodec.a(lpc.o)
  
    "_ff_inv_aanscales", referenced from:
  
        _dct_quantize_trellis_c in libavcodec.a(mpegvideo_enc.o)
  
        _decode_frame in libavcodec.a(eamad.o)
  
        _tgq_decode_frame in libavcodec.a(eatgq.o)
  
        _tqi_decode_frame in libavcodec.a(eatqi.o)
  
    "_ff_add_pixels_clamped_armv6", referenced from:
  
        _ff_dsputil_init_armv6 in libavcodec.a(dsputil_init_armv6.o)
  
    "_ff_cga_palette", referenced from:
  
        _tmv_decode_frame in libavcodec.a(tmv.o)
  
    "_ff_svq1_inter_multistage_vlc", referenced from:
  
        _encode_block in libavcodec.a(svq1enc.o)
  
        _svq1_decode_init in libavcodec.a(svq1dec.o)
  
    "_ff_simple_idct_armv6", referenced from:
  
        _ff_dsputil_init_armv6 in libavcodec.a(dsputil_init_armv6.o)
  
    "_BZ2_bzDecompressInit", referenced from:
  
        _matroska_decode_buffer in libavformat.a(matroskadec.o)
  
    "_ff_put_pixels8_y2_arm", referenced from:
  
        _ff_put_pixels16_y2_arm in libavcodec.a(dsputil_init_arm.o)
  
        _dsputil_init_arm in libavcodec.a(dsputil_init_arm.o)
  
    "_ff_simple_idct_add_armv6", referenced from:

  ...and so on.

  Anyone with experience with ffmpeg on iPhone ? Successfully ?

• Xuggler encoding images to video FPS issue

  1er novembre 2011, par Chris Robinson

  I've been experimenting with encoding a video from a series of images using CaptureScreenToFile.java as a basis. My output is to be an MP4 file. From 26 images, using the code as is (taking the images from a directory instead of from a screen capture obviously), the encoding video is 11s. However, if I change the framerate variable to :

  frameRate = IRational.make(1, 24);

  which I believe should result in a video of 24FPS. It does not however, (no change from the original video in fact). I experimented with changing the timeStamp variable in encodeImage() method to :

  long timeStamp = (firstTimeStamp*1000)+(i*40);

  where 0 < i < 25 to see if that would help but it doesn't. Can anyone explain to me how to encode a directory of images to a video with a framerate that I can set ?

• H264 encoder settings

  30 novembre 2011, par Chris Robinson

  I'm using xuggler to encode a series of images to an MP4 file. I use the following code to setup the IStreamCoder and specify the H264 codec :

  // only set if codec is H264
  
  Configuration.configure("/usr/local/xuggler/share/ffmpeg/libx264-hq.ffpreset",
  
              outStreamCoder);
  
  
  
  outStreamCoder.setNumPicturesInGroupOfPictures(12);
  
  outStreamCoder.setCodec(codec);
  
  outStreamCoder.setBitRate(videoSettings.getBitrate());
  
  outStreamCoder.setBitRateTolerance(videoSettings.getBitrateTolerance());
  
  outStreamCoder.setPixelType(IPixelFormat.Type.YUV420P);
  
  outStreamCoder.setHeight(videoSettings.getResolution().height);
  
  outStreamCoder.setWidth(videoSettings.getResolution().width);
  
  outStreamCoder.setFlag(IStreamCoder.Flags.FLAG_QSCALE, true);
  
  outStreamCoder.setGlobalQuality(0);
  
  fps = IRational.make((int) videoSettings.getFramerate(), 1);
  
  outStreamCoder.setFrameRate(fps);
  
  outStreamCoder.setTimeBase(IRational.make(fps.getDenominator(), fps.getNumerator()));

  which yields the following output :

  Codec: CODEC_ID_H264
  
  Resolution: 1280x720
  
  Bitrate: 25000
  
  Bitrate Tolerance: 1000
  
  Framerate: 25.0

  

  Now when I specify the MPEG4 codec, I get the following output :

  Codec: CODEC_ID_MPEG4
  
  Resolution: 1280x720
  
  Bitrate: 25000
  
  Bitrate Tolerance: 1000
  
  Framerate: 25.0

  

  As you can see, the only difference is the ICodec type (MPEG4 instead of H264) and the use of the preset (which is required by xuggler when using an H264 codec). Can anyone explain to me the huge difference in quality and tell me how to resolve the issue ?