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• Why does hard-coding subtitles into MKV cause resulting video length to be wildly incorrect ?

  21 mai 2018, par BudJB

  I am trying to encode an existing MKV with a video, audio, and several subtitle streams, such that video encodes with H264, audio encodes with AAC, and the second subtitle track is hard-coded into the video stream. I am using the myffmpeg GUI frontend, but can view and modify the ffmpeg command before it’s run.

  Every time that I run the encode, the MKV reports that the duration is 1195 hours and change, where it’s supposed to be around 2 hours, plus some change. If I encode without the hard-coded subtitles, things turn out alright.

  Here’s the command that’s run, with the latest ffmpeg :

  ffmpeg.exe -probesize 50M -analyzeduration 100M -i "D:\Video\in.mkv" -c:a aac -ac 6 -strict -2 -async 1 -c:v libx264 -crf 20 -r 24000/1001 -s 1920x1080 -aspect 16:9 -pix_fmt yuv420p -preset fast -partitions default  -b-pyramid 1 -weightb 1 -8x8dct 1 -fast-pskip 0 -direct-pred 1 -coder ac -trellis 1 -me_method hex -subq 6 -me_range 16 -bf 3 -b_strategy 1 -refs 3 -flags +loop -sws_flags fast_bilinear -sc_threshold 40 -keyint_min 24 -g 48 -qmin 3 -qmax 51 -qdiff 4 -filter_complex "[0:v][0:s:2]overlay[out]" -map [out]  -map 0:a:0 -sn -y "D:\Video\out.mkv"

  I’ve tried a couple other MKV’s with the same results. Anyone else run into this or know what’s going on ?

• avcodec/smacker : Use unsigned for prediction values

  26 juin 2020, par Andreas Rheinhardt

  avcodec/smacker : Use unsigned for prediction values
  Up until now, the Smacker decoder has pretended that the prediction
  
  values are signed in code like 'pred[0] += (unsigned)sign_extend(val, 16)'
  
  (the cast has been added to this code later to fix undefined behaviour).
  
  This has been even done in case the PCM format is u8.
  Yet in case of 8/16 bit samples, only the lower 8/16 bit of the predicition
  
  values are ever used, so one can just as well just use unsigned and
  
  remove the sign extensions. This is what this commit does.
  For GCC 9 the time for one call to smka_decode_frame() for the sample from
  
  ticket #2425 decreased from 1709043 to 1693619 decicycles ; for Clang 9
  
  it went up from 1355273 to 1369089 decicycles.
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/smacker.c

• Revision 6ef805eb9d : Change ref frame coding. Code intra/inter, then comp/single, then the ref frame

  6 juin 2013, par Ronald S. Bultje

  Changed Paths :
   Modify /vp9/common/vp9_blockd.h

  
   Modify /vp9/common/vp9_entropymode.c

  
   Modify /vp9/common/vp9_findnearmv.c

  
   Modify /vp9/common/vp9_findnearmv.h

  
   Modify /vp9/common/vp9_implicit_segmentation.c

  
   Modify /vp9/common/vp9_loopfilter.c

  
   Modify /vp9/common/vp9_mvref_common.c

  
   Modify /vp9/common/vp9_onyxc_int.h

  
   Modify /vp9/common/vp9_pred_common.c

  
   Modify /vp9/common/vp9_pred_common.h

  
   Modify /vp9/common/vp9_reconinter.c

  
   Modify /vp9/decoder/vp9_decodemv.c

  
   Modify /vp9/decoder/vp9_decodframe.c

  
   Modify /vp9/decoder/vp9_detokenize.c

  
   Modify /vp9/encoder/vp9_bitstream.c

  
   Modify /vp9/encoder/vp9_encodeframe.c

  
   Modify /vp9/encoder/vp9_encodeintra.c

  
   Modify /vp9/encoder/vp9_encodemb.c

  
   Modify /vp9/encoder/vp9_encodemv.c

  
   Modify /vp9/encoder/vp9_firstpass.c

  
   Modify /vp9/encoder/vp9_onyx_if.c

  
   Modify /vp9/encoder/vp9_onyx_int.h

  
   Modify /vp9/encoder/vp9_ratectrl.c

  
   Modify /vp9/encoder/vp9_rdopt.c

  
   Modify /vp9/encoder/vp9_tokenize.c

  
  
  Change ref frame coding.

  Code intra/inter, then comp/single, then the ref frame selection.
  Use contextualization for all steps. Don't code two past frames
  in comp pred mode.

  Change-Id : I4639a78cd5cccb283023265dbcc07898c3e7cf95