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• aarch64 : vp9itxfm : Skip empty slices in the first pass of idct_idct 16x16 and 32x32

  18 novembre 2016, par Martin Storsjö

  aarch64 : vp9itxfm : Skip empty slices in the first pass of idct_idct 16x16 and 32x32
  This work is sponsored by, and copyright, Google.
  Previously all subpartitions except the eob=1 (DC) case ran with
  
  the same runtime :
  vp9_inv_dct_dct_16x16_sub16_add_neon :   1373.2
  
  vp9_inv_dct_dct_32x32_sub32_add_neon :   8089.0
  By skipping individual 8x16 or 8x32 pixel slices in the first pass,
  
  we reduce the runtime of these functions like this :
  vp9_inv_dct_dct_16x16_sub1_add_neon :     235.3
  
  vp9_inv_dct_dct_16x16_sub2_add_neon :    1036.7
  
  vp9_inv_dct_dct_16x16_sub4_add_neon :    1036.7
  
  vp9_inv_dct_dct_16x16_sub8_add_neon :    1036.7
  
  vp9_inv_dct_dct_16x16_sub12_add_neon :   1372.1
  
  vp9_inv_dct_dct_16x16_sub16_add_neon :   1372.1
  
  vp9_inv_dct_dct_32x32_sub1_add_neon :     555.1
  
  vp9_inv_dct_dct_32x32_sub2_add_neon :    5190.2
  
  vp9_inv_dct_dct_32x32_sub4_add_neon :    5180.0
  
  vp9_inv_dct_dct_32x32_sub8_add_neon :    5183.1
  
  vp9_inv_dct_dct_32x32_sub12_add_neon :   6161.5
  
  vp9_inv_dct_dct_32x32_sub16_add_neon :   6155.5
  
  vp9_inv_dct_dct_32x32_sub20_add_neon :   7136.3
  
  vp9_inv_dct_dct_32x32_sub24_add_neon :   7128.4
  
  vp9_inv_dct_dct_32x32_sub28_add_neon :   8098.9
  
  vp9_inv_dct_dct_32x32_sub32_add_neon :   8098.8
  I.e. in general a very minor overhead for the full subpartition case due
  
  to the additional cmps, but a significant speedup for the cases when we
  
  only need to process a small part of the actual input data.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/aarch64/vp9itxfm_neon.S

• movenc : Allow writing a DASH sidx atom at the start of files

  21 octobre 2014, par Martin Storsjö

  movenc : Allow writing a DASH sidx atom at the start of files
  This is mapped to the faststart flag (which in this case
  
  perhaps should be called "shift and write index at the
  
  start of the file"), which for fragmented files will
  
  write a sidx index at the start.
  When segmenting DASH into files, there’s usually one sidx
  
  at the start of each segment (although it’s not clear to me
  
  whether that actually is necessary). When storing all of it
  
  in one file, the MPD doesn’t necessarily need to describe
  
  the individual segments, but the offsets of the fragments can be
  
  fetched from one large sidx atom at the start of the file. This
  
  allows creating files for the DASH ISO BMFF on-demand profile.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/movenc.c
  • [DBH] libavformat/movenc.h

• movenc : Add a flag for indicating a discontinuous fragment

  20 novembre 2014, par Martin Storsjö

  movenc : Add a flag for indicating a discontinuous fragment
  This allows creating a later mp4 fragment without sequentially
  
  writing the earlier ones before (when called from a segmenter).
  Normally when writing a fragmented mp4 file sequentially, the
  
  first timestamps of a fragment are adjusted to match the
  
  end of the previous fragment, to make sure the timestamp is the
  
  same, even if it is calculated as the sum of previous fragment
  
  durations. (And for the first packet in a file, the offset of
  
  the first packet is written using an edit list.)
  When writing an individual mp4 fragment discontinuously like this
  
  (with potentially writing the earlier fragments separately later),
  
  there’s a risk of getting a gap in the timeline if the duration
  
  field of the last packet in the previous fragment doesn’t match up
  
  with the start time of the next fragment.
  Using this requires setting -avoid_negative_ts make_non_negative
  
  (or -avoid_negative_ts 0).
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/movenc.c
  • [DBH] libavformat/movenc.h