[FFmpeg-devel] [PATCH v7 0/3] 32bps FLAC patches

[Martijn van Beurden]

Recently libFLAC gained the ability (first released in FLAC 1.4.0)
to create FLAC files containing 32-bit int PCM samples. To
keep complexity reasonable, the choice was made to limit residuals
to 32-bit integers, which the encoder must make sure of. In case
the encoder cannot find any predictor of which the residuals fit
this limit, it must default to using a verbatim subframe. Tests have
shown that this does not happen often (<0.1% of subframes on a
music corpus of various styles). See also discussion here:
https://github.com/ietf-wg-cellar/flac-specification/pull/148

These two patches implement decoding and encoding following this
format.

Changes since v1:
fix copy-paste error in encoder, several invocations of
lpc_encode_choose_datapath used wrong parameters, making FATE fail as
compression was less than it should be

Changes since v2:
Rebased decoder part as it didn't apply anymore

Changes since v3:
Moved put_golomb part to flacenc.c (as it is now quite specific to FLAC)
and renamed put_sbits64 to put_sbits63 (and changed assert accordingly)

Changes since v4:
Fix check of decoded_buffer_33bps malloc. Fix reading of wasted bits
for 33bps subframe. Add fate test

Changes since v5:
Slimmed down 32 bps fate flac test from 2 to 1 input file. Replaced
-strict -2 with -strict experimental in fate and encoder warning.

Changes since v6:
Deduplicated function bodies with preprocessor macros in both
encoder and decoder, declared variables in loop body where possible
and changed ff_ctz to ff_ctzll where necessary

Martijn van Beurden (3):
  libavcodec/flacdec: Implement decoding of 32 bit-per-sample PCM
  libavcodec/flacenc: Implement encoding of 32 bit-per-sample PCM
  fate/flac: Add test of 32 bps encoding/decoding

 libavcodec/flac.c       |   4 +-
 libavcodec/flacdec.c    | 218 ++++++++++++++++--
 libavcodec/flacenc.c    | 480 +++++++++++++++++++++++++++++++---------
 libavcodec/get_bits.h   |  12 +
 libavcodec/mathops.h    |   9 +
 libavcodec/put_bits.h   |   7 +
 libavcodec/put_golomb.h |  14 --
 tests/fate/flac.mak     |   4 +
 8 files changed, 602 insertions(+), 146 deletions(-)

-- 
2.30.2