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 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
