On Thu, May 16, 2024 at 12:08:11PM +0200, Lynne via ffmpeg-devel wrote: > AAC uses an unconventional system to send scalefactors > (the volume+quantization value for each band). > Each window is split into either 1 or 8 blocks (long vs short), > and transformed separately from one another, with the coefficients > for each being also completely independent. The scalefactors > slightly increase from 64 (long) to 128 (short) to accomodate > better per-block-per-band volume for each window. > > To reduce overhead, the codec signals scalefactor sizes in an obtuse way, > where each group's scalefactor types are sent via a variable length decoding, > with a range. > But our decoder was written in a way where those ranges were carried through > the entire decoder, and to actually read them you had to use the range. > > Instead of having a dedicated array with a range for each scalefactor, > just let the decoder directly index each scalefactor. > > This also switches the form of quantized scalefactors to the format > the spec uses, where for intensity stereo and regular, scalefactors > are stored in a scalefactor - 100 form, rather than as-is. > > USAC gets rid of the complex scalefactor handling. This commit permits > for code sharing between both. > --- > libavcodec/aac/Makefile | 3 +- > libavcodec/aac/aacdec.c | 100 ++++++++++++--------------- > libavcodec/aac/aacdec.h | 5 +- > libavcodec/aac/aacdec_dsp_template.c | 95 ++++++++++--------------- > 4 files changed, 85 insertions(+), 118 deletions(-) > > diff --git a/libavcodec/aac/Makefile b/libavcodec/aac/Makefile > index c3e525d373..8b0bfff3e5 100644 > --- a/libavcodec/aac/Makefile > +++ b/libavcodec/aac/Makefile > @@ -2,6 +2,7 @@ clean:: > $(RM) $(CLEANSUFFIXES:%=libavcodec/aac/%) > > OBJS-$(CONFIG_AAC_DECODER) += aac/aacdec.o aac/aacdec_tab.o \ > - aac/aacdec_float.o > + aac/aacdec_float.o aac/aacdec_usac.o > \ > + aac/aacdec_ac.o
AR libavcodec/libavcodec.a ar: libavcodec/aac/aacdec_ac.o: No such file or directory make: *** [ffbuild/library.mak:38: libavcodec/libavcodec.a] Error 1 [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In fact, the RIAA has been known to suggest that students drop out of college or go to community college in order to be able to afford settlements. -- The RIAA
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