Extensions in AAC USAC can be stored across multiple frames (mainly to keep CBR compliance).
This means that we need to reallocate a buffer when new data is received, accumulate the bitstream data,
and so on until the end of extension flag is signalled and the extension can be decoded.
This is made more complicated by the way in which the AAC channel layout switching is performed.
After decades of evolution, our AAC decoder evolved to double-buffer its entire configuration.
All changes are buffered, verified, and applied, on a per-frame basis if required, in often
random order.
Since we allocate the extension data on heap, this means that if configuration is applied,
in order to avoid double-freeing, we have to keep track of what we've allocated.
It should be noted that extensions which are spread in multiple frames are generally rare,
so an optimization to introduce av_refstruct_realloc() wouldn't generally be useful across the codebase.
Therefore, a copy is good enough for now.
Thanks to Michael Niedermayer for additional fixing.
Fixes: double free
Fixes: 393523547/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AAC_LATM_fuzzer-6740617236905984
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
(cherry picked from commit c05fc27dd3)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
Don't depend on the generic code setting this.
This is in preparation for a following change.
Signed-off-by: James Almer <jamrial@gmail.com>
(cherry picked from commit faea08b722)
The issue is that AOT 45 isn't defined anywhere, and looking at the git
blame, it seems to have sprung up through a reordering of the enum,
and adding a hole.
The spec does not define an explicit AOT for SBR and no SBR, and only
uses AOT 42 (previously AOT_USAC_NOSBR), so just rename AOT_USAC to
it and replace its use everywhere.
This commit adds a decoder for the frequency-domain part of USAC.
What works:
- Mono
- Stereo (no prediction)
- Stereo (mid/side coding)
- Stereo (complex prediction)
What's left:
- SBR
- Speech coding
Known issues:
- Desync with certain sequences
- Preroll crossover missing (shouldn't matter, bitrate adaptation only)
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.
This is achieved by using function pointers for AAC SBR functions.
This unfortunately necessitated to use void* in
ff_aac_sbr_apply(_fixed).
Fixes ticket #10999.
Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This allows to merge it with AACDecDSP.init and remove the latter
(it is called only once anyway); it also allows to make
the fixed/float AACDecDSP and AACDecProc implementations internal
to aacdec_fixed/float.c (which also fixes a violation of our
naming conventions). And it some linker errors when either decoder
is disabled.
Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
ff_aac_sbr_apply() and ff_aac_sbr_apply_fixed() still used
pointers to INTFLOAT which is float or int depending upon
whether USE_FIXED is set or not; in particular, according
to these declarations both functions have the same type.
But that is wrong and given that aacdec.c sets USE_FIXED,
it sees the wrong type for ff_aac_sbr_apply().
This leads to a -Wlto-type-mismatch warning when using lto [1].
Fix this by avoiding INTFLOAT in aacsbr.h (which also means
that aac_defines.h need not be included there any more).
[1]: https://fate.ffmpeg.org/log.cgi?slot=x86_64-archlinux-gcc-lto&time=20240506022217&log=compile
Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
