FFmpeg

Commit Graph

Author	SHA1	Message	Date
Lynne	ef8fd7bc3c	lavu/tx: add DCT-I and DST-I transforms These are true, actual DCT-I and DST-I transforms, unlike the libavcodec versions, which are plainly not.	1 year ago
Lynne	11e22730e1	lavu/tx: add real to real and real to imaginary RDFT transforms These are in-place transforms, required for DCT-I and DST-I. Templated as the mod2 variant requires minor modifications, and is required specifically for DCT-I/DST-I.	1 year ago
Lynne	504b7bec1a	lavu/tx: add DCT-II implementation	2 years ago
Lynne	93c30bd6f0	lavu/tx: clarify stride for RDFT transforms	2 years ago
Lynne	d4e39cae2e	lavu/tx: drop requirement of input == output for in-place transforms No longer necessary.	2 years ago
Andreas Rheinhardt	d75c4cc7c1	avutil/tx: Fix documentation of av_tx_uninit() Adapt it to the actual (sane) behaviour. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>	3 years ago
Lynne	af94ab7c7c	lavu/tx: add an RDFT implementation RDFTs are full of conventions that vary between implementations. What I've gone for here is what's most common between both fftw, avcodec's rdft and what we use, the equivalent of which is DFT_R2C for forward and IDFT_C2R for inverse. The other 2 conventions (IDFT_R2C and DFT_C2R) were not used at all in our code, and their names are also not appropriate. If there's a use for either, we can easily add a flag which would just flip the sign on one exptab. For some unknown reason, possibly to allow reusing FFT's exp tables, av_rdft's C2R output is 0.5x lower than what it should be to ensure a proper back-and-forth conversion. This code outputs its real samples at the correct level, which matches FFTW's level, and allows the user to change the level and insert arbitrary multiplies for free by setting the scale option.	3 years ago
Lynne	ef4bd81615	lavu/tx: rewrite internal code as a tree-based codelet constructor This commit rewrites the internal transform code into a constructor that stitches transforms (codelets). This allows for transforms to reuse arbitrary parts of other transforms, and allows transforms to be stacked onto one another (such as a full iMDCT using a half-iMDCT which in turn uses an FFT). It also permits for each step to be individually replaced by assembly or a custom implementation (such as an ASIC).	3 years ago
Lynne	c14976be04	lavu/tx: improve documentation for existing transforms	3 years ago
Lynne	0072a42388	lavu/tx: add full-sized iMDCT transform flag	4 years ago
Lynne	aa6c757d50	lavu/tx: add unaligned flag to the API	4 years ago
Lynne	aa910a7ecd	lavu/tx: minor code style improvements and additional comments	4 years ago
Lynne	10341743d2	lavu/tx: require output argument to match input for inplace transforms This simplifies some assembly code by a lot, by either saving a branch or saving an entire duplicated function.	4 years ago
Lynne	5ca40d6d94	lavu/tx: support in-place FFT transforms This commit adds support for in-place FFT transforms. Since our internal transforms were all in-place anyway, this only changes the permutation on the input. Unfortunately, research papers were of no help here. All focused on dry hardware implementations, where permutes are free, or on software implementations where binary bloat is of no concern so storing dozen times the transforms for each permutation and version is not considered bad practice. Still, for a pure C implementation, it's only around 28% slower than the multi-megabyte FFTW3 in unaligned mode. Unlike a closed permutation like with PFA, split-radix FFT bit-reversals contain multiple NOPs, multiple simple swaps, and a few chained swaps, so regular single-loop single-state permute loops were not possible. Instead, we filter out parts of the input indices which are redundant. This allows for a single branch, and with some clever AVX512 asm, could possibly be SIMD'd without refactoring. The inplace_idx array is guaranteed to never be larger than the revtab array, and in practice only requires around log2(len) entries. The power-of-two MDCTs can be done in-place as well. And it's possible to eliminate a copy in the compound MDCTs too, however it'll be slower than doing them out of place, and we'd need to dirty the input array.	4 years ago
Lynne	aa34e99f88	lavu/tx: space out enum AVTXType values with newlines Makes separation clearer.	4 years ago
Lynne	06a8596825	lavu: support arbitrary-point FFTs and all even (i)MDCT transforms This patch adds support for arbitrary-point FFTs and all even MDCT transforms. Odd MDCTs are not supported yet as they're based on the DCT-II and DCT-III and they're very niche. With this we can now write tests.	4 years ago
Lynne	2465fe1302	lavu/tx: add 2-point FFT transform By itself, this allows 6-point, 10-point and 30-point transforms. When the 9-point transform is added it allows for 18-point FFT, and also for a 36-point MDCT (used by MP3).	5 years ago
Lynne	9f494d1397	lavu/tx: improve documentation	5 years ago
Lynne	e8f054b095	lavu/tx: implement 32 bit fixed point FFT and MDCT Required minimal changes to the code so made sense to implement. FFT and MDCT tested, the output of both was properly rounded. Fun fact: the non-power-of-two fixed-point FFT and MDCT are the fastest ever non-power-of-two fixed-point FFT and MDCT written. This can replace the power of two integer MDCTs in aac and ac3 if the MIPS optimizations are ported across. Unfortunately the ac3 encoder uses a 16-bit fixed point forward transform, unlike the encoder which uses a 32bit inverse transform, so some modifications might be required there. The 3-point FFT is somewhat less accurate than it otherwise could be, having minor rounding errors with bigger transforms. However, this could be improved later, and the way its currently written is the way one would write assembly for it. Similar rounding errors can also be found throughout the power of two FFTs as well, though those are more difficult to correct. Despite this, the integer transforms are more than accurate enough.	5 years ago
Lynne	d500eff3cc	lavu/tx: mention FFT output is not normalized Not even FFTW's output is normalized. This should prevent at least some users from complaining that doing a forward transform followed by an inverse transform has a mismatching output to the original input.	5 years ago
Lynne	42e2319ba9	lavu/tx: add support for double precision FFT and MDCT Simply moves and templates the actual transforms to support an additional data type. Unlike the float version, which is equal or better than libfftw3f, double precision output is bit identical with libfftw3.	5 years ago
Lynne	b79b29ddb1	libavutil: add an FFT & MDCT implementation This commit adds a new API to libavutil to allow for arbitrary transformations on various types of data. This is a partly new implementation, with the power of two transforms taken from libavcodec/fft_template, the 5 and 15-point FFT taken from mdct15, while the 3-point FFT was written from scratch. The (i)mdct folding code is taken from mdct15 as well, as the mdct_template code was somewhat old, messy and not easy to separate. A notable feature of this implementation is that it allows for 3xM and 5xM based transforms, where M is a power of two, e.g. 384, 640, 768, 1280, etc. AC-4 uses 3xM transforms while Siren uses 5xM transforms, so the code will allow for decoding of such streams. A non-exaustive list of supported sizes: 4, 8, 12, 16, 20, 24, 32, 40, 48, 60, 64, 80, 96, 120, 128, 160, 192, 240, 256, 320, 384, 480, 512, 640, 768, 960, 1024, 1280, 1536, 1920, 2048, 2560... The API was designed such that it allows for not only 1D transforms but also 2D transforms of certain block sizes. This was partly on accident as the stride argument is required for Opus MDCTs, but can be used in the context of a 2D transform as well. Also, various data types would be implemented eventually as well, such as "double" and "int32_t". Some performance comparisons with libfftw3f (SIMD disabled for both): 120: 22353 decicycles in fftwf_execute, 1024 runs, 0 skips 21836 decicycles in compound_fft_15x8, 1024 runs, 0 skips 128: 22003 decicycles in fftwf_execute, 1024 runs, 0 skips 23132 decicycles in monolithic_fft_ptwo, 1024 runs, 0 skips 384: 75939 decicycles in fftwf_execute, 1024 runs, 0 skips 73973 decicycles in compound_fft_3x128, 1024 runs, 0 skips 640: 104354 decicycles in fftwf_execute, 1024 runs, 0 skips 149518 decicycles in compound_fft_5x128, 1024 runs, 0 skips 768: 109323 decicycles in fftwf_execute, 1024 runs, 0 skips 164096 decicycles in compound_fft_3x256, 1024 runs, 0 skips 960: 186210 decicycles in fftwf_execute, 1024 runs, 0 skips 215256 decicycles in compound_fft_15x64, 1024 runs, 0 skips 1024: 163464 decicycles in fftwf_execute, 1024 runs, 0 skips 199686 decicycles in monolithic_fft_ptwo, 1024 runs, 0 skips With SIMD we should be faster than fftw for 15xM transforms as our fft15 SIMD is around 2x faster than theirs, even if our ptwo SIMD is slightly slower. The goal is to remove the libavcodec/mdct15 code and deprecate the libavcodec/avfft interface once aarch64 and x86 SIMD code has been ported. New code throughout the project should use this API. The implementation passes fate when used in Opus, AAC and Vorbis, and the output is identical with ATRAC9 as well.	6 years ago

22 Commits (c4dceb83542c68311be4db5a58ffa8444172fe7c)