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https://git.ffmpeg.org/ffmpeg.git
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Kacper Michajłow
72b81d5b64
Convert DSD to PCM with the same 96-tap symmetric lowpass filter the libavcodec DSD decoders use. The implementation is copied from libavcodec/dsd.c, minus the LSBF table variants, since AV_SAMPLE_FMT_DSD is defined as MSBF. The libavcodec copy will be removed in future commits as decoders are transitioned to SWR. The conversion is stateful (per-channel filter history), so the audio conversion functions gain a per-channel state argument. DSD silence is the 0x69 bit pattern instead of the 0x80 used for PCM. Only a direct DSD to float conversion function is provided. For format pairs without a direct conversion function (e.g. DSD to s16 with equal rates), swr_init() now falls back from the full_convert shortcut to the generic two-stage path instead of failing, and reports unsupported conversions with a proper error message instead of ENOMEM. Signed-off-by: Kacper Michajłow <kasper93@gmail.com>
57 lines
1.8 KiB
C
57 lines
1.8 KiB
C
/*
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* DSD to PCM conversion
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* based on BSD licensed dsd2pcm by Sebastian Gesemann
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* Copyright (c) 2009, 2011 Sebastian Gesemann. All rights reserved.
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* Copyright (c) 2014 Peter Ross
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef SWRESAMPLE_DSD2PCM_H
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#define SWRESAMPLE_DSD2PCM_H
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#include <stddef.h>
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#include <stdint.h>
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#define DSD_HTAPS 48 /** number of FIR constants */
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#define DSD_FIFOSIZE 16 /** must be a power of two */
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#define DSD_FIFOMASK (DSD_FIFOSIZE - 1) /** bit mask for FIFO offsets */
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#if DSD_FIFOSIZE * 8 < DSD_HTAPS * 2
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#error "DSD_FIFOSIZE too small"
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#endif
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/**
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* Per-channel buffer
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*/
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typedef struct DSDContext {
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uint8_t buf[DSD_FIFOSIZE];
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unsigned pos;
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} DSDContext;
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void swri_dsd2pcm_init(void);
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/**
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* Convert one channel of MSB-first DSD data (one byte = 8 samples) to
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* float PCM at 1/8th of the DSD bit rate. Strides are in elements.
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*/
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void swri_dsd2pcm_translate(DSDContext *s, size_t samples,
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const uint8_t *src, ptrdiff_t src_stride,
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float *dst, ptrdiff_t dst_stride);
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#endif /* SWRESAMPLE_DSD2PCM_H */
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