sbcdec.c

Go to the documentation of this file.

/*
 * Bluetooth low-complexity, subband codec (SBC)
 *
 * Copyright (C) 2017  Aurelien Jacobs <aurel@gnuage.org>
 * Copyright (C) 2012-2013  Intel Corporation
 * Copyright (C) 2008-2010  Nokia Corporation
 * Copyright (C) 2004-2010  Marcel Holtmann <marcel@holtmann.org>
 * Copyright (C) 2004-2005  Henryk Ploetz <henryk@ploetzli.ch>
 * Copyright (C) 2005-2008  Brad Midgley <bmidgley@xmission.com>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
 
/**
 * @file
 * SBC decoder implementation
 */
 
#include "avcodec.h"
#include "codec_internal.h"
#include "decode.h"
#include "libavutil/channel_layout.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/mem_internal.h"
#include "sbc.h"
#include "sbcdec_data.h"
 
struct sbc_decoder_state {
    int32_t V[2][170];
    int offset[2][16];
};
 
typedef struct SBCDecContext {
    DECLARE_ALIGNED(SBC_ALIGN, struct sbc_frame, frame);
    DECLARE_ALIGNED(SBC_ALIGN, struct sbc_decoder_state, dsp);
} SBCDecContext;
 
/*
 * Unpacks a SBC frame at the beginning of the stream in data,
 * which has at most len bytes into frame.
 * Returns the length in bytes of the packed frame, or a negative
 * value on error. The error codes are:
 *
 *  -1   Data stream too short
 *  -2   Sync byte incorrect
 *  -3   CRC8 incorrect
 *  -4   Bitpool value out of bounds
 */
static int sbc_unpack_frame(const uint8_t *data, struct sbc_frame *frame,
                            size_t len)
{
    unsigned int consumed;
    /* Will copy the parts of the header that are relevant to crc
     * calculation here */
    uint8_t crc_header[11] = { 0 };
    int crc_pos;
    int32_t temp;
 
    uint32_t audio_sample;
    int ch, sb, blk, bit;   /* channel, subband, block and bit standard
                               counters */
    int bits[2][8];         /* bits distribution */
    uint32_t levels[2][8];  /* levels derived from that */
 
    if (len < 4)
        return -1;
 
    if (data[0] == MSBC_SYNCWORD) {
        if (data[1] != 0)
            return -2;
        if (data[2] != 0)
            return -2;
 
        frame->frequency = SBC_FREQ_16000;
        frame->blocks = MSBC_BLOCKS;
        frame->allocation = LOUDNESS;
        frame->mode = MONO;
        frame->channels = 1;
        frame->subbands = 8;
        frame->bitpool = 26;
    } else if (data[0] == SBC_SYNCWORD) {
        frame->frequency  = (data[1] >> 6) & 0x03;
        frame->blocks = 4 * ((data[1] >> 4) & 0x03) + 4;
        frame->mode = (data[1] >> 2) & 0x03;
        frame->channels = frame->mode == MONO ? 1 : 2;
        frame->allocation = (data[1] >> 1) & 0x01;
        frame->subbands = data[1] & 0x01 ? 8 : 4;
        frame->bitpool = data[2];
 
        if ((frame->mode == MONO || frame->mode == DUAL_CHANNEL) &&
            frame->bitpool > 16 * frame->subbands)
            return -4;
 
        if ((frame->mode == STEREO || frame->mode == JOINT_STEREO) &&
            frame->bitpool > 32 * frame->subbands)
            return -4;
    } else
        return -2;
 
    consumed = 32;
    crc_header[0] = data[1];
    crc_header[1] = data[2];
    crc_pos = 16;
 
    if (frame->mode == JOINT_STEREO) {
        if (len * 8 < consumed + frame->subbands)
            return -1;
 
        frame->joint = 0x00;
        for (sb = 0; sb < frame->subbands - 1; sb++)
            frame->joint |= ((data[4] >> (7 - sb)) & 0x01) << sb;
        if (frame->subbands == 4)
            crc_header[crc_pos / 8] = data[4] & 0xf0;
        else
            crc_header[crc_pos / 8] = data[4];
 
        consumed += frame->subbands;
        crc_pos += frame->subbands;
    }
 
    if (len * 8 < consumed + (4 * frame->subbands * frame->channels))
        return -1;
 
    for (ch = 0; ch < frame->channels; ch++) {
        for (sb = 0; sb < frame->subbands; sb++) {
            /* FIXME assert(consumed % 4 == 0); */
            frame->scale_factor[ch][sb] =
                (data[consumed >> 3] >> (4 - (consumed & 0x7))) & 0x0F;
            crc_header[crc_pos >> 3] |=
                frame->scale_factor[ch][sb] << (4 - (crc_pos & 0x7));
 
            consumed += 4;
            crc_pos += 4;
        }
    }
 
    if (data[3] != ff_sbc_crc8(frame->crc_ctx, crc_header, crc_pos))
        return -3;
 
    ff_sbc_calculate_bits(frame, bits);
 
    for (ch = 0; ch < frame->channels; ch++) {
        for (sb = 0; sb < frame->subbands; sb++)
            levels[ch][sb] = (1 << bits[ch][sb]) - 1;
    }
 
    for (blk = 0; blk < frame->blocks; blk++) {
        for (ch = 0; ch < frame->channels; ch++) {
            for (sb = 0; sb < frame->subbands; sb++) {
                uint32_t shift;
 
                if (levels[ch][sb] == 0) {
                    frame->sb_sample[blk][ch][sb] = 0;
                    continue;
                }
 
                shift = frame->scale_factor[ch][sb] +
                        1 + SBCDEC_FIXED_EXTRA_BITS;
 
                audio_sample = 0;
                for (bit = 0; bit < bits[ch][sb]; bit++) {
                    if (consumed > len * 8)
                        return -1;
 
                    if ((data[consumed >> 3] >> (7 - (consumed & 0x7))) & 0x01)
                        audio_sample |= 1 << (bits[ch][sb] - bit - 1);
 
                    consumed++;
                }
 
                frame->sb_sample[blk][ch][sb] = (int32_t)
                    (((((uint64_t) audio_sample << 1) | 1) << shift) /
                    levels[ch][sb]) - (1 << shift);
            }
        }
    }
 
    if (frame->mode == JOINT_STEREO) {
        for (blk = 0; blk < frame->blocks; blk++) {
            for (sb = 0; sb < frame->subbands; sb++) {
                if (frame->joint & (0x01 << sb)) {
                    temp = frame->sb_sample[blk][0][sb] +
                           frame->sb_sample[blk][1][sb];
                    frame->sb_sample[blk][1][sb] =
                        frame->sb_sample[blk][0][sb] -
                        frame->sb_sample[blk][1][sb];
                    frame->sb_sample[blk][0][sb] = temp;
                }
            }
        }
    }
 
    if ((consumed & 0x7) != 0)
        consumed += 8 - (consumed & 0x7);
 
    return consumed >> 3;
}
 
static inline void sbc_synthesize_four(struct sbc_decoder_state *state,
                                       struct sbc_frame *frame,
                                       int ch, int blk, AVFrame *output_frame)
{
    int i, k, idx;
    int32_t *v = state->V[ch];
    int *offset = state->offset[ch];
 
    for (i = 0; i < 8; i++) {
        /* Shifting */
        offset[i]--;
        if (offset[i] < 0) {
            offset[i] = 79;
            memcpy(v + 80, v, 9 * sizeof(*v));
        }
 
        /* Distribute the new matrix value to the shifted position */
        v[offset[i]] =
            (int)( (unsigned)synmatrix4[i][0] * frame->sb_sample[blk][ch][0] +
                   (unsigned)synmatrix4[i][1] * frame->sb_sample[blk][ch][1] +
                   (unsigned)synmatrix4[i][2] * frame->sb_sample[blk][ch][2] +
                   (unsigned)synmatrix4[i][3] * frame->sb_sample[blk][ch][3] ) >> 15;
    }
 
    /* Compute the samples */
    for (idx = 0, i = 0; i < 4; i++, idx += 5) {
        k = (i + 4) & 0xf;
 
        /* Store in output, Q0 */
        AV_WN16A(&output_frame->data[ch][blk * 8 + i * 2], av_clip_int16(
         (int)( (unsigned)v[offset[i] + 0] * sbc_proto_4_40m0[idx + 0] +
                (unsigned)v[offset[k] + 1] * sbc_proto_4_40m1[idx + 0] +
                (unsigned)v[offset[i] + 2] * sbc_proto_4_40m0[idx + 1] +
                (unsigned)v[offset[k] + 3] * sbc_proto_4_40m1[idx + 1] +
                (unsigned)v[offset[i] + 4] * sbc_proto_4_40m0[idx + 2] +
                (unsigned)v[offset[k] + 5] * sbc_proto_4_40m1[idx + 2] +
                (unsigned)v[offset[i] + 6] * sbc_proto_4_40m0[idx + 3] +
                (unsigned)v[offset[k] + 7] * sbc_proto_4_40m1[idx + 3] +
                (unsigned)v[offset[i] + 8] * sbc_proto_4_40m0[idx + 4] +
                (unsigned)v[offset[k] + 9] * sbc_proto_4_40m1[idx + 4] ) >> 15));
    }
}
 
static inline void sbc_synthesize_eight(struct sbc_decoder_state *state,
                                        struct sbc_frame *frame,
                                        int ch, int blk, AVFrame *output_frame)
{
    int i, k, idx;
    int32_t *v = state->V[ch];
    int *offset = state->offset[ch];
 
    for (i = 0; i < 16; i++) {
        /* Shifting */
        offset[i]--;
        if (offset[i] < 0) {
            offset[i] = 159;
            memcpy(v + 160, v, 9 * sizeof(*v));
        }
 
        /* Distribute the new matrix value to the shifted position */
        v[offset[i]] =
             (int)( (unsigned)synmatrix8[i][0] * frame->sb_sample[blk][ch][0] +
                    (unsigned)synmatrix8[i][1] * frame->sb_sample[blk][ch][1] +
                    (unsigned)synmatrix8[i][2] * frame->sb_sample[blk][ch][2] +
                    (unsigned)synmatrix8[i][3] * frame->sb_sample[blk][ch][3] +
                    (unsigned)synmatrix8[i][4] * frame->sb_sample[blk][ch][4] +
                    (unsigned)synmatrix8[i][5] * frame->sb_sample[blk][ch][5] +
                    (unsigned)synmatrix8[i][6] * frame->sb_sample[blk][ch][6] +
                    (unsigned)synmatrix8[i][7] * frame->sb_sample[blk][ch][7] ) >> 15;
    }
 
    /* Compute the samples */
    for (idx = 0, i = 0; i < 8; i++, idx += 5) {
        k = (i + 8) & 0xf;
 
        /* Store in output, Q0 */
        AV_WN16A(&output_frame->data[ch][blk * 16 + i * 2], av_clip_int16(
         (int)( (unsigned)v[offset[i] + 0] * sbc_proto_8_80m0[idx + 0] +
                (unsigned)v[offset[k] + 1] * sbc_proto_8_80m1[idx + 0] +
                (unsigned)v[offset[i] + 2] * sbc_proto_8_80m0[idx + 1] +
                (unsigned)v[offset[k] + 3] * sbc_proto_8_80m1[idx + 1] +
                (unsigned)v[offset[i] + 4] * sbc_proto_8_80m0[idx + 2] +
                (unsigned)v[offset[k] + 5] * sbc_proto_8_80m1[idx + 2] +
                (unsigned)v[offset[i] + 6] * sbc_proto_8_80m0[idx + 3] +
                (unsigned)v[offset[k] + 7] * sbc_proto_8_80m1[idx + 3] +
                (unsigned)v[offset[i] + 8] * sbc_proto_8_80m0[idx + 4] +
                (unsigned)v[offset[k] + 9] * sbc_proto_8_80m1[idx + 4] ) >> 15));
    }
}
 
static void sbc_synthesize_audio(struct sbc_decoder_state *state,
                                 struct sbc_frame *frame, AVFrame *output_frame)
{
    int ch, blk;
 
    switch (frame->subbands) {
    case 4:
        for (ch = 0; ch < frame->channels; ch++)
            for (blk = 0; blk < frame->blocks; blk++)
                sbc_synthesize_four(state, frame, ch, blk, output_frame);
        break;
 
    case 8:
        for (ch = 0; ch < frame->channels; ch++)
            for (blk = 0; blk < frame->blocks; blk++)
                sbc_synthesize_eight(state, frame, ch, blk, output_frame);
        break;
    }
}
 
static av_cold int sbc_decode_init(AVCodecContext *avctx)
{
    SBCDecContext *sbc = avctx->priv_data;
    int i, ch;
 
    avctx->sample_fmt = AV_SAMPLE_FMT_S16P;
 
    sbc->frame.crc_ctx = av_crc_get_table(AV_CRC_8_EBU);
 
    memset(sbc->dsp.V, 0, sizeof(sbc->dsp.V));
    for (ch = 0; ch < 2; ch++)
        for (i = 0; i < FF_ARRAY_ELEMS(sbc->dsp.offset[0]); i++)
            sbc->dsp.offset[ch][i] = (10 * i + 10);
    return 0;
}
 
static int sbc_decode_frame(AVCodecContext *avctx, AVFrame *frame,
                            int *got_frame_ptr, AVPacket *avpkt)
{
    SBCDecContext *sbc = avctx->priv_data;
    int ret, frame_length;
 
    frame_length = sbc_unpack_frame(avpkt->data, &sbc->frame, avpkt->size);
    if (frame_length <= 0)
        return frame_length;
 
    av_channel_layout_uninit(&avctx->ch_layout);
    avctx->ch_layout.order       = AV_CHANNEL_ORDER_UNSPEC;
    avctx->ch_layout.nb_channels = sbc->frame.channels;
 
    frame->nb_samples = sbc->frame.blocks * sbc->frame.subbands;
    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
        return ret;
 
    sbc_synthesize_audio(&sbc->dsp, &sbc->frame, frame);
 
    *got_frame_ptr = 1;
 
    return frame_length;
}
 
const FFCodec ff_sbc_decoder = {
    .p.name                = "sbc",
    CODEC_LONG_NAME("SBC (low-complexity subband codec)"),
    .p.type                = AVMEDIA_TYPE_AUDIO,
    .p.id                  = AV_CODEC_ID_SBC,
    .priv_data_size        = sizeof(SBCDecContext),
    .init                  = sbc_decode_init,
    FF_CODEC_DECODE_CB(sbc_decode_frame),
    .p.capabilities        = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_CHANNEL_CONF,
};