/* * Audio Processing Technology codec for Bluetooth (aptX) * * Copyright (C) 2017 Aurelien Jacobs <aurel@gnuage.org> * * 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 */ #include "aptx.h" /* * Half-band QMF analysis filter realized with a polyphase FIR filter. * Split into 2 subbands and downsample by 2. * So for each pair of samples that goes in, one sample goes out, * split into 2 separate subbands. */ av_always_inline static void aptx_qmf_polyphase_analysis(FilterSignal signal[NB_FILTERS], const int32_t coeffs[NB_FILTERS][FILTER_TAPS], int shift, int32_t samples[NB_FILTERS], int32_t *low_subband_output, int32_t *high_subband_output) { int32_t subbands[NB_FILTERS]; int i; for (i = 0; i < NB_FILTERS; i++) { aptx_qmf_filter_signal_push(&signal[i], samples[NB_FILTERS-1-i]); subbands[i] = aptx_qmf_convolution(&signal[i], coeffs[i], shift); } *low_subband_output = av_clip_intp2(subbands[0] + subbands[1], 23); *high_subband_output = av_clip_intp2(subbands[0] - subbands[1], 23); } /* * Two stage QMF analysis tree. * Split 4 input samples into 4 subbands and downsample by 4. * So for each group of 4 samples that goes in, one sample goes out, * split into 4 separate subbands. */ static void aptx_qmf_tree_analysis(QMFAnalysis *qmf, int32_t samples[4], int32_t subband_samples[4]) { int32_t intermediate_samples[4]; int i; /* Split 4 input samples into 2 intermediate subbands downsampled to 2 samples */ for (i = 0; i < 2; i++) aptx_qmf_polyphase_analysis(qmf->outer_filter_signal, aptx_qmf_outer_coeffs, 23, &samples[2*i], &intermediate_samples[0+i], &intermediate_samples[2+i]); /* Split 2 intermediate subband samples into 4 final subbands downsampled to 1 sample */ for (i = 0; i < 2; i++) aptx_qmf_polyphase_analysis(qmf->inner_filter_signal[i], aptx_qmf_inner_coeffs, 23, &intermediate_samples[2*i], &subband_samples[2*i+0], &subband_samples[2*i+1]); } av_always_inline static int32_t aptx_bin_search(int32_t value, int32_t factor, const int32_t *intervals, int32_t nb_intervals) { int32_t idx = 0; int i; for (i = nb_intervals >> 1; i > 0; i >>= 1) if (MUL64(factor, intervals[idx + i]) <= ((int64_t)value << 24)) idx += i; return idx; } static void aptx_quantize_difference(Quantize *quantize, int32_t sample_difference, int32_t dither, int32_t quantization_factor, ConstTables *tables) { const int32_t *intervals = tables->quantize_intervals; int32_t quantized_sample, dithered_sample, parity_change; int32_t d, mean, interval, inv, sample_difference_abs; int64_t error; sample_difference_abs = FFABS(sample_difference); sample_difference_abs = FFMIN(sample_difference_abs, (1 << 23) - 1); quantized_sample = aptx_bin_search(sample_difference_abs >> 4, quantization_factor, intervals, tables->tables_size); d = rshift32_clip24(MULH(dither, dither), 7) - (1 << 23); d = rshift64(MUL64(d, tables->quantize_dither_factors[quantized_sample]), 23); intervals += quantized_sample; mean = (intervals[1] + intervals[0]) / 2; interval = (intervals[1] - intervals[0]) * (-(sample_difference < 0) | 1); dithered_sample = rshift64_clip24(MUL64(dither, interval) + ((int64_t)av_clip_intp2(mean + d, 23) << 32), 32); error = ((int64_t)sample_difference_abs << 20) - MUL64(dithered_sample, quantization_factor); quantize->error = FFABS(rshift64(error, 23)); parity_change = quantized_sample; if (error < 0) quantized_sample--; else parity_change--; inv = -(sample_difference < 0); quantize->quantized_sample = quantized_sample ^ inv; quantize->quantized_sample_parity_change = parity_change ^ inv; } static void aptx_encode_channel(Channel *channel, int32_t samples[4], int hd) { int32_t subband_samples[4]; int subband; aptx_qmf_tree_analysis(&channel->qmf, samples, subband_samples); ff_aptx_generate_dither(channel); for (subband = 0; subband < NB_SUBBANDS; subband++) { int32_t diff = av_clip_intp2(subband_samples[subband] - channel->prediction[subband].predicted_sample, 23); aptx_quantize_difference(&channel->quantize[subband], diff, channel->dither[subband], channel->invert_quantize[subband].quantization_factor, &ff_aptx_quant_tables[hd][subband]); } } static void aptx_insert_sync(Channel channels[NB_CHANNELS], int32_t *idx) { if (aptx_check_parity(channels, idx)) { int i; Channel *c; static const int map[] = { 1, 2, 0, 3 }; Quantize *min = &channels[NB_CHANNELS-1].quantize[map[0]]; for (c = &channels[NB_CHANNELS-1]; c >= channels; c--) for (i = 0; i < NB_SUBBANDS; i++) if (c->quantize[map[i]].error < min->error) min = &c->quantize[map[i]]; /* Forcing the desired parity is done by offsetting by 1 the quantized * sample from the subband featuring the smallest quantization error. */ min->quantized_sample = min->quantized_sample_parity_change; } } static uint16_t aptx_pack_codeword(Channel *channel) { int32_t parity = aptx_quantized_parity(channel); return (((channel->quantize[3].quantized_sample & 0x06) | parity) << 13) | (((channel->quantize[2].quantized_sample & 0x03) ) << 11) | (((channel->quantize[1].quantized_sample & 0x0F) ) << 7) | (((channel->quantize[0].quantized_sample & 0x7F) ) << 0); } static uint32_t aptxhd_pack_codeword(Channel *channel) { int32_t parity = aptx_quantized_parity(channel); return (((channel->quantize[3].quantized_sample & 0x01E) | parity) << 19) | (((channel->quantize[2].quantized_sample & 0x00F) ) << 15) | (((channel->quantize[1].quantized_sample & 0x03F) ) << 9) | (((channel->quantize[0].quantized_sample & 0x1FF) ) << 0); } static void aptx_encode_samples(AptXContext *ctx, int32_t samples[NB_CHANNELS][4], uint8_t *output) { int channel; for (channel = 0; channel < NB_CHANNELS; channel++) aptx_encode_channel(&ctx->channels[channel], samples[channel], ctx->hd); aptx_insert_sync(ctx->channels, &ctx->sync_idx); for (channel = 0; channel < NB_CHANNELS; channel++) { ff_aptx_invert_quantize_and_prediction(&ctx->channels[channel], ctx->hd); if (ctx->hd) AV_WB24(output + 3*channel, aptxhd_pack_codeword(&ctx->channels[channel])); else AV_WB16(output + 2*channel, aptx_pack_codeword(&ctx->channels[channel])); } } static int aptx_encode_frame(AVCodecContext *avctx, AVPacket *avpkt, const AVFrame *frame, int *got_packet_ptr) { AptXContext *s = avctx->priv_data; int pos, ipos, channel, sample, output_size, ret; if ((ret = ff_af_queue_add(&s->afq, frame)) < 0) return ret; output_size = s->block_size * frame->nb_samples/4; if ((ret = ff_alloc_packet2(avctx, avpkt, output_size, 0)) < 0) return ret; for (pos = 0, ipos = 0; pos < output_size; pos += s->block_size, ipos += 4) { int32_t samples[NB_CHANNELS][4]; for (channel = 0; channel < NB_CHANNELS; channel++) for (sample = 0; sample < 4; sample++) samples[channel][sample] = (int32_t)AV_RN32A(&frame->data[channel][4*(ipos+sample)]) >> 8; aptx_encode_samples(s, samples, avpkt->data + pos); } ff_af_queue_remove(&s->afq, frame->nb_samples, &avpkt->pts, &avpkt->duration); *got_packet_ptr = 1; return 0; } static av_cold int aptx_close(AVCodecContext *avctx) { AptXContext *s = avctx->priv_data; ff_af_queue_close(&s->afq); return 0; } #if CONFIG_APTX_ENCODER AVCodec ff_aptx_encoder = { .name = "aptx", .long_name = NULL_IF_CONFIG_SMALL("aptX (Audio Processing Technology for Bluetooth)"), .type = AVMEDIA_TYPE_AUDIO, .id = AV_CODEC_ID_APTX, .priv_data_size = sizeof(AptXContext), .init = ff_aptx_init, .encode2 = aptx_encode_frame, .close = aptx_close, .capabilities = AV_CODEC_CAP_SMALL_LAST_FRAME, .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE, .channel_layouts = (const uint64_t[]) { AV_CH_LAYOUT_STEREO, 0}, .sample_fmts = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S32P, AV_SAMPLE_FMT_NONE }, .supported_samplerates = (const int[]) {8000, 16000, 24000, 32000, 44100, 48000, 0}, }; #endif #if CONFIG_APTX_HD_ENCODER AVCodec ff_aptx_hd_encoder = { .name = "aptx_hd", .long_name = NULL_IF_CONFIG_SMALL("aptX HD (Audio Processing Technology for Bluetooth)"), .type = AVMEDIA_TYPE_AUDIO, .id = AV_CODEC_ID_APTX_HD, .priv_data_size = sizeof(AptXContext), .init = ff_aptx_init, .encode2 = aptx_encode_frame, .close = aptx_close, .capabilities = AV_CODEC_CAP_SMALL_LAST_FRAME, .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE, .channel_layouts = (const uint64_t[]) { AV_CH_LAYOUT_STEREO, 0}, .sample_fmts = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S32P, AV_SAMPLE_FMT_NONE }, .supported_samplerates = (const int[]) {8000, 16000, 24000, 32000, 44100, 48000, 0}, }; #endif