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Diffstat (limited to 'cras/src/plc/cras_plc.c')
-rw-r--r--cras/src/plc/cras_plc.c285
1 files changed, 0 insertions, 285 deletions
diff --git a/cras/src/plc/cras_plc.c b/cras/src/plc/cras_plc.c
deleted file mode 100644
index 74c3568b..00000000
--- a/cras/src/plc/cras_plc.c
+++ /dev/null
@@ -1,285 +0,0 @@
-/* Copyright 2019 The Chromium OS Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#include <float.h>
-#include <math.h>
-#include <stdlib.h>
-#include <string.h>
-#include <stdio.h>
-
-#include "cras_plc.h"
-
-#define MSBC_SAMPLE_SIZE 2 /* 2 bytes*/
-#define MSBC_PKT_LEN 57 /* Packet length without the header */
-#define MSBC_FS 120 /* Frame Size */
-#define MSBC_CODE_SIZE 240 /* MSBC_SAMPLE_SIZE * MSBC_FS */
-
-#define PLC_WL 256 /* 16ms - Window Length for pattern matching */
-#define PLC_TL 64 /* 4ms - Template Length for matching */
-#define PLC_HL (PLC_WL + MSBC_FS - 1) /* Length of History buffer required */
-#define PLC_SBCRL 36 /* SBC Reconvergence sample Length */
-#define PLC_OLAL 16 /* OverLap-Add Length */
-
-#define PLC_WINDOW_SIZE 5
-#define PLC_PL_THRESHOLD 2
-
-/* The pre-computed zero input bit stream of mSBC codec, per HFP 1.7 spec.
- * This mSBC frame will be decoded into all-zero input PCM. */
-static const uint8_t msbc_zero_frame[] = {
- 0xad, 0x00, 0x00, 0xc5, 0x00, 0x00, 0x00, 0x00, 0x77, 0x6d, 0xb6, 0xdd,
- 0xdb, 0x6d, 0xb7, 0x76, 0xdb, 0x6d, 0xdd, 0xb6, 0xdb, 0x77, 0x6d, 0xb6,
- 0xdd, 0xdb, 0x6d, 0xb7, 0x76, 0xdb, 0x6d, 0xdd, 0xb6, 0xdb, 0x77, 0x6d,
- 0xb6, 0xdd, 0xdb, 0x6d, 0xb7, 0x76, 0xdb, 0x6d, 0xdd, 0xb6, 0xdb, 0x77,
- 0x6d, 0xb6, 0xdd, 0xdb, 0x6d, 0xb7, 0x76, 0xdb, 0x6c
-};
-
-/* Raised Cosine table for OLA */
-static const float rcos[PLC_OLAL] = { 0.99148655f, 0.96623611f, 0.92510857f,
- 0.86950446f, 0.80131732f, 0.72286918f,
- 0.63683150f, 0.54613418f, 0.45386582f,
- 0.36316850f, 0.27713082f, 0.19868268f,
- 0.13049554f, 0.07489143f, 0.03376389f,
- 0.00851345f };
-
-/* This structure tracks the packet loss information for last PLC_WINDOW_SIZE
- * of packets:
- * loss_hist - The packet loss history of receiving packets. 1 means lost.
- * ptr - The index of the to be updated packet loss status.
- * count - The count of lost packets in the window.
- */
-struct packet_window {
- uint8_t loss_hist[PLC_WINDOW_SIZE];
- unsigned int ptr;
- unsigned int count;
-};
-
-/* The PLC is specifically designed for mSBC. The algorithm searches the
- * history of receiving samples to find the best match samples and constructs
- * substitutions for the lost samples. The selection is based on pattern
- * matching a template, composed of a length of samples preceding to the lost
- * samples. It then uses the following samples after the best match as the
- * replacement samples and applies Overlap-Add to reduce the audible
- * distortion.
- *
- * This structure holds related info needed to conduct the PLC algorithm.
- * Members:
- * hist - The history buffer for receiving samples, we also use it to
- * buffer the processed replacement samples.
- * best_lag - The index of the best substitution samples in sample history.
- * handled_bad_frames - Number of bad frames handled since the last good
- * frame.
- * zero_frame - A buffer used for storing the samples from decoding the
- * mSBC zero frame packet.
- * pl_window - A window monitoring how many packets are bad within the recent
- * PLC_WINDOW_SIZE of packets. This is used to determine if we
- * want to disable the PLC temporarily.
- */
-struct cras_msbc_plc {
- int16_t hist[PLC_HL + MSBC_FS + PLC_SBCRL + PLC_OLAL];
- unsigned int best_lag;
- int handled_bad_frames;
- int16_t zero_frame[MSBC_FS];
- struct packet_window *pl_window;
-};
-
-struct cras_msbc_plc *cras_msbc_plc_create()
-{
- struct cras_msbc_plc *plc =
- (struct cras_msbc_plc *)calloc(1, sizeof(*plc));
- plc->pl_window =
- (struct packet_window *)calloc(1, sizeof(*plc->pl_window));
- return plc;
-}
-
-void cras_msbc_plc_destroy(struct cras_msbc_plc *plc)
-{
- free(plc->pl_window);
- free(plc);
-}
-
-static int16_t f_to_s16(float input)
-{
- return input > INT16_MAX ?
- INT16_MAX :
- input < INT16_MIN ? INT16_MIN : (int16_t)input;
-}
-
-void overlap_add(int16_t *output, float scaler_d, const int16_t *desc,
- float scaler_a, const int16_t *asc)
-{
- for (int i = 0; i < PLC_OLAL; i++) {
- output[i] =
- f_to_s16(scaler_d * desc[i] * rcos[i] +
- scaler_a * asc[i] * rcos[PLC_OLAL - 1 - i]);
- }
-}
-
-void update_plc_state(struct packet_window *w, uint8_t is_packet_loss)
-{
- uint8_t *curr = &w->loss_hist[w->ptr];
- if (is_packet_loss != *curr) {
- w->count += (is_packet_loss - *curr);
- *curr = is_packet_loss;
- }
- w->ptr = (w->ptr + 1) % PLC_WINDOW_SIZE;
-}
-
-int possibly_pause_plc(struct packet_window *w)
-{
- /* The packet loss count comes from a time window and we use it as an
- * indicator of our confidence of the PLC algorithm. It is known to
- * generate poorer and robotic feeling sounds, when the majority of
- * samples in the PLC history buffer are from the concealment results.
- */
- return w->count >= PLC_PL_THRESHOLD;
-}
-
-int cras_msbc_plc_handle_good_frames(struct cras_msbc_plc *state,
- const uint8_t *input, uint8_t *output)
-{
- int16_t *frame_head, *input_samples, *output_samples;
- if (state->handled_bad_frames == 0) {
- /* If there was no packet concealment before this good frame,
- * we just simply copy the input to output without reconverge.
- */
- memmove(output, input, MSBC_FS * MSBC_SAMPLE_SIZE);
- } else {
- frame_head = &state->hist[PLC_HL];
- input_samples = (int16_t *)input;
- output_samples = (int16_t *)output;
-
- /* For the first good frame after packet loss, we need to
- * conceal the received samples to have it reconverge with the
- * true output.
- */
- memcpy(output_samples, frame_head,
- PLC_SBCRL * MSBC_SAMPLE_SIZE);
- overlap_add(&output_samples[PLC_SBCRL], 1.0,
- &frame_head[PLC_SBCRL], 1.0,
- &input_samples[PLC_SBCRL]);
- memmove(&output_samples[PLC_SBCRL + PLC_OLAL],
- &input_samples[PLC_SBCRL + PLC_OLAL],
- (MSBC_FS - PLC_SBCRL - PLC_OLAL) * MSBC_SAMPLE_SIZE);
- state->handled_bad_frames = 0;
- }
-
- /* Shift the history and update the good frame to the end of it. */
- memmove(state->hist, &state->hist[MSBC_FS],
- (PLC_HL - MSBC_FS) * MSBC_SAMPLE_SIZE);
- memcpy(&state->hist[PLC_HL - MSBC_FS], output,
- MSBC_FS * MSBC_SAMPLE_SIZE);
- update_plc_state(state->pl_window, 0);
- return MSBC_CODE_SIZE;
-}
-
-float cross_correlation(int16_t *x, int16_t *y)
-{
- float sum = 0, x2 = 0, y2 = 0;
-
- for (int i = 0; i < PLC_TL; i++) {
- sum += ((float)x[i]) * y[i];
- x2 += ((float)x[i]) * x[i];
- y2 += ((float)y[i]) * y[i];
- }
- return sum / sqrtf(x2 * y2);
-}
-
-int pattern_match(int16_t *hist)
-{
- int best = 0;
- float cn, max_cn = FLT_MIN;
-
- for (int i = 0; i < PLC_WL; i++) {
- cn = cross_correlation(&hist[PLC_HL - PLC_TL], &hist[i]);
- if (cn > max_cn) {
- best = i;
- max_cn = cn;
- }
- }
- return best;
-}
-
-float amplitude_match(int16_t *x, int16_t *y)
-{
- uint32_t sum_x = 0, sum_y = 0;
- float scaler;
- for (int i = 0; i < MSBC_FS; i++) {
- sum_x += abs(x[i]);
- sum_y += abs(y[i]);
- }
-
- if (sum_y == 0)
- return 1.2f;
-
- scaler = (float)sum_x / sum_y;
- return scaler > 1.2f ? 1.2f : scaler < 0.75f ? 0.75f : scaler;
-}
-
-int cras_msbc_plc_handle_bad_frames(struct cras_msbc_plc *state,
- struct cras_audio_codec *codec,
- uint8_t *output)
-{
- float scaler;
- int16_t *best_match_hist;
- int16_t *frame_head = &state->hist[PLC_HL];
- size_t pcm_decoded = 0;
-
- /* mSBC codec is stateful, the history of signal would contribute to the
- * decode result state->zero_frame.
- */
- codec->decode(codec, msbc_zero_frame, MSBC_PKT_LEN, state->zero_frame,
- MSBC_FS, &pcm_decoded);
-
- /* The PLC algorithm is more likely to generate bad results that sound
- * robotic after severe packet losses happened. Only applying it when
- * we are confident.
- */
- if (!possibly_pause_plc(state->pl_window)) {
- if (state->handled_bad_frames == 0) {
- /* Finds the best matching samples and amplitude */
- state->best_lag = pattern_match(state->hist) + PLC_TL;
- best_match_hist = &state->hist[state->best_lag];
- scaler = amplitude_match(&state->hist[PLC_HL - MSBC_FS],
- best_match_hist);
-
- /* Constructs the substitution samples */
- overlap_add(frame_head, 1.0, state->zero_frame, scaler,
- best_match_hist);
- for (int i = PLC_OLAL; i < MSBC_FS; i++)
- state->hist[PLC_HL + i] =
- f_to_s16(scaler * best_match_hist[i]);
- overlap_add(&frame_head[MSBC_FS], scaler,
- &best_match_hist[MSBC_FS], 1.0,
- &best_match_hist[MSBC_FS]);
-
- memmove(&frame_head[MSBC_FS + PLC_OLAL],
- &best_match_hist[MSBC_FS + PLC_OLAL],
- PLC_SBCRL * MSBC_SAMPLE_SIZE);
- } else {
- memmove(frame_head, &state->hist[state->best_lag],
- (MSBC_FS + PLC_SBCRL + PLC_OLAL) *
- MSBC_SAMPLE_SIZE);
- }
- state->handled_bad_frames++;
- } else {
- /* This is a case similar to receiving a good frame with all
- * zeros, we set handled_bad_frames to zero to prevent the
- * following good frame from being concealed to reconverge with
- * the zero frames we fill in. The concealment result sounds
- * more artificial and weird than simply writing zeros and
- * following samples.
- */
- memmove(frame_head, state->zero_frame, MSBC_CODE_SIZE);
- memset(frame_head + MSBC_CODE_SIZE, 0,
- (PLC_SBCRL + PLC_OLAL) * MSBC_SAMPLE_SIZE);
- state->handled_bad_frames = 0;
- }
-
- memcpy(output, frame_head, MSBC_CODE_SIZE);
- memmove(state->hist, &state->hist[MSBC_FS],
- (PLC_HL + PLC_SBCRL + PLC_OLAL) * MSBC_SAMPLE_SIZE);
- update_plc_state(state->pl_window, 1);
- return MSBC_CODE_SIZE;
-}
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