#include "a2dp_aac_encoder.h"
#include <inttypes.h>
+#include <math.h>
#include <stdio.h>
#include <string.h>
typedef struct {
uint32_t counter;
- uint32_t bytes_per_tick; /* pcm bytes read each media task tick */
- uint64_t last_frame_us;
+ uint32_t bytes_per_tick; // pcm bytes read each media task tick
+ uint64_t last_frame_timestamp_100ns; // values in 1/10 microseconds
} tA2DP_AAC_FEEDING_STATE;
typedef struct {
a2dp_aac_encoder_cb.feeding_params.bits_per_sample / 8;
LOG_VERBOSE("%s: pcm_bytes_per_frame %u", __func__, pcm_bytes_per_frame);
- uint32_t us_this_tick = a2dp_aac_encoder_interval_ms * 1000;
- uint64_t now_us = timestamp_us;
- if (a2dp_aac_encoder_cb.aac_feeding_state.last_frame_us != 0)
- us_this_tick =
- (now_us - a2dp_aac_encoder_cb.aac_feeding_state.last_frame_us);
- a2dp_aac_encoder_cb.aac_feeding_state.last_frame_us = now_us;
-
- a2dp_aac_encoder_cb.aac_feeding_state.counter +=
- a2dp_aac_encoder_cb.aac_feeding_state.bytes_per_tick * us_this_tick /
- (a2dp_aac_encoder_interval_ms * 1000);
+ uint32_t hecto_ns_this_tick = a2dp_aac_encoder_interval_ms * 10000;
+ uint64_t* last_100ns =
+ &a2dp_aac_encoder_cb.aac_feeding_state.last_frame_timestamp_100ns;
+ uint64_t now_100ns = timestamp_us * 10;
+ if (*last_100ns != 0) {
+ hecto_ns_this_tick = (now_100ns - *last_100ns);
+ }
+ *last_100ns = now_100ns;
+
+ uint32_t bytes_this_tick =
+ a2dp_aac_encoder_cb.aac_feeding_state.bytes_per_tick *
+ hecto_ns_this_tick / (a2dp_aac_encoder_interval_ms * 10000);
+ a2dp_aac_encoder_cb.aac_feeding_state.counter += bytes_this_tick;
+ // Without this erratum, there was a three microseocnd shift per tick which
+ // would cause one frame mismatched after every 180 seconds
+ uint32_t erratum_100ns =
+ ceil(1.0f * bytes_this_tick * a2dp_aac_encoder_interval_ms * 10000 /
+ a2dp_aac_encoder_cb.aac_feeding_state.bytes_per_tick);
+ if (erratum_100ns < hecto_ns_this_tick) {
+ LOG_VERBOSE("%s: hecto_ns_this_tick=%d, bytes=%d, erratum_100ns=%d",
+ __func__, hecto_ns_this_tick, bytes_this_tick, erratum_100ns);
+ *last_100ns -= hecto_ns_this_tick - erratum_100ns;
+ }
result = a2dp_aac_encoder_cb.aac_feeding_state.counter / pcm_bytes_per_frame;
a2dp_aac_encoder_cb.aac_feeding_state.counter -= result * pcm_bytes_per_frame;