aes67-ESP32-P4/main/decoder.c

#include "decoder.h"

#include <stdlib.h>
#include <string.h>

#include "esp_audio_dec_default.h"
#include "esp_audio_simple_dec.h"
#include "esp_audio_simple_dec_default.h"
#include "esp_heap_caps.h"
#include "esp_log.h"

static const char *TAG = "decoder";

static esp_audio_simple_dec_handle_t s_dec;
static uint8_t *s_pcm;
static uint32_t s_pcm_size = 8192;
static esp_audio_simple_dec_info_t s_info;
static uint64_t s_seg_frames, s_seg_count, s_seg_es;

// MPEG-TS demux state: packets reassembled across HTTP chunks, PAT -> PMT -> ADTS-AAC PID.
static uint8_t s_pkt[188];
static size_t s_pkt_len;
static int s_pmt_pid = -1, s_audio_pid = -1;

static void report_segment(void)
{
    if (s_seg_count && s_info.sample_rate) {
        ESP_LOGI(TAG, "segment: %llu ES bytes -> %llu PCM frames = %.3f s (%lu Hz, %u ch, %u bit)",
                 s_seg_es, s_seg_frames, (double)s_seg_frames / s_info.sample_rate,
                 (unsigned long)s_info.sample_rate, s_info.channel, s_info.bits_per_sample);
    }
    s_seg_frames = 0;
    s_seg_es = 0;
    s_seg_count++;
}

// Feed ADTS-AAC elementary stream bytes to the decoder.
static void decode_es(const uint8_t *data, size_t len)
{
    s_seg_es += len;
    esp_audio_simple_dec_raw_t raw = { .buffer = (uint8_t *)data, .len = len };
    while (raw.len) {
        esp_audio_simple_dec_out_t out = { .buffer = s_pcm, .len = s_pcm_size };
        esp_audio_err_t err = esp_audio_simple_dec_process(s_dec, &raw, &out);
        if (err == ESP_AUDIO_ERR_BUFF_NOT_ENOUGH) {
            uint8_t *p = heap_caps_realloc(s_pcm, out.needed_size, MALLOC_CAP_SPIRAM);
            if (!p) {
                return;
            }
            s_pcm = p;
            s_pcm_size = out.needed_size;
            continue;
        }
        if (err != ESP_AUDIO_ERR_OK) {
            ESP_LOGW(TAG, "decode error %d, resetting decoder", err);
            esp_audio_simple_dec_reset(s_dec);
            return;
        }
        if (out.decoded_size) {
            if (!s_info.sample_rate) {
                esp_audio_simple_dec_get_info(s_dec, &s_info);
                ESP_LOGI(TAG, "stream: %lu Hz, %u ch, %u bit, %lu bit/s", (unsigned long)s_info.sample_rate,
                         s_info.channel, s_info.bits_per_sample, (unsigned long)s_info.bitrate);
            }
            s_seg_frames += out.decoded_size / (s_info.channel * s_info.bits_per_sample / 8);
        }
        raw.buffer += raw.consumed;
        raw.len -= raw.consumed;
    }
}

static void ts_packet(const uint8_t *p)
{
    if (p[0] != 0x47) {
        return;
    }
    bool pusi = p[1] & 0x40;
    int pid = ((p[1] & 0x1f) << 8) | p[2];
    int afc = (p[3] >> 4) & 3;
    if (!(afc & 1)) {
        return;                         // no payload
    }
    size_t off = 4 + ((afc & 2) ? 1 + p[4] : 0);
    if (off >= 188) {
        return;
    }
    const uint8_t *pl = p + off;
    size_t len = 188 - off;

    if (pid == 0 && pusi) {                                     // PAT: first program's PMT PID
        const uint8_t *sec = pl + 1 + pl[0];
        s_pmt_pid = ((sec[10] & 0x1f) << 8) | sec[11];
    } else if (pid == s_pmt_pid && pusi && s_audio_pid < 0) {   // PMT: first ADTS-AAC stream
        const uint8_t *sec = pl + 1 + pl[0];
        int slen = ((sec[1] & 0x0f) << 8) | sec[2];
        int i = 12 + (((sec[10] & 0x0f) << 8) | sec[11]);
        while (i + 5 <= 3 + slen - 4 && sec + i + 5 <= p + 188) {
            int type = sec[i], epid = ((sec[i + 1] & 0x1f) << 8) | sec[i + 2];
            if (type == 0x0F) {
                s_audio_pid = epid;
                ESP_LOGI(TAG, "TS: PMT PID 0x%x, ADTS-AAC on PID 0x%x", s_pmt_pid, epid);
                break;
            }
            i += 5 + (((sec[i + 3] & 0x0f) << 8) | sec[i + 4]);
        }
    } else if (pid == s_audio_pid) {
        if (pusi) {                                             // strip the PES header
            if (len < 9 || pl[0] || pl[1] || pl[2] != 1 || 9u + pl[8] > len) {
                return;
            }
            size_t h = 9 + pl[8];
            pl += h;
            len -= h;
        }
        decode_es(pl, len);
    }
}

// hls_sink_t: MPEG-TS bytes in any chunking.
bool decoder_feed(const uint8_t *data, size_t len, bool segment_start)
{
    if (segment_start) {
        report_segment();
        s_pkt_len = 0;                  // segments start on a packet boundary
    }
    while (len) {
        if (!s_pkt_len) {
            // resync on 0x47 if needed, then take whole packets straight from the input
            while (len && data[0] != 0x47) {
                data++;
                len--;
            }
            while (len >= 188 && data[0] == 0x47) {
                ts_packet(data);
                data += 188;
                len -= 188;
            }
            if (len && data[0] != 0x47) {
                continue;
            }
        }
        size_t n = 188 - s_pkt_len < len ? 188 - s_pkt_len : len;
        memcpy(s_pkt + s_pkt_len, data, n);
        s_pkt_len += n;
        data += n;
        len -= n;
        if (s_pkt_len == 188) {
            ts_packet(s_pkt);
            s_pkt_len = 0;
        }
    }
    return true;
}

esp_err_t decoder_init(void)
{
    esp_audio_dec_register_default();
    esp_audio_simple_dec_register_default();
    // Own TS demux (the library's TS decoder lost ~8% of the frames); AAC with ADTS headers,
    // AAC-Plus on so HE-AAC v1/v2 variants work too.
    esp_aac_dec_cfg_t aac_cfg = ESP_AAC_DEC_CONFIG_DEFAULT();
    aac_cfg.aac_plus_enable = true;
    esp_audio_simple_dec_cfg_t cfg = {
        .dec_type = ESP_AUDIO_SIMPLE_DEC_TYPE_AAC, .dec_cfg = &aac_cfg, .cfg_size = sizeof(aac_cfg),
    };
    if (esp_audio_simple_dec_open(&cfg, &s_dec) != ESP_AUDIO_ERR_OK) {
        ESP_LOGE(TAG, "AAC decoder open failed");
        return ESP_FAIL;
    }
    s_pcm = heap_caps_malloc(s_pcm_size, MALLOC_CAP_SPIRAM);
    return s_pcm ? ESP_OK : ESP_ERR_NO_MEM;
}