ESP-ADF音频框架 -- stream

由于工作需要，需要ESP32对MP3流进行软解码，为了通过文件进行实时流模拟，研究了ESP-ADF中的流类型。相关流类型及支持的操作如下表所示。

思路一

由于MP3流本质上就是二进制数据流，所以以嵌入式二进制流作为前端第一级输入，末端输出采取FatFs流，写入文件中，具体流程如下。

[sdcard] --> 嵌入式二进制文件流 --> mp3_decoder --> fatfs_stream_writer --> [sdcard]

根据应用示例player/pipeline_embed_flash_ton所示，嵌入式二进制文件流在烧录过程中已经将MP3文件写入到flash中，ESP-ADF中没有提供具体的数据流写入API（可能ESP-IDF中有对flash进行写入的API），即没办法对数据进行动态更新，此外嵌入式二进制文件流不支持AUDIO_STREAM_WRITER，所以思路1不可行。

思路二

ESP-ADF框架提供了两种方式对流数据进行处理，分别是基于Pipeline和Element。Pipeline相对于Element，中间变量环节已经由Pipeline进行实现，更加易于管理；而Element更加容易深入了解具体的调用流程，但各个Element之间需要构建缓存空间进行数据交互及输入输出进行重定向。

基于Pipeline方式

基于Element方式

 参照示例recorder/element_wav_amr_sdcard及recorder/element_cb_sdcard_amr， 为了实现流模拟，通过（fopen，fread）读取sdcard文件数据流，并写入ringbuf1中，定义为ringbuf1的输入，将输出定义为decoder的输入。具体流程如下：

[sdcard] --> FILE --> mp3_decoder --> fatfs_stream_writer --> [sdcard]

相应的测试代码如下：

void app_main() {ringbuf_handle_t ringbuf01, ringbuf12;audio_element_handle_t mp3_decoder, fatfs_stream_writer;ESP_LOGI(TAG, " Create mp3 decoder to decode mp3 file");mp3_decoder_cfg_t mp3_cfg = DEFAULT_MP3_DECODER_CONFIG();mp3_decoder = mp3_decoder_init(&mp3_cfg);ESP_LOGI(TAG, " Create fatfs stream to write data to sdcard");fatfs_stream_cfg_t fatfs_cfg_w = FATFS_STREAM_CFG_DEFAULT();fatfs_cfg_w.type = AUDIO_STREAM_WRITER;fatfs_stream_writer = fatfs_stream_init(&fatfs_cfg_w);audio_element_info_t music_info = {0};audio_element_getinfo(mp3_decoder, &music_info);audio_element_setinfo(fatfs_stream_writer, &music_info);audio_element_set_uri(fatfs_stream_writer, "/sdcard/out.wav");ringbuf01 = rb_create(RING_BUFFER_SIZE, 1);rb_reset(ringbuf01);
//    audio_element_set_output_ringbuf(i2s_stream_reader, ringbuf01);audio_element_set_input_ringbuf(mp3_decoder, ringbuf01);ringbuf12 = rb_create(RING_BUFFER_SIZE, 1);rb_reset(ringbuf12);audio_element_set_output_ringbuf(mp3_decoder, ringbuf12);audio_element_set_input_ringbuf(fatfs_stream_writer, ringbuf12);audio_element_set_event_callback(mp3_decoder, audio_element_event_handler, NULL);audio_element_set_event_callback(fatfs_stream_writer, audio_element_event_handler, NULL);FILE *fin = fopen("/sdcard/in.mp3", "r");int num = 0;// memset(buffer, 0, sizeof(buffer));char *tmp;tmp = (char *)malloc(RING_BUFFER_SIZE);int readLen = fread(tmp, sizeof(char), RING_BUFFER_SIZE, fin);int ret = rb_write(ringbuf01, tmp, readLen, 0);;free(tmp);tmp = NULL;printf("num: %d, readLen: %d\n", num++, ret);audio_element_run(mp3_decoder);audio_element_run(fatfs_stream_writer);audio_element_resume(mp3_decoder, 0, 0);audio_element_resume(fatfs_stream_writer, 0, 0);while (1){memset(buffer, 0, sizeof(buffer));readLen = fread(buffer, sizeof(char), RING_BUFFER_SIZE, fin);write_file_ringbuf(ringbuf01, buffer, readLen);printf("num: %d, readLen: %d\n", num++, readLen);if (feof(fin)){printf("finish\n");break;}}ESP_LOGI(TAG, "Release all resources");audio_element_deinit(fatfs_stream_writer);audio_element_deinit(mp3_decoder);rb_destroy(ringbuf01);rb_destroy(ringbuf12);
}

但是经测试，会导致系统崩溃，还需做进一步验证。

思路三

由于需要获取输入流的控制权，所以该流类型需要支持AUDIO_STREAM_WRITER。对具体的流类型进行逐个排除。

 此外原始流提供具体的读写API

int raw_stream_write(audio_element_handle_tpipeline, char *buffer, int buf_size);
int raw_stream_read(audio_element_handle_tpipeline, char *buffer, int buf_size);

static void raw_write_task(void *para)
{char *uri = (char *)para;char *buf = audio_calloc(1, 4096);AUDIO_MEM_CHECK(TAG, buf, return;);fatfs_stream_cfg_t fatfs_cfg = FATFS_STREAM_CFG_DEFAULT();fatfs_cfg.task_stack = 0;fatfs_cfg.type = AUDIO_STREAM_READER;audio_element_handle_t fs = fatfs_stream_init(&fatfs_cfg);audio_element_set_uri(fs, uri);audio_element_process_init(fs);audio_element_run(fs);ESP_LOGI(TAG, "Raw writing..., URI:%s", uri);while (raw_task_run_flag) {int ret = audio_element_input(fs, buf, 4096);printf(".");if (AEL_IO_OK == ret) {ESP_LOGE(TAG, "Raw write done");audio_player_raw_feed_finish();break;}audio_player_raw_feed_data((uint8_t *)buf, 4096);}audio_element_process_deinit(fs);audio_element_deinit(fs);free(buf);ESP_LOGI(TAG, "Raw write stop");vTaskDelete(NULL);
}void raw_write(const char *p)
{raw_task_run_flag = true;if (xTaskCreate(raw_write_task, "RawWriteTask", 3072, (void *)p, 5, NULL) != pdPASS) {ESP_LOGE(TAG, "ERROR creating raw_write_task task! Out of memory?");}
}

结合上述说明，具体流程如下

[sdcard] --> FILE -->raw_stream_writer--> mp3_decoder --> fatfs_stream_writer --> [sdcard]

具体实现代码如下

static void raw_write_task(void *para)
{char *buf = audio_calloc(1, MP3_PACK_SIZE);AUDIO_MEM_CHECK(TAG, buf, return;);ESP_LOGI(TAG, "Raw writing...\n");FILE *fin = fopen("/sdcard/test.mp3", "r");while (raw_task_run_flag) {int length = fread(buf, 1, MP3_PACK_SIZE, fin);printf("length: %d\n", length);if (length <= 0) {ESP_LOGE(TAG, "Raw write done");fclose(fin);audio_element_set_ringbuf_done(raw_stream_writer);audio_element_finish_state(raw_stream_writer);break;}raw_stream_write(raw_stream_writer, buf, length);
//        audio_player_raw_feed_data((uint8_t *)buf, 4096);}free(buf);ESP_LOGI(TAG, "Raw write stop");vTaskDelete(NULL);
}void app_main(void)
{audio_pipeline_cfg_t pipeline_cfg = DEFAULT_AUDIO_PIPELINE_CONFIG();audio_pipeline_handle_t pipeline = audio_pipeline_init(&pipeline_cfg);mem_assert(pipeline);raw_stream_cfg_t raw_cfg = RAW_STREAM_CFG_DEFAULT();raw_cfg.type = AUDIO_STREAM_WRITER;raw_stream_writer = raw_stream_init(&raw_cfg);ESP_LOGI(TAG, " Create mp3 decoder to decode mp3 file");mp3_decoder_cfg_t mp3_cfg = DEFAULT_MP3_DECODER_CONFIG();mp3_decoder = mp3_decoder_init(&mp3_cfg);ESP_LOGI(TAG, " Create fatfs stream to write data to sdcard");fatfs_stream_cfg_t fatfs_cfg_w = FATFS_STREAM_CFG_DEFAULT();fatfs_cfg_w.type = AUDIO_STREAM_WRITER;fatfs_stream_writer = fatfs_stream_init(&fatfs_cfg_w);ESP_LOGI(TAG, "[2.3] Register all elements to audio pipeline");audio_pipeline_register(pipeline, raw_stream_writer, "raw_writer");audio_pipeline_register(pipeline, mp3_decoder, "mp3");audio_pipeline_register(pipeline, fatfs_stream_writer, "fatfs_writer");ESP_LOGI(TAG, "[2.4] Link it together raw_stream_writer-->mp3_decoder-->fatfs_stream_writer-->[sdcard]");const char *link_tag[3] = {"raw_writer","mp3", "fatfs_writer"};audio_pipeline_link(pipeline, &link_tag[0], 3);ESP_LOGI(TAG, "[ 4 ] Set up  event listener");audio_event_iface_cfg_t evt_cfg = AUDIO_EVENT_IFACE_DEFAULT_CFG();audio_event_iface_handle_t evt = audio_event_iface_init(&evt_cfg);ESP_LOGI(TAG, "[4.1] Listening event from all elements of pipeline");audio_pipeline_set_listener(pipeline, evt);raw_task_run_flag = true;if (xTaskCreate(raw_write_task, "RawWriteTask", 3072, NULL, 5, NULL) != pdPASS) {ESP_LOGE(TAG, "ERROR creating raw_write_task task! Out of memory?");}audio_element_set_uri(fatfs_stream_writer, "/sdcard/out.wav");audio_pipeline_run(pipeline);while (1) {audio_event_iface_msg_t msg;esp_err_t ret = audio_event_iface_listen(evt, &msg, portMAX_DELAY);if (ret != ESP_OK) {continue;}if (msg.source_type == AUDIO_ELEMENT_TYPE_ELEMENT) {// Set music info for a new song to be playedif (msg.source == (void *) mp3_decoder&& msg.cmd == AEL_MSG_CMD_REPORT_MUSIC_INFO) {audio_element_info_t music_info = {0};audio_element_getinfo(mp3_decoder, &music_info);ESP_LOGI(TAG, "[ * ] Received music info from mp3 decoder, sample_rates=%d, bits=%d, ch=%d, duration=%d",music_info.sample_rates, music_info.bits, music_info.channels, music_info.duration);audio_element_setinfo(fatfs_stream_writer, &music_info);continue;}/* Stop when the last pipeline element (fatfs_stream_writer in this case) receives stop event */if (msg.source_type == AUDIO_ELEMENT_TYPE_ELEMENT && msg.source == (void *) fatfs_stream_writer&& msg.cmd == AEL_MSG_CMD_REPORT_STATUS&& (((int)msg.data == AEL_STATUS_STATE_STOPPED) || ((int)msg.data == AEL_STATUS_STATE_FINISHED)|| ((int)msg.data == AEL_STATUS_ERROR_OPEN))) {ESP_LOGW(TAG, "[ * ] Stop event received");break;}}}ESP_LOGI(TAG, "[ 6 ] Stop audio_pipeline");audio_pipeline_stop(pipeline);audio_pipeline_wait_for_stop(pipeline);audio_pipeline_terminate(pipeline);audio_pipeline_unregister(pipeline, raw_stream_writer);audio_pipeline_unregister(pipeline, mp3_decoder);audio_pipeline_unregister(pipeline, fatfs_stream_writer);/* Terminate the pipeline before removing the listener */audio_pipeline_remove_listener(pipeline);/* Make sure audio_pipeline_remove_listener is called before destroying event_iface */audio_event_iface_destroy(evt);/* Release all resources */audio_pipeline_deinit(pipeline);audio_element_deinit(raw_stream_writer);audio_element_deinit(mp3_decoder);audio_element_deinit(fatfs_stream_writer);}

经测试，可以实现解码，输入流可控，符合具体需求。

参考链接

https://docs.espressif.com/projects/esp-adf/zh_CN/latest/api-reference/streams/index.html#