CM AAC Encode

The cmAacEncode is used to encode the audio/x-raw(PCM) data to audio/mpeg(AAC) data by the library fdkaac.

API Instructions

create/destroy

gpointer cm_aac_encode_create();
void cm_aac_encode_destroy(gpointer hd);

start/stop

void cm_aac_encode_start(gpointer hd);
void cm_aac_encode_stop(gpointer hd);

parameters

/* @format Aac encode format, supports adts, adif, raw */
void cm_aac_encode_set_stream_format(gpointer hd, const char* format);

/* @br The aac bitrate */
void cm_aac_encode_set_bitrate(gpointer hd, int br);

/* @return Encode output format, "audio/mpeg,..." */
const char* cm_aac_encode_get_caps_str(gpointer hd);

data

The encoder needs to know the actual format of the input before encoding, so must ensure the source is ready to be linked(the media info is ready).

/* @src An audio/x-raw source(cmAlsaSrc, ...) */
void cm_aac_encode_link_to_source(gpointer hd, gpointer src);
void cm_aac_encode_unlink(gpointer hd);

/* @ cb data callback to get data */
void cm_aac_encode_set_data_callback(gpointerhd, cm_data_cb_ptrcb, gpointeruser_data);
void cm_aac_encode_remove_data_callback(gpointerhd, cm_data_cb_ptrcb, gpointeruser_data);

others

GstElement* cm_aac_encode_get_bin(gpointer hd);

Demo

Aac Encode Demo

Structure

Get raw data from the microphone then encode it to AAC.

Main codes

// The data will be send to here
static GstFlowReturn _out_data_cb (GstBuffer *buffer, gpointer user_data) {
    
    ......

	return GST_FLOW_OK;
}
static gboolean _main_loop(gpointer arg) {
	if(!pcm_hd) {
        // Create source and start
		pcm_hd = cm_audio_alsa_source_create("hw:0,0");
  		cm_audio_alsa_source_start(pcm_hd);
	}

    //Wait alsa source is ready to be linked
	if(!aac_hd && cm_audio_alsa_source_is_ready(pcm_hd)){		
		aac_hd = cm_aac_encode_create();

		//Link aac encode to alsa source
	  	cm_aac_encode_link_to_source(aac_hd, pcm_hd);

		//Set callback to get aac data
	  	cm_aac_encode_start(aac_hd);
	}

    ......
        
}

For more details please refer to the demo file.
Test result

The AAC data can be saved to the file and displayed on the PC.