CM OPUS Encode

The cmOpusEncode is used to encode the audio/x-raw(PCM) data to audio/x-opus(OPUS) data by the OPUS library.

API Instructions

create/destroy

gpointer cm_opus_encode_create();
void cm_opus_encode_destroy(gpointer hd);

start/stop

void cm_opus_encode_start(gpointer hd);
void cm_opus_encode_stop(gpointer hd);

parameters

/* @type Supports 2049(generic), 2048(voice), 2051(low delay), default is 2048 */
void cm_opus_encode_set_audio_type(gpointer hd, int type);

/* @br:4000-65000, default 64000 */
void cm_opus_encode_set_bitrate(gpointer hd, int br);

/* @type Supports 0(cbr), 1(vbr), 2(constrained br), default is 1 */
void cm_opus_encode_set_bitrate_type(gpointer hd, int type);

/* @size Duration per frames in ms, supports 2(2.5), 5, 10, 20, 40, 60, default is 10 */
void cm_opus_encode_set_frame_size(gpointer hd, int size);

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_opus_encode_link_to_source(gpointer hd, gpointer src);
void cm_opus_encode_unlink(gpointer hd);

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

others

/* @return Encode output format, "audio/x-opus,..." */
const char* cm_opus_encode_get_caps_str(gpointer hd);

GstElement* cm_opus_encode_get_bin(gpointer hd);

Demo

Opus PV to PB Demo

Structure

Get raw data and encode to opus, then decode them and send to speaker to play.

Main codes

//The encode data will be send to here, push it to the decode
static GstFlowReturn _out_data_cb (GstBuffer *buffer, gpointer user_data) {
	if(opus_dec){
		//Push opus data to decode
		cm_opus_decode_push_buffer(opus_dec, buffer);
	}

	return GST_FLOW_OK;
}

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

    //Wait source media info ready
	if(!opus_enc && cm_audio_alsa_source_is_ready(alsa_src)){

        //Create opus dec
		opus_enc = cm_opus_encode_create();
		//Link opus encode to alsa source 
	  	cm_opus_encode_link_to_source(opus_enc, alsa_src);
		//Set callback to get opus data
	  	cm_opus_encode_set_data_callback(opus_enc, _out_data_cb, opus_enc);
        //Start encode
	  	cm_opus_encode_start(opus_enc);	
	}
    
	if(!opus_dec){
        //Create opus decode and start
		opus_dec = cm_opus_decode_create();
		cm_opus_decode_start(opus_dec);
	}

    //Wait opus decode prase media info done 
	if(!alsa_sink && cm_opus_decode_is_ready(opus_dec)){
        //Create sink
		alsa_sink = cm_audio_alsa_sink_create("hw:0,0"); 	

		//Link alsa sink to opus decode
  		cm_audio_alsa_sink_link_to_source(alsa_sink, opus_dec);	
  		cm_audio_alsa_source_start(alsa_sink);	
	}

For more details please refer to the demo file.

Test result

The speaker can hear the sound from the microphone.