Media channel splitter/combiner

Split and combine multiple mono-channel media ports into a single multiple-channels media port. More...

Functions
pj_status_t	pjmedia_splitcomb_create (pj_pool_t *pool, unsigned clock_rate, unsigned channel_count, unsigned samples_per_frame, unsigned bits_per_sample, unsigned options, pjmedia_port **p_splitcomb)
pj_status_t	pjmedia_splitcomb_set_channel (pjmedia_port *splitcomb, unsigned ch_num, unsigned options, pjmedia_port *port)
pj_status_t	pjmedia_splitcomb_create_rev_channel (pj_pool_t *pool, pjmedia_port *splitcomb, unsigned ch_num, unsigned options, pjmedia_port **p_chport)

Detailed Description

This section describes media port to split and combine media channels in the stream.

A splitter/combiner splits a single stereo/multichannels audio frame into multiple audio frames to each channel when put_frame() is called, and combines mono frames from each channel into a stereo/multichannel frame when get_frame() is called. A common application for the splitter/ combiner is to split frames from stereo to mono and vise versa.

Function Documentation

pjmedia_splitcomb_create()

pj_status_t pjmedia_splitcomb_create	(	pj_pool_t *	pool,
		unsigned	clock_rate,
		unsigned	channel_count,
		unsigned	samples_per_frame,
		unsigned	bits_per_sample,
		unsigned	options,
		pjmedia_port **	p_splitcomb
	)

Create a media splitter/combiner with the specified parameters. When the splitter/combiner is created, it creates an instance of pjmedia_port. This media port represents the stereo/multichannel side of the splitter/combiner. Application needs to supply the splitter/ combiner with a media port for each audio channels.

Parameters

pool	Pool to allocate memory to create the splitter/ combiner.
clock_rate	Audio clock rate/sampling rate.
channel_count	Number of channels.
samples_per_frame	Number of samples per frame.
bits_per_sample	Bits per sample.
options	Optional flags.
p_splitcomb	Pointer to receive the splitter/combiner.

Returns

PJ_SUCCESS on success, or the appropriate error code.

pjmedia_splitcomb_set_channel()

pj_status_t pjmedia_splitcomb_set_channel	(	pjmedia_port *	splitcomb,
		unsigned	ch_num,
		unsigned	options,
		pjmedia_port *	port
	)

Supply the splitter/combiner with media port for the specified channel number. The media port will be called at the same phase as the splitter/combiner; which means that when application calls get_frame() of the splitter/combiner, it will call get_frame() for all ports that have the same phase. And similarly for put_frame().

Parameters

splitcomb	The splitter/combiner.
ch_num	Audio channel starting number (zero based).
options	Must be zero at the moment.
port	The media port.

Returns

PJ_SUCCESS on success, or the appropriate error code.

pjmedia_splitcomb_create_rev_channel()

pj_status_t pjmedia_splitcomb_create_rev_channel	(	pj_pool_t *	pool,
		pjmedia_port *	splitcomb,
		unsigned	ch_num,
		unsigned	options,
		pjmedia_port **	p_chport
	)

Create a reverse phase media port for the specified channel number. For channels with reversed phase, when application calls put_frame() to the splitter/combiner, the splitter/combiner will only put the frame to a buffer. Later on, when application calls get_frame() on the channel's media port, it will return the frame that are available in the buffer. The same process happens when application calls put_frame() to the channel's media port, it will only put the frame to another buffer, which will be returned when application calls get_frame() to the splitter's media port. So this effectively reverse the phase of the media port.

Parameters

pool	The pool to allocate memory for the port and buffers.
splitcomb	The splitter/combiner.
ch_num	Audio channel starting number (zero based).
options	Normally is zero, but the lower 8-bit of the options can be used to specify the number of buffers in the circular buffer. If zero, then default number will be used (default: 8). The second lowest 8 bits can be used to specify the options for the underlying delay buffer (see pjmedia_delay_buf_flag for the possible options).
p_chport	The media port created with reverse phase for the specified audio channel.

Returns

PJ_SUCCESS on success, or the appropriate error code.