Group PJMEDIA_SPLITCOMB

group PJMEDIA_SPLITCOMB

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

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.

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)

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.

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.

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.