There is a cause to add several stream types to pulse audio for the support of all the hardware's features. Current stream types can be described by ~3 dimensions (channels, bits, bit-format, rate). The first that would be necessary is raw. That is pre-mixed information that can't be further mixed. Each stream is to be given a priority ~0-15 where default for existing streams is 7 and raw streams default to 11. This makes pre-mixed sounds cause all other sounds to be silenced so they can be played. The effect is the ability to play videos(ac3/dts) while other applications are emitting data, no need to close browser/flash. The first optional extension is the ability to indicate to sources that they will not be played in the form of a warning returned to data passed and a signal indicating that play can continue. A notable improvement over the current ALSA-passthrough is the addition of framing. Currently pausing and restarting a pre-mixed stream causes loud pops and clicks, this is undesirable and as such pulse audio can offer a solution. The definition of atoms(the smallest part that can be presented to hardware as a whole). This gives several parameters... Variable sized atoms(yes/no), Time|duration of packet(*taken from size, constant, variable). This is going to add information to the pre-mixed stream, in the case of ac3/dts the size of each atom would be included as out-of-band information as well as perhaps the wall-clock length, though I believe that ac3/dts streams are already a set bits/sec. The next stream type should be a pulse audio internal type(s) used for the mixing of mp3/ac3 and perhaps dts streams. It's my understanding that ac3 uses vectors to describe 6 channels of sound much like a 2ch mp3. If I'm not mistaken these vectors can be combined mathematically as-is to represent the combination of two sounds. This would be a great achivement over any uncompress/combine/recompress senerio. It's absolutely true that an ac3 stream can not be mixed with any other stream, but it's false that a representation of that stream can not be mixed. These new stream types would be used to carry a representation of the original ac3 stream in a format that pulse-audio can standardize on and use... Perhaps for now these representations would simply be 6ch PCM. Though in that case a strem type of ac3 would be necessary. -- Mike Mestnik Technical Team ___ Nagios Enterprises, LLC Email: mmestnik at nagios.com Web: www.nagios.com
