On Mon, 2011-10-10 at 19:24 +0300, R?mi Denis-Courmont wrote: > Le lundi 10 octobre 2011 18:35:02 Pierre-Louis Bossart, vous avez ?crit : > > > Whether passing multiple format infos to negotiate digital passthrough, > > > or > > > setting one of the PA_STREAM_FIX_* flags on a record stream, I'm a bit > > > puzzled > > > how the buffering attributes are supposed to work. > > > > > > Most of the values are expressed in bytes. How should the application > > > negotiate certain timings then? The mapping of bytes to microseconds > > > depends > > > on the bitrate, which is not known to the application until after > > > PulseAudio > > > chooses the exact stream format and returns it. > > > > Actually there's no variable format. > > Yeah? I never said there were formats with variable bit rate. I said I don't > know the format, hence the bit rate, until after the buffer attributes have > already been transmitted. > > > With the IEC61937 format, the > > compressed frames are padded with zeroes to reach the same bitrate as 2ch, > > 16-bit PCM. In short if you have AC3 at 48kHz, PulseAudio will handle > > 1,536 Mbits/s. You can set the buffering as if it was a PCM stream. I > > would recommend you set -1 to all the fields and let PulseAudio select the > > best buffering for low-power. > > This is only an option if there are no latency constraints. You could pick the most conservative of your formats and then adjust after connecting using pa_stream_set_buffer_attr(). To do this the "right way", we'd need to change how stream setup is done to have an intermediate stage and it's quite a large change for benefits that don't seem to be worth the cost. -- Arun
