At Fri, 26 Jun 2009 23:56:43 -0300, Guilherme wrote:
Takashi...
The base_address and the step sounds pretty clear to me.... just the offset I could not understand.
What the difference in being .first = 0 or .first = 2??? Could you provide please a more in depth explanation. I tried really hard find this but there is nothing related in the documentation.
area[0].addr = base_address; addr[0].first = 0; addr[0].step = 4; addr[1].addr = base_address; addr[1].first = 2; addr[1].step = 4;
P.S. being a stereo or a mono pipeline I understand... just the way the offset works that is not so clear to me.
Actually, the non-interleaved formats can be represented also with a single base_address (and is so in the actual implementation).
addr[0].addr = base_addr; addr[0].first = 0; addr[0].step = 2; addr[1].addr = base_addr; addr[1].first = mono_buffer_len; addr[1].step = 2; addr[2].addr = base_addr; addr[2].first = mono_buffer_len * 2; addr[2].step = 2; ...
The "first" is the offset of the first sample. The address of the first sample of the channel is simply calculated as addr + first. This is because just we want to keep the base address same to all channels as much as possible especially in mmap mode.
Takashi