[MPlayer-dev-eng] [patch] hwac3 fixes

[Arpi]

Hi,

> I received the following patch from Steven Brookes <stevenjb at mda.co.uk>.
> He is working on fixing the digital audio output of the dxr3 driver and 
> told me he fixed some bugs in mplayer along the way. I don't know shit 
> about hwac3 output so all I did was to make sure the patch applied 
> against latest cvs.
> This is from his e-mail to me:
> 
> "Secondly there is a patch to dec_audio.c and 
> ac3-iec958 to fix the -ac hwac3 codec stuff and to use liba52 to sync it.  
> Seems to work for everything I've thrown at and maintains sync for all audio 
> types through the DXR3."

patch applied (with some comments added and an unwanted change (in software
a52 decoder) removed)

now i understand how this whole hwac3 mess work.
it's very very tricky. it virtually decodes ac3 to LPCM packets, but really
it keeps the original compressed data padded by zeros. this way it's
constant bitrate, and sync is calculated just like for stereo PCM.
(so it bypass LPCM-capable media converters...)

so, every ac3 frame is translated to 6144 byte long tricky LPCM packet.
6144 = 4*(6*256) = 4 * samples_per_ac3_frame = LPCM size of uncompressed ac3
frame.

i wanna know if it works for sblive and other ac3-capable cards too?
(i can't test it, lack of ac3 decoder)

> Arpi: Thank you (you know for what)
I promised i'll do that - when i got time to test it.


A'rpi / Astral & ESP-team

--
mailto:arpi at thot.banki.hu
http://esp-team.scene.hu