[MPlayer-dev-eng] MPEG to S/PDIF passthrough

[Ulion]

2008/3/7, Ilkka Karvinen <kartsan at gmail.com>:
> On Thursday 06 March 2008 13:57, Ulion wrote:
>  > 2008/3/6, Ulion <ulion2002 at gmail.com>:
>  > > 2008/3/5, Ilkka Karvinen <kartsan at gmail.com>:
>  > > > There have been no comments on this patch. I'm wondering if there could
>  > > > be
>  > > >
>  > >  >  people around here who have a home theater amplifier which supports
>  > >  > MPEG audio? It would be interesting to hear if this feature works with
>  > >  > your hardware. Especially if you are running mplayer on a bigendian
>  > >  > machine since I can't currently test this code on a such machine.
>  > >  >
>  > >  >  If your amplifier supports AC3/DTM decoding, its DSP may also support
>  > >  >  MPEG audio. My old Harman Kardon amplifier uses Cirrus Logic's DSP
>  > >  >  which supports it and that was my initial reason to start
>  > >  > investigating this stuff.
>  > >  >
>  > >  >  I send attached diff that Ulion made for me if you would like to give
>  > >  > a try to this feature. It adds new codec hwmp3 which redirects the
>  > >  > MPEG frames to hardware via S/PDIF.
>  > >  >
>  > >  >  I have tested it and it works with mp3 audio files and video files
>  > >  > with mp3 audio track. However, some mp3 files do not work and I don't
>  > >  > know why. My guess is that their frames are not recognised by my
>  > >  > hardware. There are no similarities with the failing samples. Another
>  > >  > sample with equal parameters (header bits are the same) may work
>  > >  > flawlessly.
>  > >
>  > > found some problem about this patch:
>  > >
>  > >  in decode_audio():
>  > >  +  uint16_t *buf16 = (uint16_t *)buf;
>  > >
>  > >  should this be put into the while loop and looks like this:
>  > >
>  > >  +  uint16_t *buf16 = (uint16_t *)(buf + toc);
>  >
>  > I mean:
>  > +  uint16_t *buf16 = (uint16_t *)(buf + tot);
>
>
> What is the problem?
>
>
>  > and there's another type value for 'MPEG-2 with extension' it should
>  > be 6 instead of 5.
>  > there's also a type value for 'MPEG-2 layer-3 low sampling frequency'
>  > referred by IEC 61937-4.
>  > should these two type be handled in the code?
>
>
> Those MPEG-2 types were so rare that I didn't put them there. Actually
>  there was type 4 in my original implementation which is MPEG-1 layer-1
>  but even that I've never seen so I dropped it. I can add them to this codec
>  to make sure. I'm pretty sure that the documentation of the DSP in my
>  amplifier said it supports only MPEG-1 layer 3 so those formats were
>  unknown for it anyway...

so what about MPEG-2 with extension? is there a flag in mp3 header to
indicate it? if there is, we should use it with proper type value.
and the buf16 code problem I metioned earlier, is your problem with
some mp3 files resolved after fix it?

-- 
Ulion