[vdr] Re: AC3 with -a

["Dr. Werner Fink" <werner@suse.de>]

On Thu, Dec 12, 2002 at 06:53:02PM +0100, Jörg Knitter wrote:
> 
> There was a discussion about this -a option in VDR 1.1.x. The current
> situation seems to be (or did I oversee something?):
> - No Live-AC3 over soundcard or DVB, only if you play a recorded VDR
> file or if you start recording
> - No AC3 when playing back DVDs :-((((((((((((((
> 
> There is patch in the forum of bashy.bei.t-online.de, that always sets
> VDR to transfer mode so Live-AC3 is always enabled, don´t know if this
> also works with DVD.
> 
> I am also still waiting for a solution but with VDR 1.2 coming closer I
> am confident that we won´t have to wait too long for this feature to
> work :-)...

Hmm ... perhaps I should port my current LiveAC3 patch for VDR 1.0.2 to
newest 1.1.19. In the last few months I've worked heavily on solving
underrun problem of the sound buffer of the CMI 8738 sound chip (the
reference clock is about 150ppm faster than the rate of the live
AC3 stream from Pro7).

Nevertheless this would require to have something like hooks where I
can add Bypass()/EndBypass() in the cases of channnel switching and
starting/ending recordings during loading such a plugin.  Also some
changes in the DVB driver would be nice to reduce live AC3 stream
leaks, video corruption during replay, and reducing ARM crashes
all during OSD popups (I'm currently use a heavily patched old DVB
driver 0.9.4-2002-04-01 with new Firmware ... nevertheless the ideas
behind this changes should be portable to NEWSTRUCT driver).

@Klaus: Does 1.1.19 have something like a hook interface at the begin
and end of switching channels and starting/ending recordings?

@Holger: Is there interest on some of my changes for the DVB driver?

    Werner

PS: With the new firmware it should be possible to warp/embed a fresh filter
    out AC3 into linear PCM in the same manner as done in my LiveAC3 patch for
    VDR. I've test this with dvb_filter.c and a simple addon head file in user
    space, see my mail at linux-dvb@linuxtv.org with
    "Sound, live AC3, timings and reinsert into DVB (AV711x)"

    In other words: at callback for filtering the private stream 1, the
    AC3 data should not put into the readout ringbuffer for the user space
    program but into the ringbuffer of the audio ipack with instant_repack()
    which does the aC3 embedding into a lPCM stream.
    If the ARM would fast enough this could also done within the firmware
    directly on the TS ... but this may reduce the time shift feature.


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