[ALSA - driver 0002159]: ac3 passthrough not working on recent versions

bugtrack
2006-06-16T14:25:34Z

Last Modified: 06-16-2006 16:25 CEST
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Summary: ac3 passthrough not working on recent versions
Description:
Using the following AC3 passthrough with mplayer works:
Linux 2.4.31
alsa-driver 1.0.8-7 (debian stable packaged)

Using Linux 2.6.15 (both with alsa-driver 1.10rc3 that ships with the
kernel and
alsa-driver 1.0.11) it doesn't work. The reciever just says "unlock" and
stays quiet.

The only change is booting with different kernels, no other config or
hardware is touched, so this must be a driver regression.

The card is YMF-754 based, connected with coax spdif to my HK reciever.

If you need more info, just tell me and I'll dig it up.
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Mimosius - 06-16-06 13:37
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Hi Raymond,

yes, I'm really sure this patch breaks AC3 passthrough. A comparison of
the /proc/asound/card0/ymfpci registers against 1.0.9b (patched up to
1.0.11 without Clemens patch) and 1.0.11 (native) is included in my
previous note.

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Raymond - 06-16-06 16:25
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I don't have this card.

The DAC resolution of STAC9708 is 18-bit , this may mean that there is
2-bit gain when 16-bit audio pass through the hardware mixer.

But AC3 stream (passthrough) don't need any gain/attenutation.