Spotted-by: ubitux

Also add notice about ffmpeg -override_ffserver option.

Also make it accept the more consistent behavior (boolean option set to
true when specified).

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

* qatar/master:
  dcadec: add disable_xch private option.

Conflicts:
	libavcodec/dcadec.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit '220494ad':
  dcadec: treat all 2-channel modes as Stereo in dca_downmix.
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit 'aaa44d02':
  dca: support mixing LFE in dca_downmix.

Conflicts:
	libavcodec/dcadec.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit '149438cf':
  dca: improve default stereo downmix coefficients.
Merged-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

* commit '44b17d79':
  dca: extract core substream's embedded downmix coeffcient codes, if present.

Conflicts:
	libavcodec/dcadata.h
	libavcodec/dcadec.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit '27245b4e':
  dca: remove embedded downmix coefficient extraction.

Conflicts:
	libavcodec/dcadata.h
	libavcodec/dcadec.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit 'b6d5e6aa':
  dca: convert dca_default_coeffs to float.

Conflicts:
	libavcodec/dcadata.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit '25609b63':
  dcadec: store the stereo downmix coefficients as float in the DCAContext.
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit '89de5157':
  dcadec: implement request_channel_layout.

Conflicts:
	libavcodec/dcadec.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

It has no effect, and it was never documented.

In particular, abort immediately in case of memory error, avoid potential
crashes.

* commit 'cf7860db':
  x86: dsputil: Suppress deprecation warnings for XvMC bits
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit 'd1916d13':
  dsputil/pngdsp: fix signed/unsigned type in end comparison

Conflicts:
	libavcodec/dsputil.c

See: 454a11a1Merged-by: Michael Niedermayer <michaelni@gmx.at>

This supplements the deprecated request_channels-based control of XCh decoding.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

The check for (prim_channels > 2) before calling dca_downmix made these
cases unreachable, but now 2.1 layouts will go through the downmix code.
Having dual mono, Lt/Rt and sum-difference layouts print errors when
regular Stereo doesn't seems pointless.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Embedded downmix coefficients can use this.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Previous coefficients were producing a non-normalized, incorrect Lt/Rt downmix.

The new coefficients produce a standard Lo/Ro downmix with 3dB attenuation.

This should match the typical default coefficients used by DTS encoders.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

As per ETSI TS 102 114 V1.4.1 specification.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

It was based on an old, seemingly incorrect specification, so default
coefficients were always used anyway.
Signed-off-by: Anton Khirnov <anton@khirnov.net>