Fixes ticket #15.

As previously discussed, the CrystalHD hardware returns exceptionally
useless information about interlaced h.264 content - to the extent
that it's not possible to distinguish most MBAFF and PAFF content until
it's too late.

In an attempt to compensate for this, I'm introducing two mechanisms:

1) Peeking at the picture number of the next picture

The hardware provides a capability to peek the next picture number. If
it is the same as the current picture number, then we are clearly dealing
with two fields and not a frame or fieldpair.

If this always worked, it would be all we need, but it's not guaranteed
to work. Sometimes, the next picture may not be decoded sufficiently
for the number to be known; alternately, a corruption in the stream may
cause the hardware to refuse to return the number even if the next
intact frame is decoded. In either case, the query will return 0.

If we are unable to peek the next picture number, we assume that the
picture is a frame/fieldpair and return it accordingly. If that turns
out to be incorrect, we discard the second field, and the user has
to live with the glitch. In testing, false detection can occur for
the first couple of seconds, and then the pipeline stabalizes and
we get correct detection.

2) Use the h264_parser to detect when individual input fields have
been combined into an output fieldpair.

I have multiple PAFF samples where this behaviour is detected. The
peeking mechanism described above will correctly detect that the
output is a fieldpair, but we need to know what the input type was
to ensure pipeline stability (only return one output frame per input
frame).

If we find ourselves with an output fieldpair, yet the input picture
type was a field, as reported by the parser, then we are dealing with
this case, and can make sure not to return anything on the next
decode() call.

Taken together, these allow us to remove the hard-coded hacks for
different h.264 types, and we can clearly describe the conditions
under which we can trust the hardware's claim that content is
interlaced.
Signed-off-by: Philip Langdale <philipl@overt.org>

Now that we know the type of the input picture, we have to bring
that information to the output picture to help identify its type.
We do this by adding a field to the opaque_list node.
Signed-off-by: Philip Langdale <philipl@overt.org>

As the hardware is unreliable, we will have to use the h.264 parser
to identify whether an input picture is a field or a frame. This
change loads the parser and extracts the picture type.
Signed-off-by: Philip Langdale <philipl@overt.org>

In preparation for adding additional fields to the node, return
the node instead of the pts value. This requires the caller to
free the node.
Signed-off-by: Philip Langdale <philipl@overt.org>

'git diff -w' confirmed to return nothing.
Signed-off-by: Philip Langdale <philipl@overt.org>

I found another MBAFF sample where the input:output pattern is
the same as mpeg2 and vc1 (fieldpair input, individual field output).
While I'm not sure how you can output individual fields from MBAFF,
if I apply the mpeg2/vc1 handling to this file, it plays correctly.

So, this changes the detection algorithm to handle the known cases.

Whitespace will be fixed in a separate change.
Signed-off-by: Philip Langdale <philipl@overt.org>

flv: Only parse keyframe index when the underlaying protocol allows seeking as we need to seek to read the index
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Current keyframes data parser unconditionally rewind metadata to the end
at the end of function. As result ALL metadata located after keyframes
index not parsed,
and as metadata object can have ANY placement inside metadata it can
lead to unpredictable result
(bitrate can not be found, etc.). As result FLV movie will not play at
all in such situation.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

FAQ could use some work. This updates a few little details.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

* qatar/master:
  lavf: bump minor and add an APIChanges entry for avformat cleanup
  lavf: get rid of ffm-specific stuff in avformat.h
Not pulled:  avio: deprecate av_protocol_next().
  avio: add a function for iterating though protocol names.
  lavf: rename a parameter of av_sdp_create from buff->buf
  lavf: rename avf_sdp_create to av_sdp_create.
  lavf: make av_guess_image2_codec internal
  avio: make URLProtocol internal.
  avio: make URLContext internal.
  lavf: mark av_pkt_dump(_log) for remove on $next+1 bump.
  lavf: use designated initializers for all protocols
  applehttp: don't use deprecated url_ functions.
  avio: move two ff_udp_* functions from avio_internal to url.h
  asfdec: remove a forgotten declaration of nonexistent function
  avio: deprecate the typedef for URLInterruptCB
Merged-by: Michael Niedermayer <michaelni@gmx.at>

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

This is more consistent with the rest of the API.

The new name is more consistent with the rest of the API.

It doesn't look very useful as a public function.

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

This is more readable and makes it easier to reorder URLProtocol
members.

There's no particular reason to pollute the namespace with a typedef for
it.

    * ffmpeg-mt/master:
DUPLICATE mingw32 compilation after 'unbreak avcodec_thread_init'
      pthread: validate_thread_parameters() ignored slice-threading being intentionally off
DUPLICATE Remove unnecessary parameter from ff_thread_init() and fix behavior
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

* qatar/master:
  proto: include os_support.h in network.h
  matroskaenc: don't write an empty Cues element.
  lavc: add a FF_API_REQUEST_CHANNELS deprecation macro
  avio: move extern url_interrupt_cb declaration from avio.h to url.h
  avio: make av_register_protocol2 internal.
  avio: avio_ prefix for url_set_interrupt_cb.
  avio: AVIO_ prefixes for URL_ open flags.
  proto: introduce listen option in tcp
  doc: clarify configure features
  proto: factor ff_network_wait_fd and use it on udp

Conflicts:
	ffmpeg.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

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

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

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

Idea borrowed from mplayer.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Fix compilation on systems without poll()

And hide request_channels AVOption under it.