examples/filtering_audio: fix frame leak.

The frame is not used after being added to the filter
graph, there is no need to keep the reference.
avcodec/mpegvideo_motion: Check P field references

If a reference is unavailable use a field from the current
picture
Fixes null pointer dereference

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Merge remote-tracking branch 'cigaes/master'

* cigaes/master:
  examples/filtering_audio: fix frame leak.

Merged-by: Michael Niedermayer <michaelni@gmx.at>
lavfi/vf_aspect: improve compatibility of parsing.

Try to accept both the old "num:den" and the new "num/den"
syntax. Fix "aspect=2" being ignored due to a missing den.

Also remove a duplicated #include.
ffmpeg: make -aspect work with -vcodec copy.
subtitles: introduce ASS codec id and use it.

Currently, we have a AV_CODEC_ID_SSA, which matches the way the ASS/SSA
markup is muxed in a standalone .ass/.ssa file. This means the AVPacket
data starts with a "Dialogue:" string, followed by a timing information
(start and end of the event as string) and a trailing CRLF after each
line. One packet can contain several lines. We'll refer to this layout
as "SSA" or "SSA lines".

In matroska, this markup is not stored as such: it has no "Dialogue:"
prefix, it contains a ReadOrder field, the timing information is not in
the payload, and it doesn't contain the trailing CRLF. See [1] for more
info. We'll refer to this layout as "ASS".

Since we have only one common codec for both formats, the matroska
demuxer is constructing an AVPacket following the "SSA lines" format.
This causes several problems, so it was decided to change this into
clean ASS packets.

Some insight about what is changed or unchanged in this commit:

  CODECS
  ------

  - the decoding process still writes "SSA lines" markup inside the ass
    fields of the subtitles rectangles (sub->rects[n]->ass), which is
    still the current common way of representing decoded subtitles
    markup. It is meant to change later.

  - new ASS codec id: AV_CODEC_ID_ASS (which is different from the
    legacy AV_CODEC_ID_SSA)

  - lavc/assdec: the "ass" decoder is renamed into "ssa" (instead of
    "ass") for consistency with the codec id and allows to add a real
    ass decoder. This ass decoder receives clean ASS lines (so it starts
    with a ReadOrder, is followed by the Layer, etc). We make sure this
    is decoded properly in a new ass-line rectangle of the decoded
    subtitles (the ssa decoder OTOH is doing a simple straightforward
    copy). Using the packet timing instead of data string makes sure the
    ass-line now contains the appropriate timing.

  - lavc/assenc: just like the ass decoder, the "ssa" encoder is renamed
    into "ssa" (instead of "ass") for consistency with the codec id, and
    allows to add a real "ass" encoder.

    One important thing about this encoder is that it only supports one
    ass rectangle: we could have put several dialogue events in the
    AVPacket (separated by a \0 for instance) but this would have cause
    trouble for the muxer which needs not only the start time, but also
    the duration: typically, you have merged events with the same start
    time (stored in the AVPacket->pts) but a different duration. At the
    moment, only the matroska do the merge with the SSA-line codec.

    We will need to make sure all the decoders in the future can't add
    more than one rectangle (and only one Dialogue line in it
    obviously).

  FORMATS
  -------

  - lavf/assenc: the .ass/.ssa muxer can take both SSA and ASS packets.
    In the case of ASS packets as input, it adds the timing based on the
    AVPacket pts and duration, and mux it with "Dialogue:", trailing
    CRLF, etc.

  - lavf/assdec: unchanged; it currently still only outputs SSA-lines
    packets.

  - lavf/mkv: the demuxer can now output ASS packets without the need of
    any "SSA-lines" reconstruction hack. It will become the default at
    next libavformat bump, and the SSA support will be dropped from the
    demuxer. The muxer can take ASS packets since it's muxed normally,
    and still supports the old SSA packets. All the SSA support and
    hacks in Matroska code will be dropped at next lavf bump.

[1]: http://www.matroska.org/technical/specs/subtitles/ssa.html
lavfi/mptestsrc: fix invalid access in case of negative linesize

In particular, fix crash with:
ffplay -f lavfi mptestsrc,vflip
avformat: Dont stop probing before the whole id3 tag is read

When a file appears to start with a id3 tag and appears to
also be something else, then try to increase the probe buffer
size if its below its limit.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Merge remote-tracking branch 'cigaes/master'

* cigaes/master:
  ffmpeg: make -aspect work with -vcodec copy.
  lavfi/vf_aspect: improve compatibility of parsing.

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Fix multithreaded MPEG-4 decoding.

Regression since c10d498bfd246a40cc7830838b74e18a79418839.
Unfortunately ff_thread_get_format can only be called from
a separate decode thread, running it during init will fail.
Fixes for that are welcome, for now just revert back to
calling avctx->get_format directly, which is correct
but having to decide on a case-by-case basis which approach
to use is a bit messy.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
mxfdec: fix return variable type for avio_seek

Signed-off-by: Marton Balint <cus@passwd.hu>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
fate/gif: create meaningful gif encoding tests.
lavc/utils: merge side data after video encode.

This allows encoders to communicate side data to the muxers.
gif: use only one graphic control extension block per image.

The encoder now doesn't produce any extra graphic control extension
block anymore. Only the image is encoded, and the muxer writing
its own GCE containing notably the timing information now includes the
optional palette transmitted through packet side data.

This commit avoid setting clashes between the two GCE, and reduce the
size of the generated file with pal8 output.
lavf/gif: fix timing.

pkt->duration can not be used since the values are only based on frame
rate.
lavfi/afade: use AV_OPT_TYPE_DURATION

Signed-off-by: Paul B Mahol <onemda@gmail.com>