The option is used to sort the streams by program.
Signed-off-by: Florent Tribouilloy <florent.tribouilloy@smartjog.com>
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
Based on the libavfilter SOC filter by Vitor Sessak, with the following additions:
* integer arithmetic
* bilinear interpolation
* RGB path
* configurable parametric angle, output width and height
Address trac issue #1500.
See thread:
Subject: [FFmpeg-devel] [WIP] rotate filter(s)
Date: 2010-10-03 17:35:49 GMT
Based on the work of Jeff Moguillansky <Jeff.Moguillansky@am.sony.com>.
See thread:
Subject: [FFmpeg-devel] x11 output device for libavdevice
Date: Wed, 10 Apr 2013 23:10:47 +0000
* commit '2d2d6a4883479403798f4ed46941d5b365823570':
lavf: add a raw WavPack muxer.
apetag: add support for writing APE tags
matroskaenc: support muxing WavPack
Conflicts:
libavformat/Makefile
libavformat/allformats.c
libavformat/apetag.h
libavformat/version.h
libavformat/wvenc.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* commit '728214992e3698305550c1762f973d2ac567f016':
vc1dec: Remove interlaced warning
vc1dec: Fix mixed field/frame intensity compensation
vc1dec: Match addressing between compensation and MC in vc1_mc_4mv_chroma4
vc1dec: Handle top and bottom blocks in vc1_mc_4mv_chroma4() differently if needed
vc1dec: Fix doxy for vc1_mc_4mv_chroma4()
vc1dec: Drop old use_ic code from vc1_b_mc
vc1: Use shuffled use_ic instead of equally shuffled mv_mode
vc1dec: Implement intensity compensation for vc1_interp_mc()
Conflicts:
Changelog
libavcodec/vc1dec.c
libavcodec/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Some fixes provided by Paul B Mahol <onemda@gmail.com>
and Michael Niedermayer <michaelni@gmx.at> and me.
Signed-off-by: Diego Biurrun <diego@biurrun.de>
Signed-off-by: Kostya Shishkov <kostya.shishkov@gmail.com>
* commit 'e3b225a4fe0ff1e64a220b757c6f0a5cf9258521':
matroskaenc: add an option to put the index at the start of the file
Conflicts:
doc/muxers.texi
libavformat/matroskaenc.c
libavformat/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* commit 'a83c0da539fb07260310bc3b34056239d2b138b2':
avconv: make -t insert trim/atrim filters.
The filter insertion code is merged but disabled as it is buggy.
For example it fails in various ways when used with -s with some files.
Also the trimming is arguably less accurate than the default without
filters in some cases.
These issues should be fixed before auto inserting the filters,
until then the user can explicitly add a trim/atrim filter when one is
wanted.
Conflicts:
Changelog
ffmpeg.c
ffmpeg_filter.c
tests/ref/fate/bethsoft-vid
tests/ref/lavf/aiff
tests/ref/lavf/asf
tests/ref/lavf/au
tests/ref/lavf/avi
tests/ref/lavf/dpx
tests/ref/lavf/ffm
tests/ref/lavf/gxf
tests/ref/lavf/jpg
tests/ref/lavf/mkv
tests/ref/lavf/mmf
tests/ref/lavf/mov
tests/ref/lavf/mpg
tests/ref/lavf/nut
tests/ref/lavf/ogg
tests/ref/lavf/pcx
tests/ref/lavf/png
tests/ref/lavf/rm
tests/ref/lavf/ts
tests/ref/lavf/voc
tests/ref/lavf/voc_s16
tests/ref/lavf/wav
Merged-by: Michael Niedermayer <michaelni@gmx.at>
This makes -t sample-accurate for audio and will allow further
simplication in the future.
Most of the FATE changes are due to audio now being sample accurate. In
some cases a video frame was incorrectly passed with the old code, while
its was over the limit.
vidstabdetect and vidstabtransform common functions for interfacing
vid.stab are in libavfilter/vidstabutils.c
Signed-off-by: Georg Martius <martius@mis.mpg.de>
Based on the 2007 GSoC project from Kamil Nowosad <k.nowosad@students.mimuw.edu.pl>
Updated to current programming standards, style and many more small
fixes by Diego Biurrun <diego@biurrun.de>.
Signed-off-by: Diego Biurrun <diego@biurrun.de>
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
* qatar/master:
FATE: add a test for the interlace filter
lavfi: new interlace filter
Conflicts:
Changelog
configure
doc/filters.texi
libavfilter/Makefile
libavfilter/allfilters.c
tests/fate/filter.mak
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* commit '2e81acc687e64d15dd93c74793060bb5a233f44d':
x86inc: Fix number of operands for cmp* instructions
af_channelmap: fix uninitialized variable use introduced in ba8efac977
lavfi: add a bump and docs entries for the AVOptions switch
Conflicts:
Changelog
doc/APIchanges
libavfilter/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* commit '1ae44c87c924b69a0657256fbaa8ad140df2f27c':
lavfi/gradfun: remove rounding to match C and SSE code.
lavfi/gradfun: fix dithering in MMX code.
lavfi/gradfun: fix rounding in MMX code.
lavfi/gradfun: do not increment DC pointer for odd values.
fate: filter: Add dependencies
avconv: add options for reading filtergraphs from a file.
Conflicts:
Changelog
doc/ffmpeg.texi
doc/filters.texi
ffmpeg.h
ffmpeg_opt.c
libavfilter/vf_gradfun.c
tests/fate/filter.mak
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* commit '666fe5da47d127074be7f0e2bac93db6af8b4a30':
atomic: Exclude the unsupported implementation headers from checkheaders
avconv: do not silently ignore unused codec AVOptions.
Conflicts:
ffmpeg_opt.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Print an error and abort when the option is of the wrong type (decoding
for output file or vice versa), since this could never be correct for
any input or output configuration.
Print a warning and continue when the option is of the correct type,
just unused, so same commandlines can be reused for different kinds of
input or output files.
* commit '2f3bada63e57345329c4f9b48e9b81b5cfc03d05':
lavf: Add a protocol for SRTP encryption/decryption
rtsp: Support decryption of SRTP signalled via RFC 4568 (SDES)
Conflicts:
libavformat/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
This only takes care of decrypting incoming packets; the outgoing
RTCP packets are not encrypted. This is enough for some use cases,
and signalling crypto keys for use with outgoing RTCP packets
doesn't fit as simply into the API. If the SDP demuxer is hooked
up with custom IO, the return packets can be encrypted e.g. via the
SRTP protocol.
If the SRTP keys aren't available within the SDP, the decryption
can be handled externally as well (when using custom IO).
Signed-off-by: Martin Storsjö <martin@martin.st>
* commit '44e065d56c87d6a9d0effccec5f31517f72924ec':
vdpau: Add context and common helpers for hwaccel support
Conflicts:
Changelog
doc/APIchanges
libavcodec/vdpau.h
libavcodec/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
This is a port of virtual dub's histogram equalization filter by Donald
A. Graft. Based on the work by Jérémy Tran <tran.jeremy.av@gmail.com>,
done for SOCIS 2012.
This is a port of the kerndeint filter (libmpcodecs/vf_kerndeint) by
Donal A. Graft (original avisynth plugin author), and is based on the
work by Jérémy Tran <tran.jeremy.av@gmail.com> done for SOCIS 2012.
* qatar/master:
cmdutils: update copyright year to 2013
h264: check SPS entries directly to detect pixel format changes
forgotten changelogs for 9_beta2
Conflicts:
Changelog
cmdutils.c
libavcodec/h264.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* qatar/master:
rtmp: Add support for limelight authentication
rtmp: Add support for adobe authentication
Conflicts:
Changelog
libavformat/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Limelight is a not too uncommon CDN. The authentication scheme is
pretty similar to the adobe authentication, but is even closer to
normal http digest authentication (but not close enough to warrant
sharing code) than the adobe version.
Signed-off-by: Martin Storsjö <martin@martin.st>
This is mostly used to authenticate the client when publishing.
Tested with wowza and akamai.
Some but not all servers support resending a new connect invoke
within the same connection, so always reconnect for sending a new
connection attempt. This matches what other applications do as well.
The authentication scheme is structurally pretty similar to http
digest authentication, but uses base64 instead of hex strings.
Signed-off-by: Martin Storsjö <martin@martin.st>
Note that the linebreaks text codec option (but not the feature) has
been removed; its main goal was to allow demuxers to configure the text
decoder (and not meant to be used by users), but the AVOption are not a
viable solution. This is solved differently in this commit.
* commit '6dd93ee6f1b050ad7c4b247899e83efa293ee405':
hlsenc: check append_entry return value
hlsenc: use the basename to generate the list entries
avstring: add av_basename and av_dirname
Conflicts:
Changelog
doc/APIchanges
libavutil/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Ported from MPlayer. Original author is A'rpi, with various
contributions from Michael Niedermayer. The original documentation was
mostly written by Diego Biurrun. See the MPlayer history for full
credits.
The filter is under GPL like the original filter, even if it differs
quite a lot. There is not much point in making it LGPL since pp is under
GPL.
This filter pads an audio stream with silence
It can together with -shortest be used to extend audio streams to
the same length as video.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
* qatar/master:
h264: slice-mt: check master context for valid current_picture_ptr
h264: slice-mt: get last_pic_dropable from master context
alacenc: add support for multi-channel encoding
Conflicts:
Changelog
libavcodec/alac.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
PIX is an image file format that was used by the BRender 3d engine.
Signed-off-by: Aleksi Nurmi <aleksi.nurmi@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
The new expansion mechanism uses the %{...} notation.
For compatibility reasons, it must be enabled explicitly,
but a warning is printed if a conflict is likely to happen.
* commit 'bf5f46b4cc47b7a4568119f224057d4ff91b6cdd':
APIChanges: add entry for av_read_packet deprecation
mxfdec: fix typo in mxf_read_seek()
avserver: use freopen to redirect stdin/out/err to /dev/null
avserver: remove daemon mode
configure: Check for -Werror parameters on clang
doxygen: remove obsolete options from Doxyfile
configure: Add option to disable all command line programs
Conflicts:
Changelog
configure
doc/APIchanges
doc/ffserver.conf
doc/ffserver.texi
ffserver.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
This code spews a multitude of warnings with glibc (unchecked
return values), some of them possibly warranted. Furthermore,
the deamonisation is not suitable for use with typical startup
scripts as it does not provide the PID of the daemon in any way.
Users wishing to run avserver as a daemon can still do so using
start-stop-daemon or equivalent tools.
Signed-off-by: Mans Rullgard <mans@mansr.com>
Signed-off-by: Janne Grunau <janne-libav@jannau.net>
* qatar/master:
flacenc: ensure the order is within the min/max range in LPC order search
avconv: rescale packet duration to muxer time base when flushing encoders
add 24-bit FLAC encoding to Changelog
rtpenc_aac: Fix calculation of the header size
x86: h264_intrapred: port to cpuflags
Conflicts:
Changelog
libavformat/rtpenc_aac.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Currently FFM files generated with one versions of ffmpeg generally
cannot be read by another.
By spliting data into chunks, more fields can saftely be appended to
chunks as well as new chunks added.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Also retroactively add a changelog entry to the 9beta1 list
for general MSVC support, which was present there already.
Signed-off-by: Martin Storsjö <martin@martin.st>
It has not worked for anything other than fringe codecs (asv1/2, mdec,
mjpeg[b]) since about 2003 and nobody ever noticed or complained. This
sufficiently proves that there are no users of this option who have a
clue of what they are doing, so it is completely useless.
This generalizes the previous work on disposition printing.
Disposition flags are shown in a dedicated section, which should improve
output intellegibility, extensibility and filtering operations.
This breaks output syntax with the recently introduced disposition
printing.
* qatar/master:
rtp: Packetization of JPEG (RFC 2435)
smoothstreamingenc: Copy the SAR on the AVStreams as well
Conflicts:
Changelog
libavformat/rtpenc.c
libavformat/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* commit '07584eaf4a95db3f11d3bc411f9786932829e82b':
mpegts: check substreams before discarding
Add a smooth streaming segmenter muxer
file: Add an avoption for disabling truncating existing files on open
img2dec: always close AVIOContexts
rtpdec_jpeg: Error out on other unsupported type values as well
rtpdec_jpeg: Disallow using the reserved q values
rtpdec_jpeg: Fold the default qtables case into an existing if statement
rtpdec_jpeg: Store and reuse old qtables for q values 128-254
rtpdec_jpeg: Simplify the calculation of the number of qtables
rtpdec_jpeg: Add more comments about the fields in the SOF0 section
rtpdec_jpeg: Clarify where the subsampling magic numbers come from
rtpdec_jpeg: Don't use a bitstream writer for the EOI marker
rtpdec_jpeg: Don't needlessly use a bitstream writer for the header
rtpdec_jpeg: Simplify writing of the jpeg header
rtpdec_jpeg: Merge two if statements
rtpdec_jpeg: Write the DHT section properly
Conflicts:
libavformat/Makefile
libavformat/allformats.c
libavformat/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
This muxer splits the output from the ismv muxer into individual
files, in realtime.
The same can also be done by the standalone tool ismindex, but this
muxer is needed for doing it in realtime (especially for live
streams that need extra handling for updating the lookahead fields
in the fragment headers).
Using this muxer, one can deliver live smooth streaming from a
normal static file web server. (Using ismindex, one can deliver
premade smooth streaming files from a static file web server,
or prepare files for serving with IIS.)
Signed-off-by: Martin Storsjö <martin@martin.st>
* qatar/master:
x86: dsputil: Only compile motion_est code when encoders are enabled
mem: fix typo in check for __ICC
fate: mp3: drop redundant CMP setting
rtp: Depacketization of JPEG (RFC 2435)
Rename ff_put_string to avpriv_put_string
mjpeg: Rename some symbols to avpriv_* instead of ff_*
yadif: cosmetics
Conflicts:
Changelog
libavcodec/mjpegenc.c
libavcodec/x86/Makefile
libavfilter/vf_yadif.c
libavformat/version.h
libavutil/mem.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* qatar/master:
MSS1 and MSS2: set final pixel format after common stuff has been initialised
MSS2 decoder
configure: handle --disable-asm before check_deps
x86: Split inline and external assembly #ifdefs
configure: x86: Separate inline from standalone assembler capabilities
pktdumper: Use a custom define instead of PATH_MAX for buffers
pktdumper: Use av_strlcpy instead of strncpy
pktdumper: Use sizeof(variable) instead of the direct buffer length
Conflicts:
Changelog
configure
libavcodec/allcodecs.c
libavcodec/avcodec.h
libavcodec/codec_desc.c
libavcodec/dct-test.c
libavcodec/imgconvert.c
libavcodec/mss12.c
libavcodec/version.h
libavfilter/x86/gradfun.c
libswscale/x86/yuv2rgb.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* commit 'ec36aa69448f20a78d8c4588265022e0b2272ab5':
x86: Fix linking with some or all of yasm, mmx, optimizations disabled
configure: Add more fine-grained SSE CPU capabilities flags
avfilter: x86: Use more precise compile template names
x86: cosmetics: Comment some #endifs for better readability
g723_1: add comfort noise generation
utvideoenc: Switch to dsputils' median prediction
utvideoenc: Avoid writing into the input picture
avtools: remove the distinction between func_arg and func2_arg.
avconv: make the -passlogfile option per-stream.
avconv: make the -pass option per-stream.
cmdutils: make -codecs print lossy/lossless flags.
lavc: add lossy/lossless codec properties.
Conflicts:
Changelog
cmdutils.c
configure
doc/APIchanges
ffmpeg.h
ffmpeg_opt.c
ffprobe.c
libavcodec/codec_desc.c
libavcodec/g723_1.c
libavcodec/utvideoenc.c
libavcodec/version.h
libavcodec/x86/mpegaudiodec.c
libavcodec/x86/rv40dsp_init.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
The cpia video decoder is intended to be used with the v4l2 demuxer.
There are some small changes to the v4l2 demuxer to support the
variable frame length of the format.
Fixes ticket #1537
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This is a port of the MPlayer smartblur filter (libmpcodecs/vf_smartblur.c)
by Michael Niedermayer.
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
While not explicitly stated in the specs, the original author
has stated that S_TEXT/UTF-8 is expected to be text using Subrip
markup, but without Subrip in-band timing.
So, now that we have a decoder that conforms to this expectation,
let's use it.
Note that this change will impact tools that use libavformat. If
they expect srt subtitles to have CODEC_ID_TEXT, they must be
adjusted to expect CODEC_ID_SUBRIP. The actual content is, obviously,
unchanged.
Signed-off-by: Philip Langdale <philipl@overt.org>
* qatar/master:
fate: Add FATE tests for the Ut Video encoder
lavc: add Ut Video encoder
mpegvideo_enc: remove stray duplicate line from 7f9aaa4
swscale: x86: fix #endif comments in rgb2rgb template file
avconv: mark more options as expert.
avconv: split printing "main options" into global and per-file.
avconv: refactor help printing.
Conflicts:
Changelog
ffmpeg_opt.c
ffserver.c
libavcodec/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* qatar/master:
mpegvideo_enc: don't use deprecated avcodec_encode_video().
cmdutils: refactor -codecs option.
avconv: make -shortest a per-output file option.
lavc: add avcodec_descriptor_get_by_name().
lavc: add const to AVCodec* function parameters.
swf(dec): replace CODEC_ID with AV_CODEC_ID
dvenc: don't use deprecated AVCODEC_MAX_AUDIO_FRAME_SIZE
rtmpdh: Do not generate the same private key every time when using libnettle
rtp: remove ff_rtp_get_rtcp_file_handle().
rtsp.c: use ffurl_get_multi_file_handle() instead of ff_rtp_get_rtcp_file_handle()
avio: add (ff)url_get_multi_file_handle() for getting more than one fd
h264: vdpau: fix crash with unsupported colorspace
amrwbdec: Decode the fr_quality bit properly
Conflicts:
Changelog
cmdutils.c
cmdutils_common_opts.h
doc/ffmpeg.texi
ffmpeg.c
ffmpeg.h
ffmpeg_opt.c
libavcodec/h264.c
libavcodec/options.c
libavcodec/utils.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
This filter is inspired upon libmpcodecs/vf_framestep.c, by Daniele
Forghieri.
Only-keyframe output is not supported, since that feature can be achieved
through the more versatile select filter.
Unsurprisingly, if a timing-less subrip decoder is desireable, an
encoder is as well. With this in place, we can move on to remove
the use of the old encoder/decoder with embedded timing and move
all timing handling the (de)muxer where they belong.
Signed-off-by: Philip Langdale <philipl@overt.org>
Signed-off-by: Michael Bradshaw <mbradshaw@sorensonmedia.com>
Reviewed-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This is a port of the MPlayer hue filter (libmpcodecs/vf_hue.c) by
Michael Niedermayer.
Signed-off-by: Jérémy Tran <tran.jeremy.av@gmail.com>
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
Patch readapted by Stefano Sabatini, color values proposed by Tim
Nicholson <nichot20@yahoo.com>.
Address trac ticket #1462.
See thread:
Subject: [FFmpeg-devel] [PATCH] smptebars filter
Date: Wed, 20 Jun 2012 01:54:58 +0000
Signed-off-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
With this feature, it becomes possible to perform commonly
requested tasks, such as hardcoding bitmap subtitles.
This will be reverted once libavfilter has proper support
for subtitles. All the changes have the string "sub2video"
in them, it makes it easy to spot the parts.
This change introduces a basic encoder for 3GPP Timed Text subtitles,
also known as TX3G, Quicktime subtitles, or "movtext" in the existing
code.
This initial change doesn't attempt to write styling information,
and just writes the plain text of the subtitles. I intend to add
support for styles eventually, but it's challenging due to a lack
of existing players that support them.
Note that an additional change is required to the mov/mp4 muxer to
write empty subtitle packets to indicate subtitle duration.
Signed-off-by: Philip Langdale <philipl@overt.org>
