On 7/27/2021 12:49 AM, Michal Vlasák via ntg-context wrote:
The viewers I tested were: Acrobat Reader DC, Foxit Reader, Sumatra PDF
on Windows and Evince, Okular, Xpdf, MuPDF, Firefox and Google Chrome on
Linux.
also add the new edge on windows .. there are subtle differences in
interfaces; although it doesn't fit into this topic, printing is also
somethign to pay attention to; browser based pdf's can crash (mem
consumption), the sometimes present doubleside directive can also
confuse viewers
when it comes to checking you need to keep in mind that some readers
start top-down (collect objects), others bottom up (xref), some use a
mix, some apply heuristics (irr xpdf did something with t1 fonts that
made cut/paste an issue), some are tolerant, others more strict,
treatment of updates objects can differ, but not always consistent ...
so, that also makes testing annotations a problem
the command line program qpdf is one of the best programs to check (when
luigi sand i were checking luatex pdf issues we used qpdf and mupdf mostly)
Now to the different mechanisms:
1) Sound objects
- First appeared in PDF 1.2 (1996), but had since been deprecated (PDF
1.5, 2003) and became unsupported (PDF 2.0, 2017).
- Only audio is supported.
- "Raw" and in practice uncompressed PCM audio can be embedded (i.e.
".wav" format without the metadata).
Otherwise an external file may be used (this one has to be in a real
audio format - like ".wav" - i.e. with metadata).
- Users usually don't have raw audio. So embedding requires
preprocessing. Some control using PDF actions is possible.
- Not supported in ConTeXt.
- None of the viewers supports the external files. Only Acrobat Reader
supports the embedded raw audio.
amazing right? all that talk of accessibility and no proper easy audio
support
2) Movie objects
- First appeared in PDF 1.2 (1996), but had since been deprecated (PDF
1.5, 2003) and became unsupported (PDF 2.0, 2017).
- Both video and audio is supported.
- Any source (embedded, external and URL file).
- In all regards superior to sound objects. Is still relatively simple
and allows some customization and control (media player controls, PDF
actions).
- This is the backing mechanism for including video and audio in
ConTeXt (\externalfigure, \useexternalsoundtrack).
- Supported only in Evince and Okular (with their usual quirks, see
below). Notably Acrobat Reader does no longer support this mechanism.
this all became an issue when they dropped the quicktime plugin
(probably also relates to the usual big companies competing politics)
3) Multimedia ("Renditions")
- First appeared in PDF 1.5 (2003). Adobe Acrobat considers them
"legacy".
- Both video and audio supported (as well as other unspecified types of
multimedia, like images and Flash, but not really, see below).
- In theory all source types should be possible.
- This mechanism was supposed to replace sound and movie objects. Hence
their deprecation. The mechanism is complex (the spec is 10 times
longer than that for movie objects). It expects the PDF viewers to
work with plugins and introduces ways for determining if a media file
is really playable in some plugin. It is allowed to even include
more media files (to serve as fallback should the primary one be
unsupported by the viewer). Other complexity is that the concept of
the rectangle where the media will be played ("screen") is separated
from the media itself ("rendition"). In theory this allows mixing and
matching them, but in practice is a lot of unnecessary complexity, at
least in my opinion.
I fully agree. As with many of these annotation pdf things it's probably
reversed engeneered from some application or plugin, not the result of
clear design. It also evolves when there is no way to generate it (tex
is often one of the first to do that and then we run into specs not
fitting reality). Kind of making equipment that should work on mars and
test it on earth (if at all).
This mechanism allows multimedia player controls, as well as PDF
actions. The PDF action can be either one of the predefined ones or
entirely specified in JavaScript (extra API is available for this).
brings us to javascript ... it would be interesting to have the 'minimal
useful' set of support needed; mupdf has javascript but nto realaly for
annotations (for instance the ability to control layers and widget
states would be nice ... it's trivial to program in viewers i bet)
- This is the mechanism behind \useexternalrendering. This has been
used for Flash (.swf files) and "manual" audio + video insertion as
far as I can tell.
- Evince and Okular support this (with usual quirks), but not for
external files (Evince segfaults). Acrobat and Foxit support this
mechanism as well, but Acrobat only allows embedded files. Okular by
mistake auto-plays all media [1].
hm, sounds bad
4) 3D art
- First appeared in PDF 1.6 (2004).
- Only 3D files supported. This means U3D and later PRC files. The 3D
objects described in the files are shown in a scene whose parameters
(like camera position, angle, background color, etc.) can be
configured.
- The source is not a file, but a "PDF stream" (which is essentially
embedded file with different metadata, but allows also "external
files" to contain the stream data).
- The 3D functionality is nice. It allows great amount of interactivity
(playing with the camera, selectively disabling 3D objects, etc.) and
also scriptability (switching between predefined "views" with PDF
actions and a _lot_ of possibilities with JavaScript scripts).
- This is the mechanism used for u3d and prc files in the ConTeXt
"figure" mechanism (\externalfigure).
- Apart from the external streams (see above) everything works in Adobe
Acrobat. Foxit Reader also has support, but it is limited (no
support for JavaScript and printing).
Wasn't that driven by apps like autocad? Is U3D kind of a standard that
will stay?
5) Rich Media
- First appeared in Adobe extension level 3 to PDF 1.7 (2008). Later
included in PDF 2.0 (2017). It was meant to replace both multimedia
(renditions) and 3D art mechanisms, with unified mechanism based on
Flash, thus also supporting arbitrary Flash applications.
- Supports video, audio and 3D.
- Only embedded files are supported.
- While the mechanism is heavily based on Flash (which is dead, since
December 2020) it allows also "plain" Rich Media without Flash.
The old idea was that the PDF viewer would support Flash (and playing
its video as well as mp4), but the audio/video wouldn't be played
directly by the PDF viewer, but by a Flash application (embedded in
the PDF along with the media file). This means that the mechanism has
inherent complexity that is not justified nowadays (essentially four
levels of indirection for a plain audio / video file).
yes, flash is gone (one can say: of course, why else would adobe has
bought them) .. i think i already moved the files to the attic .. one
had to embed a 'flash player' with gui stuff
While the same thing should have been true for 3D files I couldn't
find any real usage like that. Instead it seems that 3D files with
Rich Media have always been used like with the "3D art" mechanism
(but with different wrappers).
There is essentially no scriptability for audio and video. (Note that
in this regard 3D files work just like with the "3D art" mechanism).
There also isn't an easy way to display multimedia player controls (a
hack works for Acrobat). One thing that it allows is playing the
media in a customizable window, even full screen (not only in a part
of a page like the previous mechanisms allow).
one could / can start/stop etc from, javascript
- ConTeXt uses this mechanism for Flash (SWF) files in the figure
mechanism. This is also allows audio/video (Flash media player, like
"vplayer" is inserted and the media file is its parameter), see for
example "java-imp-vplayer.mkiv".
- Both Flash and "plain" Rich media are supported by Acrobat Reader.
Okular only supports Flash Rich Media. How is this possible,
considering that Flash player is dead? Well, both viewers have a
compatibility layer that detects embedded Flash media player file and
doesn't use it to play the video, but instead plays the video
natively. This is good, because there are a lot of documents out
there which use Flash based Rich Media. But there is absolutely no
need to create new documents with embedded Flash player applications,
it only takes space and isn't even used.
hm, i didn't know that ... is that kind of official? this 'replacement'
trick?
Okular notably doesn't support plain Rich Media. The support is easy
to add, but my proposed patch [2] depends on changes to poppler. The
poppler developers want to take this chance to improve the Rich Media
representation [3] but I haven't gotten to that, yet.
good
Support similar to Okular's should be relatively easy to add to
Evince as well.
good
The 3D support is the same as with 3D art for Acrobat Reader. Weirdly
Foxit Reader doesn't support 3D files wrapped in Rich Media, although
there doesn't seem any good reason for it.
All in all, of the five mechanisms 2 are deprecated and unfortunately no
longer supported in the most used PDF viewer and other 2 mechanisms are
needlessly complex and in reality limited. For example, while the
multimedia mechanism supports JavaScript, (AFAIK) only Acrobat Reader
supports that, this further limits the viewer support or available
features, choose one.
a more philosophical: do "standards" or "formats" guarantee fuiture
usage .. is investing time in some formats worth the effort
The support for video and audio in Okular and Evince is based on
Gstreamer. Explaining Gstreamer is tricky, but essentially it allows the
viewers to play any media type as long as the right plugin is installed.
These plugins are distributed in bundless and three of them cover all
reasonable formats and more. But while the media file format support is
great, these viewers don't really support PDF actions or JavaScript for
more control over the media playback.
Acrobat and Foxit both use Windows Media Player for playing the video.
Both support controls, but behave differently -- Acrobat displays the
controls outside of the multimedia annotation, Foxit within...
As if it wasn't enough there is other trouble with playing multimedia in
Acrobat Reader and Foxit Reader. They nag you to allow the media
playback every time. You can select to trust the file once or from now
on, but if somebody opens a foreign PDF with video, they aren't going to
get smooth experience.
Another thing (but I don't remember well) is that there is a check box
in Acrobat Reader, that allows the "legacy" Multimedia mechanism. I
don't remember its state in an unaltered installation.
ah, these properties dialogs ... with changing defaults per version,
yes, easy to forget
After evaluating these mechanisms I came to conclusion, that a PDF
writer today is best at:
- Embedding video and audio using the "multimedia" ("renditions")
mechanism. It is supported in proprietary and open source viewers
alike. Customization and scripting / PDF actions is out of the
question, though.
- Embedding 3D files using the "Rich Media" mechanism. While it is
essentially just a few differences in wrappers, it has real
advantages (data sources are files not streams, and multiple
JavaScript script files are supported), that I find nice enough for
the implementation and users alike.
maybe we need some javascript supported actions in viewers table
Some sources for this topic are also the LaTeX centric [4] and [5]. I go
into more details in the former. In the latter the "plain" Rich Media
and "multimedia" ("renditions") mechanisms are suggested as solutions
for the Flash media player approach.
but we have to stick to what we think will stay (kind of generic
features of such things)
And now for the future. What should ConTeXt do? On one hand all
available mechanisms are flawed in one way or the other. On the other
hand some users may still find the functionality useful. My suggestions
is to either delete all the support for audio/video or:
1) Delete the "Movie objects" implementation of figures. It is not
supported in viewers, where users expect it to [6].
it's actually an abstraction but we can map it onto somethign else
2) Delete all mentions of Flash. There is no reason to create new
documents with embedded Flash files, even though they may work in
some viewers. Plain Rich Media can be used instead, with hopefully
soon equal support [2].
indeed
3) The "externalrendering" mechanism (multimedia/renditions) can stay.
If the insertion of audio/video as "figures" is to stay, then I
suggest to use multimedia/renditions for it (in simplified form).
Note that the 3D support in ConTeXt is completely fine and works in
Acrobat and Foxit.
do we actually have some simple test files for that? do we need a small
set of files for media?
The "externalrendering" part currently has three "bugs". Previous
discussion at this list provides some context [7]. The following is
currently "wrong":
- Currently ConTeXt wraps a PDF file specification for embedded file
inside another file specification (i.e. embedded files don't work).
- As a result of "externalrendering" inheriting from \framed, the
PDF annotation late_lua whatsit is centered inside the frame and so
the annotation itself is offset by half its width to the right.
- ConTeXt doesn't explicitly allow the viewer to create temporary
files, hence the playback fails in Acrobat Reader.
hm, never seen that temp thing ... must be something recent (or maybe it
is a preference)
Hopefully the patch included below fixes all three. But note that while
I love ConTeXt I don't know it well and may be terribly wrong. I also
was aiming at a minimal diff for inclusion in this e-mail. This is a
test file for this:
sure
\starttext
\setupinteraction[state=start]
\useexternalrendering[myvideo][video/mp4][video.mp4][embed=yes]
\useexternalrendering[myvideo2][video/mp4][https://gitlab.com/agrahn/media9/uploads/c7e2ae944fbd711df4ad7bd58000f83a/nightseq1.mp4]
\useexternalrendering[myvideo3][video/mp4][video.mp4]
\definerenderingwindow[myrenderingwindow][width=\textwidth, height=\textwidth]
\noindent
\placerenderingwindow[myrenderingwindow][myvideo]
\goto{START}[StartRendering{myvideo}]
\goto{STOP} [StopRendering{myvideo}]
\goto{PAUSE}[PauseRendering{myvideo}]
\vfil\break\noindent
\placerenderingwindow[myrenderingwindow][myvideo2]
\vfil\break\noindent
\placerenderingwindow[myrenderingwindow][myvideo3]
\stoptext
All three file source types are demonstrated. Any "video.mp4" in the
directory you compile in will do. (Works as expected in Okular on
Linux.)
good. but not in mupdf viewers, right?
This was a dump of knowledge that I gained from writing my thesis.
Sadly its in Czech, but part of it is PDF code snippets and tables
summarizing viewer support, that I can translate and provide if there is
interest. But a large part of what I deem practical today is implemented
and documented here:
http://mirrors.ctan.org/macros/luatex/optex/pdfextra/pdfextra-doc.pdf.
The source is probably hard to read, because of the "_" and "." prefixes
in the control sequences, but those can be ignored. I posted some "real"
documents in [3] and [5].
thanks for paying attention
If more documents / snippets / explanations are needed I hope I can
provide them.
Sadly, while working on this, I didn't have access to the PDF 2.0
standard. My information mostly comes from the PDF 1.7 standard and
publicly known information about PDF 2.0 - the Rich Media mechanism got
included in PDF 2.0, but I am not sure in what extent did the Flash part
get included. I also don't know if there really is anything new, but
nothing suggests it. Regardless, viewer support isn't complete for
something standardized over 20 years ago, I don't expect revolution in
the PDF viewers, considering the price of the standard(s).
indeed. but wrt viewers, what puzzles me is that much of this rendering
stuff is around in browsers so i guess it also has to do with lack of
interest
[1]: https://bugs.kde.org/show_bug.cgi?id=436709
[2]: https://invent.kde.org/graphics/okular/-/merge_requests/426
[3]: https://gitlab.freedesktop.org/poppler/poppler/-/merge_requests/855
[4]:
https://tex.stackexchange.com/questions/516029/media9-is-becoming-obsolete-dec-2020-any-alternatives-for-embedding-video-audio/516102
[5]: https://gitlab.com/agrahn/media9/-/issues/9
[6]: https://wiki.contextgarden.net/Command/externalfigure
[7]: https://www.mail-archive.com/ntg-context@ntg.nl/msg88639.html
What actuially was also supported is
https://www.w3.org/TR/SMIL/
but somehow that became unreliable / went away .. when it first showed
up it worked perfect and i always though that it would stay
Hans
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