On Fri, Dec 09, 2011 at 03:39:25AM +0100, Luca Barbato wrote:
> Remove stale questions and try to make it less offensive.
> ---
> doc/faq.texi | 359
> +++++++---------------------------------------------------
> 1 files changed, 39 insertions(+), 320 deletions(-)
Good idea. I would suggest to push it in parts so that the size of
the patch shrinks quickly.
> --- a/doc/faq.texi
> +++ b/doc/faq.texi
> @@ -11,65 +11,11 @@
>
> @chapter General Questions
>
> -@section When will the next Libav version be released? / Why are Libav
> releases so few and far between?
> -
> -Like most open source projects Libav suffers from a certain lack of
> -manpower. For this reason the developers have to prioritize the work
> -they do and putting out releases is not at the top of the list, fixing
> -bugs and reviewing patches takes precedence. Please don't complain or
> -request more timely and/or frequent releases unless you are willing to
> -help out creating them.
> -
> -@section I have a problem with an old version of Libav; where should I
> report it?
> -Nowhere. We do not support old Libav versions in any way, we simply lack
> -the time, motivation and manpower to do so. If you have a problem with an
> -old version of Libav, upgrade to the latest git snapshot. If you
> -still experience the problem, then you can report it according to our
> -@uref{http://libav.org/bugreports.html, bug reporting guidelines}.
OK
> -@section Why doesn't Libav support feature [xyz]?
> -
> -Because no one has taken on that task yet. Libav development is
> -driven by the tasks that are important to the individual developers.
> -If there is a feature that is important to you, the best way to get
> -it implemented is to undertake the task yourself or sponsor a developer.
This could be amended.
> -@section Libav does not support codec XXX. Can you include a Windows DLL
> loader to support it?
> -
> -No. Windows DLLs are not portable, bloated and often slow.
> -Moreover Libav strives to support all codecs natively.
> -A DLL loader is not conducive to that goal.
This is not something I would remove.
> -@section My bug report/mail to libav-devel/user has not received any replies.
> -
> -Likely reasons
> -@itemize
> -@item We are busy and haven't had time yet to read your report or
> -investigate the issue.
> -@item You did not follow our
> - @uref{http://libav.org/bugreports.html, bug reporting guidelines}.
> -@item You didn't use git master.
> -@item You reported a segmentation fault without gdb output.
> -@item You describe a problem but not how to reproduce it.
> -@item It's unclear if you use ffmpeg as command line tool or use
> -libav* from another application.
> -@item You speak about a video having problems on playback but
> -not what you use to play it.
> -@item We have no faint clue what you are talking about besides
> -that it is related to Libav.
> -@end itemize
> -
> -@section Is there a forum for Libav? I do not like mailing lists.
> -
> -You may view our mailing lists with a more forum-alike look here:
> -@url{http://dir.gmane.org/gmane.comp.video.ffmpeg.user},
> -but, if you post, please remember that our mailing list rules still apply
> there.
OK
> -@section I cannot read this file although this format seems to be supported
> by ffmpeg.
> -
> -Even if ffmpeg can read the container format, it may not support all its
> -codecs. Please consult the supported codec list in the ffmpeg
> -documentation.
> +@section I cannot read this file although this format seems to be supported
> by avconv.
> +
> +Even if avconv can read the container format, it may not support all its
> +codecs. Use @command{avconv -codecs} to have a list of the codecs supported
> +in your specific build.
to see a list of the codecs
> @@ -107,155 +53,42 @@ If some MP3 codec like LAME is installed.
>
> -@chapter Compilation
> -
> -@section @code{error: can't find a register in class 'GENERAL_REGS' while
> reloading 'asm'}
> -
> -This is a bug in gcc. Do not report it to us. Instead, please report it to
> -the gcc developers. Note that we will not add workarounds for gcc bugs.
> -
> -Also note that (some of) the gcc developers believe this is not a bug or
> -not a bug they should fix:
> -@url{http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203}.
> -Then again, some of them do not know the difference between an undecidable
> -problem and an NP-hard problem...
I'd leave this, the error keeps reappearing.
> -@section ffmpeg does not work; what is wrong?
> +@section avconv does not work; what is wrong?
>
> -Try a @code{make distclean} in the ffmpeg source directory before the build.
> +Try a @code{make distclean} in the avconv source directory before the build.
> If this does not help see our
> -@uref{http://libav.org/bugreports.html, bug reporting guidelines}.
> +@url{http://libav.org/bugreports.html, bug reporting guidelines}.
OK
> -@section How do I encode single pictures into movies?
> -
> -@section How do I encode movie to single pictures?
I'm under the impression that these are still FAQs...
> -@section Why do I see a slight quality degradation with multithreaded MPEG*
> encoding?
> -
> -For multithreaded MPEG* encoding, the encoded slices must be independent,
> -otherwise thread n would practically have to wait for n-1 to finish, so it's
> -quite logical that there is a small reduction of quality. This is not a bug.
> +@section Why do I see a slight quality degradation with multithreaded
> +slice encoding?
> +For multithreaded slice encoding, the encoded slices must be independent,
> +otherwise thread n would practically have to wait for n-1 to finish, so it
> +is expected that there is a small reduction of quality.
> +If you do not have latency concern you should switch to frame multithreaded
> +encoding.
OK
> -@section -f jpeg doesn't work.
> -
> -Try '-f image2 test%d.jpg'.
> -
> @section Why can I not change the framerate?
>
> Some codecs, like MPEG-1/2, only allow a small number of fixed framerates.
> -Choose a different codec with the -vcodec command line option.
> +Choose a different codec with the -c:v command line option.
>
> -@section How do I encode Xvid or DivX video with ffmpeg?
> +@section How do I encode Xvid or DivX video with avconv?
>
> Both Xvid and DivX (version 4+) are implementations of the ISO MPEG-4
> standard (note that there are many other coding formats that use this
> -same standard). Thus, use '-vcodec mpeg4' to encode in these formats. The
> +same standard). Thus, use '-c:v mpeg4' to encode in these formats. The
> default fourcc stored in an MPEG-4-coded file will be 'FMP4'. If you want
> -a different fourcc, use the '-vtag' option. E.g., '-vtag xvid' will
> +a different fourcc, use the '-tag:v' option. E.g., '-tag:v xvid' will
> force the fourcc 'xvid' to be stored as the video fourcc rather than the
> default.
OK
> -@section How do I encode videos which play on the iPod?
> -
> -@section How do I encode videos which play on the PSP?
No longer FAQs?
> @@ -267,7 +100,7 @@ things to try: '-bf 2', '-flags qprd', '-flags mv0',
> '-flags skiprd'.
>
> -@section Interlaced video looks very bad when encoded with ffmpeg, what is
> wrong?
> +@section Interlaced video looks very bad when encoded with avconv, what is
> wrong?
>
> You should use '-flags +ilme+ildct' and maybe '-flags +alt' for interlaced
> material, and try '-top 0/1' if the result looks really messed-up.
> @@ -282,92 +115,13 @@ Just create an "input.avs" text file with this single
> line ...
> @example
> DirectShowSource("C:\path to your file\yourfile.asf")
> @end example
> -... and then feed that text file to ffmpeg:
> +... and then feed that text file to avconv:
> @example
> - ffmpeg -i input.avs
> + avconv -i input.avs
> @end example
OK
> For ANY other help on Avisynth, please visit the
> -@uref{http://www.avisynth.org/, Avisynth homepage}.
> +@url{http://www.avisynth.org/, Avisynth homepage}.
OK
> -@section How can I join video files?
I think that's still an FAQ - wasn't there some SoC project? :)
> -@section I want CBR, but no matter what I do frame sizes differ.
> -
> -You do not understand what CBR is, please read the MPEG spec.
> -Read about video buffer verifier and constant bitrate.
> -The one sentence summary is that there is a buffer and the input rate is
> -constant, the output can vary as needed.
> -
> -@section How do I check if a stream is CBR?
> -
> -To quote the MPEG-2 spec:
> -"There is no way to tell that a bitstream is constant bitrate without
> -examining all of the vbv_delay values and making complicated computations."
OK
> @@ -377,61 +131,48 @@ Yes. Read the Developers Guide of the Libav
> documentation. Alternatively,
>
> -@section Can you support my C compiler XXX?
> +@section Can you support my C compiler?
>
> -It depends. If your compiler is C99-compliant, then patches to support
> +If your compiler is C99-compliant, then patches to support
> it are likely to be welcome if they do not pollute the source code
> with @code{#ifdef}s related to the compiler.
> +We cover already a large number of compilers and operating system in our
> +@url{http://fate.libav.org, regression test system}
End the sentence in a period.
> @section Is Microsoft Visual C++ supported?
>
> No. Microsoft Visual C++ is not compliant to the C99 standard and does
> -not - among other things - support the inline assembly used in Libav.
> -If you wish to use MSVC++ for your
> -project then you can link the MSVC++ code with libav* as long as
> -you compile the latter with a working C compiler. For more information, see
> +not support the language features used by Libav.
> +
> +If you wish to use MSVC++ for your project then you can link the MSVC++
> +code with libav* as long as you compile the latter with a working C99
> +compiler. For more information, see
> the @emph{Microsoft Visual C++ compatibility} section in the Libav
> documentation.
>
> -There have been efforts to make Libav compatible with MSVC++ in the
> -past. However, they have all been rejected as too intrusive, especially
> -since MinGW does the job adequately. None of the core developers
> -work with MSVC++ and thus this item is low priority. Should you find
> -the silver bullet that solves this problem, feel free to shoot it at us.
> -
> -We strongly recommend you to move over from MSVC++ to MinGW tools.
> -
> @section Can I use Libav or libavcodec under Windows?
>
> Yes, but the Cygwin or MinGW tools @emph{must} be used to compile Libav.
> Read the @emph{Windows} section in the Libav documentation to find more
> information.
>
> -@section Can you add automake, libtool or autoconf support?
> +@section Can you move to another build system?
>
> -No. These tools are too bloated and they complicate the build.
> +No. The current one is fully portable, fast and easy to understand.
>
> -@section Why not rewrite ffmpeg in object-oriented C++?
> +@section Why not rewrite Libav in object-oriented C++?
>
> Libav is already organized in a highly modular manner and does not need to
> be rewritten in a formal object language. Further, many of the developers
> favor straight C; it works for them. For more arguments on this matter,
> -read @uref{http://www.tux.org/lkml/#s15, "Programming Religion"}.
> +read @url{http://www.tux.org/lkml/#s15, "Programming Religion"}.
>
> -@section I do not like the LGPL, can I contribute code under the GPL instead?
> +@section Can I contribute code under the GPL?
>
> Yes, as long as the code is optional and can easily and cleanly be placed
> under #if CONFIG_GPL without breaking anything. So for example a new codec
> or filter would be OK under GPL while a bug fix to LGPL code would not.
>
> -@section I want to compile xyz.c alone but my compiler produced many errors.
> -
> -Common code is in its own files in libav* and is used by the individual
> -codecs. They will not work without the common parts, you have to compile
> -the whole libav*. If you wish, disable some parts with configure switches.
> -You can also try to hack it and remove more, but if you had problems fixing
> -the compilation failure then you are probably not qualified for this.
OK
> @@ -450,34 +191,12 @@ to use them you have to append -D__STDC_CONSTANT_MACROS
> to your CXXFLAGS
>
> -@section I get "No compatible shell script interpreter found." in MSys.
> +@section I get "No compatible shell script interpreter found."
>
> -The standard MSys bash (2.04) is broken. You need to install 2.05 or later.
> +Ancient bash (2.04) is not supported. You need to install 2.05 or later.
Msys now has 3.1, so we can probably remove this.
> @section I get "./configure: line <xxx>: pr: command not found" in MSys.
>
> The standard MSys install doesn't come with pr. You need to get it from the
> coreutils package.
I also got this with my pretty standard msys install, so I think
we can drop the entry.
> -@section Where can I find libav* headers for Pascal/Delphi?
> -
> -see @url{http://www.iversenit.dk/dev/ffmpeg-headers/}
> -
> -@section Where is the documentation about ffv1, msmpeg4, asv1, 4xm?
> -
> -see @url{http://www.ffmpeg.org/~michael/}
> -
> -@section How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?
> -
> -Even if peculiar since it is network oriented, RTP is a container like any
> -other. You have to @emph{demux} RTP before feeding the payload to libavcodec.
> -In this specific case please look at RFC 4629 to see how it should be done.
> -
> -@section AVStream.r_frame_rate is wrong, it is much larger than the
> framerate.
> -
> -r_frame_rate is NOT the average framerate, it is the smallest framerate
> -that can accurately represent all timestamps. So no, it is not
> -wrong if it is larger than the average!
> -For example, if you have mixed 25 and 30 fps content, then r_frame_rate
> -will be 150.
OK
Diego
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