[MPlayer-users] VO: Description: Null video output

[The Wanderer]

On 2022-03-25 at 21:42, Craig Jameson wrote:

> In two separate blocks below, I have posted the outputs for
> 
> 	mplayer -vo help
> and
> 	mplayer -v Metallica\ -\ Nothing\ Else\ Matters.mp4
> 
> for the same user, but while running two different versions mplayer
> under two different versions of RHEL.
> 
> 
> The file .mplayer/config for this user contains a single line:
> 
> 	# Write your default config options here!

So it's effectively empty, as that line is a comment. That's useful
mainly to confirm that, in the absence of command-line options to
specify the VO, MPlayer is probably falling back on iterating through
its compiled-in defaults.

> The version of   mplayer   that   works under RHEL 7 is 1.1-4.4.7
> The version I am trying to get to work  under RHEL 8 is 1.5-8
> 
> The VO for the first version is reported to be Xv.

> ./configure for the two versions was run with the following options:
> 
> 1.1-4.4.7
>  --enable-gui --codecsdir=/home/inatps/MPlayer/essential-2007100 --
> prefix=/home/inatps/MPlayer/MPlayer2013 --yasm=
> 
> 1.5-8
> --prefix=/home/inatps/MPlayer/MPlayer-1.5/local --
> codecsdir=/home/inatps/MPlayer/MPlayer-1.5/essential-20071007
> 
> The permissions for the two installs are the same.
> 
> At first, I thought the problem was an operating system permissions
> issue.  After some research, I thought is was a security issue with
> ffmpeg.  Now, I am of the sense it is a compile-time issue.  I remember
> that there is a compile-time log.  Is that where I look next?  Where do
> I find it again?

The log you probably need is not the compile-time log, but the
configure-time log. The configure step is where the detection of
available features is performed, reported, and logged.

It should probably be in the same directory as './configure', from the
two commands above, under the name 'config.log'.

> These two outputs of mplayer are from a binary compiled under RHEL 6,
> running under RHEL 7.
> 
> [Salomon]$ mplayer -vo help
> MPlayer 1.1-4.4.7 (C) 2000-2012 MPlayer Team
> Available video output drivers:
>         xv      X11/Xv
>         gl_nosw OpenGL no software rendering
>         x11     X11 ( XImage/Shm )
>         xover   General X11 driver for overlay capable video output
> drivers
>         sdl     SDL YUV/RGB/BGR renderer (SDL v1.1.7+ only!)
>         gl      OpenGL
>         gl2     X11 (OpenGL) - multiple textures version
>         fbdev   Framebuffer Device
>         fbdev2  Framebuffer Device
>         matrixview      MatrixView (OpenGL)
>         v4l2    V4L2 MPEG Video Decoder Output
>         xvidix  X11 (VIDIX)
>         cvidix  console VIDIX
>         null    Null video output
>         mpegpes MPEG-PES to DVB card
>         yuv4mpeg        yuv4mpeg output for mjpegtools
>         png     PNG file
>         jpeg    JPEG file
>         tga     Targa output
>         pnm     PPM/PGM/PGMYUV file
>         md5sum  md5sum of each frame
>         mng     MNG file

> These two outputs of mplayer are from the fresh compile under RHEL 8.5.
> 
> 
> [Salomon]$ nmplayer -vo help
> MPlayer 1.5-8 (C) 2000-2022 MPlayer Team
> Available video output drivers:
>         fbdev   Framebuffer Device
>         fbdev2  Framebuffer Device
>         v4l2    V4L2 MPEG Video Decoder Output
>         cvidix  console VIDIX
>         null    Null video output
>         mpegpes MPEG-PES to DVB card
>         yuv4mpeg        yuv4mpeg output for mjpegtools
>         png     PNG file
>         tga     Targa output
>         pnm     PPM/PGM/PGMYUV file
>         md5sum  md5sum of each frame

That seems to confirm that, yes, the problem is that support for other
VO methods was not compiled in - which means that it was not detected at
compile time. (In the second list, the listed VO methods other than the
three which it tried are not actually for displaying the image, but for
outputting to a file or for deciding not to output video after all.)

The most likely reason for this is that the correct development-header
packages were not installed at that point. You'll probably need to
identify which packages those are, get them installed, and re-compile
MPlayer.


What I usually do when I notice that a particular feature is detected as
not available, at configure time, is to:

* Search config.log for the report about the detection of that feature,
  to determine the correct name for the feature (as used internally by
  the configure script). This step can sometimes be skipped.

* Search the configure script itself for the name of that feature, to
  find the place where the detection for that feature occurs.

* Identify the name(s) of the header and/or library files that are
  required for the detection to pass, based on the arguments that are
  being passed to the compile-check statements in the configure script.

* For each such name, search the package repository for the path and
  filename in question. (On Debian, I typically do this with 'apt-file
  search'; what tool there may be for doing it on RHEL I do not know.)

* After identifying an appropriate package, install it, and run the
  configure process again. (In some cases, there will not be any such
  package; for those cases, either more complex solutions are needed, or
  the feature simply is not available for the current environment.)

* If there are still features detected as unavailable which I think
  should be available and want to include, repeat as necessary.

-- 
   The Wanderer

The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore all
progress depends on the unreasonable man.         -- George Bernard Shaw

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