Segmentation fault when running examples/save_videos.rb about gr.rb HOT 13 OPEN

There are 2 problems:

1. GR should not call av_write_trailer() on initialization failure:

diff --git a/lib/gks/plugin/vc.c b/lib/gks/plugin/vc.c
index 6391d651..ccf76cf0 100644
--- a/lib/gks/plugin/vc.c
+++ b/lib/gks/plugin/vc.c
@@ -270,7 +270,10 @@ void vc_movie_finish(movie_t movie)
 
   if (movie->fmt_ctx && movie->cdc_ctx)
     {
-      av_write_trailer(movie->fmt_ctx);
+      if (movie->fmt_ctx->pb)
+        {
+          av_write_trailer(movie->fmt_ctx);
+        }
       avcodec_close(movie->cdc_ctx);
 
       if (!(movie->out_fmt->flags & AVFMT_NOFILE))

For example, movie->fmt_ctx->pb is NULL when avcocdec_open2() is failed: https://github.com/sciapp/gr/blob/master/lib/gks/plugin/vc.c#L185

It can be happen by specifying wrong video size (361 isn't mod 4): GKS_VIDEO_OPTS=361x240@25@2x

2. save_videos.rb should specify GKS_VIDEO_OPTS before GR.beginprint:

diff --git a/examples/save_videos.rb b/examples/save_videos.rb
index d17dbc1..68bf6a3 100644
--- a/examples/save_videos.rb
+++ b/examples/save_videos.rb
@@ -21,6 +21,9 @@ epoch.times do |i|
   y <<  i**2 * Math.cos(i * Math::PI / 10.0) / 100.0
 end
 
+# configure video size
+ENV['GKS_VIDEO_OPTS'] = '360x240@25@2x'
+
 # start
 GR.beginprint('savefig/video.mov')
 
@@ -32,9 +35,6 @@ end
 # stop
 GR.endprint
 
-# configure video size
-ENV['GKS_VIDEO_OPTS'] = '360x240@25@2x'
-
 # You can use block
 GR.beginprint('savefig/video.mp4') do
   epoch.times do |j|

If it's not specified, width and height (ws_state_list::mem[0] and ws_state_list::mem[1]) may be updated by cairoplugin: https://github.com/sciapp/gr/blob/master/lib/gks/plugin/cairoplugin.c#L894-L895

It may set invalid width and/or height (not mod 4).

Could you report 1. to GR?

from gr.rb.

x264 that is used by ffmpeg requires "mod 4" in this case: https://code.videolan.org/videolan/x264/-/blob/master/encoder/encoder.c#L529

from gr.rb.

@fapdash
Thank you for your report.

According to the official website, the following dependent libraries are required to build GR.

https://gr-framework.org/building.html

The libraries related to video output are optional, not required. Therefore, they may not be included in the pre-built binaries managed by the package manager. For example, the libgr distributed via homebrew specifies only the following dependencies, so video output is not possible.

https://github.com/kojix2/homebrew-core/blob/c064504cd502b36feb3ca4ce625c0457efb2ba00/Formula/libgr.rb#L15-L21

  depends_on "cmake" => :build
  depends_on "cairo"
  depends_on "glfw"
  depends_on "libtiff"
  depends_on "qhull"
  depends_on "qt@5"
  depends_on "zeromq"

I guess Linux can't output video for the same reason...
But to be honest, I don't understand much about the lower layers.
I think I need to look into this more closely.

from gr.rb.

Parhaps, you may be able to output video by simply installing the following dependent libraries.

• https://github.com/red-data-tools/packages.red-data-tools.org/blob/master/gr/apt/ubuntu-focal/Dockerfile

Libraries that may be related to video output are:

sudo apt install -y libavcodec-dev \
                    libavdevice-dev \
                    libavformat-dev \
                    libavutil-dev

from gr.rb.

What is your distribution?
I confirmed that it works well on Ubuntu 20.04.

from gr.rb.

I'm on Ubuntu 20.04 as well. The same error still happens after installing the packages mentioned in #46 (comment).

from gr.rb.

What about libavdevice-dev?
It's not in the Dockerfile list, but in my case Ubuntu can output with it. (Until then, similar error)

from gr.rb.

Mh, that's also already installed: libavdevice-dev is already the newest version (7:4.2.4-1ubuntu0.1).

from gr.rb.

I confirmed that the same error occurs when I set GKS_WSTYPE=100.
@kou Could you please set the environment variable GKS_WSTYPE=100 and check again?

from gr.rb.

@kou
Great investigation as always.
Can I ask you one question: what is mod 4?

from gr.rb.

Oh, sorry. It's abbreviation of "modulo 4":

• English: https://en.wikipedia.org/wiki/Modulo_operation
• Japanese: https://ja.wikipedia.org/wiki/%E5%89%B0%E4%BD%99%E6%BC%94%E7%AE%97

from gr.rb.

Thank you.
I didn't know that x264 can only support video sizes that are divisible by 4.

from gr.rb.

Reported to sciapp/gr.

from gr.rb.