av_image_fill_max_pixsteps method generates segmentation fault since v4.3.2.1

[AddictedCS]

• **I'm submitting a ... **
  • [ x] bug report

Preconditions

FFmpeg 4.4.1 (latest brew installation) OS - OSx .NET 6 (or .NET 5).

Description

The signature of the av_image_fill_max_pixsteps hasn't changed in version v4.3.2.1 By blaming imgutils, it is clear that it stayed the same for the last 9 years.

Even so, after upgrading FFmpeg.Autogen to any version >= v4.3.2.1, the method call fails with a segmentation fault. The previous version 4.3.2 works with no issues. The target FFmpeg is 4.4.1 so since it works with Autogen 4.3.2 I assume it is an Autogen issue.

It may be related to the fact that since the v4.3.2.1 method signature in Autogen changed from

// version up until v4.3.2
public static void av_image_fill_max_pixsteps(
    ref int_array4 max_pixsteps, 
    ref int_array4 max_pixstep_comps, 
    AVPixFmtDescriptor* pixdesc)

to

// version since v4.3.2.1
public static void av_image_fill_max_pixsteps(
    int_array4 max_pixsteps, 
    ref int_array4 max_pixstep_comps, 
    AVPixFmtDescriptor* pixdesc)

Notice how the first parameter changed from ref int_array4 to int_array4. Taking into account that the actual imgutils.h does not contain changes in the method signature, why does the generated code provides int_array4 instead of ref int_array4 since v4.3.2.1?

Any help will be greatly appreciated.

[Ruslan-B]

I think we already observed similar issue here #140. However, this one looks different. As original declaration:

void av_image_fill_max_pixsteps(int max_pixsteps[4], int max_pixstep_comps[4],
                                const AVPixFmtDescriptor *pixdesc);

It appears to be generation issue - I'll investigate.

[Ruslan-B]

@AddictedCS can you compile custom version of v4.3.2.1? With this as a difference:

// version since v4.3.2.1
public static void av_image_fill_max_pixsteps(
    int_array4 max_pixsteps, 
    int_array4 max_pixstep_comps, 
    AVPixFmtDescriptor* pixdesc)

And test it? As we not supposed to have second parameter by ref .

[AddictedCS]

Will do it later this week.

[Ruslan-B]

@AddictedCS do you have or can you create any minimal example how to use this function?

[AddictedCS]

@Ruslan-B it is actually quite easy.

Create a new console app and run the following code:

using System;
using FFmpeg.AutoGen;
unsafe
{
    var pixelFormat = ffmpeg.av_pix_fmt_desc_get(AVPixelFormat.AV_PIX_FMT_RGB24);
    int_array4 max_step, _;
    ffmpeg.av_image_fill_max_pixsteps(max_step, ref _, pixelFormat);
    Console.WriteLine("Hello, World!");
}

For Autogen >= 4.3.2.1 it will fail with a segmentation fault. For earlier versions, you will see the Hello World message.

OS: OSx FFmpeg: 4.4.1 dotnet: 5 or 6

[Ruslan-B]

I'll close this issue in one week as we don't have any forward moving....

[Ruslan-B]

Could you please check/test - ffmpeg_abstractions branch. I do think it should fix the problem as I forced ref for any none const array.

[Ruslan-B]

Forming new way of API here https://github.com/Ruslan-B/FFmpeg.AutoGen/issues/210 - all none const array parameters are ref now.

[AddictedCS]

Is there any way you will force ref parameters for the 4.x branch? I could test that.

[Ruslan-B]

I'll look into this however can't promise anything as having a capacity of one developer is not enough to support timeline of ffmpeg. If you can update to 5.1 would be easy.

[AddictedCS]

Understand and appreciate your efforts. I'm bundling it with Microsoft Debian Bullseye, which still marks ffmpeg 5.x package as unstable, and frankly saying I don't expect it to become stable anytime soon.

[Ruslan-B]

Okay I'll look into this have to understand how to deal with this

[Ruslan-B]

Understand and appreciate your efforts. I'm bundling it with Microsoft Debian Bullseye, which still marks ffmpeg 5.x package as unstable, and frankly saying I don't expect it to become stable anytime soon.

So I can assume you stuck with v4.3.2?

[AddictedCS]

The latest I can use is v4.3.0.3

[Ruslan-B]

When I'll finish work and newly generated API is going to stable - I'll do it once for 4.3 and 4.4. I don't think it need to so often.

[AddictedCS]

Sorry @Ruslan-B I've misunderstood your question. The version that is marked as stable and used with Microsoft Debian Bullseye is 4.3.4.

ffmpeg version 4.3.4-0+deb11u1 Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 10 (Debian 10.2.1-6)
configuration: --prefix=/usr --extra-version=0+deb11u1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil      56. 51.100 / 56. 51.100
libavcodec     58. 91.100 / 58. 91.100
libavformat    58. 45.100 / 58. 45.100
libavdevice    58. 10.100 / 58. 10.100
libavfilter     7. 85.100 /  7. 85.100
libavresample   4.  0.  0 /  4.  0.  0
libswscale      5.  7.100 /  5.  7.100
libswresample   3.  7.100 /  3.  7.100
libpostproc    55.  7.100 / 55.  7.100

The latest FFmpeg Autogen that is usable and not crashing is v4.3.0.3, which I'm using.

[Ruslan-B]

I think this problem is solved in new API - mostly drop - I'll try to create experimental packages for 4.3 from this point and it would be cool if you can participate in testing

[AddictedCS]

Once a new package is created for 4.3.x, I will give it a run.

[Ruslan-B]

Based on https://github.com/Ruslan-B/FFmpeg.AutoGen/tree/ffmpeg_abstractions_4.3 I added all four new nuget packages. However, you need this one: Install-Package FFmpeg.AutoGen.Bindings.DynamicallyLoaded -Version 4.3.2 Indexing still in progress. The API namespace is different - FFmpeg.AutoGen.Abstractions Besides, don't forget to do:

DynamicallyLoadedBindings.LibrariesPath = ...
DynamicallyLoadedBindings.Initialize();

You can check the example project. Before any API call. If any question please let me know.

[AddictedCS]

The fix is working. I could run it with ffmpeg v4.4.1 and FFmpeg.AutoGen.Bindings.DynamicallyLoaded -Version 4.3.2. Thanks for the efforts.

[Ruslan-B]

Nice, I'll add packages for 4.4+ a bit later.

[Ruslan-B]

closing the issue as fulfilled