[Libav-user] Dynamic_input filters and avfilter_pad_get_type

[Paul B Mahol]

On Wed, May 14, 2025 at 4:27 AM Andrew Randrianasulu <
randrianasulu at gmail.com> wrote:

> On Sat, May 10, 2025 at 11:14 AM Andrew Randrianasulu
> <randrianasulu at gmail.com> wrote:
> >
> > On Sat, May 10, 2025 at 9:05 AM Paul B Mahol <onemda at gmail.com> wrote:
> > >
> > >
> > >
> > > On Fri, May 9, 2025 at 11:38 PM Andrew Randrianasulu <
> randrianasulu at gmail.com> wrote:
> > >>
> > >> I was looking at why our application (cinelerra-gg) crashed at trying
> to use libplacebo
> > >>
> > >> I found that libplacebo defines itself
> > >>
> > >> https://ffmpeg.org/doxygen/7.0/vf__libplacebo_8c.html
> > >>
> > >> as
> > >>
> > >>  .flags = AVFILTER_FLAG_HWDEVICE | AVFILTER_FLAG_DYNAMIC_INPUTS,
> > >>
> > >> so only output pad is defined, as far as I can see:
> > >>
> > >> static const AVFilterPad libplacebo_outputs[] = {
> > >>   {
> > >>   .name = "default",
> > >>   .type = AVMEDIA_TYPE_VIDEO,
> > >>   .config_props = &libplacebo_config_output,
> > >>   },
> > >>  };
> > >>
> > >>
> > >>
> > >> then when our code calls
> > >>
> > >> avfilter_pad_get_type()
> > >
> > >
> > > You need to call it only after filtergraph have been configured, not
> before because in such cases number of output pads may be 0 before
> configuration.
> > > In  any case you need to check current number of input pads and output
> pads for each filter before trying to access them.
> > >
> >
> > Thanks. Attached patch  makes this crash go away, just 32-bit cingg
> > can't cope with 4k frames filtering en-masse :)
>
> Sadly wtch ffmpeg.git patch does not work anymore.
>
> I tried to use
>
> int       nb_pads = avfilter_filter_pad_count(filter,0);
>

input pads != output pads


>
> but this one apparently crashes when I try zscale :(
>
> while may be zscale was just not compiled in?
>
> I'll retry with some more env. options.
>
> On the plus side ffmpeg.git + radv + h264 video = it mostly works.
> Some vids still crash us ...
>
>
> >
> > Andrea, can you test attached patch +  this opts file put alongside
> > test 4k HDR video  decodable by hardware?
> >
> >
> >
> > >
> > >>
> > >>
> > >> it promptly crashes.
> > >>
> > >>  BC_Signals::dump_stack
> > >> cin() [0x8b2c9e2]
> > >> linux-gate.so.1(__kernel_rt_sigreturn+0) [0xf7fb8590]
> > >> cin(avfilter_pad_get_type+0x14) [0x99266a4]
> > >> cin(_ZN13FFVideoStream13create_filterEPKc+0xbc) [0x865669c]
> > >> cin(_ZN6FFMPEG12open_decoderEv+0x80f) [0x865732f]
> > >> cin(_ZN10FileFFMPEG9check_sigEP5Asset+0x81) [0x8670071]
> > >> cin(_ZN4File5probeEv+0x376) [0x867cd86]
> > >> cin(_ZN4File9open_fileEP11PreferencesP5Assetii+0x378) [0x867d628]
> > >> cin(_ZN7MWindow14load_filenamesEP9ArrayListIPcEiii+0x250) [0x87301f0]
> > >> cin(_ZN17CommandLineThread3runEv+0x53) [0x86e2cd3]
> > >> cin(_ZN6Thread10entrypointEPv+0x41) [0x8b70c11]
> > >> /lib/libpthread.so.0(+0x7328) [0xf7df9328]
> > >> /lib/libc.so.6(clone+0x66) [0xf0373f06]
> > >>
> > >>
> > >>
> > >> We still hope to get libplacebo's tonemapping  + vulkan hevc decoding
> going, so any pointers how to talk to those dynamic_input filters will be
> useful. Even swscale is dynamic_input in ffmpeg 7.1+, so I (we) really hope
> to keep it working, too.
> > >>
> > >> Code:
> > >>
> > >>
> https://git.cinelerra-gg.org/git/?p=goodguy/cinelerra.git;a=blob;f=cinelerra-5.1/cinelerra/ffmpeg.C;h=1d0979df59f932628246678a920aca002d8dd88b;hb=HEAD#l3893
> > >>
> > >>
> > >>
> > >> _______________________________________________
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> > >>
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> > >
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