How to open anullsrc input?

Question

I'm trying:

    avformat_open_input(
        &input_context,
        "anullsrc",       
        NULL,
        NULL
    );

That however does not work and input_context remains NULL.

The 3rd argument, NULL, is an optional AVInputFormat. https://ffmpeg.org/doxygen/trunk/group__lavf__decoding.html#gac05d61a2b492ae3985c658f34622c19d

fmt If non-NULL, this parameter forces a specific input format. Otherwise the format is autodetected.

I wanted to supply it by first creating the AVInputFormat with av_find_input_format - that however fails to find the format (lavfi), because it seems not to be registered in file ./libavformat/allformats.c even though it exists in ./libavdevice/lavfi.c.

Edit

I might have found an issue. When I do:

$ ffmpeg -v 0 -demuxers | grep lavfi

The output is:

 D  lavfi           Libavfilter virtual input device

However, when I do:

main | grep lavfi

Where main is my program which includes:

    while ((fmt = av_demuxer_iterate(&i)))                                      
        printf("%s\n", fmt->name);  

I get no output (I confirm that some demuxers are listed if I don't grep for lavfi).

So it seems then, that libavformat.h does not know about lavfi demuxer, whereas ffmpeg does. So it seems I need to fix this issue now.

Answer 1

I found a way.

I need to include:

#include <libavdevice/avdevice.h>

Which allows me to do:

    const AVInputFormat *ifmt = NULL;

    while ((ifmt = av_input_audio_device_next(ifmt)))
    {
        printf("%s\n", ifmt->name);
        if (!strcmp(ifmt->name, "lavfi"))
            break;
    }

And then this works:

    AVFormatContext *ic = NULL;
    avformat_open_input(
        &ic,
        "anullsrc",       
        ifmt,
        NULL
    );