[Libav-user] Getings alsa inout format fails

Marcin Wielechowski panmarcinwielechowski at gmail.com
Fri Aug 12 23:28:56 EEST 2016


I'm trying to write application that grabbs audio using alsa on 
Raspberry pi.
By I have a problem with getting alsa input format.
Function av_find_input_format("alsa") returning null.
Do You have any advices what may I be doing wrong? All help is appreciated.

The code that fails:

     const char* alsaName = "alsa";


     AVInputFormat* format = av_find_input_format(alsaName); // format  
is null here
     if(format == nullptr)
         printf("Alsa format not found.\n");

What is strange, iterating aver audio device formats return alsa:

     AVInputFormat* p = nullptr;
     format = nullptr;
     while (p = av_input_audio_device_next(p))
         if (strcmp(p->name, alsaName) == 0)
             format = p;

     if(format == nullptr) // here format is not null
         printf("Alsa format not found.\n");

And when I trying to use this format in avformat_open_input, I got SEGFAULT.

Also avdevice_list_input_sources works well, what is more strange that 
it is using internally av_find_input_format.

Also console command
ffmpeg -f alsa -ac 1 -i hw:1 -t 30 out.wav
is working.

Best regards
Marcin Wielechowski

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