Compile error 'AVFifoBuffer'

Slackware64 15.0

MPlayer At revision 38449
ffmpeg version 4.4.2

-2.0/include -c -o libao2/ao_sdl.o libao2/ao_sdl.c
libao2/ao_sdl.c:68:8: error: unknown type name 'AVFifoBuffer'
    68 | static AVFifoBuffer *buffer;
       |        ^~~~~~~~~~~~
libao2/ao_sdl.c: In function 'write_buffer':
libao2/ao_sdl.c:75:14: error: implicit declaration of function 
'av_fifo_space'; did you mean 'av_fifo_peek'? 
[-Werror=implicit-function-declaration]
    75 |   int free = av_fifo_space(buffer);
       |              ^~~~~~~~~~~~~
       |              av_fifo_peek
libao2/ao_sdl.c:77:10: error: implicit declaration of function 
'av_fifo_generic_write'; did you mean 'av_fifo_can_write'? 
[-Werror=implicit-function-declaration]
    77 |   return av_fifo_generic_write(buffer, data, len, NULL);
       |          ^~~~~~~~~~~~~~~~~~~~~
       |          av_fifo_can_write
libao2/ao_sdl.c: In function 'read_buffer':
libao2/ao_sdl.c:87:18: error: implicit declaration of function 
'av_fifo_size'; did you mean 'av_fifo_write'? 
[-Werror=implicit-function-declaration]
    87 |   int buffered = av_fifo_size(buffer);
       |                  ^~~~~~~~~~~~
       |                  av_fifo_write
libao2/ao_sdl.c:92:3: error: implicit declaration of function 
'av_fifo_generic_read'; did you mean 'av_fifo_can_read'? 
[-Werror=implicit-function-declaration]
    92 |   av_fifo_generic_read(buffer, data, len, NULL);
       |   ^~~~~~~~~~~~~~~~~~~~
       |   av_fifo_can_read
libao2/ao_sdl.c: In function 'init':
libao2/ao_sdl.c:141:18: error: implicit declaration of function 
'av_fifo_alloc'; did you mean 'av_fifo_alloc2'? 
[-Werror=implicit-function-declaration]
   141 |         buffer = av_fifo_alloc(BUFFSIZE);
       |                  ^~~~~~~~~~~~~
       |                  av_fifo_alloc2
libao2/ao_sdl.c:141:16: warning: assignment to 'int *' from 'int' makes 
pointer from integer without a cast [-Wint-conversion]
   141 |         buffer = av_fifo_alloc(BUFFSIZE);
       |                ^
libao2/ao_sdl.c: In function 'uninit':
libao2/ao_sdl.c:257:9: error: implicit declaration of function 
'av_fifo_free'; did you mean 'av_fifo_freep2'? 
[-Werror=implicit-function-declaration]
   257 |         av_fifo_free(buffer);
       |         ^~~~~~~~~~~~
       |         av_fifo_freep2
libao2/ao_sdl.c: In function 'reset':
libao2/ao_sdl.c:267:9: error: implicit declaration of function 
'av_fifo_reset'; did you mean 'av_fifo_reset2'? 
[-Werror=implicit-function-declaration]
   267 |         av_fifo_reset(buffer);
       |         ^~~~~~~~~~~~~
       |         av_fifo_reset2
cc1: some warnings being treated as errors
make: *** [Makefile:730: libao2/ao_sdl.o] Error 1

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