atempo filter fails to compile when ffmpeg is configured without rdft

[jamal]

Any ffmpeg configuration that enables the atempo filter but doesn't enable rdft will fail to compile with the following errors:

LD      ffmpeg_g.exe
libavfilter/libavfilter.a(af_atempo.o): In function `yae_flush':
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:906: undefined reference to `_av_rdft_calc'
libavfilter/libavfilter.a(af_atempo.o): In function `yae_xcorr_via_rdft':
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:611: undefined reference to `_av_rdft_calc'
libavfilter/libavfilter.a(af_atempo.o): In function `yae_release_buffers':
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:204: undefined reference to `_av_rdft_end'
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:207: undefined reference to `_av_rdft_end'
libavfilter/libavfilter.a(af_atempo.o): In function `yae_reset':
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:259: undefined reference to `_av_rdft_end'
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:262: undefined reference to `_av_rdft_end'
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:265: undefined reference to `_av_rdft_init'
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:271: undefined reference to `_av_rdft_init'
libavfilter/libavfilter.a(af_atempo.o): In function `yae_apply':
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:815: undefined reference to `_av_rdft_calc'
libavfilter/libavfilter.a(af_atempo.o): In function `yae_xcorr_via_rdft':
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:611: undefined reference to `_av_rdft_calc'
libavfilter/libavfilter.a(af_atempo.o): In function `yae_apply':
D:/msys/1.0/home/jamal/ffmpeg/src/libavfilter/af_atempo.c:847: undefined reference to `_av_rdft_calc'
collect2.exe: error: ld returned 1 exit status
make: *** [ffmpeg_g.exe] Error 1

The solution would be to either make the atempo filter depend on rdft or to force the later's compilation.
Either making

atempo_filter_deps="avcodec"

be

atempo_filter_deps="avcodec rdft"

or by adding a new line like

atempo_filter_select="rdft"

Considering that none of the other filters force the compilation of any other component, maybe the former is the better option.

[Carl Eugen Hoyos]

Changes made, thank you for the report!