avcodec/rdft: Use more specific error codes

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/rdft.c

@@ -99,16 +99,17 @@ static void rdft_calc_c(RDFTContext *s, FFTSample *data)
 av_cold int ff_rdft_init(RDFTContext *s, int nbits, enum RDFTransformType trans)
 {
     int n = 1 << nbits;
+    int ret;
 
     s->nbits           = nbits;
     s->inverse         = trans == IDFT_C2R || trans == DFT_C2R;
     s->sign_convention = trans == IDFT_R2C || trans == DFT_C2R ? 1 : -1;
 
     if (nbits < 4 || nbits > 16)
-        return -1;
+        return AVERROR(EINVAL);
 
-    if (ff_fft_init(&s->fft, nbits-1, trans == IDFT_C2R || trans == IDFT_R2C) < 0)
-        return -1;
+    if ((ret = ff_fft_init(&s->fft, nbits-1, trans == IDFT_C2R || trans == IDFT_R2C)) < 0)
+        return ret;
 
     ff_init_ff_cos_tabs(nbits);
     s->tcos = ff_cos_tabs[nbits];