Merge remote-tracking branch 'cehoyos/master'

* cehoyos/master:
  Forward interlaced field information from mov to ffv1 decoder.
  Do not suggest to use gas-preprocessor if using it would break compilation.
Merged-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -3865,7 +3865,9 @@ elif enabled ppc; then
 
     # AltiVec flags: The FSF version of GCC differs from the Apple version
     if enabled altivec; then
-        nogas=warn
+        if ! enabled_any pic ppc64; then
+            nogas=warn
+        fi
         check_cflags -maltivec -mabi=altivec &&
         { check_header altivec.h && inc_altivec_h="#include <altivec.h>" ; } ||
         check_cflags -faltivec

libavcodec/ffv1dec.c

@@ -784,6 +784,13 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
 
     f->cur = p = f->picture.f;
 
+    if (f->version < 3 && avctx->field_order > AV_FIELD_PROGRESSIVE) {
+        /* we have interlaced material flagged in container */
+        p->interlaced_frame = 1;
+        if (avctx->field_order == AV_FIELD_TT || avctx->field_order == AV_FIELD_TB)
+            p->top_field_first = 1;
+    }
+
     f->avctx = avctx;
     ff_init_range_decoder(c, buf, buf_size);
     ff_build_rac_states(c, 0.05 * (1LL << 32), 256 - 8);