swscale: replace formatConvBuffer[VOF] by allocated array.

This allows to convert between formats of arbitrary width,
regardless of the value of VOF/VOFW.

libswscale/swscale_internal.h

@@ -118,7 +118,7 @@ typedef struct SwsContext {
     int       chrBufIndex;        ///< Index in ring buffer of the last scaled horizontal chroma     line from source.
     //@}
 
-    uint8_t formatConvBuffer[VOF]; //FIXME dynamic allocation, but we have to change a lot of code for this to be useful
+    uint8_t *formatConvBuffer;
 
     /**
      * @name Horizontal and vertical filters.

libswscale/swscale_template.c

@@ -490,9 +490,10 @@ inline static void hcscale_c(SwsContext *c, uint16_t *dst, long dstWidth,
     src2 += c->chrSrcOffset;
 
     if (c->chrToYV12) {
-        c->chrToYV12(formatConvBuffer, formatConvBuffer+VOFW, src1, src2, srcW, pal);
+        uint8_t *buf2 = formatConvBuffer + FFALIGN(srcW*2+78, 16);
+        c->chrToYV12(formatConvBuffer, buf2, src1, src2, srcW, pal);
         src1= formatConvBuffer;
-        src2= formatConvBuffer+VOFW;
+        src2= buf2;
     }
 
     if (c->hScale16) {

libswscale/utils.c

@@ -798,6 +798,7 @@ int sws_init_context(SwsContext *c, SwsFilter *srcFilter, SwsFilter *dstFilter)
         av_log(NULL, AV_LOG_ERROR, "swScaler: Compile-time maximum width is "AV_STRINGIFY(VOFW)" change VOF/VOFW and recompile\n");
         return AVERROR(EINVAL);
     }
+    FF_ALLOC_OR_GOTO(c, c->formatConvBuffer, FFALIGN(srcW*2+78, 16) * 2, fail);
 
     if (!dstFilter) dstFilter= &dummyFilter;
     if (!srcFilter) srcFilter= &dummyFilter;
@@ -1522,6 +1523,7 @@ void sws_freeContext(SwsContext *c)
 #endif /* HAVE_MMX */
 
     av_freep(&c->yuvTable);
+    av_freep(&c->formatConvBuffer);
 
     av_free(c);
 }