build: Separate avisynth and avxsynth support

This simplifies the code.

configure

@@ -188,6 +188,7 @@ External library support:
   themselves, not all their features will necessarily be usable by Libav.
 
   --enable-avisynth          video frameserver
+  --enable-avxsynth          Linux version of AviSynth
   --enable-bzlib             bzip2 compression [autodetect]
   --enable-frei0r            video filtering plugins
   --enable-gnutls            crypto
@@ -1268,6 +1269,7 @@ EXTERNAL_LIBRARY_LIST="
     $EXTERNAL_LIBRARY_NONFREE_LIST
     $EXTERNAL_LIBRARY_VERSION3_LIST
     avisynth
+    avxsynth
     bzlib
     frei0r
     gnutls
@@ -2243,6 +2245,10 @@ vc1_parser_select="vc1dsp"
 mjpeg2jpeg_bsf_select="jpegtables"
 
 # external libraries
+avisynth_deps="LoadLibrary"
+avxsynth_deps="dlopen"
+avisynth_demuxer_deps_any="avisynth avxsynth"
+avisynth_demuxer_select="riffdec"
 libdcadec_decoder_deps="libdcadec"
 libfaac_encoder_deps="libfaac"
 libfaac_encoder_select="audio_frame_queue"
@@ -2302,8 +2308,6 @@ asf_muxer_select="riffenc"
 asf_stream_muxer_select="asf_muxer"
 avi_demuxer_select="iso_media riffdec"
 avi_muxer_select="riffenc"
-avisynth_demuxer_deps="avisynth"
-avisynth_demuxer_select="riffdec"
 caf_demuxer_select="iso_media riffdec"
 dash_muxer_select="mp4_muxer"
 dirac_demuxer_select="dirac_parser"
@@ -4610,9 +4614,8 @@ for func in $MATH_FUNCS; do
 done
 
 # these are off by default, so fail if requested and not available
-enabled avisynth          && { check_lib "avisynth/avisynth_c.h windows.h" LoadLibrary ||
-                               check_lib "avxsynth/avxsynth_c.h dlfcn.h" dlopen -ldl   ||
-                               die "ERROR: LoadLibrary/dlopen not found, or avisynth header not found"; }
+enabled avisynth          && { check_header avisynth/avisynth_c.h || die "ERROR: avisynth/avisynth_c.h header not found"; }
+enabled avxsynth          && require avxsynth "avxsynth/avxsynth_c.h dlfcn.h" dlopen -ldl
 enabled cuda              && check_lib cuda.h cuInit -lcuda
 enabled frei0r            && { check_header frei0r.h || die "ERROR: frei0r.h header not found"; }
 enabled gnutls            && require_pkg_config gnutls gnutls/gnutls.h gnutls_global_init

libavformat/Makefile

@@ -85,7 +85,6 @@ OBJS-$(CONFIG_AU_DEMUXER)                += au.o pcm.o
 OBJS-$(CONFIG_AU_MUXER)                  += au.o rawenc.o
 OBJS-$(CONFIG_AVI_DEMUXER)               += avidec.o
 OBJS-$(CONFIG_AVI_MUXER)                 += avienc.o
-OBJS-$(CONFIG_AVISYNTH)                  += avisynth.o
 OBJS-$(CONFIG_AVM2_MUXER)                += swfenc.o swf.o
 OBJS-$(CONFIG_AVS_DEMUXER)               += avs.o voc_packet.o voc.o
 OBJS-$(CONFIG_BETHSOFTVID_DEMUXER)       += bethsoftvid.o
@@ -379,6 +378,7 @@ OBJS-$(CONFIG_YUV4MPEGPIPE_DEMUXER)      += yuv4mpegdec.o
 OBJS-$(CONFIG_YUV4MPEGPIPE_MUXER)        += yuv4mpegenc.o
 
 # external libraries
+OBJS-$(CONFIG_AVISYNTH_DEMUXER)          += avisynth.o
 OBJS-$(CONFIG_LIBRTMP)                   += librtmp.o
 
 # protocols I/O

libavformat/avisynth.c

@@ -32,12 +32,11 @@
 #define AVSC_NO_DECLSPEC
 
 /* Platform-specific directives for AviSynth vs AvxSynth. */
-#ifdef _WIN32
+#if CONFIG_AVISYNTH
   #include <windows.h>
   #undef EXTERN_C
   #include <avisynth/avisynth_c.h>
   #define AVISYNTH_LIB "avisynth"
-  #define USING_AVISYNTH
 #else
   #include <dlfcn.h>
   #include <avxsynth/avxsynth_c.h>
@@ -66,7 +65,7 @@ typedef struct AviSynthLibrary {
     AVSC_DECLARE_FUNC(avs_release_value);
     AVSC_DECLARE_FUNC(avs_release_video_frame);
     AVSC_DECLARE_FUNC(avs_take_clip);
-#ifdef USING_AVISYNTH
+#if CONFIG_AVISYNTH
     AVSC_DECLARE_FUNC(avs_bits_per_pixel);
     AVSC_DECLARE_FUNC(avs_get_height_p);
     AVSC_DECLARE_FUNC(avs_get_pitch_p);
@@ -146,7 +145,7 @@ static av_cold int avisynth_load_library(void)
     LOAD_AVS_FUNC(avs_release_value, 0);
     LOAD_AVS_FUNC(avs_release_video_frame, 0);
     LOAD_AVS_FUNC(avs_take_clip, 0);
-#ifdef USING_AVISYNTH
+#if CONFIG_AVISYNTH
     LOAD_AVS_FUNC(avs_bits_per_pixel, 1);
     LOAD_AVS_FUNC(avs_get_height_p, 1);
     LOAD_AVS_FUNC(avs_get_pitch_p, 1);
@@ -253,7 +252,7 @@ static int avisynth_create_stream_video(AVFormatContext *s, AVStream *st)
     avpriv_set_pts_info(st, 32, avs->vi->fps_denominator, avs->vi->fps_numerator);
 
     switch (avs->vi->pixel_type) {
-#ifdef USING_AVISYNTH
+#if CONFIG_AVISYNTH
     /* 10~16-bit YUV pix_fmts (AviSynth+) */
     case AVS_CS_YUV444P10:
         st->codecpar->format = AV_PIX_FMT_YUV444P10;
@@ -509,7 +508,7 @@ static int avisynth_open_file(AVFormatContext *s)
     AviSynthContext *avs = s->priv_data;
     AVS_Value arg, val;
     int ret;
-#ifdef USING_AVISYNTH
+#if CONFIG_AVISYNTH
     char filename_ansi[MAX_PATH * 4];
     wchar_t filename_wc[MAX_PATH * 4];
 #endif
@@ -517,7 +516,7 @@ static int avisynth_open_file(AVFormatContext *s)
     if (ret = avisynth_context_create(s))
         return ret;
 
-#ifdef USING_AVISYNTH
+#if CONFIG_AVISYNTH
     /* Convert UTF-8 to ANSI code page */
     MultiByteToWideChar(CP_UTF8, 0, s->filename, -1, filename_wc, MAX_PATH * 4);
     WideCharToMultiByte(CP_THREAD_ACP, 0, filename_wc, -1, filename_ansi,
@@ -541,7 +540,7 @@ static int avisynth_open_file(AVFormatContext *s)
     avs->clip = avs_library.avs_take_clip(val, avs->env);
     avs->vi   = avs_library.avs_get_video_info(avs->clip);
 
-#ifdef USING_AVISYNTH
+#if CONFIG_AVISYNTH
     /* On Windows, libav supports AviSynth interface version 6 or higher.
      * This includes AviSynth 2.6 RC1 or higher, and AviSynth+ r1718 or higher,
      * and excludes 2.5 and the 2.6 alphas. Since AvxSynth identifies itself
@@ -605,7 +604,7 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
     if (discard)
         return 0;
 
-#ifdef USING_AVISYNTH
+#if CONFIG_AVISYNTH
     /* Detect whether we're using AviSynth 2.6 or AviSynth+ by
      * looking for whether avs_is_planar_rgb exists. */
     if (GetProcAddress(avs_library.library, "avs_is_planar_rgb") == NULL)
@@ -649,7 +648,7 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
     dst_p = pkt->data;
     for (i = 0; i < avs->n_planes; i++) {
         plane = avs->planes[i];
-#ifdef USING_AVISYNTH
+#if CONFIG_AVISYNTH
         src_p = avs_library.avs_get_read_ptr_p(frame, plane);
         pitch = avs_library.avs_get_pitch_p(frame, plane);