diff --git a/libavformat/avisynth.c b/libavformat/avisynth.c
index 55a2efd884..43b65badc9 100644
--- a/libavformat/avisynth.c
+++ b/libavformat/avisynth.c
@@ -1,5 +1,5 @@
 /*
- * AviSynth/AvxSynth support
+ * AviSynth(+) support
  * Copyright (c) 2012 AvxSynth Team
  *
  * This file is part of FFmpeg
@@ -31,20 +31,19 @@
 /* Enable function pointer definitions for runtime loading. */
 #define AVSC_NO_DECLSPEC
 
-/* Platform-specific directives for AviSynth vs AvxSynth. */
+/* Platform-specific directives. */
 #ifdef _WIN32
   #include "compat/w32dlfcn.h"
   #undef EXTERN_C
-  #include "compat/avisynth/avisynth_c.h"
   #define AVISYNTH_LIB "avisynth"
-  #define USING_AVISYNTH
 #else
   #include <dlfcn.h>
-  #include "compat/avisynth/avxsynth_c.h"
-  #define AVISYNTH_NAME "libavxsynth"
+  #define AVISYNTH_NAME "libavisynth"
   #define AVISYNTH_LIB AVISYNTH_NAME SLIBSUF
 #endif
 
+#include <avisynth/avisynth_c.h>
+
 typedef struct AviSynthLibrary {
     void *library;
 #define AVSC_DECLARE_FUNC(name) name ## _func name
@@ -62,7 +61,6 @@ 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
     AVSC_DECLARE_FUNC(avs_bits_per_pixel);
     AVSC_DECLARE_FUNC(avs_get_height_p);
     AVSC_DECLARE_FUNC(avs_get_pitch_p);
@@ -70,7 +68,6 @@ typedef struct AviSynthLibrary {
     AVSC_DECLARE_FUNC(avs_get_row_size_p);
     AVSC_DECLARE_FUNC(avs_is_planar_rgb);
     AVSC_DECLARE_FUNC(avs_is_planar_rgba);
-#endif
 #undef AVSC_DECLARE_FUNC
 } AviSynthLibrary;
 
@@ -97,14 +94,12 @@ static const int avs_planes_packed[1] = { 0 };
 static const int avs_planes_grey[1]   = { AVS_PLANAR_Y };
 static const int avs_planes_yuv[3]    = { AVS_PLANAR_Y, AVS_PLANAR_U,
                                           AVS_PLANAR_V };
-#ifdef USING_AVISYNTH
 static const int avs_planes_rgb[3]    = { AVS_PLANAR_G, AVS_PLANAR_B,
                                           AVS_PLANAR_R };
 static const int avs_planes_yuva[4]   = { AVS_PLANAR_Y, AVS_PLANAR_U,
                                           AVS_PLANAR_V, AVS_PLANAR_A };
 static const int avs_planes_rgba[4]   = { AVS_PLANAR_G, AVS_PLANAR_B,
                                           AVS_PLANAR_R, AVS_PLANAR_A };
-#endif
 
 /* A conflict between C++ global objects, atexit, and dynamic loading requires
  * us to register our own atexit handler to prevent double freeing. */
@@ -142,7 +137,6 @@ 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
     LOAD_AVS_FUNC(avs_bits_per_pixel, 1);
     LOAD_AVS_FUNC(avs_get_height_p, 1);
     LOAD_AVS_FUNC(avs_get_pitch_p, 1);
@@ -150,7 +144,6 @@ static av_cold int avisynth_load_library(void)
     LOAD_AVS_FUNC(avs_get_row_size_p, 1);
     LOAD_AVS_FUNC(avs_is_planar_rgb, 1);
     LOAD_AVS_FUNC(avs_is_planar_rgba, 1);
-#endif
 #undef LOAD_AVS_FUNC
 
     atexit(avisynth_atexit_handler);
@@ -249,7 +242,6 @@ 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
     /* 10~16-bit YUV pix_fmts (AviSynth+) */
     case AVS_CS_YUV444P10:
         st->codecpar->format = AV_PIX_FMT_YUV444P10;
@@ -434,8 +426,7 @@ static int avisynth_create_stream_video(AVFormatContext *s, AVStream *st)
     case AVS_CS_BGR64:
         st->codecpar->format = AV_PIX_FMT_BGRA64;
         break;
-#endif
-    /* AviSynth 2.5 and AvxSynth pix_fmts */
+    /* AviSynth 2.5 pix_fmts */
     case AVS_CS_BGR24:
         st->codecpar->format = AV_PIX_FMT_BGR24;
         break;
@@ -461,7 +452,6 @@ static int avisynth_create_stream_video(AVFormatContext *s, AVStream *st)
     }
 
     switch (planar) {
-#ifdef USING_AVISYNTH
     case 5: // Planar RGB + Alpha
         avs->n_planes = 4;
         avs->planes   = avs_planes_rgba;
@@ -474,7 +464,6 @@ static int avisynth_create_stream_video(AVFormatContext *s, AVStream *st)
         avs->n_planes = 3;
         avs->planes   = avs_planes_rgb;
         break;
-#endif
     case 2: // Y8
         avs->n_planes = 1;
         avs->planes   = avs_planes_grey;
@@ -556,7 +545,7 @@ static int avisynth_open_file(AVFormatContext *s)
     AviSynthContext *avs = s->priv_data;
     AVS_Value arg, val;
     int ret;
-#ifdef USING_AVISYNTH
+#ifdef _WIN32
     char filename_ansi[MAX_PATH * 4];
     wchar_t filename_wc[MAX_PATH * 4];
 #endif
@@ -564,7 +553,7 @@ static int avisynth_open_file(AVFormatContext *s)
     if (ret = avisynth_context_create(s))
         return ret;
 
-#ifdef USING_AVISYNTH
+#ifdef _WIN32
     /* 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,
@@ -588,11 +577,9 @@ 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
     /* On Windows, FFmpeg 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
-     * as interface version 3 like 2.5.8, this needs to be special-cased. */
+     * and excludes 2.5 and the 2.6 alphas. */
 
     if (avs_library.avs_get_version(avs->clip) < 6) {
         av_log(s, AV_LOG_ERROR,
@@ -600,7 +587,6 @@ static int avisynth_open_file(AVFormatContext *s)
         ret = AVERROR_UNKNOWN;
         goto fail;
     }
-#endif
 
     /* Release the AVS_Value as it will go out of scope. */
     avs_library.avs_release_value(val);
@@ -652,23 +638,21 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
     if (discard)
         return 0;
 
-#ifdef USING_AVISYNTH
+#ifdef _WIN32
     /* 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)
         avsplus = 0;
     else
         avsplus = 1;
-
-    /* avs_bits_per_pixel changed to AVSC_API with AviSynth 2.6, which
-     * requires going through avs_library, while AvxSynth has it under
-     * the older AVSC_INLINE type, so special-case this. */
-
-    bits = avs_library.avs_bits_per_pixel(avs->vi);
 #else
-    bits = avs_bits_per_pixel(avs->vi);
+    /* AviSynth+ is now the only variant of AviSynth we support
+     * on Linux and macOS. */
+    avsplus = 1;
 #endif
 
+    bits = avs_library.avs_bits_per_pixel(avs->vi);
+
     /* Without the cast to int64_t, calculation overflows at about 9k x 9k
      * resolution. */
     pkt->size = (((int64_t)avs->vi->width *
@@ -696,19 +680,11 @@ 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
         src_p = avs_library.avs_get_read_ptr_p(frame, plane);
         pitch = avs_library.avs_get_pitch_p(frame, plane);
 
         rowsize     = avs_library.avs_get_row_size_p(frame, plane);
         planeheight = avs_library.avs_get_height_p(frame, plane);
-#else
-        src_p = avs_get_read_ptr_p(frame, plane);
-        pitch = avs_get_pitch_p(frame, plane);
-
-        rowsize     = avs_get_row_size_p(frame, plane);
-        planeheight = avs_get_height_p(frame, plane);
-#endif
 
         /* Flip RGB video. */
         if (avs_is_rgb24(avs->vi) || avs_is_rgb(avs->vi)) {
@@ -716,14 +692,12 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
             pitch = -pitch;
         }
 
-#ifdef USING_AVISYNTH
         /* Flip Planar RGB video */
         if (avsplus && (avs_library.avs_is_planar_rgb(avs->vi) ||
                         avs_library.avs_is_planar_rgba(avs->vi))) {
             src_p = src_p + (planeheight - 1) * pitch;
             pitch = -pitch;
         }
-#endif
 
         avs_library.avs_bit_blt(avs->env, dst_p, rowsize, src_p, pitch,
                                  rowsize, planeheight);
