Fix Avisynth compilation and update headers

.gitignore

@@ -18,6 +18,7 @@ tools/repack-thes-dict.dSYM
 
 # Meson
 build*/
+subprojects/avisynth
 subprojects/boost*/
 subprojects/cairo*
 subprojects/ffmpeg

meson.build

@@ -1,6 +1,6 @@
 project('Aegisub', ['c', 'cpp'],
         license: 'BSD-3-Clause',
-        meson_version: '>=0.56.1',
+        meson_version: '>=0.57.0',
         default_options: ['cpp_std=c++14', 'buildtype=debugoptimized'],
         version: '3.2.2')
 
@@ -220,8 +220,21 @@ foreach dep: [
     endif
 endforeach
 
-if host_machine.system() == 'windows' and get_option('avisynth').enabled()
+if get_option('avisynth').enabled()
     conf.set('WITH_AVISYNTH', 1) # bundled separately with installer
+    dep_avail += 'AviSynth'
+
+    avs_opt = cmake.subproject_options()
+    avs_opt.add_cmake_defines({
+        'HEADERS_ONLY': true
+    })
+
+    avs = cmake.subproject('avisynth', options: avs_opt)
+    deps_inc += avs.include_directories('AviSynth-Headers')
+
+    if host_machine.system() == 'windows'
+      deps += cc.find_library('avifil32', required: true)
+    endif
 endif
 
 if host_machine.system() == 'windows' and not get_option('directsound').disabled()

src/audio_provider_avs.cpp

@@ -63,9 +63,7 @@ class AvisynthAudioProvider final : public agi::AudioProvider {
 	bool NeedsCache() const override { return true; }
 };
 
-AvisynthAudioProvider::AvisynthAudioProvider(agi::fs::path const& filename) {
-	agi::acs::CheckFileRead(filename);
-
+AvisynthAudioProvider::AvisynthAudioProvider(agi::fs::path const& filename) try {
 	std::lock_guard<std::mutex> lock(avs_wrapper.GetMutex());
 
 	try {
@@ -100,19 +98,25 @@ AvisynthAudioProvider::AvisynthAudioProvider(agi::fs::path const& filename) {
 			throw agi::AudioProviderError("Avisynth error: " + errmsg);
 	}
 }
+catch (AvisynthError& err) {
+	throw agi::AudioProviderError("Avisynth error: " + std::string(err.msg));
+}
 
 void AvisynthAudioProvider::LoadFromClip(AVSValue clip) {
 	// Check if it has audio
 	VideoInfo vi = clip.AsClip()->GetVideoInfo();
 	if (!vi.HasAudio()) throw agi::AudioDataNotFound("No audio found.");
 
 	IScriptEnvironment *env = avs_wrapper.GetEnv();
+	AVSValue script;
 
 	// Convert to one channel
-	AVSValue script = env->Invoke(OPT_GET("Audio/Downmixer")->GetString().c_str(), clip);
+	std::string downmixtype = OPT_GET("Audio/Downmixer")->GetString();
+	if (downmixtype == "ConvertToMono" || downmixtype == "GetLeftChannel" || downmixtype == "GetRightChannel")
+		script = env->Invoke(downmixtype.c_str(), clip);
+	else
+		script = clip;
 
-	// Convert to 16 bits per sample
-	script = env->Invoke("ConvertAudioTo16bit", script);
 	vi = script.AsClip()->GetVideoInfo();
 
 	// Convert sample rate
@@ -132,8 +136,8 @@ void AvisynthAudioProvider::LoadFromClip(AVSValue clip) {
 	channels = vi.AudioChannels();
 	decoded_samples = num_samples = vi.num_audio_samples;
 	sample_rate = vi.SamplesPerSecond();
-	bytes_per_sample = vi.BytesPerAudioSample();
-	float_samples = false;
+	bytes_per_sample = vi.BytesPerChannelSample();
+	float_samples = vi.IsSampleType(SAMPLE_FLOAT);
 
 	this->clip = tempclip;
 }