From af0a2436fc2465edb844f4ba5376a8c05c4e19ad Mon Sep 17 00:00:00 2001
From: Christopher Snowhill <kode54@gmail.com>
Date: Sat, 11 Jun 2022 06:39:00 -0700
Subject: [PATCH] [FFMPEG Input] Support reading more metadata

Now read all metadata and signal it, and also support pre-buffering
a small block of sample frames if there is embedded artwork, since the
embedded artwork must be handled by the sample decode function.

Signed-off-by: Christopher Snowhill <kode54@gmail.com>
---
 Plugins/FFMPEG/FFMPEGDecoder.h |  5 +++++
 Plugins/FFMPEG/FFMPEGDecoder.m | 41 +++++++++++++++++++++++++++++++---
 2 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/Plugins/FFMPEG/FFMPEGDecoder.h b/Plugins/FFMPEG/FFMPEGDecoder.h
index a817c4f61..ece485ad1 100644
--- a/Plugins/FFMPEG/FFMPEGDecoder.h
+++ b/Plugins/FFMPEG/FFMPEGDecoder.h
@@ -35,6 +35,11 @@
 	AVFrame *lastDecodedFrame;
 	AVPacket *lastReadPacket;
 
+	BOOL metadataUpdated;
+
+	int prebufferedAudio;
+	uint8_t *prebufferedAudioData;
+
 	BOOL rawDSD;
 	BOOL rawDSDReverseBits;
 	BOOL rawDSDPlanar;
diff --git a/Plugins/FFMPEG/FFMPEGDecoder.m b/Plugins/FFMPEG/FFMPEGDecoder.m
index 5bc42c975..b016f36b3 100644
--- a/Plugins/FFMPEG/FFMPEGDecoder.m
+++ b/Plugins/FFMPEG/FFMPEGDecoder.m
@@ -462,8 +462,23 @@ static uint8_t reverse_bits[0x100];
 	replayGainTrackPeak = 0.0;
 	albumArt = [NSData data];
 	id3Metadata = @{};
+	metadataUpdated = NO;
 	[self updateMetadata];
 
+	prebufferedAudio = 0;
+	prebufferedAudioData = NULL;
+
+	if(attachedPicIndex >= 0) {
+		int frameSize = rawDSD ? channels : channels * (bitsPerSample / 8);
+		prebufferedAudioData = malloc(1024 * frameSize);
+		[self readAudio:prebufferedAudioData frames:1024];
+	}
+
+	if(metadataUpdated) {
+		[self willChangeValueForKey:@"metadata"];
+		[self didChangeValueForKey:@"metadata"];
+	}
+
 	return YES;
 }
 
@@ -608,6 +623,8 @@ static uint8_t reverse_bits[0x100];
 		if(![source seekable]) {
 			[self willChangeValueForKey:@"metadata"];
 			[self didChangeValueForKey:@"metadata"];
+		} else {
+			metadataUpdated = YES;
 		}
 	}
 }
@@ -632,19 +649,35 @@ static uint8_t reverse_bits[0x100];
 		if(![source seekable]) {
 			[self willChangeValueForKey:@"metadata"];
 			[self didChangeValueForKey:@"metadata"];
+		} else {
+			metadataUpdated = YES;
 		}
 	}
 }
 
 - (int)readAudio:(void *)buf frames:(UInt32)frames {
+	int frameSize = rawDSD ? channels : channels * (bitsPerSample / 8);
+	int bytesToRead = frames * frameSize;
+	int bytesRead = 0;
+
+	if(prebufferedAudio) {
+		// A bit of ignored read-ahead to support embedded artwork
+		int bytesBuffered = prebufferedAudio * frameSize;
+		int bytesToCopy = (bytesBuffered > bytesToRead) ? bytesToRead : bytesBuffered;
+		memcpy(buf, prebufferedAudioData, bytesToCopy);
+		memmove(prebufferedAudioData, prebufferedAudioData + bytesToCopy, bytesBuffered - bytesToCopy);
+		prebufferedAudio -= bytesToCopy / frameSize;
+		bytesRead = bytesToCopy;
+
+		int framesReadNow = bytesRead / frameSize;
+		framesRead -= framesReadNow;
+	}
+
 	if(totalFrames && framesRead >= totalFrames)
 		return 0;
 
-	int frameSize = rawDSD ? channels : channels * (bitsPerSample / 8);
 	int dataSize = 0;
 
-	int bytesToRead = frames * frameSize;
-	int bytesRead = 0;
 	int seekBytesSkip = 0;
 
 	int errcode;
@@ -852,6 +885,8 @@ static uint8_t reverse_bits[0x100];
 	if(!totalFrames)
 		return -1;
 
+	prebufferedAudio = 0;
+
 	if(frame >= totalFrames) {
 		framesRead = totalFrames;
 		endOfStream = YES;