From 68461866d806d9ceee03d70049b75ca6e492aa8a Mon Sep 17 00:00:00 2001
From: _ <_@_>
Date: Sat, 13 Nov 2021 11:23:10 -0600
Subject: [PATCH] :bug: bug: popping is gone

It was a combination of two bugs:

1. For some reason, libswresample sometimes returns more data than you need.
Like, it'll return X samples but _more than_ 8X bytes, for f32 stereo.

2. I wasn't supposed to be calling `flush`. I should have been calling
`run` with a dummy frame. This isn't intuitive to me, and it required
me to construct a dummy frame and keep it around in my code. I think
this is pretty inelegant. And looking at the ffmpeg code, I think it's
a flaw in the API design of the `ffmpeg_next` crate. I may ask them
about it in the future.
---
 src/decoder.rs | 67 +++++++++++++++++++++++++-------------------------
 todo.md        |  2 --
 2 files changed, 33 insertions(+), 36 deletions(-)

diff --git a/src/decoder.rs b/src/decoder.rs
index 3b77d8c..1acb702 100644
--- a/src/decoder.rs
+++ b/src/decoder.rs
@@ -84,9 +84,11 @@ pub struct SharedState {
 
 pub struct Decoder {
 	pub input_ctx: DemuxContext,
-	best_stream_idx: usize,
 	pub decoder: DecodeContext,
 	pub resampler: ResamplingContext,
+	
+	best_stream_idx: usize,
+	dummy_frame: Option <AudioFrame>,
 }
 
 impl Decoder {
@@ -107,9 +109,11 @@ impl Decoder {
 		
 		Ok (Self {
 			input_ctx,
-			best_stream_idx,
 			decoder,
 			resampler,
+			
+			best_stream_idx,
+			dummy_frame: None,
 		})
 	}
 	
@@ -133,8 +137,8 @@ impl Decoder {
 			if actual_bytes > expected_bytes {
 				let extra_bytes = actual_bytes - expected_bytes;
 				let extra_samples = extra_bytes / 4 / 2;
-				tracing::debug! ("Extra bytes: {}", extra_bytes);
-				tracing::debug! ("Extra samples: {}", extra_samples);
+				// tracing::debug! ("Extra bytes: {}", extra_bytes);
+				// tracing::debug! ("Extra samples: {}", extra_samples);
 			}
 			
 			Some (frame)
@@ -175,26 +179,18 @@ impl Decoder {
 	}
 	
 	pub fn pump_resampler (&mut self) -> Result <Option <AudioFrame>> {
-		let delay = match self.resampler.delay () {
+		let frame_src = match self.dummy_frame.as_ref () {
 			None => return Ok (None),
 			Some (x) => x,
 		};
 		
-		let mut frame_src = AudioFrame::new (
-			Sample::F32 (sample::Type::Planar),
-			0,
-			ChannelLayout::STEREO
-		);
 		let mut frame_resampled = Self::new_frame ();
 		
-		frame_src.set_rate (44100);
-		
-		tracing::trace! ("Flushing resampler");
-		tracing::trace! ("delay: {:?}", delay);
 		let _rc = self.resampler.run (&frame_src, &mut frame_resampled)?;
 		// dbg! (&frame_resampled, rc);
 		
 		Ok (if frame_resampled.samples () > 0 {
+			// tracing::trace! ("Pulled from resampler FIFO");
 			Some (frame_resampled)
 		}
 		else {
@@ -203,28 +199,31 @@ impl Decoder {
 	}
 	
 	pub fn pump_decoder (&mut self) -> Result <Option <AudioFrame>> {
-		let mut frame_src = ffmpeg_next::util::frame::Audio::empty ();
-		let rc = self.decoder.receive_frame (&mut frame_src);
-		// dbg! (&rc);
-		Ok (if rc.is_ok () {
-			// dbg! (&frame_src);
-			
-			//let nb_output_samples = frame_src.samples () * SAMPLE_RATE as usize / frame_src.rate () as usize;
-			
-			let nb_output_samples = frame_src.samples ();
-			
-			let mut frame_resampled = AudioFrame::new (
-				Sample::F32 (sample::Type::Packed),
-				nb_output_samples,
-				ChannelLayout::STEREO
+		let mut frame_src = AudioFrame::empty ();
+		if let Err (_) = self.decoder.receive_frame (&mut frame_src) {
+			return Ok (None);
+		};
+		
+		if self.dummy_frame.is_none () {
+			let mut dummy_frame = AudioFrame::new (
+				frame_src.format (),
+				0,
+				frame_src.channel_layout (),
 			);
-			
-			self.resampler.run (&frame_src, &mut frame_resampled)?;
-			Some (frame_resampled)
+			dummy_frame.set_rate (frame_src.rate ());
+			self.dummy_frame = Some (dummy_frame);
 		}
-		else {
-			None
-		})
+		
+		let nb_output_samples = frame_src.samples ();
+		
+		let mut frame_resampled = AudioFrame::new (
+			Sample::F32 (sample::Type::Packed),
+			nb_output_samples,
+			ChannelLayout::STEREO
+		);
+		
+		self.resampler.run (&frame_src, &mut frame_resampled)?;
+		Ok (Some (frame_resampled))
 	}
 	
 	pub fn pump_demuxer (&mut self) -> Result <bool> {
diff --git a/todo.md b/todo.md
index 07505b3..f45c96a 100644
--- a/todo.md
+++ b/todo.md
@@ -1,3 +1 @@
 # Critical
-
-- Popping every 1-3 seconds-ish