Avoid decoding packets with no relevant timestamps

lib/ffmpeg_api/src/api.rs

@@ -223,6 +223,10 @@ impl AVPacket {
         unsafe { self.base.as_ref() }.unwrap_or_else(|| panic!("AVPacket base unexpectedly null"))
     }
 
+    pub fn duration(&self) -> i64 {
+        self.as_ref().duration
+    }
+
     pub fn pts(&self) -> i64 {
         self.as_ref().pts
     }

src/lib.rs

@@ -91,6 +91,23 @@ pub fn extract(
 
         while avformat_context.read_frame(&mut packet).is_ok() {
             if packet.stream_index() == index {
+                let duration = media_time::MediaTime::from_rational(packet.duration(), &time_base)?;
+                let start = media_time::MediaTime::from_rational(packet.pts(), &time_base)?;
+                let end = start + duration;
+
+                let mut skip = true;
+                if let Some(spritesheet_manager) = &mut spritesheet_manager {
+                    if spritesheet_manager.fulfils_frame_interval(end) {
+                        skip = false;
+                    }
+                }
+                if let Some(timelens_manager) = &mut timelens_manager {
+                    if timelens_manager.fulfils_frame_interval(end) {
+                        skip = false;
+                    }
+                }
+
+                if !skip {
                     codec_context
                         .in_packet(&mut packet)
                         .map_err(|error| format_err!("Could not load packet: {}", error))?;
@@ -124,6 +141,7 @@ pub fn extract(
                     }
                 }
             }
+        }
 
         if let Some(spritesheet_manager) = &mut spritesheet_manager {
             spritesheet_manager.end_frame(duration);