Fix seek and trim issues

Author: natario1

demo/src/main/java/com/otaliastudios/transcoder/demo/TranscoderActivity.java

@@ -38,7 +38,6 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.Future;
-import java.util.function.Consumer;
 
 import androidx.annotation.NonNull;
 import androidx.appcompat.app.AppCompatActivity;

lib/src/main/java/com/otaliastudios/transcoder/internal/Segments.kt

@@ -68,6 +68,18 @@ internal class Segments(
         log.i("tryCreateSegment($type, $index): created!")
         if (tracks.active.has(type)) {
             source.selectTrack(type)
+            // TODO this sucks
+            // By design, all sources must select all tracks before seeking. We can achieve this
+            // here but it still doesn't look right. The other source might be on a different
+            // point in the timeline, or it might be hidden because wrapped in a DataSourceWrapper...
+            // We have no checks for any of these options and they can all break concatenation.
+            val other = when (type) {
+                TrackType.AUDIO -> TrackType.VIDEO
+                TrackType.VIDEO -> TrackType.AUDIO
+            }
+            if (tracks.active.has(other) && sources[other].any { it === source }) {
+                source.selectTrack(other)
+            }
         }
         // Update current index before pipeline creation, for other components
         // who check it during pipeline init.

lib/src/main/java/com/otaliastudios/transcoder/source/DefaultDataSource.java

@@ -120,15 +120,19 @@ public boolean isInitialized() {
     @Override
     public void selectTrack(@NonNull TrackType type) {
         LOG.i("selectTrack(" + type + ")");
-        mSelectedTracks.add(type);
-        mExtractor.selectTrack(mIndex.get(type));
+        if (!mSelectedTracks.contains(type)) {
+            mSelectedTracks.add(type);
+            mExtractor.selectTrack(mIndex.get(type));
+        }
     }
 
     @Override
     public void releaseTrack(@NonNull TrackType type) {
         LOG.i("releaseTrack(" + type + ")");
-        mSelectedTracks.remove(type);
-        mExtractor.unselectTrack(mIndex.get(type));
+        if (mSelectedTracks.contains(type)) {
+            mSelectedTracks.remove(type);
+            mExtractor.unselectTrack(mIndex.get(type));
+        }
     }
 
     protected abstract void initializeExtractor(@NonNull MediaExtractor extractor) throws IOException;

lib/src/main/java/com/otaliastudios/transcoder/source/TrimDataSource.java

@@ -58,17 +58,29 @@ public void initialize() {
             throw new IllegalArgumentException(
                     "Trim values cannot be greater than media duration.");
         }
+        LOG.i("initialize(): duration=" + duration
+                + " trimStart=" + trimStartUs
+                + " trimEnd=" + trimEndUs
+                + " trimDuration=" + (duration - trimStartUs - trimEndUs));
         trimDurationUs = duration - trimStartUs - trimEndUs;
     }
 
+    // Assuming e.g. video of 8 seconds, trimStart=2s, trimEnd=1s.
+    // The trimmed duration is 5 seconds. Assume also that the video has sparse keyframes
+    // so that when we do seekTo(2s), it returns 0 because it couldn't seek there. We have two options:
+    // - duration=5s, position goes from -2s to 5s
+    // - duration=7s, position goes from 0s to 7s
+    // What we choose is not so important, as long as we use the same approach in getDurationUs
+    // and getPositionUs consistently. Approach 1 would be easier (no extra) but also weird.
+
     @Override
     public long getDurationUs() {
         return trimDurationUs + extraDurationUs;
     }
 
     @Override
     public long getPositionUs() {
-        return super.getPositionUs() - trimStartUs;
+        return super.getPositionUs() - trimStartUs + extraDurationUs;
     }
 
     @Override
@@ -77,6 +89,9 @@ public boolean canReadTrack(@NonNull TrackType type) {
         // tracks have been selected.
         if (!trimDone && trimStartUs > 0) {
             extraDurationUs = trimStartUs - getSource().seekTo(trimStartUs);
+            LOG.i("canReadTrack(): extraDurationUs=" + extraDurationUs
+                    + " trimStartUs=" + trimStartUs
+                    + " source.seekTo(trimStartUs)=" + (extraDurationUs - trimStartUs));
             trimDone = true;
         }
         return super.canReadTrack(type);