Make FLV video seekable by a seekMap.

library/extractor/src/main/java/com/google/android/exoplayer2/extractor/flv/FlvExtractor.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.extractor.flv;
 
 import androidx.annotation.IntDef;
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.extractor.ChunkIndex;
 import com.google.android.exoplayer2.extractor.Extractor;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.ExtractorOutput;
@@ -29,6 +30,7 @@ import java.io.IOException;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.List;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
@@ -83,6 +85,7 @@ public final class FlvExtractor implements Extractor {
   private int tagDataSize;
   private long tagTimestampUs;
   private boolean outputSeekMap;
+  private boolean seekMapIsSeekable;
   private @MonotonicNonNull AudioTagPayloadReader audioReader;
   private @MonotonicNonNull VideoTagPayloadReader videoReader;
 
@@ -133,7 +136,12 @@ public final class FlvExtractor implements Extractor {
 
   @Override
   public void seek(long position, long timeUs) {
-    state = STATE_READING_FLV_HEADER;
+    if (seekMapIsSeekable) {
+      state = STATE_READING_TAG_HEADER;
+    } else {
+      state = STATE_READING_FLV_HEADER;
+      mediaTagTimestampOffsetUs = C.TIME_UNSET;
+    }
     outputFirstSample = false;
     bytesToNextTagHeader = 0;
   }
@@ -263,11 +271,13 @@ public final class FlvExtractor implements Extractor {
       wasSampleOutput = videoReader.consume(prepareTagData(input), timestampUs);
     } else if (tagType == TAG_TYPE_SCRIPT_DATA && !outputSeekMap) {
       wasSampleOutput = metadataReader.consume(prepareTagData(input), timestampUs);
-      long durationUs = metadataReader.getDurationUs();
+      SeekMap seekMap = buildSeekMap(metadataReader.getSeekMapTimes(),
-      if (durationUs != C.TIME_UNSET) {
+          metadataReader.getSeekMapFilePositions(),
-        extractorOutput.seekMap(new SeekMap.Unseekable(durationUs));
+          metadataReader.getDurationUs(),
-        outputSeekMap = true;
+          input.getLength());
-      }
+      seekMapIsSeekable = seekMap.isSeekable();
+      extractorOutput.seekMap(seekMap);
+      outputSeekMap = true;
     } else {
       input.skipFully(tagDataSize);
       wasConsumed = false;
@@ -301,6 +311,32 @@ public final class FlvExtractor implements Extractor {
     }
   }
 
+  private SeekMap buildSeekMap(List<Double> times, List<Double> filePositions, long durationUs,
+                               long flvDataSize) {
+    if (durationUs == C.TIME_UNSET
+        || times == null || times.size() == 0
+        || filePositions == null || filePositions.size() != times.size()) {
+      // Key frames information is missing or incomplete.
+      return new SeekMap.Unseekable(durationUs);
+    }
+    int keyFrameSize = times.size();
+    int[] sizes = new int[keyFrameSize];
+    long[] offsets = new long[keyFrameSize];
+    long[] durationsUs = new long[keyFrameSize];
+    long[] timesUs = new long[keyFrameSize];
+    for (int i = 0; i < keyFrameSize; i++) {
+      timesUs[i] = (long) (times.get(i) * C.MICROS_PER_SECOND);
+      offsets[i] = (long) (filePositions.get(i) + 0);
+    }
+    for (int i = 0; i < keyFrameSize - 1; i++) {
+      sizes[i] = (int) (offsets[i + 1] - offsets[i]);
+      durationsUs[i] = timesUs[i + 1] - timesUs[i];
+    }
+    sizes[keyFrameSize - 1] = (int) (flvDataSize - sizes[keyFrameSize - 2]);
+    durationsUs[keyFrameSize - 1] = durationUs - timesUs[keyFrameSize - 1];
+    return new ChunkIndex(sizes, offsets, durationsUs, timesUs);
+  }
+
   private long getCurrentTimestampUs() {
     return outputFirstSample
         ? (mediaTagTimestampOffsetUs + tagTimestampUs)

library/extractor/src/main/java/com/google/android/exoplayer2/extractor/flv/ScriptTagPayloadReader.java

@@ -23,6 +23,7 @@ import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 /**
@@ -32,6 +33,9 @@ import java.util.Map;
 
   private static final String NAME_METADATA = "onMetaData";
   private static final String KEY_DURATION = "duration";
+  private static final String KEY_KEY_FRAMES = "keyframes";
+  private static final String KEY_FILE_POSITIONS = "filepositions";
+  private static final String KEY_TIMES = "times";
 
   // AMF object types
   private static final int AMF_TYPE_NUMBER = 0;
@@ -45,6 +49,9 @@ import java.util.Map;
 
   private long durationUs;
 
+  private List<Double> seekMapFilePositions;
+  private List<Double> seekMapTimes;
+
   public ScriptTagPayloadReader() {
     super(new DummyTrackOutput());
     durationUs = C.TIME_UNSET;
@@ -89,6 +96,16 @@ import java.util.Map;
         durationUs = (long) (durationSeconds * C.MICROS_PER_SECOND);
       }
     }
+    if (metadata.containsKey(KEY_KEY_FRAMES)) {
+      Object frames = metadata.get(KEY_KEY_FRAMES);
+      if (frames instanceof Map) {
+        Map framesMap = (Map) metadata.get(KEY_KEY_FRAMES);
+        if (framesMap.size() > 0) {
+          seekMapFilePositions = (List<Double>) framesMap.get(KEY_FILE_POSITIONS);
+          seekMapTimes = (List<Double>) framesMap.get(KEY_TIMES);
+        }
+      }
+    }
     return false;
   }
 
@@ -224,4 +241,12 @@ import java.util.Map;
         return null;
     }
   }
+
+  public List<Double> getSeekMapFilePositions() {
+    return seekMapFilePositions;
+  }
+
+  public List<Double> getSeekMapTimes() {
+    return seekMapTimes;
+  }
 }