Merge pull request #36 from Lumen5/seekingFix2

Another seeking fix
Lumen5 · May 12, 2023 · e23da4a · e23da4a
2 parents 22225ea + 625ea05
commit e23da4a
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Showing 3 changed files with 34 additions and 5 deletions.
diff --git a/package.json b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@lumen5/framefusion",
-  "version": "0.0.18",
+  "version": "0.0.19",
   "type": "module",
   "scripts": {
     "docs": "typedoc framefusion.ts",

diff --git a/src/backends/beamcoder.ts b/src/backends/beamcoder.ts
@@ -152,6 +152,12 @@ export class BeamcoderExtractor extends BaseExtractor implements Extractor {
      */
     #streamIndex = 0;
 
+    /**
+     * The number of packets we've read from the demuxer to complete the frame query
+     * @private
+     */
+    #packetReadCount = 0;
+
     /**
      * Encoder/Decoder construction is async, so it can't be put in a regular constructor.
      * Use and await this method to generate an extractor.
@@ -272,12 +278,16 @@ export class BeamcoderExtractor extends BaseExtractor implements Extractor {
         return pts * time_base[0] / time_base[1];
     }
 
+    get packetReadCount() {
+        return this.#packetReadCount;
+    }
+
     /**
      * Get the frame at the given presentation timestamp (PTS)
      */
     async _getFrameAtPts(targetPTS: number) {
         VERBOSE && console.log('_getFrameAtPts', targetPTS, '-> duration', this.duration);
-        let packetReadCount = 0;
+        this.#packetReadCount = 0;
 
         // seek and create a decoder when retrieving a frame for the first time or when seeking backwards
         // we have to create a new decoder when seeking backwards as the decoder can only process frames in
@@ -306,13 +316,14 @@ export class BeamcoderExtractor extends BaseExtractor implements Extractor {
                 VERBOSE && console.log('returning previously filtered frame with pts', (closestFrame as Frame).pts);
                 closestFramePTS = (closestFrame as Frame).pts;
                 outputFrame = closestFrame;
+                this.#previousTargetPTS = targetPTS;
             }
         }
 
         // This is the first time we're decoding frames. Get the first packet and decode it.
         if (!this.#packet && this.#frames.length === 0) {
             ({ packet: this.#packet, frames: this.#frames } = await this._getNextPacketAndDecodeFrames());
-            packetReadCount++;
+            this.#packetReadCount++;
         }
         // Read packets until we have a frame which is closest to targetPTS
         while ((this.#packet || this.#frames.length !== 0) && closestFramePTS < targetPTS) {
@@ -360,13 +371,13 @@ export class BeamcoderExtractor extends BaseExtractor implements Extractor {
             ({ packet: this.#packet, frames: this.#frames } = await this._getNextPacketAndDecodeFrames());
 
             // keep track of how many packets we've read
-            packetReadCount++;
+            this.#packetReadCount++;
         }
 
         if (!outputFrame) {
             throw Error('No matching frame found');
         }
-        VERBOSE && console.log('read', packetReadCount, 'packets');
+        VERBOSE && console.log('read', this.packetReadCount, 'packets');
 
         this.#previousTargetPTS = targetPTS;
         return outputFrame;

diff --git a/test/framefusion.test.ts b/test/framefusion.test.ts
@@ -73,6 +73,24 @@ describe('FrameFusion', () => {
         await extractor.dispose();
     });
 
+    it('only reads a few packets to get the next frame after a seek', async() => {
+        const extractor = await BeamcoderExtractor.create({
+            inputFileOrUrl: 'https://storage.googleapis.com/lumen5-prod-video/mvc-4k-new-orleans-a053c0340725rv-112014WA74Rf.mp4',
+        });
+
+        const offset = 1.0 * FPS;
+        for (let i = offset; i < offset + 10; i++) {
+            const time = i / FPS + FRAME_SYNC_DELTA;
+            await extractor.getFrameAtTime(time);
+
+            // for the first frame query we have to find the closest PTS and read several packets to get the closest
+            // frame, after that we should only have to read a few packets
+            if (i > offset + 2) {
+                expect(extractor.packetReadCount).to.equal(1);
+            }
+        }
+    });
+
     it('can identify video stream index', async() => {
         // Arrange
         const extractor = await BeamcoderExtractor.create({