Fix clipping in AudioSamplePipeline

When clipping a MediaItem with start time > 0, the audio was ending
before the video. This is because:
- Audio timestamps are computed based on the sample sizes, with a start
  time set to streamOffsetUs (i.e. the streamStartPositionUs is not
  taken into account).
- The SamplePipeline was subtracting streamStartPositionUs from the
  timestamps before sending the samples to the muxer.
- As a result, the audio timestamps were shifted by
  streamStartPositionUs, while they should be shifter by streamOffsetUs.

PiperOrigin-RevId: 511175923

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/AudioSamplePipeline.java

@@ -60,7 +60,6 @@ import org.checkerframework.dataflow.qual.Pure;
   // TODO(b/260618558): Move silent audio generation upstream of this component.
   public AudioSamplePipeline(
       Format firstInputFormat,
-      long streamStartPositionUs,
       long streamOffsetUs,
       TransformationRequest transformationRequest,
       boolean flattenForSlowMotion,
@@ -69,7 +68,7 @@ import org.checkerframework.dataflow.qual.Pure;
       MuxerWrapper muxerWrapper,
       FallbackListener fallbackListener)
       throws ExportException {
-    super(firstInputFormat, streamStartPositionUs, muxerWrapper);
+    super(firstInputFormat, /* streamStartPositionUs= */ streamOffsetUs, muxerWrapper);
 
     silentAudioGenerator = new SilentAudioGenerator(firstInputFormat);
     availableInputBuffers = new ConcurrentLinkedDeque<>();

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/CompositeAssetLoader.java

@@ -196,7 +196,7 @@ import java.util.concurrent.atomic.AtomicInteger;
                 compositeAssetLoaderListener.onTrackAdded(
                     firstAudioFormat,
                     SUPPORTED_OUTPUT_TYPE_DECODED,
-                    /* streamStartPositionUs= */ streamOffsetUs,
+                    streamStartPositionUs,
                     streamOffsetUs));
         sampleConsumersByTrackType.put(C.TRACK_TYPE_AUDIO, audioSampleConsumer);
       }

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java

@@ -434,7 +434,6 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
         if (MimeTypes.isAudio(firstInputFormat.sampleMimeType)) {
           return new AudioSamplePipeline(
               firstInputFormat,
-              streamStartPositionUs,
               streamOffsetUs,
               transformationRequest,
               firstEditedMediaItem.flattenForSlowMotion,