public final class

SectionReader

extends java.lang.Object

implements TsPayloadReader

 java.lang.Object

↳androidx.media3.extractor.ts.SectionReader

Gradle dependencies

compile group: 'androidx.media3', name: 'media3-extractor', version: '1.0.0-alpha03'

  • groupId: androidx.media3
  • artifactId: media3-extractor
  • version: 1.0.0-alpha03

Artifact androidx.media3:media3-extractor:1.0.0-alpha03 it located at Google repository (https://maven.google.com/)

Overview

Reads section data packets and feeds the whole sections to a given SectionPayloadReader. Useful information on PSI sections can be found in ISO/IEC 13818-1, section 2.4.4.

Summary

Constructors
publicSectionReader(SectionPayloadReader reader)

Methods
public voidconsume(ParsableByteArray data, int flags)

public voidinit(TimestampAdjuster timestampAdjuster, ExtractorOutput extractorOutput, TsPayloadReader.TrackIdGenerator idGenerator)

public voidseek()

from java.lang.Objectclone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructors

public SectionReader(SectionPayloadReader reader)

Methods

public void init(TimestampAdjuster timestampAdjuster, ExtractorOutput extractorOutput, TsPayloadReader.TrackIdGenerator idGenerator)

public void seek()

public void consume(ParsableByteArray data, int flags)

Source

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package androidx.media3.extractor.ts;

import static java.lang.Math.max;
import static java.lang.Math.min;

import androidx.media3.common.C;
import androidx.media3.common.util.ParsableByteArray;
import androidx.media3.common.util.TimestampAdjuster;
import androidx.media3.common.util.UnstableApi;
import androidx.media3.common.util.Util;
import androidx.media3.extractor.ExtractorOutput;

/**
 * Reads section data packets and feeds the whole sections to a given {@link SectionPayloadReader}.
 * Useful information on PSI sections can be found in ISO/IEC 13818-1, section 2.4.4.
 */
@UnstableApi
public final class SectionReader implements TsPayloadReader {

  private static final int SECTION_HEADER_LENGTH = 3;
  private static final int DEFAULT_SECTION_BUFFER_LENGTH = 32;
  private static final int MAX_SECTION_LENGTH = 4098;

  private final SectionPayloadReader reader;
  private final ParsableByteArray sectionData;

  private int totalSectionLength;
  private int bytesRead;
  private boolean sectionSyntaxIndicator;
  private boolean waitingForPayloadStart;

  public SectionReader(SectionPayloadReader reader) {
    this.reader = reader;
    sectionData = new ParsableByteArray(DEFAULT_SECTION_BUFFER_LENGTH);
  }

  @Override
  public void init(
      TimestampAdjuster timestampAdjuster,
      ExtractorOutput extractorOutput,
      TrackIdGenerator idGenerator) {
    reader.init(timestampAdjuster, extractorOutput, idGenerator);
    waitingForPayloadStart = true;
  }

  @Override
  public void seek() {
    waitingForPayloadStart = true;
  }

  @Override
  public void consume(ParsableByteArray data, @Flags int flags) {
    boolean payloadUnitStartIndicator = (flags & FLAG_PAYLOAD_UNIT_START_INDICATOR) != 0;
    int payloadStartPosition = C.POSITION_UNSET;
    if (payloadUnitStartIndicator) {
      int payloadStartOffset = data.readUnsignedByte();
      payloadStartPosition = data.getPosition() + payloadStartOffset;
    }

    if (waitingForPayloadStart) {
      if (!payloadUnitStartIndicator) {
        return;
      }
      waitingForPayloadStart = false;
      data.setPosition(payloadStartPosition);
      bytesRead = 0;
    }

    while (data.bytesLeft() > 0) {
      if (bytesRead < SECTION_HEADER_LENGTH) {
        // Note: see ISO/IEC 13818-1, section 2.4.4.3 for detailed information on the format of
        // the header.
        if (bytesRead == 0) {
          int tableId = data.readUnsignedByte();
          data.setPosition(data.getPosition() - 1);
          if (tableId == 0xFF /* forbidden value */) {
            // No more sections in this ts packet.
            waitingForPayloadStart = true;
            return;
          }
        }
        int headerBytesToRead = min(data.bytesLeft(), SECTION_HEADER_LENGTH - bytesRead);
        // sectionData is guaranteed to have enough space because it's initialized with a 32-element
        // backing array and headerBytesToRead is at most 3.
        data.readBytes(sectionData.getData(), bytesRead, headerBytesToRead);
        bytesRead += headerBytesToRead;
        if (bytesRead == SECTION_HEADER_LENGTH) {
          sectionData.setPosition(0);
          sectionData.setLimit(SECTION_HEADER_LENGTH);
          sectionData.skipBytes(1); // Skip table id (8).
          int secondHeaderByte = sectionData.readUnsignedByte();
          int thirdHeaderByte = sectionData.readUnsignedByte();
          sectionSyntaxIndicator = (secondHeaderByte & 0x80) != 0;
          totalSectionLength =
              (((secondHeaderByte & 0x0F) << 8) | thirdHeaderByte) + SECTION_HEADER_LENGTH;
          if (sectionData.capacity() < totalSectionLength) {
            // Ensure there is enough space to keep the whole section.
            int limit =
                min(MAX_SECTION_LENGTH, max(totalSectionLength, sectionData.capacity() * 2));
            sectionData.ensureCapacity(limit);
          }
        }
      } else {
        // Reading the body.
        int bodyBytesToRead = min(data.bytesLeft(), totalSectionLength - bytesRead);
        // sectionData has been sized large enough for totalSectionLength when reading the header.
        data.readBytes(sectionData.getData(), bytesRead, bodyBytesToRead);
        bytesRead += bodyBytesToRead;
        if (bytesRead == totalSectionLength) {
          if (sectionSyntaxIndicator) {
            // This section has common syntax as defined in ISO/IEC 13818-1, section 2.4.4.11.
            if (Util.crc32(sectionData.getData(), 0, totalSectionLength, 0xFFFFFFFF) != 0) {
              // The CRC is invalid so discard the section.
              waitingForPayloadStart = true;
              return;
            }
            sectionData.setLimit(totalSectionLength - 4); // Exclude the CRC_32 field.
          } else {
            // This is a private section with private defined syntax.
            sectionData.setLimit(totalSectionLength);
          }
          sectionData.setPosition(0);
          reader.consume(sectionData);
          bytesRead = 0;
        }
      }
    }
  }
}