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Search for synch' when sniffing ADTS and check four frames.

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Issue: #791
This commit is contained in:
Oliver Woodman 2015-09-15 13:43:42 +01:00
parent 721956710f
commit 908e4dfd5d
1 changed files with 47 additions and 7 deletions
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52
library/src/main/java/com/google/android/exoplayer/extractor/ts/AdtsExtractor.java
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@ -20,6 +20,7 @@ import com.google.android.exoplayer.extractor.ExtractorInput;
import com.google.android.exoplayer.extractor.ExtractorOutput;
import com.google.android.exoplayer.extractor.PositionHolder;
import com.google.android.exoplayer.extractor.SeekMap;
import com.google.android.exoplayer.util.ParsableBitArray;
import com.google.android.exoplayer.util.ParsableByteArray;
import com.google.android.exoplayer.util.Util;
@ -32,6 +33,12 @@ import java.io.IOException;
public final class AdtsExtractor implements Extractor {
private static final int MAX_PACKET_SIZE = 200;
private static final int ID3_TAG = Util.getIntegerCodeForString("ID3");
/**
* The maximum number of bytes to search when sniffing, excluding the header, before giving up.
* Frame sizes are represented by 13-bit fields, so expect a valid frame in the first 8192 bytes.
*/
private static final int MAX_SNIFF_BYTES = 8 * 1024;
private final long firstSampleTimestampUs;
private final ParsableByteArray packetBuffer;
@ -52,20 +59,53 @@ public final class AdtsExtractor implements Extractor {
@Override
public boolean sniff(ExtractorInput input) throws IOException, InterruptedException {
// Skip any ID3 headers.
ParsableByteArray scratch = new ParsableByteArray(10);
ParsableBitArray scratchBits = new ParsableBitArray(scratch.data);
int startPosition = 0;
while (true) {
input.peekFully(scratch.data, 0, 10);
int value = scratch.readUnsignedInt24();
if (value != Util.getIntegerCodeForString("ID3")) {
value = value >> 8;
} else {
scratch.setPosition(0);
if (scratch.readUnsignedInt24() != ID3_TAG) {
break;
}
int length = (scratch.data[6] & 0x7F) << 21 | ((scratch.data[7] & 0x7F) << 14)
| ((scratch.data[8] & 0x7F) << 7) | (scratch.data[9] & 0x7F);
startPosition += 10 + length;
input.advancePeekPosition(length);
}
input.resetPeekPosition();
input.advancePeekPosition(startPosition);
// Try to find four or more consecutive AAC audio frames, exceeding the MPEG TS packet size.
int headerPosition = startPosition;
int validFramesSize = 0;
int validFramesCount = 0;
while (true) {
input.peekFully(scratch.data, 0, 2);
scratch.setPosition(0);
value = scratch.readUnsignedShort();
int syncBytes = scratch.readUnsignedShort();
if ((syncBytes & 0xFFF6) != 0xFFF0) {
validFramesCount = 0;
validFramesSize = 0;
input.resetPeekPosition();
if (++headerPosition - startPosition >= MAX_SNIFF_BYTES) {
return false;
}
input.advancePeekPosition(headerPosition);
} else {
if (++validFramesCount >= 4 && validFramesSize > 188) {
return true;
}
// Skip the frame.
input.peekFully(scratch.data, 0, 4);
scratchBits.setPosition(14);
int frameSize = scratchBits.readBits(13);
input.advancePeekPosition(frameSize - 6);
validFramesSize += frameSize;
}
}
return (value & 0xFFF6) == 0xFFF0;
}
@Override