The {@link MidiDecoder} will only be called for each sample output by this extractor,
+ * meaning that the size of the decoder's PCM output buffers is proportional to the time between
+ * two samples output by the extractor. In order to make the PCM output buffers manageable, we
+ * periodically produce samples (which may be empty) so as to allow the decoder to produce buffers
+ * of a small pre-determined size, which at most can be the PCM that corresponds to the period
+ * described by this variable.
+ */
+ private static final long MAX_SAMPLE_DURATION_US = 100_000;
+
+ private static final int HEADER_LEN_BYTES = 14;
+ private final ArrayList A track event is a sequence of bytes in the track chunk, consisting of an elapsed time delta
+ * and Midi, Meta, or SysEx command bytes. A track event is followed by either another track event,
+ * or end of chunk marker bytes.
+ */
+@UnstableApi
+/* package */ final class TrackEvent {
+
+ /** The length of a MIDI event message in bytes. */
+ public static final int MIDI_MESSAGE_LENGTH_BYTES = 3;
+ /** A default or unset data value. */
+ public static final int DATA_FIELD_UNSET = Integer.MIN_VALUE;
+
+ private static final int TICKS_UNSET = -1;
+ private static final int META_EVENT_STATUS = 0xFF;
+ private static final int META_END_OF_TRACK = 0x2F;
+ private static final int META_TEMPO_CHANGE = 0x51;
+ private static final int[] CHANNEL_BYTE_LENGTHS = {3, 3, 3, 3, 2, 2, 3};
+ private static final int[] SYSTEM_BYTE_LENGTHS = {1, 2, 3, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
+
+ public int timestampSize;
+ public int eventFileSizeBytes;
+ public int eventDecoderSizeBytes;
+ public int statusByte;
+ public long usPerQuarterNote;
+ public long elapsedTimeDeltaTicks;
+
+ private int data1;
+ private int data2;
+ private boolean isPopulated;
+
+ public TrackEvent() {
+ reset();
+ }
+
+ public void writeTo(byte[] data) {
+ data[0] = (byte) statusByte;
+ data[1] = (byte) data1;
+ data[2] = (byte) data2;
+ }
+
+ public boolean populateFrom(ParsableByteArray parsableTrackEventBytes, int previousEventStatus)
+ throws ParserException {
+
+ reset();
+
+ int startingPosition = parsableTrackEventBytes.getPosition();
+
+ // At least two bytes must remain for there to be a valid MIDI event present to parse.
+ if (parsableTrackEventBytes.bytesLeft() < 2) {
+ return false;
+ }
+
+ elapsedTimeDeltaTicks = readVariableLengthInt(parsableTrackEventBytes);
+ timestampSize = parsableTrackEventBytes.getPosition() - startingPosition;
+
+ int firstByte = parsableTrackEventBytes.readUnsignedByte();
+ eventDecoderSizeBytes = 1;
+
+ if ((firstByte & 0xF0) != 0xF0) {
+ // Most significant nibble is not 0xF, this is a MIDI channel event.
+
+ // Check for running status, an occurrence where the statusByte has been omitted from the
+ // bytes of this event. The standard expects us to assume that this command has the same
+ // statusByte as the last command.
+ boolean isRunningStatus = firstByte < 0x80;
+ if (isRunningStatus) {
+ if (previousEventStatus == DATA_FIELD_UNSET) {
+ throw ParserException.createForMalformedContainer(
+ /* message= */ "Running status in the first event.", /* cause= */ null);
+ }
+ data1 = firstByte;
+ firstByte = previousEventStatus;
+ eventDecoderSizeBytes++;
+ }
+
+ int messageLength = getMidiMessageLengthBytes(firstByte);
+ if (!isRunningStatus) {
+ if (messageLength > eventDecoderSizeBytes) {
+ data1 = parsableTrackEventBytes.readUnsignedByte();
+ eventDecoderSizeBytes++;
+ }
+ }
+ // Only read the next data byte if expected to be present.
+ if (messageLength > eventDecoderSizeBytes) {
+ data2 = parsableTrackEventBytes.readUnsignedByte();
+ eventDecoderSizeBytes++;
+ }
+
+ statusByte = firstByte;
+ } else {
+ if (firstByte == META_EVENT_STATUS) { // This is a Meta event.
+ int metaEventMessageType = parsableTrackEventBytes.readUnsignedByte();
+ int eventLength = readVariableLengthInt(parsableTrackEventBytes);
+
+ statusByte = firstByte;
+
+ switch (metaEventMessageType) {
+ case META_TEMPO_CHANGE:
+ usPerQuarterNote = parsableTrackEventBytes.readUnsignedInt24();
+
+ if (usPerQuarterNote <= 0) {
+ throw ParserException.createForUnsupportedContainerFeature(
+ "Tempo event data value must be a non-zero positive value. Parsed value: "
+ + usPerQuarterNote);
+ }
+
+ parsableTrackEventBytes.skipBytes(eventLength - /* tempoDataLength */ 3);
+ break;
+ case META_END_OF_TRACK:
+ parsableTrackEventBytes.setPosition(startingPosition);
+ reset();
+ return false;
+ default: // Ignore all other Meta events.
+ parsableTrackEventBytes.skipBytes(eventLength);
+ }
+ } else {
+ // TODO(b/228838584): Handle this gracefully.
+ throw ParserException.createForUnsupportedContainerFeature(
+ "SysEx track events are not yet supported.");
+ }
+ }
+
+ eventFileSizeBytes = parsableTrackEventBytes.getPosition() - startingPosition;
+ parsableTrackEventBytes.setPosition(startingPosition);
+ isPopulated = true;
+
+ return true;
+ }
+
+ public boolean isMidiEvent() {
+ // TODO(b/228838584): Update with SysEx event check when implemented.
+ return statusByte != META_EVENT_STATUS;
+ }
+
+ public boolean isNoteChannelEvent() {
+ int highNibble = statusByte >>> 4;
+ return isMidiEvent() && (highNibble == 8 || highNibble == 9);
+ }
+
+ public boolean isMetaEvent() {
+ return statusByte == META_EVENT_STATUS;
+ }
+
+ public boolean isPopulated() {
+ return isPopulated;
+ }
+
+ public void reset() {
+ isPopulated = false;
+ timestampSize = C.LENGTH_UNSET;
+ statusByte = DATA_FIELD_UNSET;
+ data1 = DATA_FIELD_UNSET;
+ data2 = DATA_FIELD_UNSET;
+ elapsedTimeDeltaTicks = TICKS_UNSET;
+ eventFileSizeBytes = C.LENGTH_UNSET;
+ eventDecoderSizeBytes = C.LENGTH_UNSET;
+ usPerQuarterNote = C.TIME_UNSET;
+ }
+
+ private static int readVariableLengthInt(ParsableByteArray data) {
+ int result = 0;
+ int currentByte;
+ int bytesRead = 0;
+
+ do {
+ currentByte = data.readUnsignedByte();
+ result = result << 7 | (currentByte & 0x7F);
+ bytesRead++;
+ } while (((currentByte & 0x80) != 0) && bytesRead <= /* maxByteLength= */ 4);
+
+ return result;
+ }
+
+ private static int getMidiMessageLengthBytes(int status) {
+ if ((status < 0x80) || (status > 0xFF)) {
+ return 0;
+ } else if (status >= 0xF0) {
+ return SYSTEM_BYTE_LENGTHS[status & 0x0F];
+ } else {
+ return CHANNEL_BYTE_LENGTHS[(status >> 4) & 0x07];
+ }
+ }
+}
diff --git a/libraries/decoder_midi/src/main/java/androidx/media3/decoder/midi/package-info.java b/libraries/decoder_midi/src/main/java/androidx/media3/decoder/midi/package-info.java
new file mode 100644
index 0000000000..7571ab51e9
--- /dev/null
+++ b/libraries/decoder_midi/src/main/java/androidx/media3/decoder/midi/package-info.java
@@ -0,0 +1,19 @@
+/*
+ * Copyright 2022 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.
+ */
+@NonNullApi
+package androidx.media3.decoder.midi;
+
+import androidx.media3.common.util.NonNullApi;
diff --git a/libraries/decoder_midi/src/test/AndroidManifest.xml b/libraries/decoder_midi/src/test/AndroidManifest.xml
new file mode 100644
index 0000000000..bd1618dd39
--- /dev/null
+++ b/libraries/decoder_midi/src/test/AndroidManifest.xml
@@ -0,0 +1,19 @@
+
+
+
+