diff options
Diffstat (limited to 'mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/MpegAudioHeader.java')
| -rw-r--r-- | mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/MpegAudioHeader.java | 275 |
1 files changed, 275 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/MpegAudioHeader.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/MpegAudioHeader.java new file mode 100644 index 0000000000..66c3411094 --- /dev/null +++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/MpegAudioHeader.java @@ -0,0 +1,275 @@ +/* + * 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 org.mozilla.thirdparty.com.google.android.exoplayer2.extractor; + +import androidx.annotation.Nullable; +import org.mozilla.thirdparty.com.google.android.exoplayer2.C; +import org.mozilla.thirdparty.com.google.android.exoplayer2.util.MimeTypes; + +/** + * An MPEG audio frame header. + */ +public final class MpegAudioHeader { + + /** + * Theoretical maximum frame size for an MPEG audio stream, which occurs when playing a Layer 2 + * MPEG 2.5 audio stream at 16 kb/s (with padding). The size is 1152 sample/frame * + * 160000 bit/s / (8000 sample/s * 8 bit/byte) + 1 padding byte/frame = 2881 byte/frame. + * The next power of two size is 4 KiB. + */ + public static final int MAX_FRAME_SIZE_BYTES = 4096; + + private static final String[] MIME_TYPE_BY_LAYER = + new String[] {MimeTypes.AUDIO_MPEG_L1, MimeTypes.AUDIO_MPEG_L2, MimeTypes.AUDIO_MPEG}; + private static final int[] SAMPLING_RATE_V1 = {44100, 48000, 32000}; + private static final int[] BITRATE_V1_L1 = { + 32000, 64000, 96000, 128000, 160000, 192000, 224000, 256000, 288000, 320000, 352000, 384000, + 416000, 448000 + }; + private static final int[] BITRATE_V2_L1 = { + 32000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000, 176000, 192000, + 224000, 256000 + }; + private static final int[] BITRATE_V1_L2 = { + 32000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 160000, 192000, 224000, 256000, + 320000, 384000 + }; + private static final int[] BITRATE_V1_L3 = { + 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 160000, 192000, 224000, 256000, + 320000 + }; + private static final int[] BITRATE_V2 = { + 8000, 16000, 24000, 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 144000, + 160000 + }; + + private static final int SAMPLES_PER_FRAME_L1 = 384; + private static final int SAMPLES_PER_FRAME_L2 = 1152; + private static final int SAMPLES_PER_FRAME_L3_V1 = 1152; + private static final int SAMPLES_PER_FRAME_L3_V2 = 576; + + /** + * Returns the size of the frame associated with {@code header}, or {@link C#LENGTH_UNSET} if it + * is invalid. + */ + public static int getFrameSize(int header) { + if (!isMagicPresent(header)) { + return C.LENGTH_UNSET; + } + + int version = (header >>> 19) & 3; + if (version == 1) { + return C.LENGTH_UNSET; + } + + int layer = (header >>> 17) & 3; + if (layer == 0) { + return C.LENGTH_UNSET; + } + + int bitrateIndex = (header >>> 12) & 15; + if (bitrateIndex == 0 || bitrateIndex == 0xF) { + // Disallow "free" bitrate. + return C.LENGTH_UNSET; + } + + int samplingRateIndex = (header >>> 10) & 3; + if (samplingRateIndex == 3) { + return C.LENGTH_UNSET; + } + + int samplingRate = SAMPLING_RATE_V1[samplingRateIndex]; + if (version == 2) { + // Version 2 + samplingRate /= 2; + } else if (version == 0) { + // Version 2.5 + samplingRate /= 4; + } + + int bitrate; + int padding = (header >>> 9) & 1; + if (layer == 3) { + // Layer I (layer == 3) + bitrate = version == 3 ? BITRATE_V1_L1[bitrateIndex - 1] : BITRATE_V2_L1[bitrateIndex - 1]; + return (12 * bitrate / samplingRate + padding) * 4; + } else { + // Layer II (layer == 2) or III (layer == 1) + if (version == 3) { + bitrate = layer == 2 ? BITRATE_V1_L2[bitrateIndex - 1] : BITRATE_V1_L3[bitrateIndex - 1]; + } else { + // Version 2 or 2.5. + bitrate = BITRATE_V2[bitrateIndex - 1]; + } + } + + if (version == 3) { + // Version 1 + return 144 * bitrate / samplingRate + padding; + } else { + // Version 2 or 2.5 + return (layer == 1 ? 72 : 144) * bitrate / samplingRate + padding; + } + } + + /** + * Returns the number of samples per frame associated with {@code header}, or {@link + * C#LENGTH_UNSET} if it is invalid. + */ + public static int getFrameSampleCount(int header) { + + if (!isMagicPresent(header)) { + return C.LENGTH_UNSET; + } + + int version = (header >>> 19) & 3; + if (version == 1) { + return C.LENGTH_UNSET; + } + + int layer = (header >>> 17) & 3; + if (layer == 0) { + return C.LENGTH_UNSET; + } + + // Those header values are not used but are checked for consistency with the other methods + int bitrateIndex = (header >>> 12) & 15; + int samplingRateIndex = (header >>> 10) & 3; + if (bitrateIndex == 0 || bitrateIndex == 0xF || samplingRateIndex == 3) { + return C.LENGTH_UNSET; + } + + return getFrameSizeInSamples(version, layer); + } + + /** + * Parses {@code headerData}, populating {@code header} with the parsed data. + * + * @param headerData Header data to parse. + * @param header Header to populate with data from {@code headerData}. + * @return True if the header was populated. False otherwise, indicating that {@code headerData} + * is not a valid MPEG audio header. + */ + public static boolean populateHeader(int headerData, MpegAudioHeader header) { + if (!isMagicPresent(headerData)) { + return false; + } + + int version = (headerData >>> 19) & 3; + if (version == 1) { + return false; + } + + int layer = (headerData >>> 17) & 3; + if (layer == 0) { + return false; + } + + int bitrateIndex = (headerData >>> 12) & 15; + if (bitrateIndex == 0 || bitrateIndex == 0xF) { + // Disallow "free" bitrate. + return false; + } + + int samplingRateIndex = (headerData >>> 10) & 3; + if (samplingRateIndex == 3) { + return false; + } + + int sampleRate = SAMPLING_RATE_V1[samplingRateIndex]; + if (version == 2) { + // Version 2 + sampleRate /= 2; + } else if (version == 0) { + // Version 2.5 + sampleRate /= 4; + } + + int padding = (headerData >>> 9) & 1; + int bitrate; + int frameSize; + int samplesPerFrame = getFrameSizeInSamples(version, layer); + if (layer == 3) { + // Layer I (layer == 3) + bitrate = version == 3 ? BITRATE_V1_L1[bitrateIndex - 1] : BITRATE_V2_L1[bitrateIndex - 1]; + frameSize = (12 * bitrate / sampleRate + padding) * 4; + } else { + // Layer II (layer == 2) or III (layer == 1) + if (version == 3) { + // Version 1 + bitrate = layer == 2 ? BITRATE_V1_L2[bitrateIndex - 1] : BITRATE_V1_L3[bitrateIndex - 1]; + frameSize = 144 * bitrate / sampleRate + padding; + } else { + // Version 2 or 2.5. + bitrate = BITRATE_V2[bitrateIndex - 1]; + frameSize = (layer == 1 ? 72 : 144) * bitrate / sampleRate + padding; + } + } + + String mimeType = MIME_TYPE_BY_LAYER[3 - layer]; + int channels = ((headerData >> 6) & 3) == 3 ? 1 : 2; + header.setValues(version, mimeType, frameSize, sampleRate, channels, bitrate, samplesPerFrame); + return true; + } + + private static boolean isMagicPresent(int header) { + return (header & 0xFFE00000) == 0xFFE00000; + } + + private static int getFrameSizeInSamples(int version, int layer) { + switch (layer) { + case 1: + return version == 3 ? SAMPLES_PER_FRAME_L3_V1 : SAMPLES_PER_FRAME_L3_V2; // Layer III + case 2: + return SAMPLES_PER_FRAME_L2; // Layer II + case 3: + return SAMPLES_PER_FRAME_L1; // Layer I + } + throw new IllegalArgumentException(); + } + + /** MPEG audio header version. */ + public int version; + /** The mime type. */ + @Nullable public String mimeType; + /** Size of the frame associated with this header, in bytes. */ + public int frameSize; + /** Sample rate in samples per second. */ + public int sampleRate; + /** Number of audio channels in the frame. */ + public int channels; + /** Bitrate of the frame in bit/s. */ + public int bitrate; + /** Number of samples stored in the frame. */ + public int samplesPerFrame; + + private void setValues( + int version, + String mimeType, + int frameSize, + int sampleRate, + int channels, + int bitrate, + int samplesPerFrame) { + this.version = version; + this.mimeType = mimeType; + this.frameSize = frameSize; + this.sampleRate = sampleRate; + this.channels = channels; + this.bitrate = bitrate; + this.samplesPerFrame = samplesPerFrame; + } +} |