Tim Yao | cd4e4eb | 2020-07-24 01:47:28 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2014, The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #define LOG_TAG "AudioSPDIF" |
| 18 | //#define LOG_NDEBUG 0 |
| 19 | |
| 20 | #include <string.h> |
| 21 | #include <assert.h> |
| 22 | |
| 23 | #include <cutils/log.h> |
| 24 | #include <audio_utils/spdif/FrameScanner.h> |
| 25 | |
| 26 | #include "MatFrameScanner.h" |
| 27 | |
| 28 | namespace android { |
| 29 | |
| 30 | // MAT Transport stream sync word |
| 31 | const uint8_t MatFrameScanner::kSyncBytes[] = { 0x07, 0x9E }; |
| 32 | |
| 33 | // Defined in IEC61937-9 |
| 34 | #define SPDIF_DATA_TYPE_MAT 22 |
| 35 | |
| 36 | #define MAT_MAX_CHUNK_SIZE 30720 |
| 37 | |
| 38 | // MAT transport format |
| 39 | // { Syncword (16 bits) } |
| 40 | // { metadata_payload_length (16 bits), Metadata Payload, Payload CRC (16 bits) } |
| 41 | // { top_of_channels_length (16 bits), Top of Channels Audio Chunk, Payload CRC (16 bits) } |
| 42 | // { bottom_of_channels_length (16 bits), Bottom of Channels Audio Chunk, Payload CRC (16 bits) } |
| 43 | // Length does not include bytes for length itself and the CRC after payload. |
| 44 | |
| 45 | // For frame parsing, we use three frame chunks for a single IEC61937 frame |
| 46 | // 1. {syncword, metadata_payload_length, Metadata Payload} |
| 47 | // 2. {metadata_payload_crc, top_of_channels_length, Top of Channels Audio Chunk} |
| 48 | // 3. {Top channels chunk crc, bottom_of_channels_length, Bottom of Channels Audio Chunk, Bottom Channels Chunk crc} |
| 49 | // such that the header buffer for the three "virtual" frames have fixed 4 bytes size (mHeaderLength = 4) |
| 50 | // and we can control the frame size to collect in each chunk state. |
| 51 | |
| 52 | #define CHUNK_TYPE_METADATA 0 |
| 53 | #define CHUNK_TYPE_TOP 1 |
| 54 | #define CHUNK_TYPE_BOTTOM 2 |
| 55 | |
| 56 | MatFrameScanner::MatFrameScanner() |
| 57 | : FrameScanner(SPDIF_DATA_TYPE_MAT, |
| 58 | MatFrameScanner::kSyncBytes, |
| 59 | sizeof(MatFrameScanner::kSyncBytes), 4) |
| 60 | , mChunkType(CHUNK_TYPE_METADATA) |
| 61 | , mLastChunk(false) |
| 62 | { |
| 63 | } |
| 64 | |
| 65 | MatFrameScanner::~MatFrameScanner() |
| 66 | { |
| 67 | } |
| 68 | |
| 69 | void MatFrameScanner::resetBurst() |
| 70 | { |
| 71 | mChunkType = CHUNK_TYPE_METADATA; |
| 72 | } |
| 73 | |
| 74 | // Per IEC 61973-9:5.3.1, for MAT burst-length shall be in bytes. |
| 75 | uint16_t MatFrameScanner::convertBytesToLengthCode(uint16_t numBytes) const |
| 76 | { |
| 77 | return numBytes; |
| 78 | } |
| 79 | |
| 80 | bool MatFrameScanner::isLastInBurst() |
| 81 | { |
| 82 | return mLastChunk; |
| 83 | } |
| 84 | |
| 85 | bool MatFrameScanner::parseHeader() |
| 86 | { |
| 87 | size_t payload_length = ((size_t)(mHeaderBuffer[2]) << 8) | mHeaderBuffer[3]; |
| 88 | |
| 89 | if ((payload_length <= 0) || (payload_length > MAT_MAX_CHUNK_SIZE)) |
| 90 | return false; |
| 91 | |
| 92 | payload_length <<= 1; // convert to bytes |
| 93 | |
| 94 | if (mChunkType == CHUNK_TYPE_METADATA) { |
| 95 | mFrameSizeBytes = mHeaderLength; // sync word, metadata length |
| 96 | mFrameSizeBytes += payload_length; |
| 97 | mChunkType = CHUNK_TYPE_TOP; |
| 98 | mLastChunk = false; |
| 99 | } else if (mChunkType == CHUNK_TYPE_TOP) { |
| 100 | mFrameSizeBytes = mHeaderLength; // metadata crc, top length |
| 101 | mFrameSizeBytes += payload_length; |
| 102 | mChunkType = CHUNK_TYPE_BOTTOM; |
| 103 | mLastChunk = false; |
| 104 | } else { |
| 105 | mFrameSizeBytes = mHeaderLength; // top crc, bottom length |
| 106 | mFrameSizeBytes += payload_length; |
| 107 | mFrameSizeBytes += 2; // bottom crc |
| 108 | mChunkType == CHUNK_TYPE_METADATA; |
| 109 | mLastChunk = true; |
| 110 | } |
| 111 | |
| 112 | return true; |
| 113 | } |
| 114 | |
| 115 | // State machine that scans for headers in a byte stream. |
| 116 | // @return true if we have detected a complete and valid header. |
| 117 | bool MatFrameScanner::scan(uint8_t byte) |
| 118 | { |
| 119 | bool result = false; |
| 120 | |
| 121 | //ALOGV("MatFrameScanner: byte = 0x%02X, mCursor = %d", byte, mCursor); |
| 122 | assert(mCursor < sizeof(mHeaderBuffer)); |
| 123 | |
| 124 | if ((mChunkType == CHUNK_TYPE_METADATA) && (mCursor < mSyncLength)) { |
| 125 | // match sync word |
| 126 | if (byte == mSyncBytes[mCursor]) { |
| 127 | mHeaderBuffer[mCursor++] = byte; |
| 128 | } else { |
| 129 | mBytesSkipped += 1; // skip unsynchronized data |
| 130 | mCursor = 0; |
| 131 | } |
| 132 | } else if (mCursor < mHeaderLength) { |
| 133 | // gather header for parsing metadata payload length |
| 134 | mHeaderBuffer[mCursor++] = byte; |
| 135 | if (mCursor >= mHeaderLength) { |
| 136 | if (parseHeader()) { |
| 137 | result = true; |
| 138 | } else { |
| 139 | ALOGE("MatFrameScanner: ERROR - parseHeader() failed."); |
| 140 | } |
| 141 | mCursor = 0; |
| 142 | } |
| 143 | } |
| 144 | |
| 145 | return result; |
| 146 | } |
| 147 | |
| 148 | } // namespace android |