/
Cea608Decoder.java
1157 lines (1029 loc) · 40.1 KB
/
Cea608Decoder.java
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/*
* 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.text.cea;
import static java.lang.Math.min;
import android.graphics.Color;
import android.graphics.Typeface;
import android.text.Layout.Alignment;
import android.text.SpannableString;
import android.text.SpannableStringBuilder;
import android.text.Spanned;
import android.text.style.ForegroundColorSpan;
import android.text.style.StyleSpan;
import android.text.style.UnderlineSpan;
import androidx.annotation.Nullable;
import androidx.media3.common.C;
import androidx.media3.common.Format;
import androidx.media3.common.MimeTypes;
import androidx.media3.common.text.Cue;
import androidx.media3.common.util.Assertions;
import androidx.media3.common.util.Log;
import androidx.media3.common.util.ParsableByteArray;
import androidx.media3.common.util.UnstableApi;
import androidx.media3.common.util.Util;
import androidx.media3.extractor.text.Subtitle;
import androidx.media3.extractor.text.SubtitleDecoder;
import androidx.media3.extractor.text.SubtitleDecoderException;
import androidx.media3.extractor.text.SubtitleInputBuffer;
import androidx.media3.extractor.text.SubtitleOutputBuffer;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.checkerframework.checker.nullness.compatqual.NullableType;
/** A {@link SubtitleDecoder} for CEA-608 (also known as "line 21 captions" and "EIA-608"). */
@UnstableApi
public final class Cea608Decoder extends CeaDecoder {
/**
* The minimum value for the {@code validDataChannelTimeoutMs} constructor parameter permitted by
* ANSI/CTA-608-E R-2014 Annex C.9.
*/
public static final long MIN_DATA_CHANNEL_TIMEOUT_MS = 16_000;
private static final String TAG = "Cea608Decoder";
private static final int CC_VALID_FLAG = 0x04;
private static final int CC_TYPE_FLAG = 0x02;
private static final int CC_FIELD_FLAG = 0x01;
private static final int NTSC_CC_FIELD_1 = 0x00;
private static final int NTSC_CC_FIELD_2 = 0x01;
private static final int NTSC_CC_CHANNEL_1 = 0x00;
private static final int NTSC_CC_CHANNEL_2 = 0x01;
private static final int CC_MODE_UNKNOWN = 0;
private static final int CC_MODE_ROLL_UP = 1;
private static final int CC_MODE_POP_ON = 2;
private static final int CC_MODE_PAINT_ON = 3;
private static final int[] ROW_INDICES = new int[] {11, 1, 3, 12, 14, 5, 7, 9};
private static final int[] COLUMN_INDICES = new int[] {0, 4, 8, 12, 16, 20, 24, 28};
private static final int[] STYLE_COLORS =
new int[] {
Color.WHITE, Color.GREEN, Color.BLUE, Color.CYAN, Color.RED, Color.YELLOW, Color.MAGENTA
};
private static final int STYLE_ITALICS = 0x07;
private static final int STYLE_UNCHANGED = 0x08;
// The default number of rows to display in roll-up captions mode.
private static final int DEFAULT_CAPTIONS_ROW_COUNT = 4;
// An implied first byte for packets that are only 2 bytes long, consisting of marker bits
// (0b11111) + valid bit (0b1) + NTSC field 1 type bits (0b00).
private static final byte CC_IMPLICIT_DATA_HEADER = (byte) 0xFC;
/**
* Command initiating pop-on style captioning. Subsequent data should be loaded into a
* non-displayed memory and held there until the {@link #CTRL_END_OF_CAPTION} command is received,
* at which point the non-displayed memory becomes the displayed memory (and vice versa).
*/
private static final byte CTRL_RESUME_CAPTION_LOADING = 0x20;
private static final byte CTRL_BACKSPACE = 0x21;
private static final byte CTRL_DELETE_TO_END_OF_ROW = 0x24;
/**
* Command initiating roll-up style captioning, with the maximum of 2 rows displayed
* simultaneously.
*/
private static final byte CTRL_ROLL_UP_CAPTIONS_2_ROWS = 0x25;
/**
* Command initiating roll-up style captioning, with the maximum of 3 rows displayed
* simultaneously.
*/
private static final byte CTRL_ROLL_UP_CAPTIONS_3_ROWS = 0x26;
/**
* Command initiating roll-up style captioning, with the maximum of 4 rows displayed
* simultaneously.
*/
private static final byte CTRL_ROLL_UP_CAPTIONS_4_ROWS = 0x27;
/**
* Command initiating paint-on style captioning. Subsequent data should be addressed immediately
* to displayed memory without need for the {@link #CTRL_RESUME_CAPTION_LOADING} command.
*/
private static final byte CTRL_RESUME_DIRECT_CAPTIONING = 0x29;
/**
* TEXT commands are switching to TEXT service. All consecutive incoming data must be filtered out
* until a command is received that switches back to the CAPTION service.
*/
private static final byte CTRL_TEXT_RESTART = 0x2A;
private static final byte CTRL_RESUME_TEXT_DISPLAY = 0x2B;
private static final byte CTRL_ERASE_DISPLAYED_MEMORY = 0x2C;
private static final byte CTRL_CARRIAGE_RETURN = 0x2D;
private static final byte CTRL_ERASE_NON_DISPLAYED_MEMORY = 0x2E;
/**
* Command indicating the end of a pop-on style caption. At this point the caption loaded in
* non-displayed memory should be swapped with the one in displayed memory. If no {@link
* #CTRL_RESUME_CAPTION_LOADING} command has been received, this command forces the receiver into
* pop-on style.
*/
private static final byte CTRL_END_OF_CAPTION = 0x2F;
// Basic North American 608 CC char set, mostly ASCII. Indexed by (char-0x20).
private static final int[] BASIC_CHARACTER_SET =
new int[] {
0x20,
0x21,
0x22,
0x23,
0x24,
0x25,
0x26,
0x27, // ! " # $ % & '
0x28,
0x29, // ( )
0xE1, // 2A: 225 'á' "Latin small letter A with acute"
0x2B,
0x2C,
0x2D,
0x2E,
0x2F, // + , - . /
0x30,
0x31,
0x32,
0x33,
0x34,
0x35,
0x36,
0x37, // 0 1 2 3 4 5 6 7
0x38,
0x39,
0x3A,
0x3B,
0x3C,
0x3D,
0x3E,
0x3F, // 8 9 : ; < = > ?
0x40,
0x41,
0x42,
0x43,
0x44,
0x45,
0x46,
0x47, // @ A B C D E F G
0x48,
0x49,
0x4A,
0x4B,
0x4C,
0x4D,
0x4E,
0x4F, // H I J K L M N O
0x50,
0x51,
0x52,
0x53,
0x54,
0x55,
0x56,
0x57, // P Q R S T U V W
0x58,
0x59,
0x5A,
0x5B, // X Y Z [
0xE9, // 5C: 233 'é' "Latin small letter E with acute"
0x5D, // ]
0xED, // 5E: 237 'í' "Latin small letter I with acute"
0xF3, // 5F: 243 'ó' "Latin small letter O with acute"
0xFA, // 60: 250 'ú' "Latin small letter U with acute"
0x61,
0x62,
0x63,
0x64,
0x65,
0x66,
0x67, // a b c d e f g
0x68,
0x69,
0x6A,
0x6B,
0x6C,
0x6D,
0x6E,
0x6F, // h i j k l m n o
0x70,
0x71,
0x72,
0x73,
0x74,
0x75,
0x76,
0x77, // p q r s t u v w
0x78,
0x79,
0x7A, // x y z
0xE7, // 7B: 231 'ç' "Latin small letter C with cedilla"
0xF7, // 7C: 247 '÷' "Division sign"
0xD1, // 7D: 209 'Ñ' "Latin capital letter N with tilde"
0xF1, // 7E: 241 'ñ' "Latin small letter N with tilde"
0x25A0 // 7F: "Black Square" (NB: 2588 = Full Block)
};
// Special North American 608 CC char set.
private static final int[] SPECIAL_CHARACTER_SET =
new int[] {
0xAE, // 30: 174 '®' "Registered Sign" - registered trademark symbol
0xB0, // 31: 176 '°' "Degree Sign"
0xBD, // 32: 189 '½' "Vulgar Fraction One Half" (1/2 symbol)
0xBF, // 33: 191 '¿' "Inverted Question Mark"
0x2122, // 34: "Trade Mark Sign" (tm superscript)
0xA2, // 35: 162 '¢' "Cent Sign"
0xA3, // 36: 163 '£' "Pound Sign" - pounds sterling
0x266A, // 37: "Eighth Note" - music note
0xE0, // 38: 224 'à' "Latin small letter A with grave"
0x20, // 39: TRANSPARENT SPACE - for now use ordinary space
0xE8, // 3A: 232 'è' "Latin small letter E with grave"
0xE2, // 3B: 226 'â' "Latin small letter A with circumflex"
0xEA, // 3C: 234 'ê' "Latin small letter E with circumflex"
0xEE, // 3D: 238 'î' "Latin small letter I with circumflex"
0xF4, // 3E: 244 'ô' "Latin small letter O with circumflex"
0xFB // 3F: 251 'û' "Latin small letter U with circumflex"
};
// Extended Spanish/Miscellaneous and French char set.
private static final int[] SPECIAL_ES_FR_CHARACTER_SET =
new int[] {
// Spanish and misc.
0xC1, 0xC9, 0xD3, 0xDA, 0xDC, 0xFC, 0x2018, 0xA1,
0x2A, 0x27, 0x2014, 0xA9, 0x2120, 0x2022, 0x201C, 0x201D,
// French.
0xC0, 0xC2, 0xC7, 0xC8, 0xCA, 0xCB, 0xEB, 0xCE,
0xCF, 0xEF, 0xD4, 0xD9, 0xF9, 0xDB, 0xAB, 0xBB
};
// Extended Portuguese and German/Danish char set.
private static final int[] SPECIAL_PT_DE_CHARACTER_SET =
new int[] {
// Portuguese.
0xC3, 0xE3, 0xCD, 0xCC, 0xEC, 0xD2, 0xF2, 0xD5,
0xF5, 0x7B, 0x7D, 0x5C, 0x5E, 0x5F, 0x7C, 0x7E,
// German/Danish.
0xC4, 0xE4, 0xD6, 0xF6, 0xDF, 0xA5, 0xA4, 0x2502,
0xC5, 0xE5, 0xD8, 0xF8, 0x250C, 0x2510, 0x2514, 0x2518
};
private static final boolean[] ODD_PARITY_BYTE_TABLE = {
false, true, true, false, true, false, false, true, // 0
true, false, false, true, false, true, true, false, // 8
true, false, false, true, false, true, true, false, // 16
false, true, true, false, true, false, false, true, // 24
true, false, false, true, false, true, true, false, // 32
false, true, true, false, true, false, false, true, // 40
false, true, true, false, true, false, false, true, // 48
true, false, false, true, false, true, true, false, // 56
true, false, false, true, false, true, true, false, // 64
false, true, true, false, true, false, false, true, // 72
false, true, true, false, true, false, false, true, // 80
true, false, false, true, false, true, true, false, // 88
false, true, true, false, true, false, false, true, // 96
true, false, false, true, false, true, true, false, // 104
true, false, false, true, false, true, true, false, // 112
false, true, true, false, true, false, false, true, // 120
true, false, false, true, false, true, true, false, // 128
false, true, true, false, true, false, false, true, // 136
false, true, true, false, true, false, false, true, // 144
true, false, false, true, false, true, true, false, // 152
false, true, true, false, true, false, false, true, // 160
true, false, false, true, false, true, true, false, // 168
true, false, false, true, false, true, true, false, // 176
false, true, true, false, true, false, false, true, // 184
false, true, true, false, true, false, false, true, // 192
true, false, false, true, false, true, true, false, // 200
true, false, false, true, false, true, true, false, // 208
false, true, true, false, true, false, false, true, // 216
true, false, false, true, false, true, true, false, // 224
false, true, true, false, true, false, false, true, // 232
false, true, true, false, true, false, false, true, // 240
true, false, false, true, false, true, true, false, // 248
};
private final ParsableByteArray ccData;
private final int packetLength;
private final int selectedField;
private final int selectedChannel;
private final long validDataChannelTimeoutUs;
private final ArrayList<CueBuilder> cueBuilders;
private CueBuilder currentCueBuilder;
@Nullable private List<Cue> cues;
@Nullable private List<Cue> lastCues;
private int captionMode;
private int captionRowCount;
private boolean isCaptionValid;
private boolean repeatableControlSet;
private byte repeatableControlCc1;
private byte repeatableControlCc2;
private int currentChannel;
// The incoming characters may belong to 3 different services based on the last received control
// codes. The 3 services are Captioning, Text and XDS. The decoder only processes Captioning
// service bytes and drops the rest.
private boolean isInCaptionService;
private long lastCueUpdateUs;
/**
* Constructs an instance.
*
* @param mimeType The MIME type of the CEA-608 data.
* @param accessibilityChannel The Accessibility channel, or {@link Format#NO_VALUE} if unknown.
* @param validDataChannelTimeoutMs The timeout (in milliseconds) permitted by ANSI/CTA-608-E
* R-2014 Annex C.9 to clear "stuck" captions where no removal control code is received. The
* timeout should be at least {@link #MIN_DATA_CHANNEL_TIMEOUT_MS} or {@link C#TIME_UNSET} for
* no timeout.
*/
public Cea608Decoder(String mimeType, int accessibilityChannel, long validDataChannelTimeoutMs) {
ccData = new ParsableByteArray();
cueBuilders = new ArrayList<>();
currentCueBuilder = new CueBuilder(CC_MODE_UNKNOWN, DEFAULT_CAPTIONS_ROW_COUNT);
currentChannel = NTSC_CC_CHANNEL_1;
this.validDataChannelTimeoutUs =
validDataChannelTimeoutMs > 0 ? validDataChannelTimeoutMs * 1000 : C.TIME_UNSET;
packetLength = MimeTypes.APPLICATION_MP4CEA608.equals(mimeType) ? 2 : 3;
switch (accessibilityChannel) {
case 1:
selectedChannel = NTSC_CC_CHANNEL_1;
selectedField = NTSC_CC_FIELD_1;
break;
case 2:
selectedChannel = NTSC_CC_CHANNEL_2;
selectedField = NTSC_CC_FIELD_1;
break;
case 3:
selectedChannel = NTSC_CC_CHANNEL_1;
selectedField = NTSC_CC_FIELD_2;
break;
case 4:
selectedChannel = NTSC_CC_CHANNEL_2;
selectedField = NTSC_CC_FIELD_2;
break;
default:
Log.w(TAG, "Invalid channel. Defaulting to CC1.");
selectedChannel = NTSC_CC_CHANNEL_1;
selectedField = NTSC_CC_FIELD_1;
}
setCaptionMode(CC_MODE_UNKNOWN);
resetCueBuilders();
isInCaptionService = true;
lastCueUpdateUs = C.TIME_UNSET;
}
@Override
public String getName() {
return "Cea608Decoder";
}
@Override
public void flush() {
super.flush();
cues = null;
lastCues = null;
setCaptionMode(CC_MODE_UNKNOWN);
setCaptionRowCount(DEFAULT_CAPTIONS_ROW_COUNT);
resetCueBuilders();
isCaptionValid = false;
repeatableControlSet = false;
repeatableControlCc1 = 0;
repeatableControlCc2 = 0;
currentChannel = NTSC_CC_CHANNEL_1;
isInCaptionService = true;
lastCueUpdateUs = C.TIME_UNSET;
}
@Override
public void release() {
// Do nothing
}
@Nullable
@Override
public SubtitleOutputBuffer dequeueOutputBuffer() throws SubtitleDecoderException {
SubtitleOutputBuffer outputBuffer = super.dequeueOutputBuffer();
if (outputBuffer != null) {
return outputBuffer;
}
if (shouldClearStuckCaptions()) {
outputBuffer = getAvailableOutputBuffer();
if (outputBuffer != null) {
cues = Collections.emptyList();
lastCueUpdateUs = C.TIME_UNSET;
Subtitle subtitle = createSubtitle();
outputBuffer.setContent(getPositionUs(), subtitle, Format.OFFSET_SAMPLE_RELATIVE);
return outputBuffer;
}
}
return null;
}
@Override
protected boolean isNewSubtitleDataAvailable() {
return cues != lastCues;
}
@Override
protected Subtitle createSubtitle() {
lastCues = cues;
return new CeaSubtitle(Assertions.checkNotNull(cues));
}
@SuppressWarnings("ByteBufferBackingArray")
@Override
protected void decode(SubtitleInputBuffer inputBuffer) {
ByteBuffer subtitleData = Assertions.checkNotNull(inputBuffer.data);
ccData.reset(subtitleData.array(), subtitleData.limit());
boolean captionDataProcessed = false;
while (ccData.bytesLeft() >= packetLength) {
int ccHeader = packetLength == 2 ? CC_IMPLICIT_DATA_HEADER : ccData.readUnsignedByte();
int ccByte1 = ccData.readUnsignedByte();
int ccByte2 = ccData.readUnsignedByte();
// TODO: We're currently ignoring the top 5 marker bits, which should all be 1s according
// to the CEA-608 specification. We need to determine if the data should be handled
// differently when that is not the case.
if ((ccHeader & CC_TYPE_FLAG) != 0) {
// Do not process anything that is not part of the 608 byte stream.
continue;
}
if ((ccHeader & CC_FIELD_FLAG) != selectedField) {
// Do not process packets not within the selected field.
continue;
}
// Strip the parity bit from each byte to get CC data.
byte ccData1 = (byte) (ccByte1 & 0x7F);
byte ccData2 = (byte) (ccByte2 & 0x7F);
if (ccData1 == 0 && ccData2 == 0) {
// Ignore empty captions.
continue;
}
boolean previousIsCaptionValid = isCaptionValid;
isCaptionValid =
(ccHeader & CC_VALID_FLAG) == CC_VALID_FLAG
&& ODD_PARITY_BYTE_TABLE[ccByte1]
&& ODD_PARITY_BYTE_TABLE[ccByte2];
if (isRepeatedCommand(isCaptionValid, ccData1, ccData2)) {
// Ignore repeated valid commands.
continue;
}
if (!isCaptionValid) {
if (previousIsCaptionValid) {
// The encoder has flipped the validity bit to indicate captions are being turned off.
resetCueBuilders();
captionDataProcessed = true;
}
continue;
}
maybeUpdateIsInCaptionService(ccData1, ccData2);
if (!isInCaptionService) {
// Only the Captioning service is supported. Drop all other bytes.
continue;
}
if (!updateAndVerifyCurrentChannel(ccData1)) {
// Wrong channel.
continue;
}
if (isCtrlCode(ccData1)) {
if (isSpecialNorthAmericanChar(ccData1, ccData2)) {
currentCueBuilder.append(getSpecialNorthAmericanChar(ccData2));
} else if (isExtendedWestEuropeanChar(ccData1, ccData2)) {
// Remove standard equivalent of the special extended char before appending new one.
currentCueBuilder.backspace();
currentCueBuilder.append(getExtendedWestEuropeanChar(ccData1, ccData2));
} else if (isMidrowCtrlCode(ccData1, ccData2)) {
handleMidrowCtrl(ccData2);
} else if (isPreambleAddressCode(ccData1, ccData2)) {
handlePreambleAddressCode(ccData1, ccData2);
} else if (isTabCtrlCode(ccData1, ccData2)) {
currentCueBuilder.tabOffset = ccData2 - 0x20;
} else if (isMiscCode(ccData1, ccData2)) {
handleMiscCode(ccData2);
}
} else {
// Basic North American character set.
currentCueBuilder.append(getBasicChar(ccData1));
if ((ccData2 & 0xE0) != 0x00) {
currentCueBuilder.append(getBasicChar(ccData2));
}
}
captionDataProcessed = true;
}
if (captionDataProcessed) {
if (captionMode == CC_MODE_ROLL_UP || captionMode == CC_MODE_PAINT_ON) {
cues = getDisplayCues();
lastCueUpdateUs = getPositionUs();
}
}
}
private boolean updateAndVerifyCurrentChannel(byte cc1) {
if (isCtrlCode(cc1)) {
currentChannel = getChannel(cc1);
}
return currentChannel == selectedChannel;
}
private boolean isRepeatedCommand(boolean captionValid, byte cc1, byte cc2) {
// Most control commands are sent twice in succession to ensure they are received properly. We
// don't want to process duplicate commands, so if we see the same repeatable command twice in a
// row then we ignore the second one.
if (captionValid && isRepeatable(cc1)) {
if (repeatableControlSet && repeatableControlCc1 == cc1 && repeatableControlCc2 == cc2) {
// This is a repeated command, so we ignore it.
repeatableControlSet = false;
return true;
} else {
// This is the first occurrence of a repeatable command. Set the repeatable control
// variables so that we can recognize and ignore a duplicate (if there is one), and then
// continue to process the command below.
repeatableControlSet = true;
repeatableControlCc1 = cc1;
repeatableControlCc2 = cc2;
}
} else {
// This command is not repeatable.
repeatableControlSet = false;
}
return false;
}
private void handleMidrowCtrl(byte cc2) {
// TODO: support the extended styles (i.e. backgrounds and transparencies)
// A midrow control code advances the cursor.
currentCueBuilder.append(' ');
// cc2 - 0|0|1|0|STYLE|U
boolean underline = (cc2 & 0x01) == 0x01;
int style = (cc2 >> 1) & 0x07;
currentCueBuilder.setStyle(style, underline);
}
private void handlePreambleAddressCode(byte cc1, byte cc2) {
// cc1 - 0|0|0|1|C|E|ROW
// C is the channel toggle, E is the extended flag, and ROW is the encoded row
int row = ROW_INDICES[cc1 & 0x07];
// TODO: support the extended address and style
// cc2 - 0|1|N|ATTRBTE|U
// N is the next row down toggle, ATTRBTE is the 4-byte encoded attribute, and U is the
// underline toggle.
boolean nextRowDown = (cc2 & 0x20) != 0;
if (nextRowDown) {
row++;
}
if (row != currentCueBuilder.row) {
if (captionMode != CC_MODE_ROLL_UP && !currentCueBuilder.isEmpty()) {
currentCueBuilder = new CueBuilder(captionMode, captionRowCount);
cueBuilders.add(currentCueBuilder);
}
currentCueBuilder.row = row;
}
// cc2 - 0|1|N|0|STYLE|U
// cc2 - 0|1|N|1|CURSR|U
boolean isCursor = (cc2 & 0x10) == 0x10;
boolean underline = (cc2 & 0x01) == 0x01;
int cursorOrStyle = (cc2 >> 1) & 0x07;
// We need to call setStyle even for the isCursor case, to update the underline bit.
// STYLE_UNCHANGED is used for this case.
currentCueBuilder.setStyle(isCursor ? STYLE_UNCHANGED : cursorOrStyle, underline);
if (isCursor) {
currentCueBuilder.indent = COLUMN_INDICES[cursorOrStyle];
}
}
private void handleMiscCode(byte cc2) {
switch (cc2) {
case CTRL_ROLL_UP_CAPTIONS_2_ROWS:
setCaptionMode(CC_MODE_ROLL_UP);
setCaptionRowCount(2);
return;
case CTRL_ROLL_UP_CAPTIONS_3_ROWS:
setCaptionMode(CC_MODE_ROLL_UP);
setCaptionRowCount(3);
return;
case CTRL_ROLL_UP_CAPTIONS_4_ROWS:
setCaptionMode(CC_MODE_ROLL_UP);
setCaptionRowCount(4);
return;
case CTRL_RESUME_CAPTION_LOADING:
setCaptionMode(CC_MODE_POP_ON);
return;
case CTRL_RESUME_DIRECT_CAPTIONING:
setCaptionMode(CC_MODE_PAINT_ON);
return;
default:
// Fall through.
break;
}
if (captionMode == CC_MODE_UNKNOWN) {
return;
}
switch (cc2) {
case CTRL_ERASE_DISPLAYED_MEMORY:
cues = Collections.emptyList();
if (captionMode == CC_MODE_ROLL_UP || captionMode == CC_MODE_PAINT_ON) {
resetCueBuilders();
}
break;
case CTRL_ERASE_NON_DISPLAYED_MEMORY:
resetCueBuilders();
break;
case CTRL_END_OF_CAPTION:
cues = getDisplayCues();
resetCueBuilders();
break;
case CTRL_CARRIAGE_RETURN:
// carriage returns only apply to rollup captions; don't bother if we don't have anything
// to add a carriage return to
if (captionMode == CC_MODE_ROLL_UP && !currentCueBuilder.isEmpty()) {
currentCueBuilder.rollUp();
}
break;
case CTRL_BACKSPACE:
currentCueBuilder.backspace();
break;
case CTRL_DELETE_TO_END_OF_ROW:
// TODO: implement
break;
default:
// Fall through.
break;
}
}
private List<Cue> getDisplayCues() {
// CEA-608 does not define middle and end alignment, however content providers artificially
// introduce them using whitespace. When each cue is built, we try and infer the alignment based
// on the amount of whitespace either side of the text. To avoid consecutive cues being aligned
// differently, we force all cues to have the same alignment, with start alignment given
// preference, then middle alignment, then end alignment.
@Cue.AnchorType int positionAnchor = Cue.ANCHOR_TYPE_END;
int cueBuilderCount = cueBuilders.size();
List<@NullableType Cue> cueBuilderCues = new ArrayList<>(cueBuilderCount);
for (int i = 0; i < cueBuilderCount; i++) {
@Nullable Cue cue = cueBuilders.get(i).build(/* forcedPositionAnchor= */ Cue.TYPE_UNSET);
cueBuilderCues.add(cue);
if (cue != null) {
positionAnchor = min(positionAnchor, cue.positionAnchor);
}
}
// Skip null cues and rebuild any that don't have the preferred alignment.
List<Cue> displayCues = new ArrayList<>(cueBuilderCount);
for (int i = 0; i < cueBuilderCount; i++) {
@Nullable Cue cue = cueBuilderCues.get(i);
if (cue != null) {
if (cue.positionAnchor != positionAnchor) {
// The last time we built this cue it was non-null, it will be non-null this time too.
cue = Assertions.checkNotNull(cueBuilders.get(i).build(positionAnchor));
}
displayCues.add(cue);
}
}
return displayCues;
}
private void setCaptionMode(int captionMode) {
if (this.captionMode == captionMode) {
return;
}
int oldCaptionMode = this.captionMode;
this.captionMode = captionMode;
if (captionMode == CC_MODE_PAINT_ON) {
// Switching to paint-on mode should have no effect except to select the mode.
for (int i = 0; i < cueBuilders.size(); i++) {
cueBuilders.get(i).setCaptionMode(captionMode);
}
return;
}
// Clear the working memory.
resetCueBuilders();
if (oldCaptionMode == CC_MODE_PAINT_ON
|| captionMode == CC_MODE_ROLL_UP
|| captionMode == CC_MODE_UNKNOWN) {
// When switching from paint-on or to roll-up or unknown, we also need to clear the caption.
cues = Collections.emptyList();
}
}
private void setCaptionRowCount(int captionRowCount) {
this.captionRowCount = captionRowCount;
currentCueBuilder.setCaptionRowCount(captionRowCount);
}
private void resetCueBuilders() {
currentCueBuilder.reset(captionMode);
cueBuilders.clear();
cueBuilders.add(currentCueBuilder);
}
private void maybeUpdateIsInCaptionService(byte cc1, byte cc2) {
if (isXdsControlCode(cc1)) {
isInCaptionService = false;
} else if (isServiceSwitchCommand(cc1)) {
switch (cc2) {
case CTRL_TEXT_RESTART:
case CTRL_RESUME_TEXT_DISPLAY:
isInCaptionService = false;
break;
case CTRL_END_OF_CAPTION:
case CTRL_RESUME_CAPTION_LOADING:
case CTRL_RESUME_DIRECT_CAPTIONING:
case CTRL_ROLL_UP_CAPTIONS_2_ROWS:
case CTRL_ROLL_UP_CAPTIONS_3_ROWS:
case CTRL_ROLL_UP_CAPTIONS_4_ROWS:
isInCaptionService = true;
break;
default:
// No update.
}
}
}
private static char getBasicChar(byte ccData) {
int index = (ccData & 0x7F) - 0x20;
return (char) BASIC_CHARACTER_SET[index];
}
private static boolean isSpecialNorthAmericanChar(byte cc1, byte cc2) {
// cc1 - 0|0|0|1|C|0|0|1
// cc2 - 0|0|1|1|X|X|X|X
return ((cc1 & 0xF7) == 0x11) && ((cc2 & 0xF0) == 0x30);
}
private static char getSpecialNorthAmericanChar(byte ccData) {
int index = ccData & 0x0F;
return (char) SPECIAL_CHARACTER_SET[index];
}
private static boolean isExtendedWestEuropeanChar(byte cc1, byte cc2) {
// cc1 - 0|0|0|1|C|0|1|S
// cc2 - 0|0|1|X|X|X|X|X
return ((cc1 & 0xF6) == 0x12) && ((cc2 & 0xE0) == 0x20);
}
private static char getExtendedWestEuropeanChar(byte cc1, byte cc2) {
if ((cc1 & 0x01) == 0x00) {
// Extended Spanish/Miscellaneous and French character set (S = 0).
return getExtendedEsFrChar(cc2);
} else {
// Extended Portuguese and German/Danish character set (S = 1).
return getExtendedPtDeChar(cc2);
}
}
private static char getExtendedEsFrChar(byte ccData) {
int index = ccData & 0x1F;
return (char) SPECIAL_ES_FR_CHARACTER_SET[index];
}
private static char getExtendedPtDeChar(byte ccData) {
int index = ccData & 0x1F;
return (char) SPECIAL_PT_DE_CHARACTER_SET[index];
}
private static boolean isCtrlCode(byte cc1) {
// cc1 - 0|0|0|X|X|X|X|X
return (cc1 & 0xE0) == 0x00;
}
private static int getChannel(byte cc1) {
// cc1 - X|X|X|X|C|X|X|X
return (cc1 >> 3) & 0x1;
}
private static boolean isMidrowCtrlCode(byte cc1, byte cc2) {
// cc1 - 0|0|0|1|C|0|0|1
// cc2 - 0|0|1|0|X|X|X|X
return ((cc1 & 0xF7) == 0x11) && ((cc2 & 0xF0) == 0x20);
}
private static boolean isPreambleAddressCode(byte cc1, byte cc2) {
// cc1 - 0|0|0|1|C|X|X|X
// cc2 - 0|1|X|X|X|X|X|X
return ((cc1 & 0xF0) == 0x10) && ((cc2 & 0xC0) == 0x40);
}
private static boolean isTabCtrlCode(byte cc1, byte cc2) {
// cc1 - 0|0|0|1|C|1|1|1
// cc2 - 0|0|1|0|0|0|0|1 to 0|0|1|0|0|0|1|1
return ((cc1 & 0xF7) == 0x17) && (cc2 >= 0x21 && cc2 <= 0x23);
}
private static boolean isMiscCode(byte cc1, byte cc2) {
// cc1 - 0|0|0|1|C|1|0|F
// cc2 - 0|0|1|0|X|X|X|X
return ((cc1 & 0xF6) == 0x14) && ((cc2 & 0xF0) == 0x20);
}
private static boolean isRepeatable(byte cc1) {
// cc1 - 0|0|0|1|X|X|X|X
return (cc1 & 0xF0) == 0x10;
}
private static boolean isXdsControlCode(byte cc1) {
return 0x01 <= cc1 && cc1 <= 0x0F;
}
private static boolean isServiceSwitchCommand(byte cc1) {
// cc1 - 0|0|0|1|C|1|0|F
return (cc1 & 0xF6) == 0x14;
}
private static final class CueBuilder {
// 608 captions define a 15 row by 32 column screen grid. These constants convert from 608
// positions to normalized screen position.
private static final int SCREEN_CHARWIDTH = 32;
private static final int BASE_ROW = 15;
private final List<CueStyle> cueStyles;
private final List<SpannableString> rolledUpCaptions;
private final StringBuilder captionStringBuilder;
private int row;
private int indent;
private int tabOffset;
private int captionMode;
private int captionRowCount;
public CueBuilder(int captionMode, int captionRowCount) {
cueStyles = new ArrayList<>();
rolledUpCaptions = new ArrayList<>();
captionStringBuilder = new StringBuilder();
reset(captionMode);
this.captionRowCount = captionRowCount;
}
public void reset(int captionMode) {
this.captionMode = captionMode;
cueStyles.clear();
rolledUpCaptions.clear();
captionStringBuilder.setLength(0);
row = BASE_ROW;
indent = 0;
tabOffset = 0;
}
public boolean isEmpty() {
return cueStyles.isEmpty()
&& rolledUpCaptions.isEmpty()
&& captionStringBuilder.length() == 0;
}
public void setCaptionMode(int captionMode) {
this.captionMode = captionMode;
}
public void setCaptionRowCount(int captionRowCount) {
this.captionRowCount = captionRowCount;
}
public void setStyle(int style, boolean underline) {
cueStyles.add(new CueStyle(style, underline, captionStringBuilder.length()));
}
public void backspace() {
int length = captionStringBuilder.length();
if (length > 0) {
captionStringBuilder.delete(length - 1, length);
// Decrement style start positions if necessary.
for (int i = cueStyles.size() - 1; i >= 0; i--) {
CueStyle style = cueStyles.get(i);
if (style.start == length) {
style.start--;
} else {
// All earlier cues must have style.start < length.
break;
}
}
}
}
public void append(char text) {
// Don't accept more than 32 chars. We'll trim further, considering indent & tabOffset, in
// build().
if (captionStringBuilder.length() < SCREEN_CHARWIDTH) {
captionStringBuilder.append(text);
}
}
public void rollUp() {
rolledUpCaptions.add(buildCurrentLine());
captionStringBuilder.setLength(0);
cueStyles.clear();
int numRows = min(captionRowCount, row);
while (rolledUpCaptions.size() >= numRows) {
rolledUpCaptions.remove(0);
}
}
@Nullable
public Cue build(@Cue.AnchorType int forcedPositionAnchor) {
// The number of empty columns before the start of the text, in the range [0-31].
int startPadding = indent + tabOffset;
int maxTextLength = SCREEN_CHARWIDTH - startPadding;
SpannableStringBuilder cueString = new SpannableStringBuilder();
// Add any rolled up captions, separated by new lines.
for (int i = 0; i < rolledUpCaptions.size(); i++) {
cueString.append(Util.truncateAscii(rolledUpCaptions.get(i), maxTextLength));
cueString.append('\n');
}
// Add the current line.
cueString.append(Util.truncateAscii(buildCurrentLine(), maxTextLength));
if (cueString.length() == 0) {
// The cue is empty.
return null;
}
int positionAnchor;
// The number of empty columns after the end of the text, in the same range.
int endPadding = SCREEN_CHARWIDTH - startPadding - cueString.length();
int startEndPaddingDelta = startPadding - endPadding;
if (forcedPositionAnchor != Cue.TYPE_UNSET) {
positionAnchor = forcedPositionAnchor;
} else if (captionMode == CC_MODE_POP_ON
&& (Math.abs(startEndPaddingDelta) < 3 || endPadding < 0)) {
// Treat approximately centered pop-on captions as middle aligned. We also treat captions
// that are wider than they should be in this way. See
// https://github.com/google/ExoPlayer/issues/3534.
positionAnchor = Cue.ANCHOR_TYPE_MIDDLE;
} else if (captionMode == CC_MODE_POP_ON && startEndPaddingDelta > 0) {