/*
* 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.tx3g;
import static androidx.media3.common.text.Cue.ANCHOR_TYPE_START;
import static androidx.media3.common.text.Cue.LINE_TYPE_FRACTION;
import android.graphics.Color;
import android.graphics.Typeface;
import android.text.SpannableStringBuilder;
import android.text.Spanned;
import android.text.style.ForegroundColorSpan;
import android.text.style.StyleSpan;
import android.text.style.TypefaceSpan;
import android.text.style.UnderlineSpan;
import androidx.media3.common.C;
import androidx.media3.common.text.Cue;
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.SimpleSubtitleDecoder;
import androidx.media3.extractor.text.Subtitle;
import androidx.media3.extractor.text.SubtitleDecoderException;
import com.google.common.base.Charsets;
import java.util.List;
/**
* A {@link SimpleSubtitleDecoder} for tx3g.
*
* <p>Currently supports parsing of a single text track with embedded styles.
*/
@UnstableApi
public final class Tx3gDecoder extends SimpleSubtitleDecoder {
private static final String TAG = "Tx3gDecoder";
private static final char BOM_UTF16_BE = '\uFEFF';
private static final char BOM_UTF16_LE = '\uFFFE';
private static final int TYPE_STYL = 0x7374796c;
private static final int TYPE_TBOX = 0x74626f78;
private static final String TX3G_SERIF = "Serif";
private static final int SIZE_ATOM_HEADER = 8;
private static final int SIZE_SHORT = 2;
private static final int SIZE_BOM_UTF16 = 2;
private static final int SIZE_STYLE_RECORD = 12;
private static final int FONT_FACE_BOLD = 0x0001;
private static final int FONT_FACE_ITALIC = 0x0002;
private static final int FONT_FACE_UNDERLINE = 0x0004;
private static final int SPAN_PRIORITY_LOW = 0xFF << Spanned.SPAN_PRIORITY_SHIFT;
private static final int SPAN_PRIORITY_HIGH = 0;
private static final int DEFAULT_FONT_FACE = 0;
private static final int DEFAULT_COLOR = Color.WHITE;
private static final String DEFAULT_FONT_FAMILY = C.SANS_SERIF_NAME;
private static final float DEFAULT_VERTICAL_PLACEMENT = 0.85f;
private final ParsableByteArray parsableByteArray;
private final boolean customVerticalPlacement;
private final int defaultFontFace;
private final int defaultColorRgba;
private final String defaultFontFamily;
private final float defaultVerticalPlacement;
private final int calculatedVideoTrackHeight;
/**
* Sets up a new {@link Tx3gDecoder} with default values.
*
* @param initializationData Sample description atom ('stsd') data with default subtitle styles.
*/
public Tx3gDecoder(List<byte[]> initializationData) {
super("Tx3gDecoder");
parsableByteArray = new ParsableByteArray();
if (initializationData.size() == 1
&& (initializationData.get(0).length == 48 || initializationData.get(0).length == 53)) {
byte[] initializationBytes = initializationData.get(0);
defaultFontFace = initializationBytes[24];
defaultColorRgba =
((initializationBytes[26] & 0xFF) << 24)
| ((initializationBytes[27] & 0xFF) << 16)
| ((initializationBytes[28] & 0xFF) << 8)
| (initializationBytes[29] & 0xFF);
String fontFamily =
Util.fromUtf8Bytes(initializationBytes, 43, initializationBytes.length - 43);
defaultFontFamily = TX3G_SERIF.equals(fontFamily) ? C.SERIF_NAME : C.SANS_SERIF_NAME;
// font size (initializationBytes[25]) is 5% of video height
calculatedVideoTrackHeight = 20 * initializationBytes[25];
customVerticalPlacement = (initializationBytes[0] & 0x20) != 0;
if (customVerticalPlacement) {
int requestedVerticalPlacement =
((initializationBytes[10] & 0xFF) << 8) | (initializationBytes[11] & 0xFF);
defaultVerticalPlacement =
Util.constrainValue(
(float) requestedVerticalPlacement / calculatedVideoTrackHeight, 0.0f, 0.95f);
} else {
defaultVerticalPlacement = DEFAULT_VERTICAL_PLACEMENT;
}
} else {
defaultFontFace = DEFAULT_FONT_FACE;
defaultColorRgba = DEFAULT_COLOR;
defaultFontFamily = DEFAULT_FONT_FAMILY;
customVerticalPlacement = false;
defaultVerticalPlacement = DEFAULT_VERTICAL_PLACEMENT;
calculatedVideoTrackHeight = C.LENGTH_UNSET;
}
}
@Override
protected Subtitle decode(byte[] bytes, int length, boolean reset)
throws SubtitleDecoderException {
parsableByteArray.reset(bytes, length);
String cueTextString = readSubtitleText(parsableByteArray);
if (cueTextString.isEmpty()) {
return Tx3gSubtitle.EMPTY;
}
// Attach default styles.
SpannableStringBuilder cueText = new SpannableStringBuilder(cueTextString);
attachFontFace(
cueText, defaultFontFace, DEFAULT_FONT_FACE, 0, cueText.length(), SPAN_PRIORITY_LOW);
attachColor(cueText, defaultColorRgba, DEFAULT_COLOR, 0, cueText.length(), SPAN_PRIORITY_LOW);
attachFontFamily(cueText, defaultFontFamily, 0, cueText.length());
float verticalPlacement = defaultVerticalPlacement;
// Find and attach additional styles.
while (parsableByteArray.bytesLeft() >= SIZE_ATOM_HEADER) {
int position = parsableByteArray.getPosition();
int atomSize = parsableByteArray.readInt();
int atomType = parsableByteArray.readInt();
if (atomType == TYPE_STYL) {
assertTrue(parsableByteArray.bytesLeft() >= SIZE_SHORT);
int styleRecordCount = parsableByteArray.readUnsignedShort();
for (int i = 0; i < styleRecordCount; i++) {
applyStyleRecord(parsableByteArray, cueText);
}
} else if (atomType == TYPE_TBOX && customVerticalPlacement) {
assertTrue(parsableByteArray.bytesLeft() >= SIZE_SHORT);
int requestedVerticalPlacement = parsableByteArray.readUnsignedShort();
verticalPlacement = (float) requestedVerticalPlacement / calculatedVideoTrackHeight;
verticalPlacement = Util.constrainValue(verticalPlacement, 0.0f, 0.95f);
}
parsableByteArray.setPosition(position + atomSize);
}
return new Tx3gSubtitle(
new Cue.Builder()
.setText(cueText)
.setLine(verticalPlacement, LINE_TYPE_FRACTION)
.setLineAnchor(ANCHOR_TYPE_START)
.build());
}
private static String readSubtitleText(ParsableByteArray parsableByteArray)
throws SubtitleDecoderException {
assertTrue(parsableByteArray.bytesLeft() >= SIZE_SHORT);
int textLength = parsableByteArray.readUnsignedShort();
if (textLength == 0) {
return "";
}
if (parsableByteArray.bytesLeft() >= SIZE_BOM_UTF16) {
char firstChar = parsableByteArray.peekChar();
if (firstChar == BOM_UTF16_BE || firstChar == BOM_UTF16_LE) {
return parsableByteArray.readString(textLength, Charsets.UTF_16);
}
}
return parsableByteArray.readString(textLength, Charsets.UTF_8);
}
private void applyStyleRecord(ParsableByteArray parsableByteArray, SpannableStringBuilder cueText)
throws SubtitleDecoderException {
assertTrue(parsableByteArray.bytesLeft() >= SIZE_STYLE_RECORD);
int start = parsableByteArray.readUnsignedShort();
int end = parsableByteArray.readUnsignedShort();
parsableByteArray.skipBytes(2); // font identifier
int fontFace = parsableByteArray.readUnsignedByte();
parsableByteArray.skipBytes(1); // font size
int colorRgba = parsableByteArray.readInt();
if (end > cueText.length()) {
Log.w(
TAG, "Truncating styl end (" + end + ") to cueText.length() (" + cueText.length() + ").");
end = cueText.length();
}
if (start >= end) {
Log.w(TAG, "Ignoring styl with start (" + start + ") >= end (" + end + ").");
return;
}
attachFontFace(cueText, fontFace, defaultFontFace, start, end, SPAN_PRIORITY_HIGH);
attachColor(cueText, colorRgba, defaultColorRgba, start, end, SPAN_PRIORITY_HIGH);
}
private static void attachFontFace(
SpannableStringBuilder cueText,
int fontFace,
int defaultFontFace,
int start,
int end,
int spanPriority) {
if (fontFace != defaultFontFace) {
final int flags = Spanned.SPAN_EXCLUSIVE_EXCLUSIVE | spanPriority;
boolean isBold = (fontFace & FONT_FACE_BOLD) != 0;
boolean isItalic = (fontFace & FONT_FACE_ITALIC) != 0;
if (isBold) {
if (isItalic) {
cueText.setSpan(new StyleSpan(Typeface.BOLD_ITALIC), start, end, flags);
} else {
cueText.setSpan(new StyleSpan(Typeface.BOLD), start, end, flags);
}
} else if (isItalic) {
cueText.setSpan(new StyleSpan(Typeface.ITALIC), start, end, flags);
}
boolean isUnderlined = (fontFace & FONT_FACE_UNDERLINE) != 0;
if (isUnderlined) {
cueText.setSpan(new UnderlineSpan(), start, end, flags);
}
if (!isUnderlined && !isBold && !isItalic) {
cueText.setSpan(new StyleSpan(Typeface.NORMAL), start, end, flags);
}
}
}
private static void attachColor(
SpannableStringBuilder cueText,
int colorRgba,
int defaultColorRgba,
int start,
int end,
int spanPriority) {
if (colorRgba != defaultColorRgba) {
int colorArgb = ((colorRgba & 0xFF) << 24) | (colorRgba >>> 8);
cueText.setSpan(
new ForegroundColorSpan(colorArgb),
start,
end,
Spanned.SPAN_EXCLUSIVE_EXCLUSIVE | spanPriority);
}
}
@SuppressWarnings("ReferenceEquality")
private static void attachFontFamily(
SpannableStringBuilder cueText, String fontFamily, int start, int end) {
if (fontFamily != Tx3gDecoder.DEFAULT_FONT_FAMILY) {
cueText.setSpan(
new TypefaceSpan(fontFamily),
start,
end,
Spanned.SPAN_EXCLUSIVE_EXCLUSIVE | Tx3gDecoder.SPAN_PRIORITY_LOW);
}
}
private static void assertTrue(boolean checkValue) throws SubtitleDecoderException {
if (!checkValue) {
throw new SubtitleDecoderException("Unexpected subtitle format.");
}
}
}