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Update WebvttCue to use defaults from the spec

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Cue's UNSET and null values should be used when the source data
doesn't specify *and* the spec doesn't provide a clear default.
In the WebVTT case, the defaults are clear, so we use them
explicitly.

PiperOrigin-RevId: 277522899
This commit is contained in:
ibaker 2019-10-30 16:39:14 +00:00 committed by Oliver Woodman
parent 0c63362258
commit b3f94e3768
6 changed files with 206 additions and 88 deletions
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197
library/core/src/main/java/com/google/android/exoplayer2/text/webvtt/WebvttCue.java
View File

@ -15,15 +15,23 @@
*/
package com.google.android.exoplayer2.text.webvtt;
import static java.lang.annotation.RetentionPolicy.SOURCE;
import android.text.Layout.Alignment;
import androidx.annotation.IntDef;
import androidx.annotation.Nullable;
import com.google.android.exoplayer2.text.Cue;
import com.google.android.exoplayer2.util.Log;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
/**
* A representation of a WebVTT cue.
*/
public final class WebvttCue extends Cue {
private static final float DEFAULT_POSITION = 0.5f;
public final long startTime;
public final long endTime;
@ -50,26 +58,73 @@ public final class WebvttCue extends Cue {
* @return Whether this cue should be placed in the default position.
*/
public boolean isNormalCue() {
return (line == DIMEN_UNSET && position == DIMEN_UNSET);
return (line == DIMEN_UNSET && position == DEFAULT_POSITION);
}
/**
* Builder for WebVTT cues.
*/
/** Builder for WebVTT cues. */
@SuppressWarnings("hiding")
public static class Builder {
/**
* Valid values for {@link #setTextAlignment(int)}.
*
* <p>We use a custom list (and not {@link Alignment} directly) in order to include both {@code
* START}/{@code LEFT} and {@code END}/{@code RIGHT}. The distinction is important for {@link
* #derivePosition(int)}.
*
* <p>These correspond to the valid values for the 'align' cue setting in the <a
* href="https://www.w3.org/TR/webvtt1/#webvtt-cue-text-alignment">WebVTT spec</a>.
*/
@Documented
@Retention(SOURCE)
@IntDef({
TextAlignment.START,
TextAlignment.CENTER,
TextAlignment.END,
TextAlignment.LEFT,
TextAlignment.RIGHT
})
public @interface TextAlignment {
/**
* See WebVTT's <a
* href="https://www.w3.org/TR/webvtt1/#webvtt-cue-start-alignment">align:start</a>.
*/
int START = 1;
/**
* See WebVTT's <a
* href="https://www.w3.org/TR/webvtt1/#webvtt-cue-center-alignment">align:center</a>.
*/
int CENTER = 2;
/**
* See WebVTT's <a
* href="https://www.w3.org/TR/webvtt1/#webvtt-cue-end-alignment">align:end</a>.
*/
int END = 3;
/**
* See WebVTT's <a
* href="https://www.w3.org/TR/webvtt1/#webvtt-cue-left-alignment">align:left</a>.
*/
int LEFT = 4;
/**
* See WebVTT's <a
* href="https://www.w3.org/TR/webvtt1/#webvtt-cue-right-alignment">align:right</a>.
*/
int RIGHT = 5;
}
private static final String TAG = "WebvttCueBuilder";
private long startTime;
private long endTime;
private CharSequence text;
private Alignment textAlignment;
@Nullable private CharSequence text;
@TextAlignment private int textAlignment;
private float line;
private int lineType;
private int lineAnchor;
// Equivalent to WebVTT's snap-to-lines flag:
// https://www.w3.org/TR/webvtt1/#webvtt-cue-snap-to-lines-flag
@LineType private int lineType;
@AnchorType private int lineAnchor;
private float position;
private int positionAnchor;
@AnchorType private int positionAnchor;
private float width;
// Initialization methods
@ -82,23 +137,43 @@ public final class WebvttCue extends Cue {
startTime = 0;
endTime = 0;
text = null;
textAlignment = null;
// Default: https://www.w3.org/TR/webvtt1/#webvtt-cue-text-alignment
textAlignment = TextAlignment.CENTER;
line = Cue.DIMEN_UNSET;
lineType = Cue.TYPE_UNSET;
lineAnchor = Cue.TYPE_UNSET;
// Defaults to NUMBER (true): https://www.w3.org/TR/webvtt1/#webvtt-cue-snap-to-lines-flag
lineType = Cue.LINE_TYPE_NUMBER;
// Default: https://www.w3.org/TR/webvtt1/#webvtt-cue-line-alignment
lineAnchor = Cue.ANCHOR_TYPE_START;
position = Cue.DIMEN_UNSET;
positionAnchor = Cue.TYPE_UNSET;
width = Cue.DIMEN_UNSET;
// Default: https://www.w3.org/TR/webvtt1/#webvtt-cue-size
width = 1.0f;
}
// Construction methods.
public WebvttCue build() {
if (position != Cue.DIMEN_UNSET && positionAnchor == Cue.TYPE_UNSET) {
derivePositionAnchorFromAlignment();
line = computeLine(line, lineType);
if (position == Cue.DIMEN_UNSET) {
position = derivePosition(textAlignment);
}
return new WebvttCue(startTime, endTime, text, textAlignment, line, lineType, lineAnchor,
position, positionAnchor, width);
if (positionAnchor == Cue.TYPE_UNSET) {
positionAnchor = derivePositionAnchor(textAlignment);
}
return new WebvttCue(
startTime,
endTime,
text,
convertTextAlignment(textAlignment),
line,
lineType,
lineAnchor,
position,
positionAnchor,
width);
}
public Builder setStartTime(long time) {
@ -116,7 +191,7 @@ public final class WebvttCue extends Cue {
return this;
}
public Builder setTextAlignment(Alignment textAlignment) {
public Builder setTextAlignment(@TextAlignment int textAlignment) {
this.textAlignment = textAlignment;
return this;
}
@ -126,12 +201,12 @@ public final class WebvttCue extends Cue {
return this;
}
public Builder setLineType(int lineType) {
public Builder setLineType(@LineType int lineType) {
this.lineType = lineType;
return this;
}
public Builder setLineAnchor(int lineAnchor) {
public Builder setLineAnchor(@AnchorType int lineAnchor) {
this.lineAnchor = lineAnchor;
return this;
}
@ -141,7 +216,7 @@ public final class WebvttCue extends Cue {
return this;
}
public Builder setPositionAnchor(int positionAnchor) {
public Builder setPositionAnchor(@AnchorType int positionAnchor) {
this.positionAnchor = positionAnchor;
return this;
}
@ -151,29 +226,69 @@ public final class WebvttCue extends Cue {
return this;
}
private Builder derivePositionAnchorFromAlignment() {
if (textAlignment == null) {
positionAnchor = Cue.TYPE_UNSET;
// https://www.w3.org/TR/webvtt1/#webvtt-cue-line
private static float computeLine(float line, @LineType int lineType) {
if (line != Cue.DIMEN_UNSET
&& lineType == Cue.LINE_TYPE_FRACTION
&& (line < 0.0f || line > 1.0f)) {
return 1.0f; // Step 1
} else if (line != Cue.DIMEN_UNSET) {
// Step 2: Do nothing, line is already correct.
return line;
} else if (lineType == Cue.LINE_TYPE_FRACTION) {
return 1.0f; // Step 3
} else {
switch (textAlignment) {
case ALIGN_NORMAL:
positionAnchor = Cue.ANCHOR_TYPE_START;
break;
case ALIGN_CENTER:
positionAnchor = Cue.ANCHOR_TYPE_MIDDLE;
break;
case ALIGN_OPPOSITE:
positionAnchor = Cue.ANCHOR_TYPE_END;
break;
default:
Log.w(TAG, "Unrecognized alignment: " + textAlignment);
positionAnchor = Cue.ANCHOR_TYPE_START;
break;
}
// Steps 4 - 10 (stacking multiple simultaneous cues) are handled by WebvttSubtitle#getCues
// and WebvttCue#isNormalCue.
return DIMEN_UNSET;
}
return this;
}
}
// https://www.w3.org/TR/webvtt1/#webvtt-cue-position
private static float derivePosition(@TextAlignment int textAlignment) {
switch (textAlignment) {
case TextAlignment.LEFT:
return 0.0f;
case TextAlignment.RIGHT:
return 1.0f;
case TextAlignment.START:
case TextAlignment.CENTER:
case TextAlignment.END:
default:
return DEFAULT_POSITION;
}
}
// https://www.w3.org/TR/webvtt1/#webvtt-cue-position-alignment
@AnchorType
private static int derivePositionAnchor(@TextAlignment int textAlignment) {
switch (textAlignment) {
case TextAlignment.LEFT:
case TextAlignment.START:
return Cue.ANCHOR_TYPE_START;
case TextAlignment.RIGHT:
case TextAlignment.END:
return Cue.ANCHOR_TYPE_END;
case TextAlignment.CENTER:
default:
return Cue.ANCHOR_TYPE_MIDDLE;
}
}
private static Alignment convertTextAlignment(@TextAlignment int textAlignment) {
switch (textAlignment) {
case TextAlignment.START:
case TextAlignment.LEFT:
return Alignment.ALIGN_NORMAL;
case TextAlignment.CENTER:
return Alignment.ALIGN_CENTER;
case TextAlignment.END:
case TextAlignment.RIGHT:
return Alignment.ALIGN_OPPOSITE;
default:
Log.w(TAG, "Unknown textAlignment: " + textAlignment);
return null;
}
}
}
}

28
library/core/src/main/java/com/google/android/exoplayer2/text/webvtt/WebvttCueParser.java
View File

@ -16,7 +16,6 @@
package com.google.android.exoplayer2.text.webvtt;
import android.graphics.Typeface;
import android.text.Layout.Alignment;
import android.text.Spannable;
import android.text.SpannableStringBuilder;
import android.text.Spanned;
@ -87,7 +86,7 @@ public final class WebvttCueParser {
* Parses the next valid WebVTT cue in a parsable array, including timestamps, settings and text.
*
* @param webvttData Parsable WebVTT file data.
* @param builder Builder for WebVTT Cues.
* @param builder Builder for WebVTT Cues (output parameter).
* @param styles List of styles defined by the CSS style blocks preceding the cues.
* @return Whether a valid Cue was found.
*/
@ -252,14 +251,11 @@ public final class WebvttCueParser {
// Internal methods
private static void parseLineAttribute(String s, WebvttCue.Builder builder)
throws NumberFormatException {
private static void parseLineAttribute(String s, WebvttCue.Builder builder) {
int commaIndex = s.indexOf(',');
if (commaIndex != -1) {
builder.setLineAnchor(parsePositionAnchor(s.substring(commaIndex + 1)));
s = s.substring(0, commaIndex);
} else {
builder.setLineAnchor(Cue.TYPE_UNSET);
}
if (s.endsWith("%")) {
builder.setLine(WebvttParserUtil.parsePercentage(s)).setLineType(Cue.LINE_TYPE_FRACTION);
@ -274,18 +270,16 @@ public final class WebvttCueParser {
}
}
private static void parsePositionAttribute(String s, WebvttCue.Builder builder)
throws NumberFormatException {
private static void parsePositionAttribute(String s, WebvttCue.Builder builder) {
int commaIndex = s.indexOf(',');
if (commaIndex != -1) {
builder.setPositionAnchor(parsePositionAnchor(s.substring(commaIndex + 1)));
s = s.substring(0, commaIndex);
} else {
builder.setPositionAnchor(Cue.TYPE_UNSET);
}
builder.setPosition(WebvttParserUtil.parsePercentage(s));
}
@Cue.AnchorType
private static int parsePositionAnchor(String s) {
switch (s) {
case "start":
@ -301,20 +295,24 @@ public final class WebvttCueParser {
}
}
private static Alignment parseTextAlignment(String s) {
@WebvttCue.Builder.TextAlignment
private static int parseTextAlignment(String s) {
switch (s) {
case "start":
return WebvttCue.Builder.TextAlignment.START;
case "left":
return Alignment.ALIGN_NORMAL;
return WebvttCue.Builder.TextAlignment.LEFT;
case "center":
case "middle":
return Alignment.ALIGN_CENTER;
return WebvttCue.Builder.TextAlignment.CENTER;
case "end":
return WebvttCue.Builder.TextAlignment.END;
case "right":
return Alignment.ALIGN_OPPOSITE;
return WebvttCue.Builder.TextAlignment.RIGHT;
default:
Log.w(TAG, "Invalid alignment value: " + s);
return null;
// Default value: https://www.w3.org/TR/webvtt1/#webvtt-cue-text-alignment
return WebvttCue.Builder.TextAlignment.CENTER;
}
}

3
library/core/src/main/java/com/google/android/exoplayer2/text/webvtt/WebvttSubtitle.java
View File

@ -83,6 +83,9 @@ import java.util.List;
list = new ArrayList<>();
}
WebvttCue cue = cues.get(i);
// TODO(ibaker): Replace this with a closer implementation of the WebVTT spec (keeping
// individual cues, but tweaking their `line` value):
// https://www.w3.org/TR/webvtt1/#cue-computed-line
if (cue.isNormalCue()) {
// we want to merge all of the normal cues into a single cue to ensure they are drawn
// correctly (i.e. don't overlap) and to emulate roll-up, but only if there are multiple

5
library/core/src/test/assets/webvtt/with_positioning
View File

@ -21,13 +21,12 @@ NOTE Line as absolute negative number and without line alignment.
00:06.000 --> 00:07.000 line:-10 align:middle
This is the fourth subtitle.
NOTE The positioning alignment should be inherited from align.
NOTE The position and positioning alignment should be inherited from align.
00:07.000 --> 00:08.000 position:10% align:end size:10%
00:07.000 --> 00:08.000 align:right
This is the fifth subtitle.
NOTE In newer drafts, align:middle has been replaced by align:center
00:10.000 --> 00:11.000 line:45%,end align:center size:35%
This is the sixth subtitle.

11
library/core/src/test/java/com/google/android/exoplayer2/text/webvtt/Mp4WebvttDecoderTest.java
View File

@ -87,7 +87,8 @@ public final class Mp4WebvttDecoderTest {
public void testSingleCueSample() throws SubtitleDecoderException {
Mp4WebvttDecoder decoder = new Mp4WebvttDecoder();
Subtitle result = decoder.decode(SINGLE_CUE_SAMPLE, SINGLE_CUE_SAMPLE.length, false);
Cue expectedCue = new Cue("Hello World"); // Line feed must be trimmed by the decoder
// Line feed must be trimmed by the decoder
Cue expectedCue = new WebvttCue.Builder().setText("Hello World").build();
assertMp4WebvttSubtitleEquals(result, expectedCue);
}
@ -95,8 +96,8 @@ public final class Mp4WebvttDecoderTest {
public void testTwoCuesSample() throws SubtitleDecoderException {
Mp4WebvttDecoder decoder = new Mp4WebvttDecoder();
Subtitle result = decoder.decode(DOUBLE_CUE_SAMPLE, DOUBLE_CUE_SAMPLE.length, false);
Cue firstExpectedCue = new Cue("Hello World");
Cue secondExpectedCue = new Cue("Bye Bye");
Cue firstExpectedCue = new WebvttCue.Builder().setText("Hello World").build();
Cue secondExpectedCue = new WebvttCue.Builder().setText("Bye Bye").build();
assertMp4WebvttSubtitleEquals(result, firstExpectedCue, secondExpectedCue);
}
@ -104,7 +105,9 @@ public final class Mp4WebvttDecoderTest {
public void testNoCueSample() throws SubtitleDecoderException {
Mp4WebvttDecoder decoder = new Mp4WebvttDecoder();
Subtitle result = decoder.decode(NO_CUE_SAMPLE, NO_CUE_SAMPLE.length, false);
assertMp4WebvttSubtitleEquals(result);
assertThat(result.getEventTimeCount()).isEqualTo(1);
assertThat(result.getEventTime(0)).isEqualTo(0);
assertThat(result.getCues(0)).isEmpty();
}
// Negative tests.

50
library/core/src/test/java/com/google/android/exoplayer2/text/webvtt/WebvttDecoderTest.java
View File

@ -224,8 +224,8 @@ public class WebvttDecoderTest {
"This is the first subtitle.",
Alignment.ALIGN_NORMAL,
/* line= */ Cue.DIMEN_UNSET,
/* lineType= */ Cue.TYPE_UNSET,
/* lineAnchor= */ Cue.TYPE_UNSET,
/* lineType= */ Cue.LINE_TYPE_NUMBER,
/* lineAnchor= */ Cue.ANCHOR_TYPE_START,
/* position= */ 0.1f,
/* positionAnchor= */ Cue.ANCHOR_TYPE_START,
/* size= */ 0.35f);
@ -237,10 +237,10 @@ public class WebvttDecoderTest {
"This is the second subtitle.",
Alignment.ALIGN_OPPOSITE,
/* line= */ Cue.DIMEN_UNSET,
/* lineType= */ Cue.TYPE_UNSET,
/* lineAnchor= */ Cue.TYPE_UNSET,
/* position= */ Cue.DIMEN_UNSET,
/* positionAnchor= */ Cue.TYPE_UNSET,
/* lineType= */ Cue.LINE_TYPE_NUMBER,
/* lineAnchor= */ Cue.ANCHOR_TYPE_START,
/* position= */ 0.5f,
/* positionAnchor= */ Cue.ANCHOR_TYPE_END,
/* size= */ 0.35f);
assertCue(
subtitle,
@ -252,8 +252,8 @@ public class WebvttDecoderTest {
/* line= */ 0.45f,
/* lineType= */ Cue.LINE_TYPE_FRACTION,
/* lineAnchor= */ Cue.ANCHOR_TYPE_END,
/* position= */ Cue.DIMEN_UNSET,
/* positionAnchor= */ Cue.TYPE_UNSET,
/* position= */ 0.5f,
/* positionAnchor= */ Cue.ANCHOR_TYPE_MIDDLE,
/* size= */ 0.35f);
assertCue(
subtitle,
@ -262,12 +262,12 @@ public class WebvttDecoderTest {
/* endTimeUs= */ 7000000,
"This is the fourth subtitle.",
Alignment.ALIGN_CENTER,
/* line= */ -11f,
/* line= */ -11.0f,
/* lineType= */ Cue.LINE_TYPE_NUMBER,
/* lineAnchor= */ Cue.TYPE_UNSET,
/* position= */ Cue.DIMEN_UNSET,
/* positionAnchor= */ Cue.TYPE_UNSET,
/* size= */ Cue.DIMEN_UNSET);
/* lineAnchor= */ Cue.ANCHOR_TYPE_START,
/* position= */ 0.5f,
/* positionAnchor= */ Cue.ANCHOR_TYPE_MIDDLE,
/* size= */ 1.0f);
assertCue(
subtitle,
/* eventTimeIndex= */ 8,
@ -276,11 +276,11 @@ public class WebvttDecoderTest {
"This is the fifth subtitle.",
Alignment.ALIGN_OPPOSITE,
/* line= */ Cue.DIMEN_UNSET,
/* lineType= */ Cue.TYPE_UNSET,
/* lineAnchor= */ Cue.TYPE_UNSET,
/* position= */ 0.1f,
/* lineType= */ Cue.LINE_TYPE_NUMBER,
/* lineAnchor= */ Cue.ANCHOR_TYPE_START,
/* position= */ 1.0f,
/* positionAnchor= */ Cue.ANCHOR_TYPE_END,
/* size= */ 0.1f);
/* size= */ 1.0f);
assertCue(
subtitle,
/* eventTimeIndex= */ 10,
@ -291,8 +291,8 @@ public class WebvttDecoderTest {
/* line= */ 0.45f,
/* lineType= */ Cue.LINE_TYPE_FRACTION,
/* lineAnchor= */ Cue.ANCHOR_TYPE_END,
/* position= */ Cue.DIMEN_UNSET,
/* positionAnchor= */ Cue.TYPE_UNSET,
/* position= */ 0.5f,
/* positionAnchor= */ Cue.ANCHOR_TYPE_MIDDLE,
/* size= */ 0.35f);
}
@ -412,13 +412,13 @@ public class WebvttDecoderTest {
startTimeUs,
endTimeUs,
text,
/* textAlignment= */ null,
/* textAlignment= */ Alignment.ALIGN_CENTER,
/* line= */ Cue.DIMEN_UNSET,
/* lineType= */ Cue.TYPE_UNSET,
/* lineAnchor= */ Cue.TYPE_UNSET,
/* position= */ Cue.DIMEN_UNSET,
/* positionAnchor= */ Cue.TYPE_UNSET,
/* size= */ Cue.DIMEN_UNSET);
/* lineType= */ Cue.LINE_TYPE_NUMBER,
/* lineAnchor= */ Cue.ANCHOR_TYPE_START,
/* position= */ 0.5f,
/* positionAnchor= */ Cue.ANCHOR_TYPE_MIDDLE,
/* size= */ 1.0f);
}
private static void assertCue(