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CEA608: Handling XDS and TEXT modes

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This commit is contained in:
Oliver Woodman 2019-06-03 16:34:41 +01:00
parent c231e1120e
commit 19de134aa6
2 changed files with 65 additions and 7 deletions
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2
RELEASENOTES.md
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@ -3,6 +3,8 @@
### 2.10.2 ###
* Subtitles:
* CEA-608: Handle XDS and TEXT modes
([#5807](https://github.com/google/ExoPlayer/pull/5807)).
* TTML: Fix bitmap rendering
([#5633](https://github.com/google/ExoPlayer/pull/5633)).
* UI:

70
library/core/src/main/java/com/google/android/exoplayer2/text/cea/Cea608Decoder.java
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@ -80,6 +80,11 @@ public final class Cea608Decoder extends CeaDecoder {
* 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.
@ -95,25 +100,31 @@ public final class Cea608Decoder extends CeaDecoder {
* 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;
/**
* 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.
* 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_END_OF_CAPTION = 0x2F;
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;
private static final byte CTRL_DELETE_TO_END_OF_ROW = 0x24;
private static final byte CTRL_BACKSPACE = 0x21;
/**
* 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[] {
@ -237,6 +248,11 @@ public final class Cea608Decoder extends CeaDecoder {
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;
public Cea608Decoder(String mimeType, int accessibilityChannel) {
ccData = new ParsableByteArray();
cueBuilders = new ArrayList<>();
@ -268,6 +284,7 @@ public final class Cea608Decoder extends CeaDecoder {
setCaptionMode(CC_MODE_UNKNOWN);
resetCueBuilders();
isInCaptionService = true;
}
@Override
@ -288,6 +305,7 @@ public final class Cea608Decoder extends CeaDecoder {
repeatableControlCc1 = 0;
repeatableControlCc2 = 0;
currentChannel = NTSC_CC_CHANNEL_1;
isInCaptionService = true;
}
@Override
@ -363,6 +381,12 @@ public final class Cea608Decoder extends CeaDecoder {
continue;
}
maybeUpdateIsInCaptionService(ccData1, ccData2);
if (!isInCaptionService) {
// Only the Captioning service is supported. Drop all other bytes.
continue;
}
// Special North American character set.
// ccData1 - 0|0|0|1|C|0|0|1
// ccData2 - 0|0|1|1|X|X|X|X
@ -629,6 +653,29 @@ public final class Cea608Decoder extends CeaDecoder {
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 getChar(byte ccData) {
int index = (ccData & 0x7F) - 0x20;
return (char) BASIC_CHARACTER_SET[index];
@ -683,6 +730,15 @@ public final class Cea608Decoder extends CeaDecoder {
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|0
return (cc1 & 0xF7) == 0x14;
}
private static class CueBuilder {
// 608 captions define a 15 row by 32 column screen grid. These constants convert from 608