CEA608 Captions - Row count is not updated in CueBuilder inner class

[zsmatyas]

The line defines captionRowCount:

ExoPlayer/library/core/src/main/java/com/google/android/exoplayer2/text/cea/Cea608Decoder.java

Line 195 in e7c60a2

private int captionRowCount;

The inner class CueBuilder has the same member defined on line 594.

The problem is, that the value of the inner class is only updated in ResetCueBuilders(), so this order of incoming commands and characters are processed incorrectly:

11-27 17:30:01.000 D/Cea608Decoder: MISC: ROLL_UP_CAPTIONS_2_ROWS
11-27 17:30:01.063 D/Cea608Decoder: MISC: CARRIAGE_RETURN
11-27 17:30:01.136 D/Cea608Decoder: PAC: Row:15; Col:1; Color:WHITE; italic:false; underline:false
11-27 17:30:01.166 D/Cea608Decoder: Incoming char: I
11-27 17:30:01.302 D/Cea608Decoder: Incoming char:
11-27 17:30:01.331 D/Cea608Decoder: Incoming char: A
11-27 17:30:01.332 D/Cea608Decoder: Incoming char: L
11-27 17:30:01.360 D/Cea608Decoder: Incoming char: W
11-27 17:30:01.360 D/Cea608Decoder: Incoming char: A
11-27 17:30:01.400 D/Cea608Decoder: Incoming char: Y
11-27 17:30:01.400 D/Cea608Decoder: Incoming char: S
11-27 17:30:01.435 D/Cea608Decoder: Incoming char:
11-27 17:30:01.465 D/Cea608Decoder: Incoming char: F
11-27 17:30:01.465 D/Cea608Decoder: Incoming char: O
11-27 17:30:01.495 D/Cea608Decoder: Incoming char: R
11-27 17:30:01.495 D/Cea608Decoder: Incoming char: G
11-27 17:30:01.535 D/Cea608Decoder: Incoming char: E
11-27 17:30:01.536 D/Cea608Decoder: Incoming char: T
11-27 17:30:01.567 D/Cea608Decoder: Incoming char: .
11-27 17:30:02.165 D/Cea608Decoder: MISC: ROLL_UP_CAPTIONS_3_ROWS
11-27 17:30:02.206 D/Cea608Decoder: MISC: CARRIAGE_RETURN
11-27 17:30:02.240 D/Cea608Decoder: PAC: Row:15; Col:1; Color:WHITE; italic:false; underline:false
11-27 17:30:02.308 D/Cea608Decoder: Incoming char: W
11-27 17:30:02.308 D/Cea608Decoder: Incoming char: H
11-27 17:30:02.340 D/Cea608Decoder: Incoming char: A
11-27 17:30:02.340 D/Cea608Decoder: Incoming char: T
11-27 17:30:02.544 D/Cea608Decoder: Incoming char:
11-27 17:30:02.574 D/Cea608Decoder: Incoming char: H
11-27 17:30:02.574 D/Cea608Decoder: Incoming char: A
11-27 17:30:02.604 D/Cea608Decoder: Incoming char: V
11-27 17:30:02.604 D/Cea608Decoder: Incoming char: E
11-27 17:30:02.635 D/Cea608Decoder: Incoming char:
11-27 17:30:02.667 D/Cea608Decoder: Incoming char: I
11-27 17:30:02.766 D/Cea608Decoder: Incoming char:
11-27 17:30:02.766 D/Cea608Decoder: Incoming char: J
11-27 17:30:02.807 D/Cea608Decoder: Incoming char: U
11-27 17:30:02.808 D/Cea608Decoder: Incoming char: S
11-27 17:30:02.841 D/Cea608Decoder: Incoming char: T
11-27 17:30:02.868 D/Cea608Decoder: Incoming char:
11-27 17:30:02.868 D/Cea608Decoder: Incoming char: B
11-27 17:30:02.899 D/Cea608Decoder: Incoming char: I
11-27 17:30:02.900 D/Cea608Decoder: Incoming char: N
11-27 17:30:02.938 D/Cea608Decoder: Incoming char: G
11-27 17:30:02.939 D/Cea608Decoder: Incoming char: E
11-27 17:30:04.541 D/Cea608Decoder: Incoming char:
11-27 17:30:04.541 D/Cea608Decoder: Incoming char: W
11-27 17:30:04.569 D/Cea608Decoder: Incoming char: A
11-27 17:30:04.569 D/Cea608Decoder: Incoming char: T
11-27 17:30:04.602 D/Cea608Decoder: Incoming char: C
11-27 17:30:04.935 D/Cea608Decoder: Incoming char: H
11-27 17:30:05.039 D/Cea608Decoder: Incoming char: ?

The value of captionRowCount in the inner class is not updated to 3, rendering is kept using the value 2 until the next resetCueBuilders() call. Note: if I seek back to this position in the content the captionRowCount is kept on the value last set by resetCueBuilders() so any number of rows can be shown depending on the position the seek is originating from.

[ojw28]

Am I right in thinking ROLL_UP_CAPTIONS_3_ROWS should not clear the caption. So at the end you'd expect all three rows to be visible?

[ojw28]

As an additional question, if you're currently displaying three rows and get ROLL_UP_CAPTIONS_2_ROWS, would you expect that to immediately discard a row?

[zsmatyas]

Annex B.8.1 of the 608 Standard about ROLL-UP style:

Precede each new row of text with these three codes:

• RU2 or RU3 or RU4 (to set roll-up style and depth)
• CR (to roll the display up one row)
• PAC (to set the indent and base row)

Where

• RU2-3-4 is ROLL_UP_CAPTIONS_2-3-4_ROWS (3 different commands)
• CR is CARRIAGE_RETURN
• PAC is Preamble Address Code

So I think there is no need to delete any lines. The RU2-3-4 commands set up how many lines are rolling and the following carriage return will remove the appropriate ones. If the amount of lines are increased, the next CR will not remove any lines. If the amount of lines are decreased, the CR command will remove more than 1 line, so we should be good either case.

---

Annex C.10

The three roll-up commands -- RU2, RU3, and RU4 -- select roll-up style and move the cursor to column 1. The FCC requires further that, if pop-on or paint-on captioning is already present in either memory, it shall be erased. This required erasure seems reasonable, since display memory may have to be reorganized in order to prepare for roll-up style.

This aligns whit the expectation, does not mention erasing any lines when ROLL-UP style was used previously.

[ojw28]

We've merged a fix into dev-v2, but don't have a particularly great way to test it. Please verify if possible.