Closed Captioning Bug

[jonathanl]

I've been trying to do some work with the closed captioning feature, but it seems like the closed captioning decoder is not working properly when I try to use it with newer DVDs. I am using the Mac OS X version and have tried the latest in the trunk and the latest "stable" version. It seems that about half of the dialogue in newer movies is not showing up at all and what does show up is out of sync. With older DVDs I did not see this problem as much.

This may have to do with the CEA-708 standard not being implemented or possibly the hack used to re-order the 608 closed captioned titles is not working correctly.

In the source code, I see the following comment in "./modules/codec/cc.c":

/* XXX Cc captions data are OUT OF ORDER (because we receive them in the bitstream
* order (ie ordered by video picture dts) instead of the display order.
* We will simulate a simple IPB buffer scheme
* and reorder with pts.
* XXX it won't work with H264 which use non out of order B picture or MMCO
*/

I am a developer and would try to fix this problem, but I do not know the closed caption standard. I am hoping that this problem will be acknowledged and developers who do have experience (and who originally implemented this feature) can fix the bug.

Thanks.

[jonathanl]

Does anyone have an idea why this is broken?

I have tested some more and it seems like pieces of the text are being placed in the middle of other lines and timing is off. I tried to play around the conditions that reorder the buffer, but was not successful in fixing it.

Is there enough interest in this feature for others to want it fixed?

[Jean-Baptiste Kempf]

There is always interest to fix that.
The problem is that CCs are only on NTSC DVDs and VLC developers are European.

Be careful to not mistake CC and DVDsubs though

[jonathanl]

I am not mixing up the closed captioning, which is actually encoded text with the DVD, and the subtitles, which do not include the sound effects, etc. The reason that I am interested in the closed captioning is because it is actually text that can be parsed. However, I am wondering if the closed captioning will ever be fixed, or who is qualified to work on it?

[sbarella]

jonathanl please pursue this! CC has been missing for years on VLC despite claims that it may or may not have the feature.

This is arguably one of the best overall players available and there are those of us who would like to see CC added. I am not a developer but rather one who is in the US broadcast community who has lead MPEG-2 and MPEG-4 encoder development projects.

If there are any TS files you may need for test, I would be glad to provide them.

[jonathanl]

I need to find the person who originally tried to integrate the ccextractor into VLC, but did this incorrectly (or not for the US DVDs). I found a new version of the ccextractor (http://ccextractor.sourceforge.net/) that seems to work with most US DVDs. It seems like this code needs to be modified to work with VLC.

Does anyone have any suggestions on this? Would anyone like to help with this project?

I have already begun playing with this some...

[Jean-Baptiste Kempf]

Send us some broken DVDs... Or tell us where to buy them.