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View Full Version : Need to confirm: CC with extracted videos?



pheitman
04-14-2004, 09:17 AM
I'm just about to jump in and join you all here with hacking TiVos. The one thing I need to confirm before I do is that Closed Captioning is retained when you extract a video from TiVo to the PC and then either move it back to the TiVo for viewing or burn a DVD from it. Also, I guess I should include when you play a recording on one TiVo when it is stored on another one. In my household I couldn't implement a change in TiVo if it some how effected CC.

Can someone confirm this for me so that I can get started hacking? :)

Peter

Lowcarb
04-14-2004, 12:25 PM
Peter,

I've never used CC so I can't say for sure BUT a lot of people have been complaining in the video extraction forums about seeing the CC data at the top of their screen when they play back video on their PC. (it shows up as dancing white lines at the top of the screen) CC data is sent in the first few lines of the video feed and is usually outside of the visible area of your TV tube display.

So it sure looks like it is retained. It would be dificult to remove it since it isn't a separate stream it is part of teh normal video stream.

sanderton
04-14-2004, 04:17 PM
I wouldn't count on that - the MPEG encoding may have garbled it.

The "real" CC info is in a separate data stream. I would think that mfs_ftp preserves it, since it copies the data in its entirity. I would be quite surprised if it got as far as a DVD intact though.

malfunct
04-14-2004, 04:19 PM
I wouldn't count on that - the MPEG encoding may have garbled it.

The "real" CC info is in a separate data stream. I would think that mfs_ftp preserves it, since it copies the data in its entirity. I would be quite surprised if it got as far as a DVD intact though.

I'll test it out when I have a chance, its pretty easy, pop in the DVD and turn on CC on your tv. There is a requirement that CC survive mpeg encoding (I thought) so that isn't my fear, the reason it would be gone is that tivo stripped it and noone added it back in to the final stream.

pheitman
04-14-2004, 05:04 PM
Thanks - I can't tell you how much I'd appreciate it. I'm really excited about getting back in to mod'ing my TiVos, but don't want to buy and assemble everything only to find out that it is a non-starter because of losing the CC.

eastwind
04-14-2004, 06:17 PM
I'll test it out when I have a chance, its pretty easy, pop in the DVD and turn on CC on your tv. There is a requirement that CC survive mpeg encoding (I thought) so that isn't my fear, the reason it would be gone is that tivo stripped it and noone added it back in to the final stream.
I thought that the problem would be cutting the commercials out. Seems to me like the CC info shows up slightly before it gets used (altough that is clearly not the case with a live program like news) with a timecode that tells the decoder when to show it on the screen. This of course is only from empirical data as I know nothing about the spec. :)
ew

rung
04-14-2004, 06:50 PM
CC are definely toast when you convert to DVD using the current methods. tydemux (and I assume vsplit) only extract the video and audio streams. It would be simple to modify tydemux to extract the cc datastream as well - no one has bothered to go through the trouble yet. The problem is what to do with the data stream. DVD has a mechanism to put a "private" stream in the mpeg which is understood by DVD players to be a CC data stream (this is different from subtitles which are graphics - not binary data). I don't know how to convert binary CC data into something that Scenarist understands but I sure someone here does (TRILIGHT?).

malfunct
04-14-2004, 07:13 PM
I thought that the problem would be cutting the commercials out. Seems to me like the CC info shows up slightly before it gets used (altough that is clearly not the case with a live program like news) with a timecode that tells the decoder when to show it on the screen. This of course is only from empirical data as I know nothing about the spec. :)
ew

My assumption with that is you might miss a word or two but you would still get the jist of the stream. I think we have a pretty affirmative answer dealing with my other fear which is that the data is in a part of the stream that isn't preserved. Again I will test that when I get home, would take about 30 seconds to pop in one of the dvd's I made and turn on CC in the TV.

lart2150
04-14-2004, 07:17 PM
I know there is a small tivo side program that will capture the cc info when you play a show I don't think that data is in the ty stream and the other format that mfs_ftp exports to only has show info.

rung
04-14-2004, 08:32 PM
I know there is a small tivo side program that will capture the cc info when you play a show I don't think that data is in the ty stream and the other format that mfs_ftp exports to only has show info. Embeem's program retrieves the output of the Tivo cc decoder. The input to the decoder is the extended data that is contained in the tystream chunk headers. The data is definitely embedded in the mfs_ftp ty/tmf files.

modistru
04-14-2004, 08:52 PM
Mfs_ftp xferred recordings (TiVo->TiVo, TiVo->PC->TiVo) retain CC. Archive 'em raw & you can inject to TiVo.
Have not seen a DVD/TV combination that plays CC from TyTool DVD's (SomeoneelsesMMV).

eastwind
04-14-2004, 09:34 PM
Tytool doesn't seem to preserve it all the way through DVD. Don't know about re-inserting yet.
ew

TRILIGHT
04-16-2004, 12:31 PM
The CC data is definitely not part of a regular extraction (a la TyTool, TyStudio). As was mentioned, the only thing that retains it is a MFS_FTP extraction since it copies all data and you have the ability to re-insert. An MFS_FTP extraction is NOT in the proper format for DVD authoring though. In converting it, you would lose the CC data. Other extraction methods do not take into account anything other than just the proper way to handle the audio and video. DVD is a much different animal than analog methods of recording things. For instance, if you record a show on a VHS tape, you'll see the CC data actually is preserved. The way we digitally handle the extractions though corrupts this.

The only way to get the CC data onto your DVD (at this time) would be to follow a number of steps. The first is to capture the CC data. I've not done this myself with TiVo scripts but it was mentioned earlier in the thread there is software to do this. Once you had this data, you would need to convert it to the proper format for import into your DVD authoring software. In the DVD world, CC is referred to as Line 21 data. You'll find though that most consumer DVD authoring software does not support Line 21 data. Scenarist does but you won't be able to use Scenarist for a straight DirecTV extraction with TyTool or something. It will not accept the 480x480 video. Personally, I would recommend converting the captured CC data to BMP files (a la SubRip) and then import them as a subpicture (read "subtitles"). It would be simpler than trying to find an app to support both Line 21 data and 480x480.

ANYWAY... There's still one last big problem to this if you've gotten that far and it is the timecodes for display. This would be a huge issue if you were editing commercials out. In doing so, you would TOTALLY screw up any of the timecode information you gathered during your capture. You would have to manually edit the timecodes to remove the unwanted CC data and to make sure your other data lined up correctly with what was being said at the time. So... long story short... can it be done? Sure! Would I want to try? Certainly not if I was editing commercials out! It would be extra work enough just to do it in the first place without worrying about manually editing timecodes.

pheitman
04-16-2004, 12:58 PM
Incredible - thank you for the detailed response! I don't know if they would be interested, but I use VideoRedo for my MPEG editing. I'll see if they are interested in maintaining the CC information.

Thanks again, Peter

FredThompson
04-16-2004, 03:35 PM
Somebody foudn this a while ago. There are a lot of tools here. It might be possible to combine this with TivoVBI

http://www.geocities.com/mcpoodle43/SCC_TOOLS/DOCS/SCC_FORMAT.HTML

http://alt.org/wiki/index.php/TivoVBI

However, there's still the challenge of messed up timecodes. Maybe Josh will incorporate this into a future version of TyTool. I hope so.

Waruwaru
04-16-2004, 04:18 PM
<noob idea> Maybe someone can come up with an util to just convert the CC to DVD subtitle?

FredThompson
04-16-2004, 04:28 PM
That's not the challenge. Trimming and removing sections changes the offset from the beginning of the recording. That's where the problem comes from. Subtitle is actually harder to do than CC because you have to create a set of sub-pictures then fold that into the VOB. Far better to go with CC if at all possible unless you want custom fonts. I've already discussed these tools with Josh. A blank subtitle could be used to obscure news scrolls on stations like Fox News, CNN and MSNBC but there are some technical issues with how the audio and video are multiplexed.

rung
04-16-2004, 09:38 PM
Anyone interesting in a utility that would extract the raw cc data (with timestamps) from a ty?

FredThompson
04-17-2004, 12:11 AM
I'm pretty sure there's a TiVo-side util to do it at alt.org but have never used it.

rc3105
04-17-2004, 02:31 AM
the tivo-side util grabs the cc data as it's decoded during playback, won't do any good for parsing ty


tydemux/typrocess can pull the cc data out 2 ways - set maximum logging & parse the log (which will end up larger than the original ty) or tweak the source ;)

(here's a hint, add a new cc logging level)

AlphaWolf
04-17-2004, 02:47 AM
The CC data is definitely stored in tivo tystreams. That said, all archive formats include CC data, be it TMF, TY, TY+, etc. The CC data is indexed by the E01 record in a given tystream. As far as most are aware, UK tivos also store TeleText data in the tystreams under the E04 record. See this (http://dvd-create.sourceforge.net/tystudio/tystream.shtml) page.

EDIT: doh, should have kept my eyes more open and noticed that this thread had 2 pages.

rung
04-25-2004, 02:55 PM
Somebody foudn this a while ago. There are a lot of tools here. It might be possible to combine this with TivoVBI

http://www.geocities.com/mcpoodle43/SCC_TOOLS/DOCS/SCC_FORMAT.HTML

http://alt.org/wiki/index.php/TivoVBI

However, there's still the challenge of messed up timecodes. Maybe Josh will incorporate this into a future version of TyTool. I hope so.

Thanks for the link! I have created a version of tydemux that will output this scc format. See new thread: tydemux modification (http://dealdatabase.com/forum/showthread.php?t=34436)